Genetic Dissection of QTLs Controlling Brittle Rachis on Chromosomes 3A and 3B in Tetraploid Wheat

Wheat is one of the most important food crops, domesticated about 10,000 years ago from wild emmer wheat (Triticum turgidum ssp. dicoccoides). The spikes of wild emmer completely shatter at senescence (brittle rachis, BR) while the spikes of all domesticated wheats remain intact (non-BR), enabling easier harvesting. Quantitative trait analysis using a population derived by crossing wild emmer ('Zavitan') with domesticated durum wheat ('Svevo') revealed five significant QTLs for BR with LOD scores ranging from 3 to 8.3 and explaining 5.7 to 18.6% of the variation. The two major loci were mapped on chromosomes 3A and 3B confirming previous reports. Using the recently assembled genome of wild emmer we identified the homologous sequences of the Brittle Rachis 1 (Btr1) and Brittle Rachis 2 (Btr2) genes controlling spike BR in barley. The identification of causative mutations for the 3A and 3B BR QTLs and the application of the wild wheat assembly in underpinning and accelerating genome-assisted research will be discussed.