Genetic Characterization of Resistance in Wheat to the Root-Lesion Nematode Pratylenchus Thornei

The root-lesion nematodes Pratylenchus neglectus and P. thornei are economically damaging pathogens of wheat in the Pacific Northwest (PNW). Growing resistant and tolerant varieties is the best approach to minimize yield loss. All PNW wheat varieties were found to be susceptible. Crosses were made between the PNW-adapted varieties (Alpowa Louise, Otis) and the Australian wheat GS50a with resistance to P. thornei. Resistance evaluations were performed under controlled greenhouse conditions using six check varieties, parents, 203 F2 and 194 F3 recombinant inbred lines (RILs) of GS50a x Alpowa, 102 F2 RILs of GS50a x Otis, and 120 F2 RILs of GS50a x Louise, each of which was inoculated with 1,500 or 2,000 P. thornei/kg of soil. RIL populations segregated in a continuous variation indicating that resistance in GS50a was quantitatively inherited. The heritability estimate for the resistance in GS50a was 0.68. The frequency distribution of F2 and F3 progeny suggested that resistance in GS50a is controlled by more than one gene and is additive in gene action. F3 RILs of GS50a x Alpowa showing levels of resistance or susceptibility higher than their parents will be used in bulk segregant analysis for molecular marker development. The highly resistant lines obtained in this study will provide a source of resistance for breeding wheat varieties with improved genetic resistance.