Screening of antidotes to toxin produced by Fusarium oxysporum f.sp.cubense race 4 and their effects on defensive enzyme activities of banana

Two best antidotes,zinc sulfate and Jinggangmycin,to toxin of Fusarium oxysporum f.sp.cubense race 4(Foc 4) were screened out from 15 candidates.It was found that the inhibitory rates of zinc sulfate and Jinggangmycin at concentration of 2 g·L-1 to Foc.toxin were 76.67% and 71.33%,respectively;while those at concentration of 5 g·L-1 were 90.33% and 80.00%,respectively.The effects of toxin-zinc sulfate and toxin-Jinggangmycin treatment systems at concentrations of 2 g·L-1 and 5 g·L-1 on the activities of five defensive enzymes(PAL,POD,PPO,SOD and CAT) in banana plantlets were explored,the results showed that the peaks of PAL and PPO activities in banana plantlets appeared earlier(PAL 36 h,PPO 36 h and 48 h) in the treatment systems than in toxin alone treatment(PAL 48 h,PPO 60 h);the peaks of SOD and CAT activities were basically consistent with those of control;and the peaks of POD activity were more complicated.Generally,the overall activities of defensive enzymes were higher in the treatment systems than in toxin alone treatment and sterile water control.The overall activities of PAL and SOD in toxin-zinc sulfate treatment system were higher than those in toxin-Jinggangmycin treatment system,whereas the activities of other three defensive enzymes of the latter were higher than those of the former.