EFFECT OF GRAFTING ON 2-METHYL-1-BUTYL ACETATE BIOSYNTHESIS IN ORIENTAL SWEET MELON (CUCUMIS MELO VAR. MAKUWA MAKINO) PEEL AND FLESH TISSUES
The biosynthesis of 2-methyl-1-butyl acetate proceeds from the amino acids, which is one of major branched-chain esters in oriental sweet melon. In this study, effects of grafting on 2-methyl-1-butyl acetate content and its biosynthesis pathway in oriental sweet melon were investigated with squash Shengzhen1 as rootstock. The 2-methyl-1-butyl acetate content was decreased by grafting in peel of oriental sweet melon, while increased in flesh at 30 days after anthesis. The content was significantly higher in peel than in flesh. Using peel and flesh tissues discs incubated in the presence of various precursors of different stages of the 2-methyl-1-butyl acetate synthetic pathway, the esterification of 2-methylbutanol, as well as the conversion of L-isoleucine to 2-methylbutanal and 2-methylbutanol in peel tissue were reduced by grafting, while the transformation from 2-methylbutanal into ester was unaffected. In flesh tissue, conversion of aldehyde, alcohol and L-isoleucine to 2-methyl-1-butyl acetate were all unaffected by grafting. This indicated that effects of grafting on biosynthesis mechanism in peel and flesh of oriental sweet melon were different. Simultaneously, grafting significantly decreased the enzyme activities of alcohol acyltransferase (AAT) and alcohol dehydrogenase (ADH) in peel and flesh tissues, which were higher in peel than in flesh. These findings indicated that the biosynthesis of 2-methyl-1-butyl acetate was affected by grafting mainly through the aroma volatile-related enzymes, including ADH and AAT, and conversion of amino acid to its corresponding branched-chain aldehyde and branched-chain alcohol, after that, to its corresponding ester in oriental sweet melons.
Hong-yan Qi, , Xiao-chuan Guan, , Yan Li, , Jin-ran Li, and Peng Jing, (2012). EFFECT OF GRAFTING ON 2-METHYL-1-BUTYL ACETATE BIOSYNTHESIS IN ORIENTAL SWEET MELON (CUCUMIS MELO VAR. MAKUWA MAKINO) PEEL AND FLESH TISSUES. Acta Hortic. 932, 271-277
grafting, alcohol dehydrogenase, alcohol acyltransferase