COMPARATIVE TRIALS OF SEVERAL CLONAL PLUMS, PEACH SEEDLINGS AND HYBRIDS TESTED AS PEACH ROOTSTOCKS
Seventeen rootstocks were compared: Prunus persica selected lines ('Rutgers Red Leaf', 'Veteran', 'G.F. 763', 'P.S.A6', 'P.S.C10', 'P.S.C12', 'P.S.C.14'), some interspecific hybrids of Prunus Besseyi ('South Dakota Ruby', 'Yuksa', 'Sapa', 'S. Anthony, 'Manson', '248', '299'), other Prunus hybrids ('G.F. 1869', 'Mr.S.2/5') and a Prunus insititia clone ('G.F. 655/2').
Maiden trees were planted in February 1978 at 4.25 x 2 m and trained to free spindle. Data recorded over the first six years showed that higher vigour and yield were induced by all three plum rootstocks and the hybrid '299' in comparison with the peach rootstocks. Prunus Besseyi hybrids generally reduced the size and the yield of the trees too much. Sometimes clear symptoms of suffering and dead trees were observed, particularly in '248', 'South Dakota Ruby', 'S. Anthony' and 'Yuksa'.
Average fruit weight was not strictly related to the cumulative yield per tree, even though 'Mr.S.2/5' gave the best fruit size, and the Prunus Besseyi hybrids the smallest.
The highest values of cropping efficiency (expressed as a ratio between cumulative yield and canopy area) were recorded with 'Rutgers Red Leaf', 'P.S.A6', 'G.F.655/2' and 'Mr.S.2/5' rootstocks.
In view of the economically viable life of the orchard, the plum clone 'Mr.S.2/5', selected by Prof. Scaramuzzi, seems to be the most suitable rootstocks for the aforesaid pedoclimatic conditions, considering its high vigour and yield, its good compatibility with the peach and its very low suckering ability.