Breeding for root lesion nematode resistance in Montana winter wheat
May, David Bruce, III
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Root lesion nematodes (RLN; Pratylenchus spp.) present a serious challenge to dryland wheat production worldwide. Development of resistant cultivars would provide great economic benefit to growers. From 2012-2013, a set of backcross lines (MT08185//MT08184/Persia 20) was screened twice for resistance to P. neglectus. Progeny and parent lines were grown in infested soil for 16 to 18 weeks. Nematodes were then extracted from roots of individual plants and counted to obtain per plant final populations. ANOVA results from the 2013 screen showed significant differences in mean P. neglectus populations among lines (p < 0.01). The median final population of susceptible parent MT08184 was an estimated 4.9 times greater than that of resistant parent Persia 20. A 2013 field trial in the absence of root lesion nematodes indicated reductions in grain yield, volume weight, and protein were not associated with resistance. Seven RLN-resistant lines were identified in field evaluations with agronomic phenotypes for yield, volume weight and protein comparable to those of five widely-grown checks. Identification of quantitative trait loci (QTL) for resistance to RLN will facilitate marker-assisted introgression of resistance genes in a backcross-breeding program. Single-marker analysis of 218 genome-wide single nucleotide polymorphism markers (SNPs) was performed to identify genomic regions associated with resistance to P. neglectus. The analysis identified putative marker-trait associations on chromosomes 1AL, 1DS, 2BL, 5BL, 5DL, 7AL and 7DL (all p < 0.05). Overall, phenotypic screens as applied were inadequate to consistently characterize wheat lines for RLN resistance. As such, RLN resistance phenotypes and putative QTL effects identified in the study must be verified in future experiments.