Effects of Powdery Mildew Stress on Isoenzymes of Melon

【Objective】To determine the relationship between isozymes of SOD,POD,CAT of melon seedlings and powdery mildew.【Method】The changes of three kinds of isozymes in susceptible variety of Jiashi melons and MR-1 of resistance variety before and after inoculating powdery mildew were analyzed by using PAGE electrophoresis.【Result】Activity of the 3 kinds of isoenzyes changed and POD emerged a new enzyme after inoculating powdery mildew three days compared with control: jiashi P4(Rf=0.80),MR-1:P1(Rf=0.68),and the changes of the activity of POD isozyme in Jiashi was violent than that in MR-1 during the treatment.The isoenzyes of CAT didn't produce new lane,but two peaks emerged after inoculating powdery mildew 3 days and 12 days.The activity change of SOD was weak compared with others,but the lane of S1(Rf=0.68) had a trend that was higher than that of contrast in day 6 and were lower in day 9.【Conclusion】The defense enzymes SOD,CAT,POD can be used as a measure of indicators of resistance to powdery mildew in melon.