Gene effects for specific leaf area and harvest index in three crosses of groundnut (Arachis hypogaea)

Groundnut productivity is low in the semiarid tropics mainly because of drought caused by low and erratic rainfall. Genotypes that have ability to use limited available water efficiently are required to enhance productivity of the crop. In groundnut, water use efficiency (WUE) is correlated with specific leaf area (SLA). The latter can be used as a surrogate trait for selecting for WUE. Partitioning of assimilates as measured by the harvest index (HI) has the greatest effect on pod yield. In order to improve SLA and in turn WUE and HI, a good knowledge of genetic systems controlling the expression of these traits is essential for the choice of an efficient breeding procedure. This study was conducted to investigate inheritance of SLA and HI in three crosses involving Chico, TMV 2 NLM, and ICGV 86031 groundnut genotypes. The crosses used were Chico × TMV 2 NLM, Chico × ICGV 86031 and TMV 2 NLM × ICGV 86031. The study included parents, F1, F2, and backcross generations. Generation means analysis indicated that the additive effects were more important than the dominance effects in the expression of SLA and HI. In addition to additive and dominance effects, additive × additive type of epistasis, which can be fixed in groundnut (a self pollinated crop), was also significant for SLA in all the three and for HI, in two crosses (Chico × TMV 2 NLM and Chico × ICGV 86031). The selection for SLA and HI can be effective in early generations in some crosses and to exploit the additive × additive type of interaction, it can be done in large populations of later generations.