Study On The Effect Of Low Temperature During Flowering Period On The Yield Of Different Late Rice Varieties And Its Mechanism

In this study,a pot experiment was used to promote the contemporary late hybrid rice varieties Shengtaiyou 018 and Taiyou 390,as well as the conventional late rice varieties Xiangwanxian 17,Xiangwanxian 8 and Xiangwanxian 2,which were certified in 2008,1998 and 1991,respectively.Artificial temperature control for 5 days during late rice flowering.Manually control the temperature for 5 days during the flowering period of late rice,and set the average temperature to 17°C and 20°C 2 low temperature treatments,and the control treatment at room temperature in the greenhouse.By probing the effect of low temperature on the yield of different late rice varieties by comparing yield differences and analyzing the heading and flowering traits,anther traits and the relative content of chlorophyll in the flag leaf(SPAD value),chlorophyll a,chlorophyll b,antioxidant enzyme activity,soluble protein,soluble sugar and proline during low temperature and recovery period,discuss the possible mechanism of low temperature affecting the yield of different late rice varieties.The main results are as follows:1.Under low temperature stress,the heading speed and flowering number of the five late rice varieties were inhibited,the heading time was prolonged,and the flowering time was delayed.Low temperature stress reduces chlorophyll content,and the lower the stress temperature,the greater the reduction.Under low temperature stress,anther size,anther dehiscence length,and pollen vigor are all reduced.The lower the stress temperature,the more obvious the inhibition of anther traits.The low temperature stress made the yield and yield components of the tested late rice significantly lower than the normal temperature control.The lower the stress temperature,the greater the decline in the yield and yield components of each late rice.Correlation analysis shows that low temperature stress mainly affects late rice’s fertilization rate,seed setting rate,thousand-grain weight,total grains per panicle,pollen vigor and anther cracking length to further affect the yield of late rice.2.Low temperature stress has no significant difference in the degree of inhibition of flowering,heading characteristics and yield formation of contemporary conventional rice Xiangwanxian 17 and hybrid rice varieties.However,there are differences in the decline in the indexes of conventional rice varieties bred in different years.Under low temperature stress,the reduction of anther length,width,volume,anther dehiscence length,total number of flowering,total grains per panicle,fertilization rate and seed setting rate of the modern conventional rice variety Xiangwanxian 17 was significantly less than that of the early conventional rice variety Xiangwan 2.Under the low temperature stress of 20℃,the yield per plant of the modern conventional rice variety Xiangwanxian 17 was significantly lower than that of the early conventional rice variety Xiangwanxian 2,which was not significantly different from Shengtaiyou 018.3.Further analysis found that the differences in flowering and fertilization characteristics of different varieties under low temperature stress may be caused by differences in the increase in antioxidant systems,osmotic adjustment substance content,and so on.Under low temperature stress,the activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)of Xiangwanxian 17 increased significantly than that of Xiangwanxian 2.The increase in malondialdehyde(MDA)content of 3 conventional rice varieties was significantly lower than that of 2 hybrid rice varieties.The soluble protein,soluble sugar and proline content of the conventional rice variety Xiangwanxian 17 increased significantly than the other four varieties.4.In general,the cold tolerance of the conventional rice variety Xiangwanxian 17 among the five late rice varieties is better than that of the early conventional rice varieties Xiangwanxian 8 and Xiangwanxian 2.The cold tolerance of hybrid rice is better than that of the early conventional rice varieties Xiangwanxian 8 and Xiangwanxian 2,and there is no significant difference from the modern conventional rice variety Xiangwanxian 17.