Effects of tree-spray of calcium agent, coating agent, GA₄₊₇ + BA and paper bagging on russet prevention and quality of ‘Gamhong’ apple fruits

This study was conducted to examine the effect of 0.4% of CaCl₂, 2H₂O, 1 mg·L^-1 of Calmodulin (CaM)-SH, 250-folds of coating agent (WE-36), 1,000-folds of GA₄₊₇+BA and 3 types of paper bagging treatments on russet incidence and fruit quality attributes of ‘Gamhong’ apple. The pattern of russet occurrence was slightly different for 4 years (from 2012 to 2015) in ‘Gamhong’ apple. The russet occurrence was lowest in GA₄₊₇+BA treatment at 20 days after full bloom (DAFB), compared with other treatments. The GA₄₊₇+BA treatment increased fruit weight at 20 DAFB, while the other fruit quality attributes were not influenced. The russet occurrence was lower not only in a single bag application than in untreated ones but also in yellow bagging and discolored bagging applications than in a white bagging application. The russet occurrence in a bagging application was lower at 20 DAFB than at 30 and 40 DAFB, while fruit quality attributes were not affected by bagging applications. The russet incidence was lower in GA₄₊₇+BA twice treatments at 20 and 30 DAFB, and calcium coated bag at 30 DAFB after GA₄₊₇+BA treatment at 20 DAFB than in untreated fruit. The rate of russet incidence was lowest at equator region in GA₄₊₇+BA treatment, compared with the other fruit regions. Overall, the results suggest that one and/or two applications of GA₄₊₇+BA (1,000-folds) treatment at 20 DAFB should reduce the risk of russet incidence in ‘Gamhong’ fruit.