Seed dormancy QTL identification across a Sorghum bicolor segregating population

Abstract

Pre-harvest sprouting (PHS) in Sorghum bicolor is one of the main constrains for its production in the central region of Argentina, as grain maturation often coincides with rainy or high environmental humidity conditions. The obtention of more dormant genotypes with higher PHS resistance has always been a desirable trait for breeders but the typical quantitative nature of seed dormancy makes its manipulation difficult through classical breeding. Dissecting this quantitative variability into quantitative trait loci (QTL) is a main concern especially in cereal species. In this work, a sorghum segregating population including 190 families was genotyped with microsatellite markers and the SbABI5 candidate gene. A genetic map encompassing 96 markers and a total length of 1331 cM was built. Seed dormancy was phenotyped in F3 and F4 panicles in two contrasting Argentinean environments (Castelar and Manfredi). Six seed dormancy QTL for mature grains were identified (qGI-1, qGI-3, qGI-4, qGI-6, qGI-7 and qGI-9) with the aid of QTL Cartographer and QTLNetwork, three of them (qGI-3, qGI-7 and qGI- 9) being co-localised by both approaches. No epistasis was detected for the identified QTL but QTL-byenvironment interaction was significant for qGI-7 and qGI-9. Interestingly, seed dormancy candidate genes SbABI3/VP1 and SbGA20ox3 were located within qGI-3, which makes them noteworthy candidate genes for this QTL.