Effect of high temperature stress at early grain-filling stage on plant morphology and grain yield of different heat-resistant varieties of wheat

As one of the major crops in China, wheat has direct relationship with living standard and national food security. Wheat suffers high temperature stress often at late growth period which negatively impacted wheat yield and quality. Under the steadily increasing global temperature, the frequency of high temperature stress in wheat has increased. There are many indicators used for heat resistance screening and evaluation of wheat, including chlorophyll fluorescence, cell membrane, canopy temperature, thermal index, etc, in previous researches. However, most researches were limited to laboratory analysis, and neglected yield investigation. Considering wheat as a group crop, the chlorophyll content of population canopy and NDVI were used for wheat heat-resistance evaluation in this study. The grain-filling characteristics and yield outputs were also investigated. The study aimed at providing reliable methods of breeding, and theoretical basis for cultivation of high-yielding and stress-resistant wheat varieties. In this study, the effect of high temperature stress for 3 days at early grain-filling stage on morphology and grain yield of different heat-resistant wheat varieties (lines), including heat-resistant varieties (lines) of JM22 and 056852, and heat-sensitive varieties (lines) of XM26 and GC8901, were investigated through erecting artificial greenhouse to increase on-field temperature. The highest temperature during the 3-day high temperature stress was 43.13℃ and the average temperatures in every day were respectively 10.48℃, 9.71℃ and 9.84℃ higher than that of the control. Different heat-resistance varieties (lines) varied in response of plant and grain morphologies to high temperature stress. NDVI and canopy chlorophyll content of four varieties (lines) decreased after high temperature stress. These changes of JM22 and 056852 were not significant, while NDVI values and chlorophyll contents of XM26, GC8901 significantly decreased by 9.66%, 12.10%, and 6.26%, 10.73%, respectively. High temperature stress accelerated the senescence process of wheat. The grain-filling duration were significantly shortened by 1.4 d, 0.8 d, 2.4 d and 3.0 d for JM22, 056852, XM26 and GC8901, respectively. High temperature stress significantly decreased 1000-kernel weight and grain yield of wheat. The yield reductions of heat-sensitive varieties (lines) of XM26 and GC8901 were 11.43% and 10.05%, those of heat-resistant varieties (lines) of JM22 and 056852 were 6.41% and 6.93%, respectively. In conclusion, high temperature stress at early grain-filling stage accelerated canopy chlorophyll degradation, shortened grain-filling duration, reduced grain yield of wheat. JM22 showed better heat resistant ability and yield performance. 056852 had better heat resistance ability but normal yield performance. XM26 and GC8901 were worse both in heat resistance and in grain yield.