Ethylene production by Sclerotinia sclerotiorum and influence of exogenously applied hormone and its inhibitor aminoethoxyvinylglycine on white mold

Ethylene production by Sclerotinia sclerotiorum isolates reached a peak of 400 μl g^-1 h^-1 after 6 d incubation followed by a decline to 155 μl g^-1 h^-1 at day 10. The mean level of ethylene production at the peak by eleven isolates, was 373 μl g^-1 h^-1 and ranged from 267 to 588 μl g^-1 h^-1. The effect of ethephon (an ethylene releaser) and Aminoethoxyvinylglycine (AVG, an inhibitor of ethylene production) on interactions of S. sclerotiorum with host plants was investigated. AVG significantly inhibited fungal growth rate and decreased white mold disease severity on bean and cucumber plants at concentrations up to 300 μg ml^-1. Ethephon increased fungal growth rate at 400 μg ml^-1 (P=0.05). Above a threshold concentration of 250 μg ml^-1 ethephon, increasing ethephon concentration dramatically promoted lesion development. Ethephon increased bean and cucumber white mold disease severity on whole plants at 200-600 μg ml ^-1(P=0.05). A positive correlation was found between ethephon concentration and white mold disease severity.