The Study On Drought Resistance Identification Methods And Indexes Of Citrullus Lanatus

sand mulching is the unique cultivation model in the arid and semi-arid regions of Northwest China, as countermeasure to adapt water shortage and drought climate which restrict the development of watermelon industry seriously. It is particularly important to breed new cultivars with drought tolerance, and quick and effective screening of the drought resistant cultivars and germplasms is therefore crucial. In this dissertation, ten watermelon strains or hybrids with different drought-resistant are employed in three experiments of seed germination under PEG-6000 Stress, seedling evaluating under controled water stress and field testing under controled soil water moistures, a number of growth, morphological, physiological and biochemical parameters were measured as the markers indicating the differences among the materials. Direct comparison, subordinate function, grading evaluation and drought resistance index were used as the evaluating methods. The main results obtained are as follows:1. Applied the identification method of field testing, the drought resistance index sequence based on the yield of the ten cultivars is 328(1.12)>238(1.00)> Xinongbahao(0.88)>Jincheng 5 (0.77)>Tianziyihao(0.75)>Baierhao(0.63)>Jing xin 2 (0.46)>483(0.44)>Sweet Crimson(0.44)>618(0.35), and the result are basically the same with the reported literature or commercially produced(R=0.942,P=0.000). According to the drought resistance index of the yield, tested materials were divided into three groups: there are 328, 238, Xinongbahao and Jincheng 5 are the most drought adaptable; and the more drought adaptation are Tianziyihao and Baierhao; the sensitive cultivars to drought are Jingxin 2, 483, Sweet Crimson and 618.2. The experiment of seed germination under PEG-6000 Stress show that the osmotic pressure from -0.10Mpa to -0.80Mpa, using the average subordinate function value of seed germination rate, germination potential and germination drought indices to sequence the drought tolerance, the result is significant positive correlation with the field testing (R=0.605, P=0.011). Controlled soil moisture percent is at the 40%-45% and 60%-65% of the maximum water holding capacity, using single seedling morphological, physiological and biochemical indexes to identify the drought tolerance is different with the field testing; but combined morphological, physiological and biochemical indexes to calculate the average subordinate function value to identify the drought tolerance is significant positive correlation with the field testing (R=0.622, P=0.009). So, the experiment of seed germination under PEG-6000 Stress and controlled soil moisture percent which kept the same result with the field testing are the comfortable drought resistance identification methods.3. The different evaluation ways of direct comparison, subordinate function, grading evaluation methods and drought resistance index of yield differ in screening drought resistance indexes, drought resistance index of yield can be a more accurate evaluation way to selected indexes of drought resistance, grading evaluation method and subordinate function are auxiliary method to make more accurate identification results.4. Different evaluation ways screen different drought resistance indexes which are analyzed by Data Reduction of factor. According to the ratio of each variables variance and the total variance, we selected five factors. Remove the loading that are less than 0.5, and then using the method of Varimax with Kaiser Normalization to suppress absolute values less than 0.65, we could get five independent factors and the loading of every variables. Factor 1 include chlorophyll (0.964), chlorophyll a (0.870) and chlorophyll b (0.924), in essence, the variables is the chlorophyll factor. Factor 2 include stomatal aperture (0.880) and stomatal density (-0.795), in essence, the variables is the stomatal. Factor 3 include plant height stress index (0.741) and crown/root ratio (0.696), in essence, the variables is morphological indicators. Factor 4 include soluble protein (0.863), in essence, the variables is the penetration of material factors. Factor 5 include the activity of SOD (0.874), in essence, the variables is the antioxidant enzyme factors. Compared with the absolute values of loading to screen the comfortable drought resistance indexes.5. Under normal irrigation, stomatal characteristics (stomatal length, stomatal width, stomatal density) and watermelon anatomical structures (upper epidermis, lower epidermis, palisade / spongy, fence / leaf). At stage of seed germination is the absolute value of germination potential and seed germination drought resistance index; at the stage of seedling is the chlorophyll content, stomatal aperture, plant height stress index, soluble protein and the activity of SOD; at the field testing is the change percent of yield (fruiting number and single fruit weight), drought resistance index and crown/root ratio.