Comparing Study Of Some Agronomic And Physiological Characters Of F₁ Hybrid And Parents On Cucumber

Cucumber (Cucumis sativus L.) is one of the staple vegetables and very popular for consumers. Cucumber breeding keeps attracting breeders' attention and there are numerous commercial varieties were bred by making use of the heterosis, which is the prime approach for cucumber improvement. However, up to now, less attention was put on how to predict the heterosis about the cucumber F₁ hybrid in early stage.In order to predict the cucumber heterosis in early stage and promote new varieties breeding, two crosses (9514, 9518) with excellent heterosis and their parents were used in the experiment. Some agronomic traits, physiological and biochemical characteristics were measured and compared between the crosses and their parents to study the possibility of predicting cucumber heterosis in early stage. The main results are as following:1. The measurement on the agronomic traits indicted: cucumber heterosis could be predicted in the early stage with the traits of cucumber cotyledon area, seedling leafs area, fresh weight of seedling; The first pistillate node was significantly negative related with the yield of early stage; The traits of the width, length and weight of the fruit could be improved by the way of heterosis. The long of melon bar had obviously negative heterosis.2. The study on the physiology and biochemical indexes suggested: The cotyledon chlorophyll content could be used as a reference index to predict heterosis and the disease resistant, as well as the anti- stress of the cucumber in early stage. Heterosis could be used to raise the F₁ hybrids' content of soluble protein and Vc. However, further experiment should be employed to determine whether F₁ hybrids could be used to improve cucumber soluble sugar.3. The investigation on photosynthetic characters showed: (1) Change of net photosynthesis rate on cucumber in the day time presented obviously two high peaks from 11:00 tol2:00 and about 16:00 of the afternoons respectively, and the peak value of morning is more effective than that in afternoon; (2) The peak value of the F₁ hybrid was always higher than its parents. When the temperature was between 25℃and 30℃, net photosynthesis rate of cucumber was the most effective than other temperature. Besides, the characters of transpiration rate, stomatal conductance, and internal CO₂ concentration in F₁ hybrid were higher than their parents.4. Study on activity of the protective enzyme showed: (1) Enzyme activities of SOD and POD gradually increased until the maximum fruit setting period and then began todecrease. (2) Enzyme activities of SOD and POD could be regarded as a reference index to predict the disease resistance and anti- stress for the Fi hybrid. (3) The SOD activity of the hybrid was lower than its parents. However, the activity of SOD was higher than its parents.5. The study on the isozyme electrophoresis pattern showed: It was not effective way to predict the cucumber heterosis with the pattern of POD and SOD in the cotyledon and seedling stage.