Abstract
Superficial scald is a physiological disorder that develops during cold storage affecting apples and causes substantial market losses. Malus × domestica cv. Ladina, a new scab resistant and fire blight tolerant variety, commercialized in 2012, shows a physiological disorder similar to superficial scald after storage. Here, we used different pre- and postharvest approaches to characterize the occurrence of these superficial scald symptoms in Malus × domestica cv. Ladina. Over a period of seven years, fruits from multiple orchards were stored for five to seven months and the occurrence of superficial scald was assessed in fruits after cold storage and controlled atmosphere (CA) storage. Apples picked at different stages of ripeness within the same year differed in superficial scald development. Additionally, superficial scald differed significantly between years and locations, strongly suggesting that maturity at harvest, weather during the growing season, and orchard management play important roles in scald occurrence. Treatment with 1-methylcyclopropene (1-MCP) after harvest, and storage in a dynamically controlled atmosphere (DCA) significantly reduced the occurrence of superficial scald, whereas storage under ultralow oxygen concentrations (ULO) showed mild but not significant effects. Low calcium concentrations in the fruit flesh and peel were associated with stronger superficial scald occurrence.
Highlights
Superficial scald developed only after the fruits were exposed to a shelf life period of seven days at 20 °C
17.7% of fruits removed from storage early (February) and 35.5%6 of of16 fruits removed late (April) developed symptoms of superficial scald (Figure 1)
Ladina can produce a form of superficial scald, which was shown to vary in extent depending on the growing season and ripeness degree at harvest
Summary
A new variety, originated from a cross between Malus × domestica cv. Fuji performed in 1999 at Agroscope in Wädenswil, Switzerland, and was first commercialized in 2012 [1]. Ladina has been selected as cultivar because of its genetic resistance against apple scab (Venturia inaequalis, Rvi resistance) and low susceptibility towards powdery mildew. Ladina has been successfully screened for its low susceptibility against fire blight (Erwina amylovora) in shoot and flower inoculation tests in the glasshouse and orchards, respectively [2], increasing its potential for use in organic apple production systems. Concern has arisen as Malus × domestica cv. Ladina has shown a considerable amount of superficial scald after a few months of storage (Figure 1)
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