Crude Toxin Isolated from Verturia noshicola on Physiological Charateristics of in vitro Leaves of Susceptible and Resistant Pear

The different disease resistant pear cultivars were inoculated with crude toxin isolated from Verturia noshicola.The result showed that the peroxidase(POD) and phenylalanine ammonialyase(PAL) activities,the malondialdehyde(MDA) content and electrical conductivity of susceptible and resistant pear cultivars in vitro leaves displayed ascending trend.Meanwhile,they had one or two peak value.The POD and PAL activities of resistant cultivars in vitro leaves were higher than that of susceptible cultivar,and resistant cultivars in vitro leaves showed a lower increasing rate than susceptible cultivar in MDA content and relative conductance.In addition,chlorophyll and carotenoid content in leaves decreased.There were more injured degree in susceptible cultivar than in resistant cultivar.To sum up,the variation of POD and PAL activities had positive correlation with disease resistant ability,and the variation of MDA content and relative conductance had negative correlation with disease resistant ability in different cultivars.This proved that the latter have a better ability in pear scab resistance.