Reasearch On Cucumber Alien Translocation Line Possessing Resistance To Downy Mildew And Its Application In Cucumber Breeding

Downy mildew is caused by Pseudoperonospora cubensis (Berk.& Curt.) Rostov, and is a major foliar disease of cucumber in the world. Owning to narrow genetic base and lack of resistant resource, downy mildew resistance is still a problem to be solved in cucumber breeding program. In this dissertation, amphidiploid species Cucumis hytivus containing whole sour cucumber genome, in which there is resistant gene to downy mildew, was backcrossed to cultivated cucumber and its progenies were selfed. The identification of resistance, morphology, cytology and RAPD marker were done to above progenies, and cucumber primary alien translocation line CT-01 with resistance to downy mildew was identified. Genetic stability of CT-01 was analyzed by testing its advanced selfed-progenies continuously. The phylogenetic relationship of alien translocation lines with other progenies in Cucumis species were studied by using AFLP technique. The related resistant gene cpc-1 was isolated using designed specific primers. With the advanced alien translocation line CT01R as parent, the new pickle type cultivar- 'Ningjia No.3' was bred.1. Related techniques and mechanism study on breeding cucumber alien translocation lineChromosome preparation was studied using root tip and tissue culture in cultivated cucumber. By pretreatment with a new appropriate reagent, metaphase chromosomes were lengthened in cucumber root cells. good tissue culture chromosome preparation was achieved by 4-4.5 h pre-treatment of low temperature 0 °C plus 0.002 mol ? L^-1 8-hydroxyquinoline, and by 4-4.5h hydrolyzation of 2.5% mixed enzyme liquid at 25 °C.Study on cultivated cucumber meiosis and male gametophyte development using improved staining and chromosome preparing methods. The results obtained included: the meiosis in PMCs of cucumber was simultaneous cytokinesis. Chiasmata could be seen clearly in diplotene and the chromosomes could be identified as rod or ring bivalents. The multi-nucleoli and the nucleoli fusion were observed at both telophase I and telophase II; Two nucleuses were centrally. placed in male gametophyte development. Only one layer of...