Prevention of New Cork Spot-like Physiological Disorder in ‘Kurenainoyume’ Apples by Pre-harvest Fruit Bagging

Abstract

'Kurenainoyume' is a new red-fleshed apple cultivar with a gradually increasing cultivation area. However, cork spot-like physiological disorder (CSPD) of the apple skin has become a serious problem over the years. Therefore, the development of strategies to reduce and prevent CSPD is strongly desired by farmers. To this end, we investigated the effectiveness of i) spraying calcium (Ca), boron (B), or both on the tree and ii) preharvest fruit bagging. Ca or B solutions or both did not decrease CSPD incidence. Furthermore, no relationship was detected between CSPD and the Ca/B content of fruit and leaves, demonstrating that the occurrence of CSPD might not be due to a deficiency in these elements. Pre-harvest fruit bagging reduced the development of CSPD depending on the light permeability of the paper bags used. Moreover, CSPD development was positively correlated with sunshine duration. Therefore, to prevent CSPD, fruit should be covered with light-impermeable paper bags at least from mid-July to late-September because the fruit covered for a shorter period developed CSPD. Thus, we propose that pre-harvest fruit bagging with light impermeable paper could be a useful and practical strategy to reduce or prevent CSPD in 'Kurenainoyume'.

Sunlight Differentially Affects the Fruit Skin, Flesh, and Core Coloration of the Type 2 Red-fleshed Apple ‘Kurenainoyume’: Optimization of Fruit Bagging Treatment

“…The 2-layer bag completely prevented a light permeability from 280-750 nm (Matsumoto et al, 2018c). Half of the paper bags were removed at 96 DAFB (August 22) (bag-removal treatment), and the remaining half were covered continuously until harvest at 146 DAFB (October 11) (continuous-bagging treatment).…”

“…However, as mentioned earlier, fruit bagging treatment using a 2-layer bag is necessary to improve/prevent CSPD in 'Kurenainoyume' because it would not be possible for growers to produce apples of commercial value without the use of fruit bagging treatment (Matsumoto et al, 2018c). In contrast, since both 1-layer white and red bagging treatments developed some extent of CSPD, these two bags are not practically used for commercial cultivation (Matsumoto et al, 2018c). Therefore, the optimal bagging duration with a 2-layer bag has not yet been established even for skin coloration in 'Kurenainoyume'.…”

“…Different types of paper bags with different degrees of light permeability have been developed for use in fruit bagging treatments (Matsumoto et al, 2018c), and each bag can differentially affect the external appearance, such as red coloration, depending on the fruit. To elucidate the effects of different light permeabilities on the skin, core, and flesh coloration, bag-removal and continuous-bagging treatments were employed for both type 1 and type 2 apples using three different types of paper bags, i.e., a 2-layer bag, a 1-layer white bag, or a 1-layer red bag.…”

“…However, along with cultivation expansion, cork spot like physiological disorder (CSPD) in the skin has become a serious problem in recent years; the disorder markedly lowers the commercial value, resulting in a complete loss of value in the worst cases. Therefore, to meet the demand of growers, we successfully developed a cultivation technique to alleviate and/or completely prevent CSPD by fruit bagging treatment using a light impermeable double-layered paper bag (2-layer bag) from mid-July to late-August (Matsumoto et al, 2018c). This means that paper bagging treatment is a prerequisite for the production of good-quality 'Kurenainoyume' fruit.…”

An Ordinary Multilayer Fruit Paper Bag Supplying Device for Fruit Bagging

“…Lower quality and poor market competitiveness are concerning problems for Chinese fruit growers (Zhang, 2017). Fruit bagging is a favorable solution to raise fruit prices and increase economic benefits for Chinese fruit farmers (Guo, 2017;Li et al, 2016;Matsumoto et al, 2018;Sharma et al, 2014;Zhou et al, 2019). Compared with the singlelayer fruit paper bag, the multilayer fruit paper bag has been used more widely, because it provides larger lightproof property and lower temperature for better coloration of fruits (Zhao and Wu, 2015).…”