Influence of Monosporascus root rot and vine decline disease on the amino acid metabolism of watermelon fruit

Abstract

Monosporascus root rot and vine decline (MRRVD) is a severe disease of watermelon, melon, and other cucurbits, characterized by root necrosis and sudden wilting at the later stage of fruit maturation. The present study examined the effects of MRRVD on the metabolism in watermelon fruits. The MRRVD-affected watermelon fruits had significantly lower lycopene and total solid contents, but polyphenols content and total antioxidant activities were comparable with the controls, suggesting that MRRVD inhibited the ripening processes but maintained defensive processes in the fruits. The MRRVD fruits showed a lower level of calcium than the controls, while the contents of other major nutrition minerals were not significantly altered. The MRRVD fruits had a lower content of total amino acids, and their composition was characterized by an increase in the percentage fractions for several amino acids including citrulline, which may reflect the physiological response to the MRRVD-related water deficit condition.