| In the arid and semi-arid regions which account for1/2of land area in China, thedrought not only has a very serious effect on the agricultural production, but also severelyrestricts their economic development, social progress and the protection of ecological.Therefore, it is particularly important and urgent to breeding the drought-resistant germplasmresources by identifying, modifying and improving the drought of plant. Watermelon acts as aimportant economic crop and it is particularly important to identity drought resistance andbreeding drought resistant variety. This research project mainly contained the PEG stressexperiment at germinate stage, recurrent drought experiment at seedling stage, continuousdrought experiment at seedling stage, moisture gradient experiment at seedling stage. Amongthem, the experiment at seedling stage got the statistics of multiterm morphology physiologybiochemistry indexes by simulation drought stress method of potting and evaluated droughtresistance of different watermelon variety, screened severel drought resistance indexes andvarieties, established a system of watermelon drought resistance appraisal and evaluationmethod by drought resisting exponent analysis,(PCA) Principal Component Analysis, Clusteranalysis and so on. The main results were as follows:1．Recurrent drought stress experiment at seedling stage: Hongguanlong,148, M08,Jing5, Zhong10Fu3, and F09were used as materials, and the growth condition and thesurvival rate after repeated two drought of the varieties was recorded at2day intervals. Thedeterminated growth indexes include plant height, leaf curl and plant straight, etc. And theplant growth morphology is divided into5levels according to the plant growth situation, andrecording the all levels of plant number at every period. The plant high stress index, leavesdamage rate, all levels of plant ratio and survival rates are done related analysis and grayrelational analysis. The results show that plant high stress index, leaf damage rate, all levelsof plant ratio can be used as the appraisal index of identifying watermelon variety droughtresistance. The observation method of plant growth morphology can do a preliminaryjudgment for varieties of drought resistance. The comprehensive analysis of more indexes is done to evaluate accurately the varieties drought resistance.2．Sustainable drought experiment at seedling stage:11materials were chosen to make astatistical analysis of the many biological drought resistance indexes, which mainly includedthe morphology damage index and growth index, and graded for single index according toeach drought resistance index,5levels of the watermelon varieties drought resistance wereset through grading method, namely the extremely drought resistance, a drought resistance,medium drought resistance, weak drought resistance, very weak drought. Finally, droughtresistance levels of11test varieties were determined; a biological index verification methodwas preliminary established for identification and evaluation of watermelon droughtresistance.3．Bud state drought stress and seedling stage drought stress test:11materials weremade PEG stress processing of seeding germination and drought stress seedling state. Doingstatistics and measurement on seed germination rate, sprout potential, germination droughtindex, MDA, SOD, Proline, POD, Chl and Carotinoid. Screening out the MDA, SOD, Pro,germination drought resistance index these four indexes to identify the drought resistance ofthe watermelon variety by using system clustering analysis, drought resistance coefficientanalysis, correlation analysis, the principal component analysis.4．Water gradient experiment at seedling stage: according to5drought resistance levelsestablished using the biological index in the seeding stage continuous drought experiment,choosing six different drought resistance varieties as tested material, setting five moisturegradient and analyzing the change rules of MDA, SOD and Pro in different five moisturegradient after dry treatment. The results show tha the difference level of each index indifferent moisture treatment level is different, and difference of each index is the mostsignificant in the fourth moisture stress processing level(moisture content20%). The sixvarieties drought resistances are determined by using cluster analysis combining droughtresistance coefficient.5. Drought resistances of20varieties were identified using the biological index appraisaland evaluation method determined in the earlier experiments. |
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