Genetic dissection of early-season cold tolerance in sorghum (Sorghum bicolor (L.) Moench)

Soil temperatures at 15°C or below limit germination and seedling establishment for warm season cereal crops such as sorghum ( Sorghum bicolor (L.) Moench) during early-season planting. To better understand the genetics of early-season cold tolerance in sorghum, mapping of quantitative trait loci (QTL) associated with germination, emergence and vigor using a recombinant inbred mapping population was carried out. A mapping population consisting of 171 F 7 –F 8 recombinant inbred lines (RILs) derived from the cross between RTx430 (cold-sensitive) and PI610727 (cold-tolerant) was developed and a genetic map was constructed using 141 microsatellites or simple sequence repeat (SSR) markers. The RILs were evaluated for cold and optimal temperature germinability in the laboratory, field emergence, and seedling vigor in two locations during early-season planting. Two or more QTL were detected for all traits, except for seedling vigor, with only one QTL was detected in the population. A QTL for cold germinability ( Germ 12 - 2.1 ) showed the highest LOD value and was also associated with optimal germinability. One of the QTL for field emergence, Fearlygerm - 9.3, a contribution from PI610727, was found significant in both locations used for the study. This study showed alignment of QTL in SBi1 ( Fearlygerm - 1.2 and FGerm30 - 1.2 ) with previously reported QTL associated with late field emergence identified from a different mapping population. This indicates that PI617027 shares some common loci with other known early-season cold-tolerant sorghum germplasm but also harbors novel QTL that could be useful in introgression of enhanced laboratory germination and early-season field emergence.