Identification Of Waterlogging-tolerance And Its Mechanism Of Different Watermelon Varieties

Waterlogging or submergence is one of the most serious abiotic stress, which effects the growth and development of crops badly.Watermelon(Citrullus lanatus),a waterlogging-sensitive species, is often subjected to excess water in area of south china and middle-downstream of Yangtze River,resulting the reduction of production.Thus, the study on the mechanism of waterlogging-tolerance of watermelon is meaningful for guiding watermelon breeding and cultivation.In this thesis, We identified the waterlogging-tolerance of20watermelon varieties under waterlogging (water level is3cm above soil surface) condition and submergence (whole plant is under water) condition. Furthermore, HD26and XFM were chosen as waterlogging-tolerant and-sensitive material respectively, which were used for research of waterlogging-tolerant mechanism. The main results are shown below:1.HD26and XN were relative tolerant while XFM and LFM were relative sensitive to waterlogging and submergence respectively.We got the rank of waterlogging-tolerance and submergence-tolerance of20watermelon genotypes.Among20watermelon genotypes,HD26showed the best performance under waterlogging condition,while XFM showed the worst;XN was relative the most submergence-tolerant variety, while LFM was relative the most submergence-sensitive variety.2. The root of HD26is more functional than XFM under waterloggingRoot growth of both HD26and XFM was restricted under hypoxia stress,compared with HD26,the adverse effection of hypoxia on XFM root growth was more remarkable.Root activity of both HD26and XFM decreased to30%of control,but HD26showed better performance than XFM during1st day of waterlogging.Cla0025P7which related to glycolysis responsed to waterlogging more quickly and higher in hypocotyl of HD26than XFM.These results revealed that the root of HD26is more functional than XFM under waterlogging3. The relative expression of genes related in ethylene biosynthesis,response and auxin trantsport,response were higher in HD26than XFM under waterlogging.We measured the ethylene released amount and found out that the amount of ethylene released was higher in hypocotyl of HD26than XFM.The expression of Cla011522and Cla018296which related in ethylene biosynthesis and response respectively was induced in hypocotyl of HD26and the expression was higher in hypocotyl of HD26than XFM.The IAA content in leaf,hypocotyl,root of both HD26and XFM under Waterlogging is lower than control.The result of expression of Cla006955which related to IAA response,Cla018455and Cla017975which related to IAA trantsport were similar with the expression of Cla011522and Cla018296.4.Appropriate concentration of exogenous IAA can induce ethylene biosynthesis and adventitous root formation under waterloggingThe apply of NPA which is a kind of polar transport inhibitor of IAA reduced adventitious root formation significantly in both HD26and XFM,while10μM IAA induced adventitious root formation significantly when compared with control. Ethylene released amount of LFM hypocotyl was induced by1μM,10μM and100μM IAA treatment.