Posted on Dec 01, 2009
Cool temperatures during the early growing season are a major limitation to growing sorghum (Sorghum bicolor (L.) Moench) in the northern mid-west regions of the United States, and other temperate areas. Sorghum originated in tropical and subtropical regions of Africa. Sorghums from these primary centers of crop origin of tropical north-east Africa, lack this trait. China is the only place in the world where sorghum evolved under temperate condition. Perhaps as a result, many sorghum landraces introduced from China exhibit higher emergence and greater seedling vigor when grown under cool conditions than typical US-bred lines. Unfortunately, however, Chinese sorghums also possess several undesirable agronomic traits. Introgression of seedling cold-tolerance genes from these landraces into elite inbred lines requires careful manipulation to avoid genetic drag and, such a feat could potentially be facilitated by marker-assisted selection (MAS). However, empirical studies that have demonstrated the value of MAS for quantitatively inherited agronomic traits in field crops have been few. In our laboratory, we recently completed a successful step-wise study where we first observed segregation of QTL for early-season cold tolerance in a recombinant inbred (RI) population one parent of which was a cold-tolerant Chinese line, Shan Qui Red (SQR). We followed that observation by the further identification of three SSR markers each representing a QTL for cold tolerance. And finally, we were then able to validate the association between the presence of these markers and the phenotypic expression of seedling cold tolerance in two newly created segregating populations with SQR as a donor parent for the cold tolerance trait. In the current study, we propose to introgress these three markers into selected inbred lines of sorghum, both pollinators and seed parents, to generate isogenic hybrids with and without the SSR markers as a proof of concept to further verify the efficacy of these markers as selective tools for marker-based selection for seedling cold tolerance in sorghum. This is a necessary step before broader use of these markers that we identified is recommended for commercial application of sorghum breeding for early-season cold tolerance in sorghum.