Gene action for surrogate traits of water-use efficiency and harvest index in peanut (Arachis hypogaea)

Low peanut productivity in the semi-arid tropics is attributed mainly to drought caused by low and erratic rainfall. Genetic improvement in water-use efficiency (WUE) could potentially lead to improved yield under limited moisture availability. In peanut, WUE is correlated with SPAD chlorophyll meter reading (SCMR), specific leaf area (SLA), and carbon isotope discrimination (Delta C-13). These traits can be used as surrogates for selecting for WUE. Partitioning of assimilates as measured by the harvest index (HI) has the greatest effect on pod yield. To improve these traits for tailoring peanut genotypes well matched for water-limited conditions, a good knowledge of genetic systems controlling the expression of these traits is essential. This study was undertaken to work out the gene action for the surrogates of WUE and HI in a 6 x 6 full diallel mating design. Two of the studied surrogates (SCMR and Delta C-13) for WUE were found to be under the influence of both additive and nonadditive gene effects with preponderance of the former. SLA and HI were controlled by genes that are mainly additive in nature. Selection for these traits can be effective in the early generations. Maternal effects observed for SLA and Delta C-13 are suggestive of the crucial role of selection of female parent in improvement of these traits. The parental lines, TMV 2 NLM (for SCMR, SLA and Delta C-13) and ICGV 86031 (for SCMR and SLA), were found to be good general combiners each for more than one character. TAG 24 and Chico (for HI) and CSMG 84-1 (for SLA) were the other good general combiners.