TaqSH1-D, wheat ortholog of rice seed shattering gene qSH1, maps to the interval of a rachis fragility QTL on chromosome 3DL of common wheat (Triticum aestivum)

Abstract

Wheat domestication was a crucial step in the evolution of stable human societies. The loss of rachis brittleness is a major change that differentiates the earliest forms of domesticated wheat from their wild ancestors. We recently identified a novel quantitative trait locus (QTL) for rachis fragility on the long arm of chromosome 3D using an F₂ mapping population derived from the cross between Triticum aestivum ‘Chinese Spring’ (CS) and a synthetic wheat line, S-6214. Here, we show that the QTL region, in the deletion bin 3DL2-0.27-0.81, is syntenous to the rice chromosome 1 region harboring the seed shattering gene qSH1. We isolated the wheat qSH1 ortholog, TaqSH1-D, on chromosome 3DL. The gene mapped into the confidence interval of the rachis fragility QTL, indicating that it represents a potential candidate gene. Sequence comparison between the parental lines revealed a 189-bp repetitive sequence insertion located 275 bp downstream of the translation termination site of the gene in CS. Although the putative parental proteins are identical, as in rice, a polymorphism in the regulatory regions may specifically affect its control of rachis fragility.