Abstract
A set of 96 Brassica juncea–Erucastrum cardaminoides introgression lines (ILs) were developed with genomic regions associated with Sclerotinia stem rot (Sclerotinia sclerotiorum) resistance from a wild Brassicaceous species E. cardaminoides. ILs were assessed for their resistance responses to stem inoculation with S. sclerotiorum, over three crop seasons (season I, 2011/2012; II, 2014/2015; III, 2016–2017). Initially, ILs were genotyped with transferable SSR markers and subsequently through genotyping by sequencing. SSR based association mapping identified six marker loci associated to resistance in both A and B genomes. Subsequent genome-wide association analysis (GWAS) of 84 ILs recognized a large number of SNPs associated to resistance, in chromosomes A03, A06, and B03. Chromosomes A03 and A06 harbored the maximum number of resistance related SNPs. Annotation of linked genomic regions highlighted an array of resistance mechanisms in terms of signal transduction pathways, hypersensitive responses and production of anti-fungal proteins and metabolites. Of major importance was the clustering of SNPs, encoding multiple resistance genes on small regions spanning approximately 885 kb region on chromosome A03 and 74 kb on B03. Five SNPs on chromosome A03 (6,390,210-381) were associated with LRR-RLK (receptor like kinases) genes that encode LRR-protein kinase family proteins. Genetic factors associated with pathogen-associated molecular patterns (PAMPs) and effector-triggered immunity (ETI) were predicted on chromosome A03, exhibiting 11 SNPs (6,274,763-994). These belonged to three R-Genes encoding TIR-NBS-LRR proteins. Marker trait associations (MTAs) identified will facilitate marker assisted introgression of these critical resistances, into new cultivars of B. juncea initially and, subsequently, into other crop Brassica species.
Highlights
IntroductionOf the diseases occurring on mustard, Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot, is damaging (Purdy, 1979; Bolton et al, 2006; Saharan and Mehta, 2008)
Brassica juncea (2n = 36; AABB) or Indian mustard, is a premier oilseed crop of India, contributing nearly 28% of total edible oil supplies (Kumar, 2012)
Introgression lines were morphologically similar to the natural B. juncea cv
Summary
Of the diseases occurring on mustard, Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot, is damaging (Purdy, 1979; Bolton et al, 2006; Saharan and Mehta, 2008). It causes extensive yield losses world-wide including India (Shivpuri et al, 2000; Ghasolia et al, 2004), Australia (Kirkegaard et al, 2006), Germany (Horning, 1983), Canada (Morrall et al, 1976), United Kingdom (Hims, 1979; Rawlinson and Muthyala, 1979), and China (Li et al, 1999). Host resistance offers the only economic and sustainable method for managing this disease
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