| Melon(Cucumis melo L.) is an important economic species of the Cucurbitaceae family. China has a long cultivating history of melon. Its planting area and yeild are all the first in the world. Powdery mildew of melon can reduced photosynthetic capability, lead to plant senescence, even death, effect seriously on the quality and yield of melon. With the degree of large-scale and commercialization of production increased, powdery mildew of melon has spread rapidly and became an important disease of melon throughout the world. It is difficult to reach on perfect results by fungicide control because of the rapid physiological race differentiation, and is not meets the needs of green food. So find and utilization of resistant resources to develop disease resistant varieties is the most economical and environmental approach..We used resistant parent, susceptible parent and its F2 segregating population as materials to study on the molecular marking linked with resistance gene to powdery mildew of melon with BSA and SRAP . In addition, we also analysised the change of related defense enzymes activity in the resistant reaction of melon powdery mildew, through determining and comparing the activity of POD,CAT,PPO of resistant and susceptible materials after inoculation. The main results as follows:(1) Optimum SRAP marker system for melon was developed. Each 10-μl PCR reaction mixture consisted of 10×Taq buffer(Tri-HCl 10mmol-1 PH 8.0,KCl 50 mmol-1),2.0 mM of MgCl2, 20 ng of genomic DNA, 0.25 mM of dNTPs, 24 ng of primers, and 0.75 unit of Taq polymerase. Sample were subjected to the following thermal profile for amplification: 5 min of denaturing at 95℃, 5 cycles of three steps: 1 min of denaturing at 94℃, 1 min of annealing at 35℃and 1 min of elongation at 72℃. In the following 35 cycles the annealing temperature was increased to 51℃, with a final elongation step of 10 min at 72℃.(2) Two primers that could stably amplify the same polymorphic bands were gained through amplifing by PCR to resistant pool and susceptible pool with 294 primers. Eight high-resistant individuals and eight high-susceptible individuals were used to amplify. Eight high-susceptible individuals were amplified one band of 210bp and only one high-resistant individual has signature band by me46em51. Eight high-susceptible individuals were amplified one band of 205bp and high-resistant individuals has not this band by me46em51. The two primers were checked in 133 individuals of F2. The results showed that me46em51 and me3em6 obtained 87 and 85 signature band respectively. Based on the linkage analysis by JoinMap3.0, the distance between the two markers and the powdery mildew resistance gene were 23.4cM and 18.2cM separately.(3) Activity of POD, CAT, PPO had not obvious difference between resitant and susceptible control. The three kind of enzyme activity all increased compared with their control after inoculation. CAT activity of resistant variety was higher than susceptible variety. POD activity is opposite, susceptible variety was higher than resistant variety. PPO activity of resistant variety was higher than susceptible variety until five days after inoculation. |
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