Changes in timing of water uptake and phenology favours yield gain in terminal water stressed chickpea AtDREB1A transgenics

Terminal drought causes major yield loss in chickpea, so it is imperative to identify genotypes with best suited adaptive traits to secure yield in terminal drought-prone environments. Here, we evaluated chickpea (At) rd29A:: (At) DREB1A transgenic events (RD2, RD7, RD9 and RD10) and their untransformed C235 genotype for growth, water use and yield under terminal water-stress (WS) and well-watered(WW) conditions. The assessment was made across three lysimetric trials conducted in contained environments in the greenhouse (2009GH and 2010GH) and the field (2010F). Results from the greenhouse trials showed genotypic variation for harvest index (HI), yield, temporal pattern of flowering and seed filling, temporal pattern of water uptake across crop cycle, and transpiration efficiency (TE) under terminal WS conditions. The mechanisms underlying the yield gain in the WS transgenic events under 2009 GH trial was related to conserving water for the reproductive stage in RD7, and setting seeds early in RD10. Water conservation also led to a lower percentage of flower and pod abortion in both RD7 and RD10. Similarly, in the 2010GH trial, reduced water extraction during vegetative stage in events RD2, RD7 and RD9 was critical for better seed filling in the pods produced from late flowers in RD2, and reduced percentage of flower and pod abortion in RD2 and RD9. However, in the 2010F trial, the increased seed yield and HI in RD9 compared with C235 came along only with small changes in water uptake and podding pattern, probably not causal. Events RD2 (2010GH), RD7 (2010GH) and RD10 (2009GH) with higher seed yield also had higher TE than C235. The results suggest that DREB1A, a transcription factor involved in the regulation of several genes of abiotic stress response cascade, influenced the pattern of water uptake and flowering across the crop cycle, leading to reduction in the percentage of flower and pod abortion in the glasshouse trials.