Arachis Gene Pools and Genetic Improvement in Groundnut

Abstract

Groundnut (Arachis hypogaea L.) is an important oilseed and food crop in the world. The crop is predominantly grown in low input production systems in developing countries in Asia and Africa. There are several production constraints, both biotic and abiotic, to groundnut. Some of these are global in nature and the others are either regional or local. Four Arachis gene pools contain 80 species, distributed among nine sections are native to five countries of South America. Section Arachis contains tetraploid cultivated groundnut, divided into two subspecies and six botanical varieties and a number of cross-compatible diploid species with rich genetic diversity. International efforts have made significant progress in collection and conservation of these genetic resources, facilitating genetic improvement. Groundnut is an autogamous crop. The pedigree and bulk selection methods are more commonly used by the groundnut breeders. Conventional breeding, including cytogenetic manipulations introgressing genes from cross-compatible wild diploid species has been effective in some areas, while in others it has been tardy due to lack of proper and effective phenotyping tools and limited understanding of the genomics, genetics/inheritance, and underlying mechanisms influencing targeted traits. A greater diversification of parental resources (both cultivated and wild Arachis species) in breeding programs is required to develop new cultivars with diversified genetic backgrounds, which will enable them to perform better under the changing climatic/adverse conditions. Molecular breeding is in infancy. Infrequent and low polymorphisms have restricted the progress in the development and application of genetic maps, except in cases where polymorphic chromosomal regions have been introgressed from diploid wild Arachis species into A. hypogaea. Both conventional and nonconventional crop improvement efforts in groundnut need to concentrate on bridging the yield gap between the potential yield and the realized yield by alleviating major production constraints particularly in rainfed environment.