Preliminary evaluation of six Prunus rootstocks for peach in Italy

In Italy, the evaluation of rootstocks is supported by the Ministry of Agriculture and carried out in a network of trials along the Country. This study evaluated growth and yield performance of ‘Big Top’ nectarine and ‘Rome Star’ peach grafted on six rootstocks of different origin and vigor, namely GF677 (the most widespread in Italy), Garnem, Adesoto, RootPac®20, RootPac®40, and RootPac®90, in three different locations, Castelvetrano (Sicily), Forlì and Cesena (Emilia-Romagna). Yield, number of fruits, trunk cross-sectional area (TCSA), average fruit weight, flesh firmness, soluble solids content (SSC) and titratable acidity (TA) were determined at the third leaf (2015). In all sites, trees on GF677, Garnem, and RootPac®90 were the most vigorous, and trees on RootPac®40 (-40 to -51% of GF677 TCSA) and RootPac®20 (-48 to -60% of GF677 TCSA) the least vigorous. In Castelvetrano, trees on Adesoto and RootPac®20 matured fruit slightly earlier than trees on other rootstocks; trees on RootPac®40 were the most productive and yield efficient, followed closely by trees on Adesoto and RootPac®20, the latter exhibiting the highest SSC; yield differences were mainly due to differences in fruit weight rather than in fruit number. In Emilia-Romagna, yield was directly related to tree vigor, with trees on GF677 being the most productive. In this case, yield differences were mainly due to differences in the number of fruits. Yield efficiency was also higher in the most vigorous trees, with the only exception of RootPac®40, which combined a size-controlling effect with high yield efficiency and large fruit size. While GF677 confirmed a good yield performance, RootPac®40 seems promising for high-density plantings, as it associates high yield efficiency and reduced tree vigor.