Inhibitory effect of salicylhydroxamic acid on theobroxide-induced potato tuber formation

Theobroxide is a natural compound from the fungus Lasiodiplodia theobromae and has a significantly inductive effect on potato tuber formation in vitro and in vivo. Considering the similar roles of theobroxide and jasmonic acid (JA) in tuberization, we investigated the influence of theobroxide on endogenous levels of JA and its analogue tuberonic acid (TA), as well as on lipoxygenase (LOX) activity in potato leaves. Salicylhydroxamic acid (SHAM), the JA biosynthesis inhibitor, was used to test its effect on theobroxide-induced tuber formation, on endogenous JA and TA levels, and on LOX activity. The results showed that theobroxide increased endogenous levels of JA and TA, and LOX activity. However, this inductive effect was inhibited by SHAM, associated with a reduction in tuber formation. These results suggest that the inductive effect of theobroxide on tuber formation is probably achieved by stimulating JA and TA synthesis.