Effect Of Submergence Stress During Rice Tillering Stage On Its Agronomic Trait, Grain Quality And Physiological Characteristics

Waterlogging disaster is one of the major limiting factor in rice production of themiddle and lower reaches of the Yangtze river and south of the region. Thus, it is of greatimportance to investgate on the effects of submergence stress on rice important traits, themechanism of responces to submergence stress, and screen the varieties with tolerance tosubmergence. In this study, we selected twenty varieties of rice to researched the effectof Submergence stress on the yield and rice quality of different genotypes in tilleringstage, and physiological and biochemical processes respond to submergence stress. Themain results are as follows:1Submergence stress caused the effective panicle number per plant, total grains perear, grain per spike, seed setting rate and1000-grain weight reduced, the effect on earlength was not significant. Changes of rice agronomic trait showed genotype differencesunder submergence stress. Correlation analysis showed that, there is a positivecorrelation between yield per plant stress index and effective panicle number per plant,grain per spike, seed setting rate. Then, using yield(Y) as independent variables, stepwiseregression analysis was made to understand the relationship between yield andagronomic trait. The stepwise regression equation is:Y=-0.632+0.574X1+0.326X3+0.491X4，R=0.897(effective panicle number per plant(X1), panicle length (X2), total grains per ear (X3), grain per spike(X4), seed settingrate(X5) and1000-grain weight(X6)). Using effective panicle number per plant, grain perspike, seed setting rate,1000-grain weight and yield stress index to evaluate ability ofsubmergence tolerance in rice. Tested varieties is divided into three categories: sensitivevarieties, neutral varieties and submergence-tolerant varieties. Screened sixsubmergence-tolerant varieties: Ⅱ you52, IR64(transferred sub-1), Ⅲyou98,Chuanxiagnyou165, Xieyou158and Huiliangyou630.2The effect of submergence stress in tillering stage on brown rice rate, milled ricerate, head rice rate and aspect ratio is not significant, effect on chalkiness is significant.Under submergence stress, the chalkiness of tested varieties decreased compared with thecontrast, changes of varieties chalky grain rate is difference. Chalky grain rate of ninevarieties such as liangyou127decline, other varieties chalky grain rate rise. The effect ofsubmergence stress on rice cooking and eating and nutritional quality is significant, Thesubmergence stress causes alkali spreading value increased, pasting temperaturedecreased. Gel consisteney and Amylose content associate with genetic characteristic ofvarieties. Besides, submergence stress also leads to the Protein content of the testedvarieties increased.3Response of rice RVA profile to submergence stress showed genotype differences:whole of viscosity curve of five varieties such as Liangyou127is higher than that of the contrast; whole of viscosity curve of twelve varieties such as Ⅱ you128is lower than thatof the contrast, the viscosity curve of three varieties such as Ⅱy ou52compared with thecontrast emerged after the former low-high trend. Different response patterns have led tothe breakdown of the tested materials decreased.4Submergence stress caused the activity of POD and content of MDA increased,and caused SOD, CAT, content of Pro and AOC decreased. The change of eachindicator depend on genotypes of varieties.