ROOTSTOCK INFLUENCES THE FRUIT MINERAL, SUGAR AND ORGANIC-ACID CONTENT OF A VERY EARLY-RIPENING PEACH CULTIVAR

The influence of rootstocks differing in genetic origin and agronomic performance on the commercial characteristics and chemical composition of the fruit was investigated on the low-chill, very early ripening ( fruit development period = 100 d) cv. Maravilha (Prunus persica (L.) B atsch) trained to a Y in a high density planting (2,500 trees per ha). Of the rootstocks tested, five belonged to P. persica (Harrow Blood, Ps B2, Ps C14, Rubira and Rutgers Red Leaf), three were hybrids of P. persica x P. dulcis (GF677, Hansen 2168 and Hansen 536) and two were c omplex hybrids of P. cerasifera (Mr S 2/5, M x P). The more vigorous g raft combinations gave significantly higher yields. Rootstocks signifi cantly influenced mineral content (N, K, Fe and Zn), sugars (sucrose a nd fructose) and organic acids (succinic) of the fruit, although these differences are not so important as to affect the commercial value of the fruit and to direct the choice towards one rootstock rather than another. Neither fruit weight, skin overcolour, shape not refractomete r value (degrees Brix) were affected by rootstocks. The short fruit de velopment period together with the heavy pruning required for high den sity plantings presumably minimized differences in fruit quality betwe en the graft combinations.