Candidate Gene Expression Profiling in Contrasting Groundnut Genotypes Differing in Moisture Stress Adaptation

Groundnut is cultivated largely as a rain-fed crop and hence the crop is exposed to intermittent moisture stress resulting in reduced productivity and crop loss. Therefore, there is a need to tolerate dehydration stress by maintaining superior water relations to sustain the growth under water deficit stress conditions. The plant has evolved several mechanisms to maintain water relations such as better water mining by water use efficiency (WUE) and water conservation traits. The present study was focused to evaluate the alterations in physiological parameters: relative water content (RWC), canopy temperature, cell membrane leakage, photosynthesis, transpiration, stomatal conductance and water use efficiency and biochemical attributes: total chlorophyll and proline content at different water regimes/field capacities (FC) (100% FC (control), 50% FC and 25% FC). Tolerant genotypes revealed significantly higher values of RWC and lower cell membrane leakage at the end of stress induction period than the sensitive genotypes. The gas exchange traits viz., photosynthetic rate, stomatal conductance and transpiration rate also recorded high in tolerant genotypes under stress conditions. Further the major aim of the study was to analyze the expression pattern of seven candidate drought responsive genes in drought stress tolerant (Kadiri-9 and TCGS-1694) and sensitive (Kadiri-6 and JL-24) groundnut genotypes. Among the seven genes, HSP17.9 exhibited the highly elevated transcript accumulation in all the genotypes under stress conditions and the relative expression of the gene was profoundly higher (10.7-folds) in the tolerant genotypes compared to the susceptible types followed by HSP60 , PRP2 and LEA5 genes. The differential expression of these important drought responsive genes in tolerant genotypes of groundnut indicates its further usefulness in developing varieties with improved water deficit stress tolerance.