Genetic Enhancement of Cold Tolerance in Sorghum:QTL Analysis of New Sources of Early Season Cold Tolerance in Sorghum.

Sorghum is known for its drought tolerance and overall adaptation to high temperature.  However, it generally lacks cold tolerance and is vulnerable to cooler temperature specifically during stand establishment in early season planting from April to May in most areas of the US sorghum belt.  Stand establishment of sorghum is adversely affected in multifaceted manner by air and soil temperature below 60ºF (15ºC) at germination, emergence and early seedling growth. Thus, it is deemed desirable to introduce cold tolerance into elite sorghum lines to improve yield potential and stability for the crop. Fortuitously, sources of cold tolerance are available in the diverse gene pool of sorghum.  To elucidate the genetics of early season cold tolerance and identify useful markers for marker assisted selection, a recombinant inbred population from the cross between RTx 430 (cold susceptible) and PI610727 (cold tolerant) was developed.  A total of 180 F₇-F₈ recombinant inbred lines were evaluated for low temperature germinability under controlled conditions and for emergence, emergence index and seedling vigor in two field locations during early season planting (April, 2009). QTL analysis was conducted to identify gene regions controlling cold tolerance from the population. Novel QTLs with strong effects on cold tolerance were identified and introgressed to a number of progenies.  These results indicate that early season cold tolerance in sorghum is controlled by a suite of genes which exert varying levels of effects over a number of cold tolerance associated traits.