SCREENING OF AGRO-PHYSIOLOGICAL TRAITS FOR THERMOTOLERANCE IN WHEAT (Triticum aestivum L.)
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PAU
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Field and laboratory experiments were conducted at PAU, Ludhiana during rabi season 2006-07, to find out suitable agro-physiological traits for screening thermotolerance and relationship between yield and quality parameters in wheat. The five wheat varieties namely PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765 were sown at five dates at weekly interval starting from 7th November. The Thermal unit (GDD) accumulated more during reproductive stages than those from vegetative stages in all the varieties. This shows that rising temperature after anthesis is associated with grain filling and crop maturity. The cv. PBW-343 had higher grain yield (51.44 q ha-1) due to its higher dry matter partitioning to spike at anthesis stage (0.31 g), crop growth rate after anthesis (6.75 mg cm-2 day-2), number of spike m-2 (523.60), 1000 grain weight (33.01 g) and chlorophyll content at milky stage (0.967 mg g-1 FW) followed by cv. WH-542. With delay in sowing from 7th Nov. to 6th Dec., grain yield declined by 34.43, 37.89, 36.49, 28.89 and 33.16% in cvs. PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765 respectively. The regression model showed significant positive correlation between grain yield and GDD accumulated during watery ripe (r=0.854), hard dough (r=0.849), anthesis (r=0.833) and physiological maturity (r=0.815) stages. The correlation coefficient analysis also showed significant positive relationship between grain yield and physiological traits i.e. 1000-grain weight (r=0.9304), partitioning to spike at anthesis (r=0.8948), biological yield (r=0.8922), number of grains per spike (r=0.8351) and number of effective tillers m-2 (r=0.8323). Under late sown conditions, the amylose-amylopectin ratio increased and this character can be correlated with the superior end-use quality of grains. These results indicated that number of effective tillers, leaf area index, pre-anthesis dry matter production, partitioning to spike at anthesis, grain growth duration, number of spikes m-2, number of grains per spike, 1000-grain weight, chlorophyll content at milky stage and thermal use efficiency which can be used as an index for screening thermotolerance in wheat cultivars.
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