| The Genus Cucurbita mainly includes five cultivated species: C. moschato Duch, C. pepo L, C. maxima Duch, C. mixta and C. ficifolia.In china, the former three cultivated species are widely planted.and Heizi Nangua belonging to C. ficifolia is a wild culitivar in Yunnan province.In this study.we analyzed the content of seed proteins and discussed the relationship of four cultivated species in Cucurbita through seed proteins and POD,Est,Amy isozyme electrophoresis.RAPD analysis and calculation of chromosome number of some cultivars in order to display their genetic backgrounds in Cucurbita from biochemistry, molecule and chromosome levels, so we can provide method and theory evidence to apply the idioplasmic resources effectively to accelerate the steps of breeding.we also tried to establish a system to evaluate the resistance of cultivars to powdery mildew in Cucurbita,so we can provide a simple,convenient and fast method to select the breeding parent with high-resistance .What we have done and the results were displayed below: 1. Analyzing the content of seed proteins ,the results showed : seed proteins content was different among four cultivated species , the highest is C. pepo L ,that is 37. 68 percent.then C. moschato Duch and C. maxima Duch,they are 29. 84~33. 48 percent and 29. 16—31. 81 percent separately, the lowest is C. ficifolia,,that is 21.81 percent. Using Miben Nangua as a material, we established the extraction method of seed protein , that is extracting the seed powder 1. Oh at 37°C with a 100:1 ratio of water (pH12. 0).2.Discussing the relationship of four cultivated species in Cucurbita through seed proteins and POD, Est, Amy isozyme electrophoresis.RAPD analysis.the results showed: C. pepo L is closer to C. moschato Duch comparing to C. maxima Duch; C. ficifolia is a little far to C. moschato Duch and C.pepo L while is far to C. maximaDuch.3. Using seed proteins and isozyme electrophoresis,RAPD technology to analyzed the cultivars o f four c ultivated s pecies , each s pecies g ot t heir o wn s pecial b ands, e ven some differences were showed among the cultivars of the same specie.As to the cultivar—Riben Nangua, Guo Qinping(2001) ascribed it to C. moschato Duch, Cui Huimei (1999) ascribed it to C. maxima Duch..In our study,we found that it had the special bands of C. moschato Duch and C. maxima Duch at the same time, so we concluded the it maybe the crossbreed of C. moschato Duch and C. maxima Duch. we drew the dendrogram by cluster analysis based on peroxidase isozyme map and RAPD.we got the same results, Riben Nangua was closer to C. moschato Duch than to C. maxima Duch, if ascribing it to one specie, we hold out the point of Guo Qinping ascribing it to C. moschato Duch.4. Chromosome numbers were calculated with chromosomes in root tip cell made by the wall degradation hypotonic with enzymes .After calculating ,we primely comfirmed the chromosome numbers of some cultivars in Cucurbita: the chromosome numbers of Miben Nangua(C. moschato Duch),Zaoqing Yidai(C. pepo L ),Heizi Nangua(C . ficifolia ) are 2n=40;some cultivars except BS2-3(2n=42) in C. maxima Duch ,the chromosome numbers of Baizi Nangua,Danhong Yihao.Riben Nangua, BSl-l,BS2-l,BS3-l,BS2-2,BS3-2 are 2n=40.5.To evaluate two cultivars' resistance to powdery mildew ,we analyzed them with detached-leaf-segment (preserved green with benizimidazole) test, seedlings and adult plant tests,the results showed: As to Yichuanling Yihao, the result of identifying its resistance to powdery mildew using deteched-leaf-segment test was similar to that by seedling and adult plant tests, it was mid-resistance to powdery mildew. As to Miben Nangua, the result of identifying its resistance to powdery mildew using deteched-leaf-segment test (it was mid- hypersensitive to powdery mildew) was not accordant with that by seedling and adult plant test (it was high-hypersensitive to powdery mildew), the final result should be based on...
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