Using resistant and susceptible cultivars as controls,the resistant evaluation to Pseudoperonospora cubensis was carried out in 12 introgression lines from wide cross between cucumber(Cucumis sativus L.)and sour cucumber(Cucumis hystrix Chakr.).Three enzyme activities including POD,SOD and PAL were analyzed before and 7 d after inoculation,and the POD isozyme was detected by polyacrylamide electrophoresis.The inoculation results showed that,of the 12 accessions,3 were identified as high resistant,5 were moderately resistant and 4 were moderately susceptible to downy mildew.The enzyme activities of POD,SOD and PAL were greatly increased in resistant accessions after inoculation.PAL enzyme activities showed close correlation with disease rating before or after inoculation,which implicated that PAL enzyme activity might be used to estimate the resistance to downy mildew.POD isozyme electrophoresis showed that the number and intensity for the bands of resistant lines were significantly increased more than those of susceptible lines after inoculation.
