Detection of Resistance, Susceptibility, Tolerance, and Virulence in Plant-Nematode Interactions: Part II: Migratory and Semi-endoparasitic Nematodes

This chapter is a continuation of Chap. 3 . Initially, protocols for the screening of several host plants to their major migratory and semi-endoparasitic nematodes are presented. Then the problems related to assessment of tolerance to these nematodes are described, followed by the determination of nematode races. The main plant-nematode interactions considered are annuals and perennials to Pratylenchus spp.; banana to Radopholus similis; potato to Nacobbus aberrans; several crop plants, including onion, alfalfa, clovers, and potato, to Ditylenchus dipsaci; broad bean to D. giga; potato and sweet potato to D. destructor; peanut to D. africanus; rice to D. angustus and Aphelenchoides besseyi; wheat to Anguina tritici; different plants to Rotylenchulus reniformis; and citrus to Tylenchulus semipenetrans. Schemes to identify races or biotypes are only presented for D. dipsaci and T. semipenetrans. The occurrence of pathotypes in other nematode species is also discussed. Finally, comments are made on ectoparasitic nematodes.

DNA polymorphism in the stem nematode Ditylenchus dipsaci: development of diagnostic markers for normal and giant races

DNA polymorphism in the Ditylenchus dipsaci complex was investigated using amplified fragment length polymorphism (AFLP) to determine the relationships among populations growing mainly on Vicia faba and to develop diagnostic markers. Twenty-two populations of D. dipsaci originating from different geographical areas and one population of Ditylenchus myceliophagus were used. AFLP proved to be a powerful method to reveal intraspecific polymorphism even within the giant type. The analysis showed a clear distinction between the giant and normal populations, with genetic distances similar to those observed between normal populations and D. myceliophagus or giant populations and D. myceliophagus, strengthening the hypothesis that these two nematode types could be considered distinct species. Two specific AFLP markers differentiating the two types were converted into sequenced characterized amplified region (SCAR) markers. Used in a multiplex PCR, the SCAR primers proved to be a rapid and efficient tool to identify the giant and the normal types of D. dipsaci.