Cluster Bean [Cyamopsis tetragonoloba (L.) Taub] Breeding

Abstract

Cluster bean is an important leguminous annual crop of arid and semiarid regions of northwestern India, mainly in Rajasthan and parts of Gujarat, Haryana and Punjab. India contributes about 80% of the global cluster bean production. It is a source of gum (guar gum/galactomannan), a natural hydrocolloid having unique qualities and wide applicability. It is a highly self-pollinated crop with very limited outcrossing. Limited genetic diversity for the different traits coupled with yield losses caused by different biotic and abiotic stresses have constrained intensive breeding efforts of this crop. Despite these limitations, progress has been achieved by exploiting the available diversity and different breeding methods like pedigree selection in the cluster bean improvement program with good results. Hybridization has not been successful due to the small, delicate flower resulting in a low percentage of hybrid seed setting. Mutation breeding has helped to generate some genetic variability in certain important traits, but it has had limited impact on cluster-bean breeding. DNA-based molecular markers are being extensively used in genetic diversity analysis and phylogenetic studies. Efforts are also underway to develop genomic resources (SSR and SNP markers) that could be used in cluster-bean breeding. Limited transcriptomic and mi-RNA studies have also been recently reported. With the availability of advanced molecular tools it would be feasible to develop resources to aid in high-yielding, cluster-bean varieties with moderate to high gum content for a much preferred export commodity.