Postharvest quality of plums in response to the occurrence of leaf scald disease

Plum leaf scald (PLS) is considered the main barrier to expanding plum cultivation in Brazil. The disease causes water flow to be obstructed in the xylem of infected plants. Infected host plants produce fruit of lower quality; however, no information is available about the postharvest quality attributes in plum. Fruit from the 'Gulfblaze' and 'Reubennel' plant cultivars, both with and without PLS symptoms, were collected from commercial orchards. Bacterial presence was confirmed using a polymerase chain reaction, and the physicochemical, biochemical, and physiological properties were evaluated. Brown rot incidence was also determined during the ripening period. According to a molecular analysis, symptomatic plants used in the assay carried Xylella fastidiosa (which causes PLS), but healthy plants did not. Fruit collected from infected plants had a reduced diameter and weight in the 2015/2016 growing season. There was a greater reduction in pulp firmness and higher pectin methylesterase enzyme activity in fruit harvested from infected compared with healthy plum trees. The total soluble solids content was higher in fruit from 'Gulfblaze' and 'Reubennel' diseased compared with disease-free plants. A higher incidence of brown rot was observed in plants with leaf scald symptoms. The highest phenylalanine ammonia-lyase activity was observed in fruit from 'Gulfblaze' diseased plants. CO2 and ethylene production was higher in the infected than healthy plants, indicating that the presence of X. fastidiosa can accelerate fruit ripening mechanisms.