The changes in L-phenylalanine ammonia-lyase (PAL) activity were investigated during berry ripening in relation to the coloration of 3 grape cultivars;‘Muscat of Alexandria’(white grapes), ‘Kyoho’(purple grapes) and‘Super Hamburg’(black grapes).
In all cultivars, higher PAL activity in the skin was observed at the earlier stages of berry development, followed by a rapid decline toward veraison to a considerably lower level.
In‘Kyoho’and‘Super Hamburg’, PAL activities gradually increased again with the beginning of berry coloration.‘Super Hamburg’had more anthocyanin content and higher PAL activity than‘Kyoho’.
The sugar content in the skin rose rapidly in the ripening period in all cultivars, preceding the increases in both PAL activity and anthocyanin content in‘Kyoho’ and‘Super Hamburg’grapes.
Free-abscisic acid (ABA), also, rapidly accumulated in the early stages of ripening in each cultivar and maintained a considerably higher level. However, there was no much difference in the maximum ABA content among 3 cultivars.