Heritability Estimates for Drought Resistance Related Traits in Cultivated Peanut (Arachis hypogaea L.).

Drought is a major factor in reduced productivity in peanuts. Cultivars that have high water-use efficiency have the potential to enhance the yield of the crop.  Studies have shown that pod yield is a function of water transpired (T), water-use efficiency (WUE), and harvest index (HI). It is logistically difficult to measure WUE (the ratio of biomass by water transpired) in a field environment, making selection of high WUE genotypes in a breeding program challenging. However, WUE is often correlated with specific leaf area (SLA) and leaf carbon isotopic composition (δ ¹³C) in peanuts. A good knowledge of the inheritance of SLA, δ ¹³C, and HI may facilitate selection for drought resistant cultivars in peanut breeding programs. The objectives of this study were to estimate the heritability of SLA, δ ¹³C, and HI traits in peanuts and investigate the relationships among these traits. Fifteen genotypes were selected to measure the heritability of these traits using the variance component method based on an entry-mean basis. These 15 genotypes were planted in a randomized complete block design with three replications in 2007 at Headland, Alabama and Dawson, Georgia with and without irrigation. The leaf samples were taken at the 85^th day after planting for measurements of SLA, and δ ¹³C. The HI was calculated on mature plants at 135 days after planting. Analysis of variance (ANOVA) was conducted to evaluate the differences among genotypes, locations, and means of blocks.
Highly significant differences were found for location, genotype, and genotype x location for SLA and HI traits (p= 0.01). The results from variance component analysis demonstrated that the heritability for SLA and HI was 0.32 and 0.61, respectively. SLA and HI were negatively correlated and HI had a stronger association than SLA with pod yield. This implies that the selection for HI would result in a greater response to drought resistance and yield than the selection for SLA in breeding programs. The data for δ ¹³C will also be discussed.