| Submergence frequently occurs in rice production, which could often result in loss of grain yield. For increasing the resistance of rice to submergence, it is important to screen germplasm with high resistance to submergence, and to introduce genes for submergence resistance to current rice varieties. In the study, survival ratio of rice plants were investigated under complete submergence conditions. Additionally, several submergence-tolerant lines were screened from F2generations. For physiological mechamsims, the carbohydrate metabolism related two main enzymes and the content of three kinds of carbohydrate in rice plant were studied.1. Different water conditions had different damage on rice. Plants were damaged most severely in pure tap water (TW), in which the survivals of IR64-Sub1, IR64and Yangdao6were54.69%,0.63%and0.31%. And in the treatments of tap water floating Lemna minor L.(FL) and tap water covered with shade net (CSN), the survivals of the three varieties were62.50%,1.88%,17.50%and83.13%,27.81%,34.38%. In all the three treatments,IR64-Sub1showed the highest tolerance ability among three varieties.2. In the F2generations derived from IR64-Sub1//Minghui63and Minghui63/IR64-Sub1, the survivals were60.78%and37.92%, higher than2.57%,10.94%and4.63%derived from Zhenshan97/IR64-Sub1, IR64-Sub1/Zhenshan97and Yangdao6/IR64-Sub1. The result suggested that Minghui63was more suitable to be receptor than Zhenshan97and Yangdao6in the development of submergence-tolerant Sub1rice. Additionally, when IR64-Sub1is to be female in cross breeding, the generations had more tolerant plants that that when IR64-Subl is to be male. This result suggested that the tolerance ability was also influenced by cytoplasmic genetic.3. The submerged plants were higher than the control plants on both the sixth day of submergence (DS6d) and the eighth day of recovery (PS8d).The non-Sub1varieties, IR64, Shanyou63, Yangdao6and Zhenshan97, grew faster than the Sub1varieties, Swarna-Sub1and IR64-Sub1under water. The submergence decreased the rice dry matter weight. However, the relative increase in dry weight did not show significant difference between Sub1varieties and non-Sub1varieties. 4. The amylase activity was decreased significantly after submergence, except Swama-Sub1and Yangdao6. However, there was no consistent difference of amylase activity between Sub1varieties and non-Sub1varieties. In the first batch, the alcohol dehydrogenase (ADH) activity increased in the submerged plants of all varieties expect Swarna-Sub1, in which the ADH activity in submerged plant was8.15g-1(DW) min-1, lower than10.62g-1(DW) min-1.in control plant. And in the second batch, the ADH activity between Sub1varieties and non-Sub1varieties did not show a consistent difference, although the submergence had a certain influence on ADH activity.5. Submergence significantly reduced the soluble sugar content. The relative increase in soluble sugar of Swarna-Sub1and IR64-Sub1reached to-94.67%and95.39%in the first batch and-65.36%and-71.12%in the second batch after6-day submergence. But comparing to non-Sub1varieties, IR64, Shanyou63and Zhenshan97, Sub1varieties consumed less soluble sugar relatively. Submergence also reduced the starch content. The relative increase in starch content among varieties reached to maximum value of-61.48%in Shanyou63after6-day submergence. And the minimum relative increase was-19.70%in Yangdao6. After8-day recovery, the starch content in submerged plants was still lower than that in control. Neither starch content nor relative increase in content showed consistent difference between Sub1and non-Sub1varieties. In this study, the cellulose content was barely influenced by submergence. In the two batches, the cellulose content did not show statistic difference between Sub1and non-Sub1varieties. |
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