Prevention of peel splitting of loquat

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1. It was observed by light and scanning electron microscopy that for both 'Mogi' and 'Nagasaki-Wase', fruits from Amami Oshima Island which are prone to peel splitting, had the larger cortex cells than those from Tarumizu which scarcely show splitting. Fruits from Oshima also continued transvese growth after cross growth ceased. Splitting occurred only longitudinally and only at peel, not extending to cortex area. It was observerd that 4-6 layrs of cells in the peel split by an increase of turgor pressure of inside cortex cells.2. Strength of resistance to pulling of peel was considerably weaker in the fruits from Oshima island which are more prone to splitting. Split fruit showed much weaker strength cross-wise compared to that of longitudinal direction.3. Split fruits seemed to be more advanced stage of ripening as shown by higher coloration and brix and lower acidity.4. Survey of growers' orchards revealed that less splitting occurred in the orchards of which cultural practices were better in terms of fertilization and soil management, drainage practice and pest and desease management. Improvement of soil physical and chemical properties tended to decrease the occurrence and severity of splitting. Trees under plastic roof showed less occurrence of splitting.5. These reults strongly suggest that rapid increase of absorption of water from roots during fruit maturation periods resulted in rapid increase in the size of cortex cells and the turgor pressure of these cells also increased, which in turn caused peel splitting if the peel strength was not strong enough to resist the pressure. Application of calcium which is thought to strengthen the peel, and growth regulators to control fruit growth, failed to control the occurrence of splitting. Further research is needed to find out better soil water management, selection of cultivars, the peel of which is stronger and resistant to pulling force, and proper methods of judging ripening strage.