Disease development of several fungi on Arabidopsis can be reduced by treatment with methyl jasmonate

Pretreatment of Arabidopsis plants with gaseous methyl jasmonate (MeJA) caused efficient reduction of disease development by either the necrotrophic fungi Alternaria brassicicola, Botrytis cinerea or Plectosphaerella cucumerina. Protection by gaseous MeJA was also observed on the salicylic acid (SA)-degrading transformant NahG and the ethylene non-responsive mutant ein2-1, but not on the jasmonate non-responsive mutant coi1-1. In general, protection conferred by spraying with a MeJA solution was much lower compared to exposure to gaseous MeJA. 2,6-Dichloroisonicotinic acid (INA), a compound that activates SA- but not JA-dependent defence responses, failed to cause protection against either A. brassicicola or B. cinerea. On the other hand, INA treatment was efficient in reducing disease development by P. cucumerina.