| Rice is one of the most important food crops in China.Its planting area is the second in the world,and the total yield is the first in the world.It plays a very important role in China's food production and national economic construction.With the improvement of people's living standards,the dietary structure and eating habits have changed greatly,and the requirements of rice quality,especially the taste quality,are higher and higher.Although the previous studies on rice yield have been more,but the research on quality is not much,especially in recent years,the climate conditions have changed greatly,especially the greenhouse effect leads to global warming,climate anomalies and extreme weather are more and more frequent,abnormal climate will have a very adverse impact on the growth,yield and quality of rice.Therefore,in this study,the Yangtze River Basin,the largest rice planting area in China,was selected to study the influence of actual light intensity and temperature on the yield and quality characteristics of mid season rice in different regions of the Yangtze River Basin under the current actual light intensity and temperature conditions,so as to select,regionalize and improve the quality of high-yield and high-quality varieties of rice widely planted in this area Cultivation and other aspects provide important basis.According to the climate characteristics of mid season rice area in the Yangtze River Basin,10 field test sites were set up in 10 cities and 8 provinces in 2018.Representative fine varieties were selected for field test.The differences of natural temperature and light were produced by sowing in three stages,and the yield and quality of tested rice under different natural temperature and light were analyzed.On this basis,six representative mid season rice will be selected in 2019(indica rice:Zhongxian 2503,Diantun 502,Japonica Rice: Huaidao No.5,Nanjing 9108,hybrid rice: C-Liangyou huazhan,Yixiangyou 2115)were also divided into three sowing dates.Based on the difference of natural temperature and light,artificial shading was carried out in Nanjing experimental site at the full heading stage of rice(light intensity is 70% of natural light intensity).After 20 days of continuous shading,the shading net was removed,and then it continued to grow under natural light and temperature conditions For mature harvest,the activities of starch related enzymes closely related to yield and quality and the expression of related genes in different types of rice varieties under different temperature and light conditions and different days after anthesis were studied,and the correlation between the changes of these enzymes and genes and yield and quality characteristics was analyzed,so as to provide the basis for the formation of high yield and good quality of different types of mid season rice Theoretical mechanism provides a theoretical basis.The main results are as follows1.The results of field stage sowing experiment under natural light and temperature conditions in 2018 showed that: the rice planted in the experimental site selected in this study had enough accumulated temperature and sunshine hours in the whole growth period,give full play to the potential of rice yield in this area.Appropriate temperature reduction and sunshine duration reduction in the late growth stage are conducive to improving rice yield,but different varieties have different forms At present,the higher the temperature in the growth period of indica rice and hybrid rice,the higher the yield,while the longer the growth period and sunshine from full heading to maturity of Japonica rice,the higher the yield.However,the influence of light and temperature on rice quality is more complex and has regional characteristics.Among them,the chalky grain rate of conventional japonica rice and Conventional Indica rice planted in the eastern region is lower,that is,the optimal light and temperature conditions can be obtained The results showed that the chalky grain rate of Japonica Rice and indica rice in central and western regions was lower in the third sowing time,that is,lowering temperature was beneficial to obtain better appearance quality.The light and temperature conditions from full panicle to maturity stage had the greatest impact on rice quality,and there were differences among varieties.The higher the temperature from full panicle to maturity and the longer sunshine,the better appearance quality of Indica and indica hybrid rice was The shorter the light,the better the cooking quality of indica rice;the longer the sunshine time 20 days after heading,the better the cooking quality of Japonica rice,while the performance of hybrid rice is contrary to that of conventional japonica rice;the higher the temperature from full panicle to maturity stage,the better nutritional quality of three types of rice varieties;the shorter the sunshine in the whole growth period,it is conducive to the formation of better nutritional quality of indica rice,but the performance of hybrid rice is the opposite The longer sunshine time from panicle to maturity was beneficial to the formation of better nutritional quality of Conventional Indica and japonica rice.2.The results of shading test after anthesis in Nanjing showed that the yield,quality,enzyme activities and gene expression levels related to yield and quality changed with the external light and temperature conditions.However,the protein content,milled rice rate and gel consistency of Huaidao No.5 increased and the rice became soft.However,the weakening of light intensity also delayed the grain filling to maturity and delayed the growth period,which was beneficial to the yield potential of Huaidao No.5 at the third sowing date.The weakening of light intensity increased the yield potential of Nanjing 9108 Wx gene expression level and GBSS enzyme activity,and the SSS enzyme activity and SBE enzyme activity increased,amylose content and milled rice rate increased in the middle grain filling stage;on the contrary,the light intensity decreased and the Zhongxian 2503 decreased Wx gene expression level,GBSS enzyme and SSS enzyme activity,while SBE enzyme activity increased,milled rice rate decreased,gel consistency decreased and rice quality hardened;light intensity decreased also reduced the Wx gene expression level and GBSS enzyme activity of Diantun 502,but its SBE enzyme activity also decreased,which was different from that of Conventional Indica rice Zhongxian 2503.In addition,the SSS enzyme activity of Diantun 502 decreased in the early stage of grain filling,but increased in the late stage of grain filling.The peak of SS?-3 gene expression level appeared in the middle stage of grain filling,with the increase of milled rice rate,the decrease of gel consistency and the hardening of rice quality.Therefore,the effects of light intensity on the quality of different rice subtypes were different. |
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