Abstract
‘Akituki’ (Pyrus pyrifolia Nakai.) is a very popular and profitable pear cultivar in China. However, its high susceptibility to cork spot disorder has limited its expansion of cultivated area. The mechanisms of cork spot disorder have been discussed extensively, focusing on Ca2+ deficiency, yet no consensus has been made. In this study, we applied nitrendipine (NI) as a Ca2+ uptake inhibitor to explore the role of calcium in cork spot disorder occurrence. Results showed that NI treatment on the fruit remarkably increased the incidence of cork spot disorder; alteration of mineral contents happened at the early developmental stage of the fruit, especially on the outer flesh and the peel of the fruit; and this gap was filled gradually along with the expansion of the fruit. Significant differences in the expression levels of Ca2+ transport-related genes were found in the inner flesh, outer flesh and peel during the fruit growth period. The observation of free Ca2+ localization indicated the intracellular imbalance of Ca2+ in the NI-treated fruit. In conclusion, NI treatment reduced the calcium content in the fruit at an early developmental stage, altered the related expression of genes and influenced the cellular Ca2+ balance in the fruit, which prompted the occurrence of cork spot disorder. Measures for the prevention and control of cork spot disorder should be taken at the early stage of the fruit development in the field.
Highlights
We explored the relationship between calcium deficiency and cork spotpresent disorder using we NI to inhibit the of calcium in the fruit of
Ca cork spot disorder using NI to inhibit the absorption of calcium in the fruit of ‘Akituki,’
NI (Yuanye Biology, Shanghai, China) was dissolved in lanolin at the concentration of 0.2 mg/mL and homogeneously smeared on the fruit pedicels at 47 days after full bloom (DAFB), and solvent lanolin was used as control to smear on the fruit pedicel
Summary
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]. ‘Akituki’ is very susceptible to cork spot disorder [1], which has caused great economic loss in pear industry and has become a major obstacle to the continuing expansion of the cultivated area [1]. The mechanisms of cork spot disorder remain poorly understood; the management techniques to prevent this disorder are often inadequate
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