Variations in Yield Components, Photosynthetic Rate, Transpiration Rate and Instantaneous Water Use Efficiency and their Interrelations among the Selected Set of Elite Germplasm Lines of Finger Millet

Finger millet has gained considerable attention worldwide, particularly in south Asia and Africa, due to its nutritional and health benefits. Recent studies indicated that this crop is vulnerable to drought and other major abiotic stresses. Examining traits related to drought and identifying genotypes having higher intrinsic stress tolerance to drought are of utmost important for yield improvement under water limiting situations. To address this, thirty-two germplasm lines were evaluated under well watered (WW) and water stressed (WS) conditions in field with the objectives to assess the range of variation in a selected set of finger millet germplasm for photosynthetic rate (Pn), transpiration rate (Tr) and Instantaneous water use efficiency (WUE) and evaluate their interrelations with yield components under water stress conditions. The results indicated that WS imposed at 40 days after sowing resulted in the decrease of 23.7%, 32.1% and 12.8% in shoot biomass, grain yield and harvest index, respectively as compared with WW. Wider genetic variations in shoot biomass than grain yield under WS conditions confirm that the reproductive growth is more sensitive to water stress than the vegetative growth. Our data indicated clearly that low drought susceptible index (DSI) values of a genotype did not give a clear indication of higher productivity under WS conditions. Higher decrease in Tr (31.1%) than Pn (17.4%) under WS resulted in 22.9% improvement in integrated water use efficiency (WUE) under WS as compared with WW. Positive relationships of Pn with both shoot biomass and grain under WW and absence of these relationships under WS suggested that the genotypes responded differentially to water limited conditions in terms of Pn under WS. Absence of relationships of Tr with both shoot biomass and grain yield under WW conditions and negative relationship under WS conditions with both biomass and grain yield suggested Tr is vital under WS and both shoot biomass and grain yield improved with lower Tr. Positive and highly significant relationship of WUE with both shoot biomass (R²=0.37) and grain yield (R²=0.42) under WS suggested that WUE can be a potential criterion to select drought tolerant cultivars of finger millets.