Marker-Assisted Selection in Sorghum

Abstract

Sorghum [Sorghum bicolor (L.) Moench] is an important food and feed crop in many parts of the world, and has potential uses in the biofuels industry. Compared to most other cereals, sorghum is more tolerant to many abiotic stresses, including heat, drought, and flooding, making it an ideal crop for growing on marginal lands as demands for food, feed, and energy increase. Though it is generally stress-tolerant, the true potential of sorghum can only be realized through concerted genetic improvement programs. The use of DNA-based markers for the genetic analysis and manipulation of important agronomic and stress-tolerance traits is becoming an increasingly useful tool in sorghum improvement. The known germplasm of sorghum is incredibly diverse, and molecular markers are being used to assess this diversity to help manage large germplasm collections, and to make these collections more useful to breeders. Molecular markers have been used in sorghum to identify quantitative trait loci (QTL) for many complex traits, including pre-flowering and post-flowering drought tolerance, early-season cold tolerance, and resistance to the parasitic weed Striga. However, progress in utilizing these QTL had been limited by the lack of a standard genetic map and a common nomenclature for the various linkage groups of sorghum. Fortunately, the genetic map of sorghum has recently become standardized, and has also been linked to physical chromosomes. The use of a common map will facilitate the exchange of marker and QTL information between sorghum research groups. This will allow independent validation of QTL and should expedite efforts to use these QTL for the development of improved sorghum cultivars through marker-assisted selection and trait introgression. Newer, faster marker technologies based on single nucleotide polymorphisms (SNPs), and mapping methods based on linkage disequilibrium (association mapping), will soon become useful tools for future efforts to improve this important crop.