Investigation and analysis of relationship between mineral elements alteration and cork spot physiological disorder of Chinese pear ‘Chili’ (Pyrus bretschneideri Rehd.)

Nitrendipine-Treatment Increases Cork Spot Disorder Incidence in Pear ‘Akituki’ (Pyrus pyrifolia Nakai.) by Altering Calcium Distribution Inside the Fruit

“…In our study, even though NI treatment did not influence the fruit attributes, it apparently increased the incidence of cork spot disorder in ‘Akituki’ pears by approximately 12% ( Figure 1 ), indicating that NI altered the Ca distribution inside the fruit, which was confirmed by the observation of free Ca 2+ localization ( Figure 7 ). The cork spot distributed close to the calyx-end and outer flesh of fruit ( Figure 2 ), which was consistent with other studies of cork spot in pears [ 1 , 2 ] and bitter pits in apples [ 18 ]. This also suggests the abnormal distribution of calcium inside the fruit.…”

“…The observation of free Ca 2+ distribution showed intracellular imbalance in the NI-treated healthy fruit at 107 and 127 DAFB ( Figure 7 ), indicating that the intracellular imbalance of Ca 2+ happened prior to the formation of cork spots, which was accordant with the analysis of mineral element content above ( Figure 3 ). Free Ca 2+ was found to be enriched in the cell wall in the cork spotted pear tissues, but the total Ca content was even higher in the cork spotted tissues [ 1 , 2 ]. In other pear Ca 2+ deficiency-related disorders, such as superficial scald and hard end [ 24 , 25 ], the disordered fruits also had higher levels of free Ca 2+ and Ca 2+ mainly concentrated in the cell wall; and no relationship between Ca content and cork spot-like physiological disorder was found in apples [ 13 ].…”

“…The fruit quality was evaluated at harvest time by measuring the single fruit weight, vertical and horizontal length, total soluble solids, titratable acidity and fruit firmness. All the operations and calculation referred to Cui et al [ 2 ].…”

“…Cork spot is a physiological disorder of fruit which occurs most in pears and apples. The typical characteristics of this disorder in pears are brown desiccated flesh or grayish corky lesions beneath the fruit skin [ 1 ], and a bumpy fruit surface in some cultivars [ 2 ]. This disorder in pears initiates in the early developmental stage of the fruit and continues to harvest time, depending on cultivar specificity [ 3 ].…”

“…However, a recent study found that spraying a calcium solution, a boron solution or a mixture solution of calcium and boron during the growing period could not reduce the incidence of cork spot-like physiological disorder in apples, and there was no correlation between the incidence of cork spot-like physiological disorder and Ca/B content in fruit or leaves [ 13 ]. Interestingly, higher levels of total calcium were found in cork spotted ‘Akituki’ [ 1 ] and ‘Chili’ [ 2 ] pear fruit than healthy fruit. These findings suggested that calcium plays an important role in cork spot disorder, but its mechanism is unclear and needs further exploration.…”