9th. World Congress on Parasitic Plants

Charlottesville, VA 3-7 June 2007

Alphabetical List of Presentations.  See below for Abstracts.

Ahom, RI, and Okereke, OU. Varietal Differences in Ability of Sesame and Pigeon pea as Trap Crops to Induce Suicidal Seed Germination in Striga hermonthica (Scrophulariaceae)

Alejandro Pérez-de-Luque. Mechanisms of Resistance to Parasitic Plants: from Field Screenings to Laboratory Microscopic Studies

Alers-Garcia, J, and Bever, JD. Size Dependent Parasitism of Cuscuta gronovii: Its Implications on Host Population Size Structure and Dynamics

Alers-Garcia, J, Lewis, KC, and Wright, LJ. Parasite Mediated Maternal Effects in Bitter and Sweet Lupins

Aly, R, Shomin, H, Joel, DM, Steinitz, B, Zelcer, A, and Gal-On, A. A New Approach to Parasitic Weed Control Based on Silencing of a Key Metabolic Gene in the Parasite

Aouali, S, Bouznad, Z, Zermane, N, El Khishine, D, Madkour, M, Faied, M, Chaabane, M. Genetic Diversity Among Orobanche crenata Ecotypes Revealed by RAPD and AFLPs Markers, in Algeria

Bewick, TA., and Cascino, J. Development of a Biological Herbicide for Control of Cuscuta spp.

Bolin, JF, Tennakoon, KU, and Musselman, LJ.  Stable Isotope and Nutrient Relationships of the Root Holoparasite Hydnora (Hydnoraceae) in Southern Africa

Bouwmeester, HJ , Cardoso, C, Zhongkui, S, Matusova, R , Lopez-Raez, JA, Charnikhova, T, Verstappen, FWA , Rochange, S, Bécard, G, and Ruyter-Spira, C. Strigolactones, Signals for Friends and Enemies

Cameron, DD, Keith, AM, and Seel, WE .Rhinanthus minor as an Ecosystem Engineer: Understanding the Mechanistic Basis of Parasitic Plant-Induced Changes in Community Structure.

Castillejo, MA, Maldonado, AM, Dumas-Gaudot, E, Pérez de Luque, A, Rubiales, D, and Jorr’n, J. Differential expression proteomics to investigate responses and resistance to Orobanche crenata in legumes

Chachalis, D, and Murdoch, AJ. Potential Use of Nijmegen-1 and Smoke Water Solutions to Deplete Orobanche ramosa Seed Banks in Greece

Chiang, MY, Hsieh, YC, Yuan, CI, and Lin, FY. Cuscuta Species in Taiwan: Molecular Differentiation and Related Findings

De Mol, M, and Heller, A Sap Flow from Host to Mistletoe: an Anatomical Approach

de Zélicourt, A, Letousey, P, Thoiron, S, Montiel, G, Simier, P, and Delavault, P. Molecular analysis of resistance mechanisms to Orobanche cumana in sunflower

dePamphilis, C, McNeal, J, and Zhang, Y. Genome Evolution in Parasitic Plants:  New Genomes, Surprising Findings

Dewaele, D, Elsen, A, and Obiudoh, CA. A Study of Biodiversity of African Radopholus Similis In Uganda.

Dhanapal, GN, Borg, SJ ter, and Struik, PC(3)Integrated Management of Broomrape in India

Draie, R, Pouvreau, JB, Véronési, C, Théodet, C, Thoiron, S, Delavault, P and Simier, P. The Sucrose-Degrading Enzymes in Orobanche ramosa. Characterization and Involvement in Growth, Cell Wall Synthesis and Starch Accumulation.

Dubé, M-P, and Belzile, FJ. Genetic variability among five races of Striga gesnerioides (Willd.) Vatke detected by ISSR, AFLP and cpSSR analysis.

Dunlavey, R, Logan, BA and Reblin, JS. The Influence of Arceuthobium pusillum Infection on the Hydraulic Architecture of White Spruce Stems

Dzomeku, IK, and Murdoch, AJ. Studies on Seed Dormancy, Germination and Seedling Emergence of Striga Hermonthica

Echevarr’a-Zome–o, S, Pérez-de-Luque, A, Jorr’n, J, and Maldonado, AMHistochemical analysis of defense responses involved in resistance of sunflower ( Helianthus annuus ) to Orobanche cumana

Eizenberg, H, Ephrath, J, Lande, T, Achdari, G, and Hershenhorn, J. Temporal Thermal and Special Model for Orobanche Management.

Elzein, A, Fen, B, Kroschel, J, Marley, P, and Cadisch, G. Synergy Between Striga- Mycoherbicides "Fusarium oxysporum f.sp. strigae" and Resistant Cultivars Under Field Conditions: Step Towards Integrated Striga Control in Africa.

Elzein, A, Kroschel, J, Fen, B, Marley, P, and Cadisch, G. Compatibility of Striga-Mycoherbicides with Fungicides Delivered Using Seed Treatment Technology and its Implication For Striga and Cereal Fungal Diseases Control.

Fan, ZW, Buschmann, H, Shen, YD, Lu, Y, and Sauerborn, J. Induced Host Resistance as a Control Method for Parasitic Weeds

Fernández-Aparicio, M, Flores, F, Pérez-de-Luque, A and Rubiales, D. Yield losses in pea as a function of Orobanche crenata levels of infection.

Fernández-Aparicio, M, Pérez-de-Luque, A, and Rubiales, D. Response of Medicago truncatula Accessions to Various Species of Orobanche.

Fernández-Aparicio, M, Pérez-de-Luque, A, Sillero, JC and Rubiales, D. Yield increase in oat-faba bean intercrops under heavy Orobanche crenata infections.

Funk, H, Berg, S, Krupinska, K, Maier, U and Krause, K. Complete DNA Sequences of the Plastid Genomes of Two Parasitic Flowering Plant Species, Cuscuta reflexa and Cuscuta gronovii.

Gebeyehu, S, Belayneh, A and Tesfamariam, M. Parasitic Weeds in Ethiopia: Challenges to Resource Poor and Small Scale Farmers.

Gharib, C, Haidar ,MA, Sleiman, FT. and Sidahmed, MM. Germination and Viability of Cuscuta spp. (Dodder) Seeds after Digestion in Sheep Rumen.

Goldwasser, Y, Yoneyama, K, Xie, X, and Yoneyama, K. Identification of the Stimulants Produced by Arabidopsis thaliana Responsible for the Induction of Orobanche Seed Germination.

Gunathilake, P, Tomilov, A, Tomilova, N, Fillapova, T and Yoder, JI. Macromolecular Trafficking from Host Plants into the Hemiparasitic Plant Triphysaria versicolor.

Haddad, A and Pala, M. Significance of Parasitic Weeds for Food Legumes in Syria.

Harrison, MJ. The Arbuscular Mycorrhizal Symbiosis; Genomics Approaches to Dissect Development and Function.

Heller, A, Elzein, A, De Mol, M, Kroschel, J and Cadisch, G. Colonization of F. oxysporum f.sp. strigae (Foxy 2) on roots of sorghum plants and its implication for Striga control using a seed treatment delivery system: an anatomical study.

Hšniges, A, Ardelean, A, and Wegmann, K. Ecological and Physiological Investigations on Orobanche Species in the Spontaneous Flora of Romania

Kaldenhoff, RWE. Molecular Events During Cuscuta Infection.

Kanampiu, F. Striga Weed Management Options under Smallholder Agriculture in Africa.

Kusumoto, D, Yoneyama, K, Yoneyama, K, Takeuchi, Y. Induction of Systemic Acquired Resistance in Root Parasitic Weeds.

Lanini, WT, Miranda, M, and Aouali, S. Dodder (Cuscuta pentagona) Control in Roundup Ready Alfalfa.

Liu, Y, Liang, L and Lynn DG. Gene Regulation during Haustorial Development and Shoot Initiation in Striga asiatica.

Lopez-Raez, JA, Charnikhova, T , Gomez-Roldan, V,  Matusova, R , de Vos, R, Schipper, B, Verstappen, F , Bino, R , Becard, G, and Bouwmeester, HJ. The Biosynthesis of the Tomato Germination Stimulants is Promoted by Phosphate Starvation.

Lozano-Baena, MD, Lindsey, K, Moreno MT, Rubiales, D, and Pérez-de-Luque, A. Laser Capture Microdissection (LCM): New Technologies Apply to Study of the Parasitic Plant Interactions.

Lozano-Baena, MD, Moreno, MT, Rubiales, D, and Pérez-de-Luque A. Analyses of Medicago truncatula Resistance Against Orobanche crenata Using Citochemical Techniques.

Matusova, R , and Bouwmeester, HJ. The Strigolactone Germination Stimulants of the Plant-Parasitic Striga and Orobanche spp are Derived from the Carotenoid Pathway.

Miegel, D, Hayton, D, and Matthews, JM. Seedbank and Seedbank Management of Orobanche ramosa in South Australia.

Murdoch, AJ, and Kebreab. Predictive Empirical Modeling of Parasitic Weed Life Cycle.

Nickrent, DL, and Vidal-Russell, R.The Evolutionary Origins of Aerial Parasitism in Santalales.

Ogbebor, NO, Omorusi, VI and Evueh, GA. Evaluation of Mistletoe Incidence on Nine Rubber Clones and its Effects on Latex Yield in Nigeria.

Okazawa, A, Wada, Y, Fukusaki, E, Yoneyama, K, Takeuchi, Y, and Kobayashi, A. Trehalose Promotes Seed Germination of a Holoparasitic Plant, Orobanche minor Sm.

Pacureanu-Joita, M, Raranciuc, S, Procopovic, E, and Sava, EAO - 548, a Sunflower Inbred Line, Carrying Two Genes for Resistance Against a New Highly Virulent Romanian Population of Orobanche cumana.

Palmer, AG, Liang, L, OÕMalley, R, and Lynn, DG. Calcium Mediated Transduction of Haustorial Inducing signals in Striga asiatica.

Palmer, AG, Liang, L, Keyes, J, and Lynn, DG. ROS production and Semagenesis in Pathogenesis.

Palmer, J. Horizontal Gene Transfer Gone Wild in Parasitic and Other Flowering Plants.

Plakhine, D, Tadmor, Y, Levin, I and Joel, DM. Non-Stimulated Spontaneous Germination of Orobanche is Genetically Controlled.

Riches, CR, and Mbwaga, AM. Green manure: A Striga Management Technology Whose Time Has Come?

Roney, JK, Khatibi, PA, Stromberg, VK, and Westwood, JH. Trafficking of Host mRNAs into Dodder: A New Frontier in Host-Parasite Communication.

Saadoun, I, Hameed, KM, Ababneh, Q, Bataineh, S and Foy, CL. Biological Control of Orobanche cernua Seed Germination Utilizing an Indigenous Actinomycete Isolate in Jordan.

Sandler, HA. Integrating Germination Patterns, Chemical, and Nonchemical Options to Manage Swamp Dodder in Massachusetts Cranberry Production.

Schneeweiss, GM, Park, JM, Manen, JF, and Colwell, AE. Phylogeny and Evolution of Orobanche and Related Genera (Orobanchaceae).

Scholes J., and Press, M. The Molecular Basis of Susceptibility and Resistance to Striga: insights from Transcript Profiling.

Shamoun, SF, Rietman, LM, Askew, SE, and van der Kamp, BJ. Development of a Biological Control Strategy for Management of Hemlock Dwarf Mistletoe in Coastal British Columbia, Canada.

Sugimoto, Y, Ueyama, T, and Yasuda, N. In vitro Production of Strigolactones by Plant Root Cultures.

Takagi, K, Okazawa, A, Wada, Y, Trakulnaleamsai, C, Fukusaki, E, Yoneyama, K, Takeuchi, Y, and Kobayashi, APhotoresponse Analysis of Phytochrome A in the Non-photosynthetic Parasitic Plant; Orobanche minor Sm.

Tennakoon, KU, Bolin, JF, and Musselman, LJ. Structural and Functional Attributes of the Hypogeous Root Holoparasite Hydnora triceps Drege & Meyer (Hydnoraceae).

Stefanovic, S, and Costea, M. Reticulate Evolution in the Parasitic Genus Cuscuta (Dodders; Convolvulaceae).

Tennakoon, KU. Potential of Establishing Root Hemiparasitic Sandalwood (Santalum album  L.) as a NTF Species in the Buffer Zones of Forests and Degraded Lands in Australasia: a Sri Lankan Experience.

Thorogood, CJ, Rumsey, FJ, and Hiscock, SJ. Speciation and Host Specificity in Orobanche.

Timko, MP,Gowda, BS, Li, J, and Lis, K, Deciphering the Interaction of Striga with Hosts and Non-hosts.

Tomilov, A, Tomilova, N, Filappova, T, Gunathilake, P, Wu, D-Y, Hoang, N, and Yoder, JI. Early Haustorium Development in Triphysaria: A View from Inside the Nucleus.

van der Kooij,TAW, Krupinska K, and Krause, K. Characterization of the Tocochromanol Content and Composition of Different Species of the Parasitic Flowering Plant Genus Cuscuta.

Virupakshaiah, DBM, Ameresh, SH, and Mirji, SB. Structure Analysis of Computer Generated Homologous Models of pm3 Protein in Triticum aestivum (Wheat).

Wegmann K. 2000 Years of Observation, Knowledge and Research on Orobanche.

Williams, AM, and Virtue, JG. Calculation of Growing Degree Days to Determine Optimum Timing of Herbicide Application for Control of Branched Broomrape Orobanche ramosa in Pastures.

Xie, X, Awad, AA, Yoneyama, K, Sekimoto, H, Kusumoto, D, Takeuchi, Y, Yoneyama, K. Qualitative and Quantitative Differences of Strigolactone Exudation Determine Host Specificity of Root Parasites Orobanche and Striga.

Yoneyama, K, Sekimoto, H, Takeuchi, Y, and Yoneyama, K. Nitrogen and Phosphorus Deficiencies Promote the Production and Exudation of 5-Deoxystrigol in Sorghum.

Yonli, D, Traoré, H, Sérémé, P, Hess, DE, and Sankara, P. Integrated Striga hermonthica Management Based Fusarium.

Yoshida, S, and Shirasu, K. Agrobacterium-Mediated Transformation of Striga hermonthica.

 

Abstracts (replace [at] with @ in email addresses; done to prevent spam)

A

Ahom, RI (1), and Okereke, OU (2)

Varietal Differences in Ability of Sesame and Pigeon pea as Trap Crops to Induce Suicidal Seed Germination in Striga hermonthica (Scrophulariaceae)

1. Department of Crop and Environmental Protection, University of Agriculture, Makurdi, Benue State, Nigeria. Email: ie

2. Department of Crop Science, University of Nigeria, Nsukka

Striga hermonthica is the most serious constraint to maize production in West Africa Savannah. Seventeen (17) varieties of sesame and 13 accessions of pigeon pea were evaluated for their ability to stimulate Striga seed germination in vitro using cut-root technique. The test crop varieties evaluated showed significant differences in their ability to stimulate seed germination in S. hermonthica. On the basis of the results, the trap crops varieties were grouped into five with respect to stimulant production, viz., very high, high, moderate, low and very low. For Sesame: Very high (none), high (69B and Yandev _ 55) moderate (Ex-Pankshin-98, 73A-79B, Cross-95, E-8, Ncriben-01M, 73A-H2B, 60-2-3-1-8B and Ciano-16), Low (Yandev-75, Type-4, Ciano _ 27, Eva and 69-1-1) and very low (Pachequeno and Ncriben-03L). For Pigeon pea: very high (TCC1035, Cita 4, TCC6, TCC8126, Cita 3, TCC 87 and Cita 2), high (TCC2, TCC 8127, TCC 151, and Cita 1), and moderate (TCC8 and TCC 8129). The use of trap crops, which stimulate suicidal seed germination in Striga fits into the cultural practices of the small - scale farmer in Nigeria. The traps crops used in this study are cash crops and commonly grown in Benue State - Nigeria. However, varietal differences exist between and within trap crops. The varieties of sesame and pigeon pea belonging to the very high and high stimulants production groups are therefore recommended for use by farmers in Nigeria to clean up or reduce the reserve of Striga seeds in the soil. 

 

Alers-Garcia, J (1), Lewis, KC (1), and Wright, LJ (1)

Parasite Mediated Maternal Effects in Bitter and Sweet Lupins

1. Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge, Massachusetts, 02142, USA.  E-mails: alers-garcia[at]rowland.harvard.edu, lewis[at]rowland.harvard.edu, wright[at]rowland.harvard.edu.

A strong emphasis has been placed in the study of parasitic plants in forestry and agricultural settings given the potential for economic losses these "pests" have in their hosts via marked changes in growth, allometry and in many cases total crop failure.  Most studies have overlooked the fact that parasitic plants can directly affect the growth environment of the maternal parent and thereby the development, size, viability and chemical composition of its progeny.  Our research focuses on environmentally-mediated maternal effects of Castilleja indivisa, a hemiparasite, on high and low alkaloid content isogenic lines of Lupinus albus. We are particularly interested in examining the role and mechanisms by which the parasite affects host nutritional content and its implications in plant defense and reproduction. Castilleja indivisa is known to alter nutrient availability and allocation patterns of its hosts.  Castilleja preferential uptake of N from its hosts is expected to result in a reduction in growth rate of host sinks (flowers and fruits) and seed provisioning (i.e. quality).  Parasitized hosts are predicted to have lower seed size and greater seed C: N ratios than unparasitized hosts.  However, since the intensity of parasitism is usually correlated with host N content, we predict a greater magnitude of maternal effects on high alkaloid hosts compare to low alkaloid hosts.

Alers-Garcia, J (1), and Bever, JD (2)

Size Dependent Parasitism of Cuscuta gronovii: Its Implications on Host Population Size Structure and Dynamics

1. Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge, Massachusetts, 02142, USA.  E-mail: alers-garcia[at]rowland.harvard.edu.

2. Department of Biology, Indiana University, 1001 East Third St., Bloomington, Indiana 47405-3700, USA. E-mail: jbever[at]indiana.edu.

Parasitic plants can have negative effects on the fitness of their hosts. However less is known of how parasitic plants affect the population properties of their host plants.  Our research focuses on the genus Cuscuta (dodder), a holoparasitic plant that exhibits active host choice.  We particularly examined: 1) the effects of parasitism by Cuscuta gronovii on mean population performance and size structure of its host Pilea pumila, 2) the mechanisms underlying active host choice in dodder, and 3) the relationship between size dependent selection and length of the parasitic association on the interactions of individuals within a population. The results of our experiments show that size dependent parasitism and compensation at the population level are the mechanisms underlying the increase of size inequality on parasitized plant populations. Dodder selectively establishes on the tallest individuals, suppresses their growth and continues to spread onto unparasitized plants that have become taller.  Dodder is able to discriminate among potential hosts and choose the tallest ones within the population at least fifteen days prior to parasitism. The effects of dodder on host individuals are dependent on the length of parasitism; dodder causes a drastic reduction on vegetative and reproductive parameters on early attacked hosts compared to those attacked later.  Under the studied scenario as well as in situations on which host plant size exhibits a positive correlation with competitive dominance, parasite foraging behavior as well as the responses of unparasitized individuals are crucial in understanding and predicting the outcome of parasitism in population plant properties.

 

Aly, R (1), Shomin, H (1), Joel, DM (1), Steinitz, B (2), Zelcer, A (2), and Gal-On, A (1)

A New Approach to Parasitic Weed Control Based on Silencing of a Key Metabolic Gene in the Parasite

1. Department of Plant Pathology, Virology and Weed  Research, ARO, Newe-Yaar Research Center, P.O.Box 1021, Ramat Yeshai 30095, Israel. E-mail: radi[at]volcani.agri.gov.il, shominh[at]gmail.com, dmjoel[at]volcani.agri.gov.il, amit[at]volcani.agri.gov.il

2. Department of Plant Genetics, ARO, The Volcani Center, Israel. E-mail: steintz[at]volcani.agri.gov.il, zelcer[at]volcani.agri.gov.il

The silencing approach has already been demonstrated as an effective control method against various pathogens. Gene silencing provides plants with defense against various pathogens, and is a tool of immense importance for research on plant development. The introduction of double-stranded RNA (dsRNA) proved to be a powerful tool for suppressing gene expression through a process known as post-transcriptional gene silencing in plants. In our study we used the inverted repeat technique for gene silencing of Mannose 6-phosphate reductase (M6PR), a key-gene in Orobanche spp. in order to provide the host plant with resistance against the parasite. A gene construct fusing the key gene for silencing to the binary vector (pBin-19) was already transformed to tobacco and tomato host plants. By PCR and RT-PCR analysis, transgenic plants were proved to have a specific PCR fragment (286 bp) which was designated on the mRNA of the O. aegyptiaca  M6PR for silencing. Our results indicated that in-vitro production of small interfering RNAs (siRNAs) by introducing short double-stranded RNA molecules of the M6PR gene into O. aegyptiaca tubercles grown on tomato plants, facilitate suppression and degradation of the native M6PR mRNA, thereby reduction of total soluble solids (sugars) in the treated tubercles. Real-Time RT-PCR analysis showed that the endogenous M6PR mRNA of O. aegyptiaca tubercles or shoots grown on transgenic tomato plants harboring the M6PR silencing construct were reduced by 60-80% compared with the control (O. aegyptiaca grown on non-transgenic plants).

 

Aouali, S (1), Bouznad, Z (2), Zermane, N (2), El Khishine, D (3), Madkour, M (3), Faied, M (3), Chaabane, M (3)

Genetic Diversity Among Orobanche crenata Ecotypes Revealed by RAPD and AFLPs Markers, in Algeria

1. Institut Technique des Grandes Cultures, 1, rue Pasteur, Hassan-Badi BP16-El-Harrach- Alger-Algérie. E-mail: saouali[at]yahoo.fr

2. Institut National Agronomique, El-Harrach-Alger-Algérie. E-mail: bouznad[at]wissal.dz; nzermane[at]hotmail.com

3. Agricultural Engineering Research Institute (AGERI)-Cairo-Egypt. E-mail: el_khishin_dina[at]hotmail.com; m.madkour[at]cgiar.org; solygene[at]yahoo.com

The objectives of this study were to investigate the efficiency of RAPD and AFLP marker systems in detecting intraspecific genetic polymorphism, and to determine the level of diversity among six O. crenata ecotypes, from different geographical localities of El Mitidja. Ten decamer RAPD primers and, three AFLP primer combinations (EcRI/MseI), generated a total of 144 and 429 markers respectively. Dice's similarity matrices were prepared and used for analysis. The diversity index, effective multiplex ratio, and marker index values were higher for the AFLP. This technique appears to be more useful than RAPD in the analysis of limited genetic diversity among the 6 ecotypes of O. crenata tested. Both marker systems were able to discriminate among materials analyzed, but clear distinction between all ecotypes was obtained with AFLP markers. AFLP is therefore another tool for assessing genetic relationships among O. crenata ecotypes along with RAPD. The study, showed a proportional increase in genetic distance with geographical distance, when going from the center of El Mitidja to the eastern-center and the western-center respectively. It is probable that the dissemination center of this parasitic plant is the center of El Mitidja.

B

 

Bewick, TA. (1), and Cascino, J (2)

Development of a Biological Herbicide for Control of Cuscuta spp.

1. U.S. Department of Agriculture, Mailstop 2220, Washington, D.C. 20250

2. Sylvan Bioproducts, Inc, 198 Nolte Drive, Kittanning, Pennsylvania 16201

On May 18, 2005 the U.S. Environmental Protection Agency published a regulation that established an exemption from the requirement of a tolerance for residues of the microbial pesticide Alternaria destruens  Strain 059, marketed commercially as Smolder_, on all agricultural commodities when applied and used in accordance with label directions for the control of dodder.  This represented the culmination of 20 years of research but the beginning of efforts at commercial development.  Large scale demonstrations were conducted in 2006 in several states in the U.S. with both a granular and a wetable powder formulation.  Success was mixed.  In Wisconsin cranberry fields, dodder control ranged from 52 to 100 per cent.  In Massachusetts cranberry fields, dodder control ranged from 20 to 60 per cent.  In Iowa carrot fields, dodder control ranged from 0 to 100 per cent.  Differences in climatic conditions and, possibly, the genetic makeup of the dodder populations tested could account for this variability.

Bolin, JF (1), Tennakoon, KU (2), and Musselman, LJ (1)

Stable Isotope and Nutrient Relationships of the Root Holoparasite Hydnora (Hydnoraceae) in Southern Africa

1. Department of Biology, Old Dominion University,   Norfolk, VA 23529, USA. E-mail: jbolin[at]odu.edu, lmusselm[at]odu.edu

2. Department of Botany, University of Peradeniya,  Peradeniya 20400, Sri Lanka. E-mail: kushant[at]pdn.ac.lk

Hydnora is a genus of unusual plant parasites with a mainly African distribution. Most species of Hydnora reside underground and all lack stomata and leaves. Estimated transdermal water loss in Hydnora africana and Hydnora triceps rhizomes was 0.14_.02 and 0.19_.02 mg cm-1 hr-1, respectively. Due to its extremely water conservative nature Hydnora may be a useful model for parasite-host uptake. We measured carbon and nitrogen natural abundance stable isotope ratios for 11 Hydnora-host associations in southern Africa, including host plants with dominantly CAM or C3 metabolism. Hydnora-host isotope ratios were compared to 12 mistletoe-host associations, emphasizing relationships between host plants shared by Hydnora and mistletoes including Tapinanthus and Viscum species. Carbon and nitrogen isotope values for Hydnora are negatively correlated and carbon isotope ratios mirrored the host photosynthetic metabolism. For the first time we report mineral nutrition relationships for three holoparasite-CAM host associations. Total P and K levels were significantly elevated in the holoparasite relative to the host in most associations. Total Ca, Cl, Mg, N, Na, and S levels were significantly lower in the host.

Bouwmeester, HJ (1,2), Cardoso, C (1), Zhongkui, S (2), Matusova, R (1,2), Lopez-Raez, JA (2), Charnikhova, T (1), Verstappen, FWA (1,2), Rochange, S (3), Bécard, G (3) and Ruyter-Spira, C (1)

Strigolactones, Signals for Friends and Enemies

1. Laboratory for Plant Physiology, Wageningen University, Arboretumlaan 4, 6703 BD  Wageningen, The Netherlands. E-mail: harro.bouwmeester[at]wur.nl; catarina.cardoso[at]wur.nl; radoslava.matusova[at]wur.nl; tatsiana.charnikhova[at]wur.nl; francel.verstappen[at]wur.nl; carolien.ruyter-spira[at]wur.nl

2. Plant Research International, P.O. Box 16, 6700 AA  Wageningen, The Netherlands. E-mail: sun.zhongkui[at]wur.nl; juan.lopez-raez[at]wur.nl

3. UMR 5546 CNRS/Université Paul Sabatier, 24, chemin de Borde-Rouge, BP 42617, Auzeville 31326, Castanet-Tolosan, France. E-mail: rochange[at]scsv.ups-tlse.fr; becard[at]scsv.ups-tlse.fr

The strigolactones are signaling molecules that are used by the root parasitic broomrapes (Orobanche spp) and witchweeds (Striga spp) as well as the symbiotic arbuscular mycorrhizal (AM) fungi to detect the presence of their plant host. The requirements for such signaling molecules are that these compounds should be specifically indicative of the presence of a plant host. We are elucidating the biosynthetic origin of the strigolactones in several host plants of AM fungi as well as parasitic plants. This led to the discovery that the strigolactones are derived from the carotenoids - and should therefore be called apocarotenoids and not sesquiterpene lactones - and as such are quite "plant-specific". Considering the dual signaling role of the strigolactones it is interesting that there is an interaction between AM fungi and parasitic plants through the host plant, resulting in reduced parasitism by Striga hermonthica on sorghum and maize that are colonized by AM fungi. We will discuss the evidence that this interaction is mediated through the production of strigolactones. Also the further elucidation of the strigolactone biosynthetic pathway, initially focusing on the first dedicated step that is probably catalyzed by a carotenoid cleavage dioxygenase will be discussed. We are cloning genes from the pathway to make transgenic plants with altered strigolactone biosynthesis. These plants will be a great tool to study the importance of these signaling molecules for the interaction of plants with friends as well as enemies.

C

Cameron, DD (1), Keith, AM (2), and Seel, WE (3)

Rhinanthus minor as an Ecosystem Engineer: Understanding the Mechanistic Basis of Parasitic Plant-Induced Changes in Community Structure.

1. Department of Animal and Plant Sciences, University of Sheffield, UK.

E-mail: d.cameron[at]shef.ac.uk

2. Centre for Ecology and Hydrology - Banchory, UK

3. School of Biological Sciences, University of Aberdeen, UK

The root hemiparasite Rhinanthus minor, can suppress the abundance of grasses whilst promoting forbs in grassland communities, however, the outcome of its introduction is highly variable.  We investigated the factors influencing this variability by studying the mechanisms through which the parasite acts to facilitate changes in community structure. Field manipulations confirmed that R. minor, suppresses the growth of grasses and whilst promoting that of forbs in the first growing season of a newly sown meadow.  In contrast the removal of R. minor from mature meadow plots did not influence their floristic composition. In pot-based studies the parasite was highly damaging to grasses but had no significant effect on forbs although it did attach to them.  Moreover, the parasite performed worst in terms of growth and photosynthesis when attached to forbs, even compared with unattached individuals.  We hypothesized that forbs express resistant to the parasite.  Tracer experiments using 1N-nitrate supplied to the host confirmed this as the parasite abstracts more nutrients from grasses than from forbs. Histological studies established that all of the forbs possessed successful resistance mechanisms to haustorial penetration of host vascular tissues whilst no successful resistance was observed in the grasses.  Two different resistance mechanisms were observed in the forbs; hypersensitive cell-death and host lignification at the host-parasite interface. Our results establish that differential host resistance underlies the community level effects of R. minor as forbs possess a resistance capacity that other potential hosts do not, consequently the parasite moderates intra-specific competition within grassland communities promoting forb abundance.

Castillejo, MA (1), Maldonado, AM (1), Dumas-Gaudot, E (2), Pérez de Luque, A (3), Rubiales, D (3), and Jorr’n, J (1)

Differential expression proteomics to investigate responses and resistance to Orobanche crenata in legumes

1. Department of Biochemistry and Molecular Biology, University of Cordoba, C—rdoba, Spain. E-mail (corresponding author): bf1jonoj[at]uco.es

2. UMR 1088 INRA/CNRS/UB (Plant-Microbe Environment) INRA-CMSE, Dijon, Cedex, France

3. IAS-CSIC, Cordoba, Spain.

In order to study the plant response to parasitic plants and the molecular basis of the resistance we have used a proteomic approach. The root proteome of two accessions of the model legume Medicago truncatula  and crop pea displaying differences in their resistance phenotype, in control as well as in infected plants have been compared. We report quantitative and qualitative differences in the two-dimensional gel electrophoresis (2-DE) maps of different plant genotypes and plant subjected to different treatments (control, non-infected, and infected). Differential spots were successfully identified by peptide mass fingerprinting (PMF) following MALDI-TOF mass spectrometry. Many of the proteins identified that show significant differences between genotypes and after parasitic infection belong to the functional category of photosynthesis and energetic metabolism, and defense and stress-related proteins. Data will be presented and discussed in terms of plant spp. and genotype common and differential responses, as well as compared with those previously obtained by using classical biochemical and transcriptomic approaches. Data have been published or submitted (Castillejo et al., 2004. Phytochemistry 65: 1817; Jorrin et al., 2006. Euphytica 147: 37; Rossignol et al., 2006. Proteomics 6: 5529; Rispail et al., 2007. New Phytologist 173: 703; Castillejo et al., 2007. Plant Physiology (submitted).

 

Chachalis, D (1), and Murdoch, AJ (2)

Potential Use of Nijmegen-1 and Smoke Water Solutions to Deplete Orobanche ramosa Seed Banks in Greece

1. National Agricultural Research Foundation (NAGREF), Plant Protection Institute of Volos, P.O. Box 1303, Fitoko, Volos 38001, Greece.

2. Department of Agriculture, The University of Reading, Earley Gate, P.O. Box 237, Reading RG6 6AR, UK   E-mail: a.j.murdoch[at]reading.ac.uk

Laboratory and field experiments were conducted to study the effect of using stimulants to deplete Orobanche ramosa seed banks. Germination stimulants tested in the laboratory were Nijmegen-1 (NE-1: 10-4, 10-6, 10-8 and 10-10 mol/L) and two smoke water (SW) solutions, ("Seed Starter" from Australia and a comparable solution produced by burning hay in Greece) were studied. SW concentrations tested were 100, 10, 1, 0.1 and 0.01% v/v aqueous solutions. In the field experiment, five treatments (10-5, 10-6, 10-8 mol/L of NE-1 respectively, 1% v/v local SW, and 10-5 mol/L of NE-1+ 1% v/v local SW) were tested in a tobacco field.  The field was initially uninfected with Orobanche and 500-1000 O. ramosa seeds were placed at marked locations to which tobacco plants were subsequently transplanted. The field site was kept moist for a week to allow the seeds to precondition after which the stimulant solutions were sprayed using a backpack sprayer at 93.5L/ha spray volume and 207 kPa of pressure. Plots were then kept moist for two weeks to allow seeds to germinate and die before transplanting tobacco to each location.  Additionally, in each plot at least 100 seeds were placed in nylon mesh packets at 2.5 cm depth.  These packets were exhumed and germination was recorded.  The non-germinated seeds on exhumation were placed in Petri-dish (1wk, 23¼C) with distilled water for further estimation of germinability of seeds. In the laboratory, 10-6 mol/Litre NE-1 induced 38% germination as did the standard 10-6 mol/Litre GR24. Lower and higher NE-1 concentrations exhibited much lower germination, at levels similar to water control (4% germination).  The local SW stimulated 78% germination at 1% v/v concentration, higher than the "Seed Starter" SW (52%). At high concentrations, both SW strongly inhibited (less than 13%) germination.  The "Seed Starter" SW at more diluted concentrations (0.1 and 0.01% v/v) exhibited a gradual decline of germination (45, 32% germination, respectively).  In contrast, the local SW showed a 48% germination even at the lowest concentration (0.01%).  Depletion of O. ramosa seeds, as recorded in the exhumed seed packets, was well over 50% with the optimum local SW treatment compared to 38% with 10-6 mol/L NE-1.  There was little difference between the other treatments (max. depletion 32%).  Some caution should be exercised as germination was incomplete at the time of exhumation and was allowed to continue in petri dishes moistened with water. Germination of O. ramosa seeds in situ in the soil was ½ to 1/3 of the total seed germination.  The use of smoke and smoke water to stimulate germination in both laboratory and field is well-known for a wide range of species although very little work has been carried out on parasitic weeds. The potential of smoke water to deplete the Orobanche soil seed bank is therefore interesting and the implications of smoke water and other stimulants such as NE-1 to deplete O. ramosa seed banks before transplanting susceptible crops will be discussed.

 

Chiang, MY (1), Hsieh, YC (1), Yuan, CI (1), and Lin, FY (1)

Cuscuta Species in Taiwan: Molecular Differentiation and Related Findings

1. Taiwan Agricultural Chemicals and Toxic Substances Research Institute, 11 Kuang Ming Road, Wufeng, Taichung, Taiwan 413. E-mail: Chiang myc[at]tactri.gov.tw, Hsieh ych[at]tactri.gov.tw, Yuan yci[at]tactri.gov.tw, Lin mtlin[at]tactri.gov.tw

Cuscuta in Taiwan consists of mainly three taxa: C. japonica, C. japonica var. formosana, and C. campestris.  C. japonica and C. japonica var. fomosana parasitize woody hosts of lowland and mountain areas, respectively. C. campastris is predominantly associated with herbaceous hosts of lowland habitats. Additionally, C. chinense and C. australis have been documented, but the former is rare and the later has been noted as mis-identification of C. campestris.  We used different PCR methods to study samples collected from widespread areas. ISSR (Inter Simple Repeat) markers could clearly differentiated morphologically diversified taxa of Cuscuta. ITS (Internal Transcribed Spacer) data revealed that C. campestris from different sites were relatively homogenous with similarity higher than 98%. However, ITS sequences among populations of C. japonica or C. japonica var. formosana were abnormally variable (similarity could be lower than 80%) for the species level.  Our further investigations on ITS led to interesting findings on possible DNA transfer between C. japonica complex and their hosts.

D

 

De Mol, M (1), and Heller, A (1)

Sap Flow from Host to Mistletoe: an Anatomical Approach

1. Institute of Botany, University of Hohenheim, Garbenstrasse 30, 70599 Stuttgart, Germany. E-mail: mdemol[at]uni-hohenheim.de, heller[at]uni-hohenheim.de

The mistletoe Viscum album L. is a hemiparasitic flowering plant. It is (partially) carbon autotrophic, but obtains water and nutrients by tapping into the wood of the host. Classical light microscopical methods and high-resolution 3D X-ray computed tomography were used on poplar (Populus x canadensis Moench, Salicaceae) infected with mistletoe (Viscum album L., Viscaceae) to understand water flow and development of the endophytic system. Direct vessel-vessel connections at the interface host-mistletoe ensure mass water and nutrient transport to the parasite. Almost every host vessel bordering the mistletoe haustorium had a simple perforation that directly connected them with the xylary elements of the parasite. The presence of the parasite showed a high and well directed influence not only on the quantity of wood produced by the host (hypertrophy), but also on the grain of the host wood. The mistletoe seems to direct actively the sap flow of the host towards its haustoria. In this respect, dimensions and morphology of the haustoria and host-mistletoe interface are of significant importance. The broad parasite vessels near the interface transport the sap to xylary elements with a smaller diameter, which conduct the water towards the cortical strands and the aerial parts of the mistletoe. Could this transition to narrower xylem elements pose a significant resistance for water conduction?

 

dePamphilis, C (1), McNeal, J (2), and Zhang, Y (1)

Genome Evolution in Parasitic Plants:  New Genomes, Surprising Findings

1.  Department of Biology, Penn State University, University Park, PA, 16802

2.  Department of Plant Biology, University of Georgia, Athens, GA, 30602

Although most species of flowering plants are free-living and fully photosynthetic about 1% of plant species are direct parasites of photosynthetic plants, and as a result lead partly to fully heterotrophic lifestyles.  How parasitism originated and how their genomes evolve under dramatically altered evolutionary constraints are fundamental problems. Here we report on the sequences of plastid genomes from two Cuscuta and one Pholisma (Lennoaceae) species, and compare them to Epifagus (Orobanchaceae), collectively representing three independent heterotrophic lineages.  These genomes show unexpected retention of photosynthetic genes and pathways in some entirely heterotrophic species and almost perfect parallel reduction in gene content in others.  There is even the possibility that some non-photosynthetic plants have lost their plastid genomes entirely. While plastid and mitochondrial genomes are now focus of intensive study in parasitic plants, nuclear genomes of parasites remain relatively understudied due to their large size and complexity.  Large-scale EST studies and gene sequencing of parasites and parasite-host interactions are now feasible targets for research.  These will provide crucial data for understanding parasite biology and developing effective strategies for parasite control.

Dewaele, D (1), Elsen, A (1), and Obiudoh, CA (2)

A Study of Biodiversity of African Radopholus Similis In Uganda.

1. Department of Biosystems, Kasteelpark Arenberg 13 - Bus 02455, B - 3001 Heverlee, Katholic Universiteit, Leuven, Belgium.  E-mail: dirk.dewaele[at]biw.kuleuven.be, annemie.elsen[at]biw.kuleuven.be

2. Biology Department, University Gent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium. E-mail: cobiudoh[at]yahoo.com

The main problem that nematologist are facing during screening for nematode resistance is the variability in the reproduction of different R. similis populations. Assessment of this variability will be highly useful to banana breeding programs for incorporating resistance to nematodes. The reproductive fitness of four Radopholus similis populations (Ikulwe, Sendusu, Mukono and Mbarara) were studied on carrot disc (in vitro) and on plantain cultivar (in vivo) Obino l Ewai, as a function of time, inoculum densities and its pathogenicity on plant. In the first experiment, the reproductive fitness of the isolates was followed during two, four, six and ten weeks after inoculation. There were significantly (p<0.05) differences in the reproductive fitness of R. similis populations from Uganda as an effect of time. Increase in time increases the final nematode population. The experiment to test the effect of different inoculum density with respect to the reproduction of these populations on the carrot discs shows no significant different in their rate of reproduction at 6 weeks after inoculation. Regarding reproduction and pathogenicity of R. similis on plants, no definite conclusion can be drawn from the result obtained.

de Zélicourt, A (1), Letousey, P (2), Thoiron, S (1), Montiel, G (1), Simier, P (1), and Delavault, P (1)

Molecular analysis of resistance mechanisms to Orobanche cumana in sunflower

1. Université de Nantes, Nantes Atlantique Universités, Laboratoire de Biologie et Pathologie Végétales, EA1157, 2 rue de la Houssini�re, BP 92208, Nantes, F-44000 France. Axel.De-Julien-De-Zelicourt[at]univ-nantes.fr, philippe.delavault[at]univ-nantes.fr

2. Université de Reims, Laboratoire de Stress, Défenses et Reproduction des Plantes, UFR Sciences, BP 1039, Reims F-51687 Cedex 2, France

In sunflower, resistance to Orobanche cumana is characterized by a low number of parasite attachments and a confinement of the parasite in host tissues leading to its necrosis. To help understand what are the mechanisms governing such resistance, a molecular approach was employed during both early and late responses of susceptible (2603) and resistant (LR1) sunflowers infected by O. cumana. The expression patterns of defense-related genes were investigated. The resistant genotype exhibited a stronger overall defense response against O. cumana than the susceptible one, involving preferentially marker genes of JA and SA pathways. Among them, HaDef1 (defensin), appeared to be characteristic of the LR1 resistance. Plant defensins are small basic peptides of 5-10 kDa and most of them exhibit antifungal activity. In LR1, among the three defensin encoding cDNA identified, only HaDef1 presented a preferential root expression pattern and was induced upon infection by the root parasitic plant O. cumana few days before necrosis occurred. A 5.8 kDa recombinant peptide, Ha-DEF1, was produced in E. coli. Investigation of in vitro antifungal activity of Ha-DEF1 showed a strong growth inhibition of Saccharomyces cerevisiae and a morphogenetic activity on Alternaria brassicicola germ tube development. Bioassays also revealed that Ha-DEF1 rapidly induced cell death at the radicle apex of Orobanche seedlings but not of another parasitic plant, Striga hermonthica, nor of Arabidopsis thaliana. These results demonstrate for the first time a lethal effect of defensins on plant cells. The putative mode of action of defensin in Orobanche cell death and its possible involvement in sunflower resistance will be discussed.

 

Dhanapal, GN(1), Borg, SJ ter (2), and Struik, PC(3)

Integrated Management of Broomrape in India

1. Department of Agronomy, University of Agricultural Sciences, GKVK Campus, Bangalore-560 065, India. E-mail: gndhanapal[at]yahoo.co.in

2. Hamelakkerlaan, 11, 6703 EE, Wageningen, The Netherlands. E-mail: Siny.terBorg[at]staf.TON.WAU.NL

3. Plant Sciences,Crop and Weed Ecology, Wageningen Agricultural University, Haarweg 333, 6709 RZ, Wageningen, The Netherlands. E-mail: Paul.Struik[at]wur.nl

Bidi tobacco is a non-Virginia tobacco, being cultivated in Nipani (India) for the 45 years under rainfed conditions. In India, Orobanche cernua is the most pernicious parasitic weed in tobacco cultivation. The severity of broomrape problem is increasing because of mono-cropping of tobacco and hand weeding is the only practice to control it. Among different chemicals tested GR 24 induced 58% germination of broomrape seeds under laboratory conditions. The positive interaction between GR 24 (I.0 ppm) and the root exudates of few crops deserves further attention. In trap crop field experiment, sunhemp and greengram crops reduced broomrape population by 68% and increased tobacco yields by 45% at 90 days after transplanting (DAT). Glyphosate and Imazaquin at 0.50 kg ai/ha and 0.01 kg ai/ha, respectively, reduced the number and dry weight of broomrape spikes. However, we suggest the following integrated cultural and chemical control approaches to obtain higher tobacco yields and minimize broomrape population in the soil for tobacco areas in Nipani and areas of similar conditions in India: (1) Grow trap crops (sunhemp/greengram) in the early spring and incorporate in situ at 45 days after sowing; (2) Transplant tobacco after 15-20 days; (3) Take up general hand weeding within 45 DAT; (4) Apply glyphosate at 60 DAT at 0.50 kg at ai/ha (or less); (5) Remove the remaining few broomrapes spikes by hands or apply plant oils to prevent seed formation. Also a cropping system with trap crop - short fallow - tobacco is an ideal practice to reduce the broomrape seed inoculumÕs potential in the soil.

 

Draie, R (1), Pouvreau, JB (1), Véronési, C (1), Théodet, C (1), Thoiron, S (1), Delavault, P (1) and Simier, P (1)

The Sucrose-Degrading Enzymes in Orobanche ramosa. Characterization and Involvement in Growth, Cell Wall Synthesis and Starch Accumulation.

1. Université de Nantes, Nantes-Atlantique Universités, Laboratoire de Biologie et Pathologie Végétales, EA 1157, UFR Sciences et Techniques, 2 rue de la Houssinire F44322 Nantes, France. ridadraie[at]hotmail.com, jean-bernard.pouvreau[at]univ-nantes.fr, christophe.veronesi[at]univ-nantes.fr, catherine.theodet[at]univ-nantes.fr, severine.thoiron[at]univ-nantes.fr, philippe.delavault[at]univ-nantes.fr, philippe.simier[at]univ-nantes.fr.

O. ramosa is an obligate parasite of major crops such as tobacco, tomato, oil seed rape and hemp. It has been known for more than two decades that the host-derived sucrose supports parasite growth. Nevertheless, sucrose metabolism in the parasite remains to be elucidated. We have initiated studies aiming at characterizing the molecular components, such as cell wall invertase (CWI), vacuolar invertase (VI), neutral/alkaline invertase (NI) and sucrose synthase (SuSy), involved in sucrose mobilization in Orobanche ramosa growing on tomato roots. Our first data show that tubercles display an equilibrated VI / NI ratio while this ratio is stronger in the growing subterranean stems due to a specific increase in VI activity. This reflects the key role of this enzyme during sucrose utilization in the growing stem where cell expansion occurs through vacuolar hexose and mannitol accumulation. The VI enzyme was purified using affinity and gel filtration chromatography. Only one isoenzyme was detected in stems, and the native form shows a pI of 3.8 and a molecular mass of 98  7 kDa. Protein sequencing is in progress. CWI activity is constant to a basal level in tubercles and stems. In contrast, tubercles display a significant SuSy activity. Using antibodies raised against faba bean SuSy, we show that this enzyme is strongly associated to tracheids and amyloplasts contained in parenchyma cells. It suggests that in tubercles SuSy is involved in the sucrose mobilization required for cell wall polysaccharide synthesis in tracheids and for starch accumulation in parenchyma cells.

 

Dubé, M-P (1), and Belzile, FJ (1)

Genetic variability among five races of Striga gesnerioides (Willd.) Vatke detected by ISSR, AFLP and cpSSR analysis.

1. Departement de phytologie, Université Laval, Québec City, QC G1K 7P4, Canada.

Striga gesnerioides (Willd.) Vatke is an obligate root parasite of several dicotyledonous species including cowpea (Vigna unguiculata (L.) Walp.), an important legume crop of the semi-arid regions of West Africa. Based on host-parasite interactions in the field, various races of S. gesnerioides attacking cowpea have been identified. In this study, we investigated the genetic variability within and between 44 populations of five of the previously recognized races of the parasite present in West Africa. Three different types of molecular markers were used on up to 10 individuals from each population. ISSR (inter-simple sequence repeat) markers showed no genetic variability within populations. The variability between the populations was also extremely low and did not allow discrimination of the five races. A few populations were more closely related (notably two populations from Togo), but no geographical or "racial" clustering could be seen. Further work with ISSR and AFLP (amplified fragment length polymorphism) markers is in progress to improve the accuracy of the analysis. Finally, we used cpSSR (chloroplastic simple sequence repeat) markers as these have been shown, in many studies, to reveal greater amounts of polymorphism at the intraspecific level. A total of 34 cpSSR primer pairs from various species were used, 26 of which produced amplicons in Striga. Absolutely no polymorphism was observed with cpSSR markers emphasizing that despite a large geographical distribution, very low genetic variability can be found in the different populations of S. gesnerioides. This may be due in part to the autogamous mode of reproduction of the parasite.

 

Dunlavey, R (1), Logan, BA (1) and Reblin, JS (1)

The Influence of Arceuthobium pusillum Infection on the Hydraulic Architecture of White Spruce Stems

1. Department of Biology, Bowdoin College, Brunswick, ME 04011USA 

         E-mail: rdunlave[at]bowdoin.edu, blogan[at]bowdoin.edu, jreblin[at]bowdoin.edu

Arceuthobium pusillum (eastern dwarf mistletoe) is an aerial hemiparasitic angiosperm whose primary hosts are white spruce (Picea glauca), red spruce (Picea rubens) and black spruce (Picea mariana).  Although the biology, ecology, and population genetics of Arceuthobium species have been examined in some depth, comparatively less is known about the impacts of Arceuthobium infection on the physiological performance of their hosts.  Arceuthobium infection is characterized by the establishment of an endophytic system that taps directly into host xylem and phloem, through which the parasite withdraws all of the water, mineral nutrients and much of the fixed carbon that it needs to support its growth.  Along the coast of Maine, Arceuthobium pusillum infection causes severe mortality in white spruce stands.  We investigated the impact of Arceuthobium pusillum infection on white spruce stem hydraulic conductivity.  Infection reduced white spruce stemsÕ capacity to deliver water (specific conductivity) by more than 25%.  This perturbation may explain the dramatic reduction (>40%) in needle size distal to infection.  Needle size reductions may offset reductions in hydraulic conductivity and water use by Arceuthobium to restore the balance between host leaf area and the capacity to transport water through stems.  As a result, infection had no significant impact on a stemÕs capacity to deliver water when expressed on the basis of leaf area distal to infection (leaf specific conductivity).  Furthermore, we found that infection did not have an impact on the occurrence of cavitation in white spruce stems.

Dzomeku, IK (1), and Murdoch, AJ (2)

Studies on Seed Dormancy, Germination and Seedling Emergence of Striga Hermonthica

1  Department of Agronomy, Faculty of Agriculture, University of Development Studies, P.O. Box TL 1882. Nyankpala, Tamale, Ghana.

2. The University of Reading, School of Agriculture, Seed Science Laboratory.  P. O. Box 236. Reading UK.

This paper represents the first attempt to apply a conditioning model for parasitic weeds to seeds in soil in the glasshouse. The previous models developed for Striga hermonthica and for three Orobanche species were only applied empirically and were not validated on independent data sets. The results indicate that S. hermonthica seeds recovered from eight soil environments of different drought and urea treatments, attained germination within 14-28 days and these optimum periods were similar to predictions based on the in vitro model, Once the seeds have been in imbibed storage in the soil for more than about 28 days in this experiment, induction of secondary dormancy increased but gradually, leading to a slow decrease in germination over a period of 91 days which in most environments did not terminate in zero germination. After 119 days of conditioning in the soil, germination percentages remain significantly high compared to the model predictions. The implication of the present findings for the control of S. hermonthica was discussed.

 

E

 

Echevarr’a-Zome–o, S (1), Pérez-de-Luque, A (2), Jorr’n, J (1), and Maldonado, AM (1)

Histochemical analysis of defense responses involved in resistance of sunflower ( Helianthus annuus) to Orobanche cumana

1. Agricultural and Plant Biochemistry Research Group, Dpt. of Biochemistry and Molecular Biology, University of Cordoba. Cordoba, Spain, E-mail: g72eczos[at]uco.es; bf1jonoj[at]uco.es; bb2maala[at]uco.es

2. IFAPA-CICE (Junta de Andalucia), CIFA, çrea de Mejora y Biotecnolog’a, C—rdoba, Spain.

         E-mail: bb2pelua[at]uco.es

Sunflower broomrape (Orobanche cumana  Wallr.) is considered as one of the major constraints for sunflower production in Mediterranean areas1. Breeding for resistance is regarded as the most effective and environmental friendly solution to control this parasite. However, the existing sources of genetic resistance are defeated by emergence of new more virulent races of the parasite.

In this work we have analysed the interaction between sunflower and O. cumana in order to get insights into the mechanisms involved in resistance. The interaction between O. cumana  and two sunflower genotypes showing different behavior against the race F of O. cumana, HE-39998 (susceptible) and HE-39999 (resistant), were monitored by pot and Petri dish bioassays. Then, using histochemical procedures and microscopic observations, compatible and incompatible interactions were compared and several defense responses involved in resistance were identified2. Suberization and protein cross-linking at the cell wall were observed in the resistant sunflower cells in contact with the parasite, preventing parasite penetration and connection to the host vascular system. In addition, fluorescence and confocal laser microscopy observations revealed accumulation of phenolic compounds during the incompatible interaction, which is in agreement with these metabolites playing a defensive role during H. annuus - O. cumana interaction3.

1. Shindrova, et al. (1998) Helia 21: 55.
2. Echevarr’a-Zome–o, et al. (2006) Journal of Experimental Botany, 57: 4189.
3. Serghini, et al. (2001) Journal of Experimental Botany 52: 2227.

 

Eizenberg, H (1), Ephrath, J (2), Lande, T (1), Achdari, G (1), and Hershenhorn, J (1)

Temporal Thermal and Special Model for Orobanche Management

1. Agricultural Research Organization, Newe-Ya'ar Research Center, Ramat Yishay, Israel. eizenber[at]volcani.agri.gov.il

2. Wyler Department of Dryland Agriculture, Jacob Blaustein Institutes for Desert Research, Sede-Boqer, Ben-Gurion University of the Negev, Israel.

The overall goal of our study is to develop a decision support system for Orobanche control base on spatial and temporal sub-models. a) Temporal model: in previous studies, a mathematically relations between temperature and the parasitism process of O. aegyptiaca, O. minor and O. cumana, in tomato, red clover, and sunflower, respectively, was shown. A Growing Degree Days (GDD) model was developed to predict Orobanche parasitism in these crops. Using a sigmoid function allows us to predict the timing of the various Orobanche spp. developmental including subsurface stages. Herbicidal control of Orobanche was achieved in tomato, red clover, and sunflower using ALS inhibitors. The most effective control was achieved in the subsurface parasitism phase. Optimized chemical control is achieved when minimal herbicide rates are applied to the host at the most susceptible stage of the parasite. Herbicide application timing is based on the GDD model mentioned above. Recently, the option of in-situ monitoring sub-surface parasitism was introduced by using the minirhizotron camera. This is a non-destructive tool for detecting and monitoring parasitism over time. The minirhizotron technology is essential for verifying the herbicide rate models. This will allow making proper decisions regarding to herbicide application timing. b) Remote sensing approach was used for modeling the spatial distribution of O. aegyptiaca in tomato and in dill fields. IR, NIR and RGB aerial images were taken from satellite and from air for tomato and parsley fields infected with O. aegyptiaca. Orobanche aegyptiaca could be partially detected only by RGB aerial images.

 

Elzein, A (1), Fen, B (2), Kroschel, J (3), Marley, P (4), and Cadisch, G (1)

Synergy Between Striga- Mycoherbicides "Fusarium oxysporum f.sp. strigae" and Resistant Cultivars Under Field Conditions: Step Towards Integrated Striga Control in Africa

1. Institute for Plant production and Agroecology in the Tropics and Subtropics (380), University of Hohenheim, D-70593, Stuttgart, Germany. Email: gasim[at]uni-hohenheim.de, cadisch[at]uni-hohenheim.de.

2. International Institute of Tropical Agriculture (IITA), 08 BP 0932 Tri Postal, Cotonou, Republic of Benin. E-mail: f.beed[at]iita-uganda.org.

3. Integrated Crop Management Division, International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. E-mail: j.kroschel[at]cgiar.org.

4. Department of Crop Protection, Faculty of Agriculture/Institute for Agricultural Research, Ahmadu Bello University, Samaru, Zaria, Nigeria. E-mail: psmarley[at]yahoo.co.uk.

Striga spp. are important constraints in cereal and legume production in semi-arid tropical Africa. An integrated approach, in which biocontrol represents an important component, appears to be a promising strategy for reducing Striga infestation. Fusarium oxysporum f.sp. strigae (isolates Foxy 2 & PSM197) are potential, highly host specific mycoherbicides against S. hermonthica. For facilitating practical field application, our recent research focuses on the development of appropriate mycoherbicidal formulations and delivery systems. Hence, Pesta formulation made by encapsulating fungal inoculum in a matrix composed of durum wheat-flour, kaolin, and sucrose, was developed. Seed treatment technology for coating sorghum and maize seeds as an attractive option for further minimizing the inoculum amount and facilitating delivery of Striga-mycoherbicides was also provided. Integration of Pesta formulation and treated seeds containing Striga-mycoherbicides (Foxy 2 & PSM197) with Striga resistant and susceptible maize and sorghum cultivars under field conditions of West Africa was investigated. The combination Pesta granules or treated seeds and resistant maize and sorghum cultivars enhanced clearly both mycoherbicides efficacy, and showed the strongest suppressive effect on Striga compared to susceptible cultivars. The difference between the resistant and the susceptible cultivars was stronger for maize than for sorghum. On average (i.e. the average effect of both isolates), they reduced the number of emerged Striga plants per plot by 96% or 89% when the two isolates formulated as Pesta granules or delivered as coated seeds, respectively, and combined with the resistant maize cultivars compared with the control of the susceptible cultivars. On the other hand, the respective reductions when the two isolates integrated with the susceptible maize cultivars were 85 %, and 21%. Improvement in maize and sorghum performances (height, grain yield, stalks dry weight, etc.) was recorded. Further, both mycoherbicides maintained excellent viability (shelf-life) on Pesta products and treated seeds after one year of storage which would be sufficient for their use under practical conditions of storage, handling and delivery. The suitability of Pesta and seed treatment technology for formulating and delivering Striga-mycoherbicides and their compatibility and synergy with Striga resistant cultivars, are highly relevant to the realization of an integrated Striga control approach adoptable and applicable by subsistence farmers in Africa.

Key words: Weed biological control, Mycoherbicide, Encapsulation, Seed coating, Integrated control, Fusarium oxysporum, Striga hermonthica, Striga-resistant cultivars, Sorghum bicolor, Zea mays

 

Elzein, A (1), Kroschel, J (2), Fen, B (3), Marley, P (4), and Cadisch, G (1)

Compatibility of Striga-Mycoherbicides with Fungicides Delivered Using Seed Treatment Technology and its Implication For Striga and Cereal Fungal Diseases Control

1. Institute for Plant production and Agroecology in the Tropics and Subtropics (380), University of Hohenheim, D-70593, Stuttgart, Germany E-mail: gasim[at]uni-hohenheim.de, cadisch[at]uni-hohenheim.de.

2. Integrated Crop Management Division, International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. Email: j.kroschel[at]cgiar.org).

3. International Institute of Tropical Agriculture (IITA), 08 BP 0932 Tri Postal, Cotonou,Republic of Benin. E-mail: f.beed[at]iita-uganda.org.

4. Department of Crop Protection, Faculty of Agriculture/Institute for Agricultural Research, Ahmadu Bello University, Samaru, Zaria, Nigeria. E-mail: psmarley[at]yahoo.co.uk.

Root parasitic weeds of the genus Striga and fungal diseases constitute a major biotic constraint to staple food production in Africa, and consequently aggravate hunger and poverty. With the aim of improving sorghum and maize performance and yield, an investigation on the possibility of delivering the potential Striga-mycoherbicides (Foxy 2 & PSM197) and some selected fungicides using seed treatment technology to control simultaneously Striga and sorghum and maize fungal diseases was made for the first time. Sorghum film-coated seeds with different application rates (dosages) of Apron XL and Ridomil Gold in combination with the mycohericides Foxy 2 and PSM197 and different coating adhesives were used. The effects of Apron XL and Ridomil Gold fungicides on growth and sporulation of the two isolates was examined by growing the film-coated sorghum seeds on PDA media. Delivering of the fungicides Apron XL and Ridomil with Striga-mycoherbicides Foxy 2 and PSM197 using seed treatment technology did not interfere with seed coating process as well as with the initial survival of fungal isolates on coated sorghum seeds. Apron XL clearly enhanced the growth, sporulation and viability of both isolates, indicating strong compatibility with Striga- mycoherbicides. However, Ridomil Gold was not compatible on PDA medium. Under filed conditions of West Africa, the integration of fungicide Apron XL (at a rate of 0.5 ml /kg of seeds) with Striga-mycoherbicides (Foxy2 & PSM197) and resistant maize cultivars using seed treatment technology and Arabic gum as adhesive showed significant reduction in Striga emergence by 81% and 90% compared to the respective resistant and susceptible controls. Improved performance of maize treated with Striga-mycoherbicides and fungicide was recorded. The compatibility between Striga-mycoherbicides and Apron XL fungicide has significant implication for controlling simultaneously Striga and sorghum and maize fungal diseases and improving crops performance and yield.

 

 

F

Fan, ZW (1), Buschmann, H (2), Shen, YD (1), Lu, Y (1), and Sauerborn, J (2)

Induced Host Resistance as a Control Method for Parasitic Weeds

1. Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences; Key Laboratory for Pest Detection and Monitor of Tropical Agriculture of Hainan Province, Hainan 571737, China 

2. Institute of Plant Production and Agroecology in the Tropics and Subtropics, University of Hohenheim, Stuttgart 70593, Germany

Parasitic weeds restrict crop production in many countries. Plant induced resistance is against not only pathogens and herbivores, but also parasitic weeds. Induced resistance against parasitic weeds has been demonstrated in the associations of sunflower-Orobanche cumana, tobacco/hemp-O. ramosa and pea-O. crenata under greenhouse conditions and/or in the field. Plant activators include biotic and abiotic agents. Host plants underlay systemic acquired resistance (SAR) or induced systemic resistance (ISR) pathway against parasitic weeds. Induced resistance should be integrated in the parasitic weed management systems. This paper reviews the history and development, pathway and mechanism, as well as prospect and outlook of plant induced resistance on the control of parasitic weeds.

 

Fernández-Aparicio, M (1), Pérez-de-Luque, A (2), Sillero, JC (2) and Rubiales, D (1)

Yield increase in oat-faba bean intercrops under heavy Orobanche crenata infections.

1. CSIC, Instituto de Agricultura Sostenible, Apdo. 4084, 14080 C—rdoba, Spain. E-mail: monfapru[at]yahoo.com, ge2ruozd[at]uco.es

2. IFAPA Centro "Alameda del Obispo", Apdo 3092, 14080 C—rdoba, Spain. E-mail: bb2pelua[at]uco.es, josefa.sillero.ext[at]juntadeandalucia.es

Orobanche crenata (crenata broomrape) causes severe damage on legumes. Several cultural, biological, and chemical strategies have been suggested but none is completely successful or practicable in low input farming systems. We showed previously that broomrape infection on legumes is reduced in intercrops with oat. In the present experiment we studied the effect of broomrape reduction due to oat-faba bean intercrops on faba bean and broomrape biological dry matter (BDM). The assay was conducted in an infested experimental field in C—rdoba, Spain in organic conditions. Susceptible faba bean cv. "Prothabon" was grown as sole crop and mixed with oat cv. "Cory" in 50% replacement model intercrop. Crops were laid out on plots (1.5x8 m2) in a complete randomized block design with three replicates. The high Land Equivalent Ratio value (LER=1.3) achieved shows that environmental sources for oat-faba bean growth are used on average 30% more efficiently in the intercrops than in the respective sole crops due to a) the degree of resource complementarity of faba bean-oat system in absence of any fertilization and b) the reduction of crenata broomrape attached per faba bean plant due to the inhibitory effect of oat. Faba bean BDM was 928 g/m2 in sole crop and 666 g/m2 in intercrop. Broomrape BDM was reduced from 193 g/m2 to 42 g/m2 due to intercrop, reducing proportionally the number of seeds laid in soil.

 

Fernández-Aparicio, M (1), Pérez-de-Luque, A (2), and Rubiales, D (1)

Response of Medicago truncatula Accessions to Various Species of Orobanche

1. CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba, Apdo. 4084, Spain. monfapru[at]yahoo.com, ge2ruozd[at]uco.es.

2. IFAPA-CICE, "Alameda del Obispo", 14080 C—rdoba, Apdo. 3092, Spain. bb2pelua[at]uco.es

There is increasing interest in the legume species Medicago truncatula as a model in genomic studies. Genotypic variation for the mechanisms of resistance was found between M. truncatula accessions with an accession highly resistant and another highly susceptible to O. aegyptiaca, O. foetida var broteri and O. ramosa. Similar variation, but in reverse, was observed with O. nana. In vitro studies showed that M. truncatula can induce high levels of O. aegyptiaca, O. foetida var broteri, O. nana, O. minor and O. ramosa seed germination, but rather low levels of O. cumana, O. crinita and O. crenata. Differences in germination level among accessions were highly significant. Accessions also significantly varied in the penetration response to O. aegyptiaca, O. foetida var broteri, O. ramosa and O. nana. Increasing the germination level on O. cumana, O. aegyptiaca, O. ramosa and O. minor through applications of the synthetic germination stimulant GR24 did not result in increased infection. However, infection by O. nana increased markedly in the resistant accession. GR24 was no effective inducing germinating O. crinita, O. foetida var broteri and O. foetida var foetida seeds. The variation observed for induction of germination of these species by M. truncatula and of subsequent attachment will be useful to isolating and characterising genes involved in early stages of Orobanche - host plant interaction and for the study of the biosynthetic pathways of production for germination stimulants.

Fernández-Aparicio, M (1), Flores, F (2), Pérez-de-Luque, A (3) and Rubiales, D (1)

Yield losses in pea as a function of Orobanche crenata levels of infection.

1. CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba, Apdo. 4084, Spain

         E-mail: monfapru[at]yahoo.com, ge2ruozd[at]uco.es

2. Escuela Politécnica la Rábida, Universidad de Huelva, 21819 Palos de la Frontera, Spain

         E-mail: fflores[at]uhu.es

3. IFAPA Centro "Alameda del Obispo", Apdo 3092, 14080 C—rdoba, Spain

         E-mail: bb2pelua[at]uco.es

Reduction of biomass and seed yield and size were studied on pea (Pisum sativum L.) as a function of level of infection by crenata broomrape (Orobanche crenata Forsk). The susceptible pea cultivar "Messire" was sown in a distance between plants and rows of 0.5 meter in a highly but no homogeneously naturally infested plot, what allowed us to study yield components in pea plants with a variable level of infection, ranging from 0 to 21 emerged broomrapes per pea plant. Pea productivity was measured as dry total biomass (DMp), seed yield (SYp) and number of seeds (NSp) measured per pea plant. The infection level was studied per pea plant determining the number of emerged broomrapes (Nb) and parasitic dry matter (DMb) measured at harvest. The following models were used for the prediction of productivity losses. Dry total biomass of pea was reduced with infection, as a function of number of emerged broomrapes DMp = 8.66+15.04e-0.20*Nb (r2=0.64), or broomrape biomass, DMp = 8.38+16.23e-0.30*DMb (r2=0.63).  Pea seed yield were influenced by the infection level, both by number of broomrapes SYp = -3.96 + (103.86/(6.14+Nb)) (r2=0.73) and broomrape biomass, SYp = -3.20+13.74e-0.12*DMp (r2=0.67). This reduced yield was due to a decrease of number of seeds per pea plant NS p = -2.30+54.98e-0.14*Np (r2=0.70) and NSp = -17.49+70.30e-0.11*DMb (r2=0.66)), whereas seed weight was not influenced by infection level.