title: Characterization of Root-Knot Nematode Resistance in Medicago truncatula.
abstract: Root knot (Meloidogyne spp.) and cyst (Heterodera and Globodera spp.) nematodes infect all important crop species, and the annual economic loss due to these pathogens exceeds $90 billion. We screened the worldwide accession collection with the root-knot nematodes Meloidogyne incognita, M. arenaria and M. hapla, soybean cyst nematode (SCN-Heterodera glycines), sugar beet cyst nematode (SBCN-Heterodera schachtii) and clover cyst nematode (CLCN-Heterodera trifolii), revealing resistant and susceptible accessions. In the over 100 accessions evaluated, we observed a range of responses to the root-knot nematode species, and a non-host response was observed for SCN and SBCN infection. However, variation was observed with respect to infection by CLCN. While many cultivars including Jemalong A17 were resistant to H. trifolii, cultivar Paraggio was highly susceptible. Identification of M. truncatula as a host for root-knot nematodes and H. trifolii and the differential host response to both RKN and CLCN provide the opportunity to genetically and molecularly characterize genes involved in plant-nematode interaction. Accession DZA045, obtained from an Algerian population, was resistant to all three root-knot nematode species and was used for further studies. The mechanism of resistance in DZA045 appears different from Mi-mediated root-knot nematode resistance in tomato. Temporal analysis of nematode infection showed that there is no difference in nematode penetration between the resistant and susceptible accessions, and no hypersensitive response was observed in the resistant accession even several days after infection. However, less than 5% of the nematode population completed the life cycle as females in the resistant accession. The remainder emigrated from the roots, developed as males, or died inside the roots as undeveloped larvae. Genetic analyses carried out by crossing DZA045 with a susceptible French accession, F83005, suggest that one gene controls resistance in DZA045.
authors.affiliation: Center for the Biology of Nematode Parasitism, NC State University, Campus Box 7253, Raleigh, NC 27695-7253 Department of Plant Pathology, 348 Hutchinson Hall, One Shields Avenue, University of California, Davis, CA 95616-8680 Department of Plant Pathology and Microbiology, 118 B L.F. Peterson Hall, Texas A & M University, College Station, TX 77843 CNRS-INRA BP 27 UMR215, 31326 Castanet Tolosan Cedex, France INRA-SGAP, Montpellier, Domaine de Melgueil, 34130, Mauguio, France.
authors.forename: Murali
authors.initials: M
authors.lastname: Dhandaydham
authors.forename: Lauren
authors.initials: L
authors.lastname: Charles
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhu
authors.forename: James L
authors.initials: JL
authors.lastname: Starr
authors.forename: Thierry
authors.initials: T
authors.lastname: Huguet
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Cook
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Prosperi
authors.forename: Charles
authors.initials: C
authors.lastname: Opperman