Susceptibility of ‘Honeycrisp' Apple to Injury by Modified Atmospheres and Strategies to Reduce Disorder Incidence and Severity

‘Honeycrisp’ apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit develops a number of storage disorders including soggy breakdown, soft scald, bitter pit, lenticel breakdown, and internal browning. The susceptibility of this cultivar to damage by the low O₂ and elevated CO₂ partial pressures in controlled atmosphere (CA) storage has not been previously described. Over a three-year period, we stored ‘Honeycrisp’ fruit in various combinations of O₂ and CO₂ that in year 1 included 6 different atmosphere combinations 1%, 3%, and 21% O₂ with 0% and 3% CO₂ for fruit from four orchards.  Fruit were evaluated after 1, 3, and 6 months storage at 3 °C.  In years 2 and 3 of the study, seven and eight orchards, respectively, were included in the study and we used only 3 % and 21% O₂ in combination with 0% or 3% CO₂. In addition, we imposed preconditioning treatments of 3, 10 and 20 °C for 5 days prior to storage with and without a diphenylamine (DPA, 1000 ppm) drench before atmospheres were established. Fruit were evaluated after 3 and 6 months storage at 3 °C. Low O₂ (1% and 3%) and elevated CO₂ (3%) caused damage to the cortex of the fruit, but not to the skin, and seldom to the fruit core. The injury took the form of small to extensive dark brown lesions in the cortex and lens-shaped openings typical of CO₂ injury reported for other apple varieties. The browning was somewhat more patchy and less smooth-edged than that of the chilling injury soggy breakdown when viewed in transverse cross section. Although injury severity varied from orchard to orchard and from year to year, preconditioning at elevated temperatures reduced the incidence and severity of the CA injury relative to fruit held at 3 °C throughout. Injury incidence was 17.5%, 10.5%, and 2% damage, respectively, for fruit preconditioned at 3, 10, and 20 °C.  DPA reduced injury symptoms to near zero.  The potential for use of preconditioning treatments and/or DPA to control CA injury appears promising.