Effect of moisture regimes and sowing dates on wheat physiological process and yield attributes under rain-fed ecosystem in Eastern Indo Gangetic Plain

Drought stress severely limits wheat production worldwide. Availability of moisture for crop during critical growth stages is one of the important factors that determine grain yield. An experiment was conducted with five wheat genotypes (HD 2987, K 7903, HI 1563, HD 2824 and HD 2967) and dates of sowing (15th and 30th November) and 2 moisture regimes (one irrigation at crown root initiation stage and completely rainfed) during rabi (dry) seasons of 2014–2015 and 2015–2016, in order to determine their potential in terms of physiological parameters viz., relative water content (RWC), membrane stability index (MSI), chlorophyll content, proline content, gas exchange parameters and yield attributes. Study revealed that the physiological traits viz., RWC, MSI and total chlorophyll content declined, while moisture-deficit stress indicator level (proline level) increased under rainfed condition across the wheat genotypes, at both the developmental stages (anthesis and A + 20 days). At both stages, genotypes HI 1563 followed by HD 2987 were able to maintain high RWC (69.5 and 65.1%; 68.7 and 65%), MSI (75.2 and 64.5%; 63.1 and 57.7%), chlorophyll content (4.7 and 2.6 mg g⁻¹ D.W.; 3.3 and 2.13 mg g⁻¹ D.W), respectively as compared to other genotypes. High RWC, chlorophyll content and photosynthetic rate are important for maintaining physiological efficiency under deficit moisture condition to harness optimum yield. Further, high RWC led to more osmotic regulation or less elasticity of tissue cell wall. Moreover, growth and yield attributes were significantly higher under one irrigation as compared to complete rainfed condition. Wheat variety ‘HD 2967’ produced significantly higher number of grains ear⁻¹(44.75). The test weight ranged from 33.2 g in K 7903 to 35.6 g in HD 2824. Wheat sown on 15th November produced higher grain yield (2.9 t ha⁻¹) as compared to 30th November sowing (2.7 t ha⁻¹), but the difference was not significant. One irrigation at CRI stage produced significantly higher grain yield (3.26 and 3.18 t ha⁻¹) as compared to no irrigation (2.52 and 2.30 t ha⁻¹).