Variation in reproductive capacity and virulence on different genotypes and resistance genes of Triticeae, in the cereal cyst nematode species complex

Abstract

AbstractTwo sets of experiments in 1998 and 1999 studied the (a)virulence status of 14 populations of Heterodera avenae, and two populations each of H. filipjevi and H. latipons towards the resistance genes and genotypes of Triticeae, presently known to be resistant to H. avenae, the main species of the cereal cyst nematode (CCN) species complex. Susceptible controls were Triticum aestivum cv. Arminda and Triticum turgidum cv. Cham1. Even in controlled experimental conditions, host responses differed between replicates in the same test and between consecutive tests for unexplained reasons. In spite of that, it has been confirmed that several of these CCN populations differ in their intrinsic capacity to reproduce, and this has to be taken into account in resistance screening. Consequently, the (a)virulence status of a CCN population is better established by a qualitative demarcation between resistant and susceptible plant genotypes based on an average of one cyst limit per plant. The matrix inferred from such a classification of host responses of pooled 1998 and 1999 data showed a complex distribution of avirulent and virulent phenotypes in these CCN populations which seems to arise from a mosaic-like evolution. The more or less wide virulence spectrum shown by this complex of populations and species is discussed in relation to their phylogenetic relationships. Correspondence factor analysis of the pooled data demonstrated a geographical demarcation between several populations of H. avenae and the representatives of H. filipjevi and H. latipons for their (a)virulence to either Cre1 or Cre3 genes and T. aestivum AUS4930 genotype. This could reveal local or regional selection of new pathotypes, more particularly in H. avenae. Genetic introgression to improve resistance to these nematodes in both bread and durum wheats is discussed for regional and global applications.