Causes of occurrence and prevention of russet on loquat fruit

WANG Li; HU You-li; HUANG Xu-ming; WANG Hui-cong

Abstract：Three loquat cultivars, Zaozhong No.6, Changhong No.3 and Jiefangzhong were used as materials to study the occurrence and possible causes of fruit russeting so as to prevent this physiological disorder. Different loquat cultivars displayed different susceptibility to russeting. Zaozhong No.6 showed the highest incidence of russet, followed in order by Jiefangzhong and Changhong No. 3. Russet susceptibility was found to have a close relationship with the structure of the cuticle layer of fruit skin. Under florescent microscope, Changhong No. 3 had the thickest cuticle and cell walls with strongest and uniform auto-fluorescence, while Zaozhong No.6 had the thinnest cuticle and the weakest cell wall auto-fluorescence. Russeting might be derived from micro-wounds formed on the skin under some adverse conditions. The micro-wounds lancinated with the expansion of the fruit pulp, and at the same time, some of the cells beneath the epidermis resumed cell division and phellogen developed. The outgrowth of suberized cells broke through the epidermis and formed the visible russet spots. Artificial removal of the skin hairs created such micro-wounds and induced severe russeting in cuhivar Jiefangzhong. Fruit bagging significantly reduced russet incidence and the effect was better if bagging was conducted earlier.