A restriction-site-associated DNA (RAD) linkage map, comparative genomics and identification of QTL for histological fibre content coincident with those for retted bast fibre yield and its major components in jute

Abstract

We used RAD (restriction-site-associated DNA) sequencing to detect genome-wide SNPs and construct a dense linkage map using an intercross F2 population in jute (Corchorus olitorius). The linkage map comprising a total of 503 RAD markers in seven linkage groups spanned 358.5 cM with an average marker interval of 0.72 cM and covered 87.0 % of the genome. Genome-wide segregation distortion of the mapped loci (34.4 %) was non-random across the linkage map, with a directional bias mostly towards the female genotypes. Jute had maximum syntenic relationships with cocoa (47.5 % homology) and diploid cotton (29.2 % homology). However, synteny and collinearity were not conserved. Histological fibre content (FC; total number of fibre cell bundles in a stem cross section) was positively correlated with fibre yield (FY), plant height (PH), root weight (RW) and stem-base diameter (SBD). Broad-sense heritability estimates were high for all traits, with FC and FY showing maximum heritability (~93 %). QTL mapping based on the F2:3 phenotypes detected nine QTL across the two environments. The QTL for FC was coincident with one QTL each for FY, PH, RW and SBD on top of a single-SNP (C/T) marker at 40.2 cM on LG1, each accounting for ~7–11 % of the phenotypic variance. Two QTL linked in repulsion one each for PH and SBD, with varying degrees of overdominance, were associated with two single-SNP (C/T) markers on LG2, each accounting for ~17–18 % of the phenotypic variance. Few candidate genes were identified within the QTL regions. Our results would enable development of tools for marker-assisted selection in jute.