PHENOLIC-COMPOUNDS IN PEANUT SEEDS - ENHANCED ELICITATION BY CHITOSANAND EFFECTS ON GROWTH AND AFLATOXIN B-1 PRODUCTION BY ASPERGILLUS-FLAVUS

Effects of chitosan and Aspergillus flavus to enhance elicitation of p henolic compounds in viable peanut seeds were conducted at two water a ctivity levels. In vitro effects of phenolic acids on A. flavus growth and aflatoxin B-1 production were also studied. Chitosan enhanced eli citation of free phenolic compounds (FPC) at Aw. 85 and .95 levels. A. flavus treatment initially decreased and subsequently increased FPC c ontent, but bound phenolic compounds (BPC) decreased during incubation . Chitosan + A. flavus treatments caused an increase in FPC that reach ed a plateau between 24-48 h at Aw .85 while BPC levels increased over the same time period at both Aw levels. The major free and bound phen olic acids detected were p-coumaric and ferulic acids and an unknown p henol that eluted at a retention time of 22 min. Generally, chitosan t reatment significantly enhanced elicitation of free ferulic and p-coum aric acids and bound p-coumaric acid at Aw .95. Free unknown phenolic and bound ferulic acids at Aw .85 were enhanced by chitosan. A. flavus treatment caused significant induction of bound p-coumaric and feruli c acids and free unknown phenol at Aw .85. Chitosan + A. flavus treatm ent measure to reduce or eliminate pre-harvest contamination by A. fla vus and aflatoxins contributes to sustainable agriculture, especially to developing countries. The enhanced elicitation of preformed phenoli c compounds by chitosan may provide seed tissues an additive or synerg istic effect in controlling aflatoxin-producing fungi and preventing a flatoxin contamination. Further, such investigation will help elucidat e the biochemical basis of elicitor-host interaction that contribute t o defensive responses of host tissues. Identification of biochemical f actors in induced resistance involves a refinement in the separation a nd identification of induced phenolic compounds. Methodologies such as spectrophotometric assay or reverse-phase high performance liquid chr omatography (HPLC) may be used to evaluate phenolic compound induction by these elicitors. Tn addition, these compounds can be tested on the ir effects on A. flavus mycelial growth and subsequent aflatoxin produ ction in vitro. Hence, a study on the possible role of phenols on the natural resistance of peanuts to A. flavus invasion was conducted with the following objectives: 1) to quantitate changes in free and bound phenolic compounds influenced by chitosan, A. flavus, and water activi ty (Aw) levels by Folin-Ciocalteu assay; 2) to separate, identify, and quantitate free and bound phenolic acids influenced by elicitors and Aw levels; and 3) to determine the effects of phenolic acids in liquid cultures at different concentrations on mycelial growth and aflatoxin B-1 production by A. flavus.