Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/10/2013
Publication Date: 5/17/2013
Publication URL: doi:10.2135/cropsci2012.07.0426
Citation: Chen, C.Y., Rowland, D., Nuti, R.C., Faircloth, W.H., Lamb, M.C., Harvey, E. 2013. Heritability and genetic relationships for drought-related traits in peanut. Crop Science. 53(4):1392-1402. Interpretive Summary: Drought is the most severe environmental factor limiting the productivity of agricultural crops worldwide and is economically and sociologically devastating when it occurs at a critical crop growth stages. To ensure food production for growing populations, to develop cultivars with drought resistance through conventional and genomic approaches will be the best long term solution to overcome drought limitations in crop production. Lack of information of phenotypic response by crop genotypes to environment dramatically hinders breeding efforts for drought tolerance. This inspires a strong emphasis on investigating traits associated with drought tolerance that can be used in breeding programs. Yield under drought conditions is driven by water uptake (WU), water use efficiency (WUE), and harvest index (HI) as shown by the relationship: Yield (water limited) = WU x WUE x HI. Physiological surrogates for WUE have been explored including: SPAD chlorophyll meter reading (SCMR), harvest index (HI), to specific leaf area (SLA), and 13C/12C isotope composition. Knowledge of the inheritance of HI, SLA, and d13C and the genetic correlations between yield and these traits will be essential for planning an appropriate breeding strategy for improving peanut drought tolerance. The objectives of this study were: to estimate the heritability of SLA, d13C, and HI traits in peanut and to investigate the relationships among these traits and how pod yield responded to SLA and d13C in peanut. Fifteen genotypes were selected to conduct this study. The heritability estimates for SLA, d13C, HI, and pod yield ranged from 0.54 to 0.78, 0.88 to 0.91, 0.75 to 0.78 and 0.23 to 0.35 under non-irrigated and irrigated conditions, respectively. Specific leaf area had the poorest relationship with HI, pod yield and d13C; while HI had the strongest association with d13C. d13C composition could be used as a surrogate to access drought tolerance in peanut breeding if we can afford to do that.
Technical Abstract: Drought is a major factor in reduced productivity in peanut. Cultivars that have high water-use efficiency have the potential to enhance crop yield. Water-use efficiency (WUE) is often correlated with specific leaf area (SLA) and leaf carbon isotopic composition (d13C) in peanut. A good knowledge of the inheritance of SLA, d13C, and harvest index (HI) may facilitate selection for drought resistant cultivars in peanut breeding programs. The objectives of this study were to estimate the heritability of SLA, d13C, and HI traits in peanut 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 the within-plot variance method. Genotypes were planted in a randomized complete block design with three replications in 2007 and 2008 at Headland, Alabama and Dawson, Georgia with and without irrigation. Leaf samples were taken at the 85 days after planting (DAP) for measurements of SLA, and d13C. The HI was calculated on mature plants at 135 DAP. Mixed-model analysis of variance (ANOVA) was conducted to evaluate the differences among genotypes, locations, and means of blocks. Highly significant differences were found for year, environment, and genotype, for SLA, d13C, HI, and pod yield traits (p= 0.01). Significant G x E interaction was found for SLA, HI, and pod yield, but not for d13C. The heritability estimates for SLA, d13C, HI, and pod yield ranged from 0.54 to 0.78, 0.88 to 0.91, 0.75 to 0.78 and 0.23 to 0.35 under non-irrigated and irrigated conditions, respectively. Specific leaf area had the poorest relationship with HI, pod yield and d13C; while HI had the strongest association with d13C. Although, d13C has a high heritability, and a relatively high association with yield, it is not feasible to apply d13C as a surrogate to access drought tolerance in peanut breeding until the findings of quantitative trait loci (QTL) underlying d13C in peanuts.