Field reactions of plum cultivars to the shot-hole disease in southern Italy

The reactions to shot-hole disease (Stigmina carpophila) of nine plum cultivars and seed-propagated myrobalan trees were evaluated during three years in three commercial orchards located at Nova Siri, Matera, Italy. In July 2006, May 2007, June 2007 and June 2008, shot-hole severity and twig defoliation were assessed. Pathogen pressure was higher in 2007 and 2008 than in 2006. In the three years of study, cultivar Golden Plumza was the most susceptible to the shot-hole measured by leaf severity, however it showed variable defoliation percentages in different years. The seed-propagated myrobalan trees were the most resistant, although they showed a slight degree of defoliation in 2007 and 2008. Intermediate reactions to the disease occurred in cultivars Angeleno, Autumn Giant, Fortune, Green Sun, October Sun, Santa Rosa, Sorriso di Primavera and T.C. Sun. A significant correlation between shot-hole leaf severity and twig defoliation was detected. To our knowledge, this is the first report on screening for resistance of plum cultivars to shot-hole disease.

Research Highlights►This is the first report worldwide describing the occurrence of levels of resistance/susceptibility in plum cultivars commonly grown in Southern Italy and in other parts of the world. ► Twelve plum cultivars were observed through three years: Golden Plumza, Angeleno, Autumn Giant, Fortune, Green Sun, October Sun, Santa Rosa, Sorriso di Primavera, T.C. Sun, and Myrobalan. Golden Plumza was the most susceptible, while Myrobalan was the most resistant. ► Shot-hole disease severity up to 60% and twig defoliation up to 50%were observed. Severity and twig defoliation were significantly correlated.