Comportamento agronomico di quattro nuovi portinnesti ibridi pesco x mandorlo in un impianto ad alta densità in Sicilia

The present study was aimed to evaluate the agronomic behavior of different rootstocks, recently licensed by the Dipartimento di Coltura e Difesa delle Specie Legnose of the University of Pisa, and tested in a high density planting system (2220 trees/ha). Trials were carried out in an experimental orchard established by the Dipartimento di Colture Arboree of the University of Palermo and located in Sicily (Sciacca – Agrigento – 150 m a.s.l.). The observations were carried out on clonal rootstocks: I.S. 5/8 (Polluce); I.S. 5/19 (Castore); I.S. 5/23; I.S. 5/29 and GF 677 grafted at dormant bud with the low chill requirement cultivar “Tropic Snow”. The orchard was established in 2004, trees were spaced 4,5 m x 1 m a part and trained at “V” shape. In the three-year period 2006-2008 phenological, morphological, biometrical and ecophysiological traits were studied. Plants grafted onto clones of the I.S. series resulted less vigorous than those grafted onto GF 677. The highest levels of production/tree were observed in GF 677, however, in relation to the different development of the trunk cross section area (TCSA), differences statistically significant in terms of production efficiency among the various graft combinations were observed. The highest average fruit weight was observed in plants grafted onto I.S. 5/29, while the rootstock I.S. 5/23 induced a greater scalarity of maturation. Despite the young age of plants, some of the I.S. series rootstocks seemed to help to overcome some agronomic limitations produced by GF 677, with particular reference to vegetative growth and fruit quality.Observations carried out on the effects of water stress showed that plants grafted onto GF 677 attained values of water potential less negative and maximum assimilation rates higher than plant grafted onto I.S. series rootstocks. Among I.S. clones, more intense levels of water stress were detected in Castore and I.S. 5/23, while a more moderate stress was observed in I.S. 5/29 and Polluce; results also confirmed by measurements on the photosynthetic activity.