A new Romanian Prunus domestica L. cultivar exhibiting high tolerance to natural infections to plum pox virus

This study evaluates the long-term behaviour of plum pox virus (PPV) infections within a genetically diverse plum orchard established in 1998 at the Fruit Research & Development Station Bistrița, Romania. The experimental plot comprises six hybrids, including the recently homologated ‘BN 4/1’ hybrid as ‘Zandra’ cultivar, and ten plum cultivars, with a total of 534 trees. Over 20 years (2003–2024), the temporal progression of PPV was monitored through visual inspections and serological tests (DAS-ELISA), revealing a consistent increase in virus incidence from 11.4% to 58.4%. Significant differences in PPV susceptibility were found among the genotypes. Highly susceptible genotypes (‘Diana’, ‘Geta’, ‘HAS 2G’, ‘Tuleu timpuriu’) exhibited infection rates exceeding 83%, while susceptible genotypes showed incidence levels over 60%. Tolerant cultivars such as ‘Stanley’ and ‘Čačanska Najbolja’, displayed moderate infection rates ranging from 40% to 60%. Remarkably, the hybrid ‘BN 4/1’ (‘Zandra’ cultivar) displayed the lowest PPV incidence at just 20%. Infected ‘Zandra’ trees exhibited localized symptoms, confined to one or two shoots per tree, with no evidence of systemic infection throughout the canopy. Detailed serological analyses confirmed the restricted viral movement in symptomatic ‘Zandra’ trees. Moreover, 80% of the trees remained uninfected despite long-term exposure to high inoculum pressure from surrounding infected trees, indicating a high level of tolerance to natural PPV infection. In addition to its viral tolerance, ‘Zandra’ exhibits superior organoleptic qualities, highlighting its potential as a valuable cultivar for sustainable plum production systems.