SNP-based identification of QTL for resistance to black point caused by Bipolaris sorokiniana in bread wheat

Abstract

Black point disease caused by Bipolaris sorokiniana is a problem in wheat production worldwide. We aimed to identify major quantitative trait loci (QTL) for resistance to black point and develop molecular markers for marker-assisted selection (MAS). A recombinant inbred line (RIL) population derived from a cross between Wanyuanbai 1 (susceptible) and SN4143 (resistant) was evaluated for black point response at three locations during two years under artificial inoculation with B. sorokiniana, providing data for six environments. Thirty resistant and 30 susceptible RILs were selected to form resistant and susceptible bulks, respectively, that were genotyped by the wheat 660K SNP array; 685 single-nucleotide polymorphisms (SNPs) were identified, among which 385 (56.2%) and 115 (16.8%) were located on chromosomes 4A and 2B, respectively. Bulked segregant RNA-Seq analysis identified candidate regions on chromosomes 4A (4.60–40.28 Mb) and 5A (1.22–48.47 Mb). Genetic linkage maps were constructed for chromosomes 2B, 4A, and 5A using 59 polymorphic dCAPS and SSR markers. Finally, two QTL, designated QBB.hau-4A and QBB.hau-5A, were detected on chromosomes 4A and 5A, respectively. The resistance allele of QBB.hau-4A was derived from SN4143, and that of QBB.hau-5A came from Wanyuanbai 1. QBB.hau-4A with a large and consistent effect (15.1%) is likely to be a new locus for black point resistance. The markers linked to QBB.hau-4A and QBB.hau-5A have potential application in MAS-based breeding.