Genetic manipulation of root system architecture to improve drought adaptation in sorghum

Drought is one of the most important abiotic stresses and severely affects global agricultural production. Root system architecture (RSA) is the key determinant of water acquisition under moisture stress, and therefore has utility in breeding for drought tolerance in sorghum. Various components of RSA are known to influence drought tolerance in sorghum without any negative impact on yield. The growth angle of nodal roots is an important target trait for improving drought tolerance. Genetic variation for nodal root angle has been reported in sorghum, and this has been associated with grain yield under drought stress. Rapid advances in sorghum genomics have led to the identification of various quantitative trait loci (QTL) governing RSA, but the accuracy and preciseness in identification of QTL is the major hindrance in development of drought-tolerant cultivars through genetic manipulation of root traits. Hence, the complex genetic control of RSA and the lack of a high-throughput phenotyping platform have hampered integration of selection for RSA in breeding programs. These limitations can be overcome by designing a robust phenotyping platform that can maximize heritability and repeatability of RSA. Inclusion of the extensive phenotyping information with the recently developed genomic resources of sorghum will lead to mining of alleles that govern RSA and tailor a cultivar harboring genes for RSA that improve sorghum production under drought stress. This chapter provides an overview of the latest developments in RSA research in sorghum and gives direction to future breeding strategies to enhance the genetic gain for root traits