Interactive Effects of CA Storage, I-Methylcyclopropene and Methyl Jasmonate on Quality of Apple Fruit Keywords: Malus »domestica, fruit quality, storage, COrinjury

INTRODUCTION Firmness and titratable acidity retention in 'Fuji' and 'Braeburn' apples is enhanced by controlled atmosphere (CA) storage (Elgar et al., 1998, Argenta et al., 2002). However, these cultivars are susceptible to development of internal browning with characteristics of CO2-related injuries including brown-heart and cavities in the flesh (Meheriuk et al., 1994; Elgar et al., 1998). These disorders known as CO2-injury and 'Braeburn' browning disorder (BBD) are induced in 'Fuji' by high CO2 CA (Argenta et al., 2002) and/or by low O2 CA storage in 'Braeburn' (Elgar et al., 1998). Some factors contributing to greater incidence and severity of internal C02-injury in 'Fuji' and 'Braeburn' apples include harvest at advanced maturity, presence of severe watercore, light crop load, and production in colder regions or seasons or at relatively high altitude (Lau, 1998; Elgar et al., 1999; Argenta et al., 2002). Susceptibility of 'Fuji' Abstract The present study evaluated how post-harvest treatments with 1methylcyclopropene (1-MCP) or methyl jasmonate (MJ) impact 'Fuji' and 'Braeburn' apple fruit tolerance to controlled atmosphere (CA) storage conditions. Fruit harvested from a commercial orchard in north central Washington were cooled to 0.5°C within 36 h of harvest and then stored in air or CA with 2 kPa O2+ 0.05 kPa CO2; 0.25 kPa O2+ 0.05 kPa CO2 or 2 kPa O2+ 3 kPa CO2 for up to 6 months. Fruit were treated with 2 mM MJ or 1 ~1.L-I1-MCP at harvest. Both CA conditions and 1-MCP treatment reduced ethylene production, improved maintenance of firmness and titratable acidity and reduced incidence of core flush during long-term storage compared with untreated fruit stored in air. Treatment with 1-MCP was as or more effective than low CO2-CA storage for reducing ethylene production and preservation of firmness and acidity for both cultivars. 'Fuji' apples stored in 3 kPa C02 developed internal browning (C02-injury) while fruit stored in 0.25 kPa O2with 0.05 kPa C02 or air did not, regardless of 1-MCP treatment. 'Braeburn' apples also developed internal browning during airor CAstorage, regardless of CO2 concentration. Severity of browning in 'Fuji' and 'Braeburn' apples stored in 3 kPa CO2 was not altered by previous 1-MCP treatment. However, browning severity increased by the 1-MCP treatment when 'Braeburn" fruit were stored in air or low CO2 CA. Treatment with MJ reduced severity of C02-injury in fruit of both cultivars stored in high CO2 CA. The treatment with 1-MCP and storage in air or CA with 2 kPa O2 and low (::;0.05 kPa) C02 may be a practical strategy for maximum retention of firmness and acidity with minimum development of CO2-injury in susceptible cultivars. Interactive Effects of CA Storage, I-Methylcyclopropene and Methyl Jasmonate on Quality of Apple Fruit