Effect of postharvest treatments on physiological disorders of `Galant´: a new scab resistant apple cultivar

Traditional varieties are still in demand, but growers are weeding them out in favor of varieties which they say taste better, have crunchier texture and sell for a higher price. The success of new varieties will depend on it distinctiveness, consistence of quality and the efforts of those growing, packing and marketing it. New varieties offer enhanced quality often coupled with unique attributes but there are still many aspects that need to be investigated. Generally, apple are stored many months at low temperature under controlled atmosphere (CA) in order to reduce the metabolic rate. The storability of several new introduced varieties is, however, limited by physiological disorders occurring naturally during storage which seem to cause the main postharvest fruit losses. Here we focused on the promising apple scab resistant cultivar Galant (Lumaga A 913) developed in Switzerland as a cross between Resi and Delbar Jubilèe. Galant shows great interest as an alternative cultivar for organic production as well as good tree growth habitat, productivity and excellent taste. However, little is known about its storage features. Preliminary experiments by Neuwald et al. (2014) showed Galant softens quickly with the development of internal browning in the period between January and May. Therefore, it has a limited postharvest storage life. In our trials performed from 2015 to 2019, a complex of different physiological disorders were observed: superficial scald, flesh browning and browning of the skin and underlying flesh (soft scald & soggy breakdown). Here, we present the results of different postharvest treatments applied in order to avoid fruit injury, including ultra low oxygen atmosphere conditions (ULO), 1-methylcyclopropene (1-MCP) application and management of storage temperature. Superficial scald increases on early stages of maturity but the reduction of the respiratory metabolism by using ULO allows to keep it under a certain level (4%) in comparison with CA (35%) after 200 days storage. On the other hand, both ULO and CA storage do not affect the incidence of internal browning and the incidence rates is always higher than 80 %. Based on flesh browning disorders, the storability of Galant is always limited to 120 days. Regarding 1-MCP treatment, it inhibits ethylene production but may induce stress-like conditions and also increase polyphenol oxidase activity, which is the main enzyme responsible for browning reactions. Nevertheless, the superficial scald and flesh browning incidence were similar in both 1-MCP treated and untreated apples. Furthermore, the relationship of soft scald incidence caused by chilling injury and special post-harvest treatment - such as delayed cooling and/or storage temperatures - was examined in a short term storage.