Effects of methyl jasmonate on phytoalexin production and aflatoxin control in the developing cotton boll

Artificially wounded 22-27-day old developing cotton bolls were initially inoculated with, (1) a cell-free, hot water-soluble mycelial extract (CFME) of an atoxigenic strain of Aspergillus flavus or with, (2) chitosan lactate (CHL) or with, (3) CFME or CHL and then exposed to gaseous methyl jasmonate (MJ) or, (4) exposed to MJ alone. Five days after these treatments, the induction of the sesquiterpenoid naphthol phytoalexins, 2,7-dihydroxycadalene (DHC) and 2-hydroxy-7-methoxy cadalene (HMC), lacinilene C, lacinilene C7-methyl ether, and the coumarin phytoalexin-scopoletin was determined on the excised carpel discs surrounding the inoculated surfaces of the developing cotton bolls. The results indicated a two- or three-fold increase in the production of the phytoalexins when gaseous MJ was added in combination to the CFME or the CHL elicitors. In a separate experiment, 22-27-day old developing cotton bolls were pretreated for a five-day period as described above and then a spore suspension of a toxigenic strain of A. flavus was introduced into a second artificial wound which was produced adjacent to the first wound. On boll maturity, the cottonseeds located within the locules underlying the areas that were pretreated with both elicitors and MJ then later infected with toxigenic A. flavus exhibited a 75-95% aflatoxin B-1 inhibition. These results suggest a host defense mechanism which may be triggered by both elicitors and MJ. Published by Elsevier Science Ltd.