Assessment of eleven South African peach cultivars for susceptibility to brown rot and blue mould

Abstract

Species of Penicillium (blue mould) and Monilinia (brown rot) are major causes of postharvest loss of stone fruit. Breeding for resistance to these pathogens is a sustainable option that could reduce over reliance on postharvest chemical interventions to control the diseases. This study was aimed at selecting peach cultivars that are resistant to blue mould and brown rot pathogens through in vivo assays against the causative agents. Red and yellow skinned peach cultivars were artificially infected with Monilinia laxa and Penicillium expansum whilst the same cultivars were also assessed as naturally infected fruit. Fruit were stored at 0 °C for 14 and 21 days, and thereafter kept at 15 °C for 3 days to simulate market shelf condition. Physicochemical traits, such as fruit pH, antioxidant activity, total anthocyanins, and total phenols were measured at harvest, and after 14 days and 21 days of storage. The blue mould pathogen was more virulent than the brown rot pathogen in the fruit. The red cultivars showed less brown rot incidence (20%–35%) compared to the yellow cultivars (35%–65%). Artificial infections stimulated a higher biochemical activity in the fruit compared to natural infections. In general peach cultivars with high contents of antioxidant compounds had lower pathogen incidence. ‘Temptation’, (a red cultivar) showed highest resistance compared to the other peach cultivars used in this experiment and this was correlated to the high phenylalanine lyase activity, phenolic compounds, and concentrations of chlorogenic, caffeic acid and anthocyanin exhibited by the cultivar. Breeders can use these tests as indicative for blue and brown mould resistance.