Effects Of Field Experimental Warming On Yield And Quality Of High-quality Late Rice

Rice is an important food crop,and climate warming is one of the important factors restricting global rice security.Studies on different temperature sensitive rice cultivar to warming have been conducted,however the impact of increasing temperature on highquality rice varieties with similar amylose content was not documented.Therefore,field experiment was carried out in Shanggao County,Jiangxi Province in 2021 and 2022 using a free-air temperature increase system,assessed four high-quality rice varieties(indicajaponica hybrid rice,hybrid indica rice,indica rice and japonica rice).With ambient condition as control,we set up the whole day temperature increase treatment during the rice growth season,and compared the responses of the growth period,plant height,yield and it’s components of the different high-quality rice to warming.The study further assessed rice milled quality,appearance quality,nutritional quality,cooking and eating qualities to warming.This study provides a theoretical basis for high-quality,high-yield rice and highcultivation efficiency under climate warming.The specific results of the study were:1.Warming generally prolonged the growth period from transplanting to heading,while it reduced the growth period of heading to maturity and plant height.Compared with control,Yongyou 5550(YY5550,Indica-Japonica hybrid rice),Wanxiangyouhuazhan(WXYHZ,Indica hybrid rice),Ganningjing 2(GNJ2,Japonica rice)and Jiuxiangzhan(JXZ,Indica rice)growth periods under warming were prolonged by 3.5,4.5,1.5 and 1 day,respectively.The growth period from heading to maturity were shortened by 0.5,3,1.5 and 1 day,respectively.Warming reduced the plant height of cultivar YY5550,WXYHZ and JXZ significantly by 7.4%,3.8% and 3.9%,respectively though the japonica rice GNJ 2 showed little change.2.During the rice growing season,warming reduced the yield of high-quality late rice of each subspecies.Compared with control,warming decreased the yields of YY5550,WXYHZ,GNJ2 and JXZ decreased by 17.8 %,16.9 %,16.7 % and 9.3 % on average in two years.Further analysis of the yield components showed that,warming reduced the thousandgrain weight of YY5550,WXYHZ,and GNJ2 significantly by 3.8%,3.0% and 12.6%,respectively in 2021,and the consistent trend also was found in 2022.The grain filling dynamics also showed that although warming increased the grain weight of hybrid rice during 0-15 days after heading,warming eventually decreased the grain weight because of the lower grain weight of upper and middle,while conventional indica rice and japonica rice showed a decreasing trend throughout the grain filling period.3.Warming reduced the total biomass and nitrogen accumulation of high-quality late rice.Compared with the control,warming reduced average total biomass over two years of YY5550,WXYHZ,GNJ2 and JXZ by 19.5%,8.9%,20.6% and 14.8%,respectively.In addition,the total amount of nitrogen accumulation and absorption in the aboveground part of the mature period decreased by 19.8%,18.4%,13.5% and 11.0% on average,which mainly concentrated in biomass of stem and panicle.4.Warming led to poor appearance quality,but improved the nutritional and eating qualities.Compared with control,warming increased the chalky grain rate of YY5550,WXYHZ,GNJ2 and JXZ increased by 21.3%,54.9%,97.5% and 83.0% on average,and the chalkiness correspondingly increased by 54.4%,91.6%,99.9% and 148.1% on average,Poor appearance quality;the contents of gliadin and glutelin in protein components and protein content increased,which was beneficial to the improvement of nutritional quality;warming increased the peak viscosity and breakdown of grain starch while significantly decreasing the hardness and viscosity,and the eating quality of rice increased.In conclusion,warming prolonged the pre-anthesis growth period of different types of high-quality late rice,shortened the post-anthesis growth period,and the whole growth period remained unchanged or prolonged.Warming reduced grain yield,total biomass,nitrogen accumulation of whole plant and appearance quality of different high-quality late rice cultivar,but benefited to the nutritional quality and eating qualities because of the improvements of gelatinization characteristics and the lower hardness and chewiness.Different types of high-quality late rice varieties had different responses to warming.