EFFECT OF AMINOCYCLOPROPANE-1-CARBOXYLIC ACID OXIDASE ANTISENSE GENE ON THE FORMATION OF VOLATILE ESTERS IN CANTALOUPE CHARENTAIS MELON (CVVEDRANDAIS)

The role of ethylene on volatile formation associated with ripening wa s investigated on melon hybrids transformed with an aminocyclopropane- l-carboxylic acid oxidase antisense gene. The headspace of four antise nse hybrid fruits was analyzed by GC/MS and compared to that of nontra nsformed hybrid fruit. The major volatiles extracted from nontransform ed hybrids were esters, mostly acetates. However, the most potent odor ants were ethyl esters, such as ethyl butanoate, and branched-chain es ters, such as ethyl 2-methylpropanoate and ethyl 2-methylbutanoate. In antisense hybrids, the total volatiles were 60-85% lower than that of the nontransformed hybrids. Volatiles with low odor values, such as e thyl, 2-methylpropyl and 2-methylbutyl acetates, were half to a fifth lower than in nontransformed hybrids, whereas potent odorants, such as ethyl 2-methylpropanoate and ethyl 2-methylbutanoate, were <3% that o f nontransformed hybrids. Examination of the biosynthetic pathways of volatile esters derived from amino acids demonstrates that ethylene st imulated preferentially the synthesis of the most potent odorants.