Combination of empirical and trait-based approaches for breeding drought tolerance in groundnut (Arachis hypogaea L.)

Breeding groundnut varieties that combine improved pod yield under water-deficit stress, and enhanced water use efficiency (WUE) is an important strategy to overcome the challenges in water-limited conditions. SPAD chlorophyll meter reading (SCMR) and specific leaf area (SLA) are the two important traits associated with WUE. SCMR is simple, non-destructive and robust method. Maintaining high chlorophyll density under water stress conditions is associated with high WUE in groundnut, and SCMR measures green colour intensity associated with chlorophyll density. A RIL population (280) was evaluated during 2015/16 under well-watered (WW) and water-deficit stress (WS) for yield parameters and SCMR. Pod yield is independent of SCMR (R2=0.003), suggesting the importance of simultaneous selection for both these traits in breeding programs. For breeding varieties suitable for water-stress conditions, measuring both pod yield under stress and WUE through its surrogate SCMR are useful. In Africa and Asia, groundnut is largely a rainfed crop. The frequency of drought is variable, and every year is not a drought year. Therefore, the commercial groundnut varieties should perform well under normal rainfall years, and have less yield penalty during drought years. The approach of measuring pod yield penalty under water-deficit stress compared to WW condition is a useful selection criterion in breeding programs, wherein the lines with minimum yield penalty are selected. Such a selection criteria enable selection of genotypes that perform well under normal seasons and have less yield penalty during drought seasons. In this paper, we discuss progress in groundnut breeding at ICRISAT using these two approaches