FROST INJURY IN BUDS AND WOOD OF SEVERAL PEACH AND NECTARINE CULTIVARS

Frost incidence during winter 2008 in Mashhad (northeast of Iran) caused different ranges of injuries to reproductive and vegetative organs (buds, bark and wood) of stone fruit trees, chiefly, peach. In this study the rate of relative resistance to intense cold temperatures was assessed in nine peach and nectarine (Prunus persica L.) cultivars during 2008. Minimum subzero temperature registered on the 13^th of January 2008 was about minus 22°C. The electrolyte leakage of tree organs such as reproductive and vegetative buds and annual wood was measured in peach (‘J.H. Hale’, ‘Elberta’, ‘Redhaven’, ‘Mashhad Sorkhosephid’ and ‘Mashhad Ghermez’) and nectarine (‘Independence’, ‘Qiuta’, ‘Nectared 6’ and ‘Stargold’) cultivars. Among studied cultivars, ‘Mashhad Sorkhosephid’ and ‘Mashhad Ghermez’ cultivars (which are native from Iran), had the most resistance in reproductive buds. Also, visual observations on nectarine reproductive buds showed that ‘Independence’ cultivar was the most sensitive cultivar. Regarding vegetative buds, ‘Mashhad Sorkhosephid’ and ‘Redhaven’ were considered resistant peach cultivars, while ‘Nectared 6’ and ‘Qiuta’ were so among nectarine cultivars. Electrolyte leakage in annual wood from peach cultivars was more evident than in nectarine cultivars. But, ‘Nectared 6’ cultivar did not have any difference compared to peach cultivars. Differences in electrolyte leakage between peach cultivars were not significant. Finally, the carbohydrates measurements on reproductive buds and annual wood, showed a direct correlation between increased carbohydrate concentration and increased resistance.