Alleviation of Vascular Bundle Browning in the Japanese Pear ‘Rinka’ by Preharvest Application of Ethephon

Abstract

Vascular bundle browning (VBB) of the flesh tissue of the Japanese pear ‘Rinka’ was observed when the fruit was stored at 4°C. This symptom was not observed in mature fruit at harvest nor after storage at 25°C for one week following harvest; however, VBB frequently appeared when fruit was stored at 4°C. More than 50% of the fruit had the VBB symptom after storage at 4°C for one week. Further incidences and degrees of the symptoms were observed when the fruit was stored at 4°C for longer periods. No other cultivars have shown this kind of disorder induced by a short period of cold storage, indicating that VBB is a novel type of chilling injury (CI) in pears. The application of a 100 ppm ethephon (2-chloroethylphosphonic acid) solution at approximately 100 days after full flowering (DAF) significantly reduced the occurrence of VBB. Ethephon advances maturation and leads to an early harvest, causing a significant reduction in VBB, but ethephon-treated fruit harvested at the same harvest time as untreated fruit showed a reduced incidence of VBB. Treatment with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, increased the VBB development during cold storage and a subsequent storage period at 25°C. These results suggest that ethylene has a positive effect on alleviating the VBB development in the Japanese pear ‘Rinka’.