An experiment was conducted during rabi seasons of 2002-03 and 2003-04 to quantify the light interception and radiation use efficiency for three wheat varieties as affected by variable number of irrigations with the combination of three wheat varieties viz., HUW-234, HD-2285 and PBW-154. The light interception increased successively till 90 days after sowing (DAS) and thereafter a gradual decrease was observed till maturity of the crop. Four irrigations given at CRI, late tillering, late jointing and ear head formation stages showed highest radiation interception followed by three and two irrigations, however, the lowest radiation interception was observed for wheat crop receiving one irrigation only. On an average, 19.08 % and 12.79 % increase in radiation interception was found for wheat crop irrigated four and three times respectively as compared to singly irrigated crop. Highest radiation interception was recorded with HUW 234 followed by HD 2285 at all the growth stages except 15, 30, 45 DAS. More light interception reflected in significantly superior yield and yield attributes in the order of I4>I3>I2>I1. Subsequently, radiation useefficiency (RUE) also followed the similar trend showing highest and lowest RUE with four and one irrigation respectively. Among the different varieties, HUW-234 recorded highest radiation use efficiency followed by HD-2285. The average RUE during the entire growing period for HUW-234 and HD-2285 was found to be 1.68 g MJ-1 and 1.63 g MJ-1 respectively, which was 4.83 and 1.95 % higher than PBW-154.

Climate change and global warming have increasingly become relevant factors in recent years in determining the success of wheat production under heat stress conditions. Throughout its growth period wheat crop requires varying degrees of temperature to achieve ideal growth. Any variation from optimal temperature adversely affects plant growth and development. Many places where wheat is grown have high temperatures at the time of grain filling which is a major constraint on yield potential. A field experiment was conducted during the Rabi season of 2020-21 at Student’s Instructional Farm of Acharya Narendra Deva University of Agriculture and Technology, Kumarganj, Ayodhya, Uttar Pradesh to evaluate the performance of wheat varieties under heat stress conditions. The treatment for the experiment consisted of sowing on three different dates i.e. D1 (30th November), D2 (15th December), D3 (30th December). It was observed that time of sowing decreased substantially almost all the yield components measured viz; number of ear bearing tillers per plant, number of grains per ear, ear length (cm), grain yield per plant (g), biological yield per plant (g), which caused severe reduction of yield in V1 (PBW-343) and V2 (HD-2967). This reduction was caused due to onset of high temperature during crop growth and particularly grain filling. Variety V3 (Halna) reduced the detrimental effect of heat stress by improving physiological traits which ultimately helped in obtaining higher yield.

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