Phenolic contents and L-phenylalanine ammonia-lyase activity in peach fruit as affected by rootstocks

Phenolic contents in ripe fruit of six peach cultivars (Prunus persica Bats ch) grafted on P. persica ('Juseito' or 'Nagano-yaseito'), P. tomentosa (Na nking cherry) or P. japonica (Japanese bush cherry) rootstocks were evaluat ed. In all cultivars, fruit from trees grafted on Nanking cherry contained more total phenolic compounds than did those on 'Juseito' or 'Nagano-yaseit o', However, there were wide variations in total phenolic contents among th e cultivars; being low in 'Saotome', 'Yahata-hakuho', and 'Chikuma' but hig h in 'Sanyo-suimitsu', 'Setouchi-hakuto', and 'Golden Peach'. 'Sanyo-suimit su'/Japanese bush cherry combination had the highest total phenolic content , compared with the same cultivar grafted on Nanking cherry or 'Juseito'. T he level of higher molecular fraction of phenolic compounds was positively correlated with the total phenolic concentration. In addition, phenolic con tents, L-phenylalanine ammonia-lyase (PAL) activity and L-phenylalanine con tent in fruit of 'Sanyo-suimitsu' trees, grafted on 'Juseito' and Nanking c herry, were investigated during fruit growth. Although the seasonal trends of total and higher molecular phenolic contents in 'Sanyo-suimitsu' grafted on 'Juseito' and Nanking cherry were similar, they were higher in Nanking cherry throughout fruit development, especially during Stage 2. PAL activit y was high during Stage 1 and the first half of Stage 2, followed by a decr ease to undetectable levels by harvest. During the early growth stages, hig her PAL activity and lower L-phenylaIanine content were found in fruit from trees on Nanking cherry than 'Juseito'.