Studies On The Physiological Mechanism, Molecular Markers And Related Gene Isolation Of Chilling Tolerance In Cucumber

As a environment stress, low temperature is often suffered in the protected field at winter and spring, and the chilling sensitivity of cucumber, a major vegetable cultivated in protected condition, has become the main factor disturbing its normal growth, so how to improve the chilling tolerance of cucumber has been the research focus on special breeding for protected growth of cucumber. In this dissertation, the physiological mechanisms, molecular markers and related genes isolation of chilling tolerance in cucumber were studied, in order to deeply understand the mechanism of chilling tolerance and get the molecular markers tightly linking to this trait. The follows were researched:1 Studies on the physiological mechanisms of chilling tolerance in cucumberThe germination ability at low temperature of 15℃ of cucumber cultivars were measured and two cultivars, "Beijing jietou" and "Changchun mici", with significant difference in this trait were identified. Using the two cultivars as main experimental materials, we studied the effects of low temperature (15℃) on the hydrolases activities, including proteases and lipases, during cucumber seeds germination and the effects of exogenous Ca²⁺ and its chelator EGTA on the activities of three antioxidative enzymes, SOD, CAT and POD, in cucumber leaves during chilling stress(7℃).The results of hydrolases activities experiments revealed that the low temperature slowed down the change rate of hydrolases activities of cucumber seeds and postponed the appearance of their peeks, and then delayed the germination. The activities of chilling sensitive cultivar the former were obviously less than those of chilling tolerance cultivar, which suggested that the ability to germinate under low temperature in cucumber was related to the hydrolases activities. According to the suddenly increment of activity only presenting in chilling tolerance cultivar but not in the sensitive one, we can deduced that the reason for the difference of germination ability under low temperature between different genetic types of cucumber was that there are hydrolases to be activated in chilling tolerance seeds. At the early stage of low temperature treatment, the activity inhibition of was...