Cultivar differences in gaseous 1-methylcyclopropene accumulation in whole and fresh-cut apple fruit

A number of studies have shown that responses of apple fruit to 1-methylcyclopropene (1-MCP) vary considerably among cultivars. This study was designed to determine if cultivars show differences in accumulation of gaseous 1-MCP. Apple fruit were placed in 1.76L jars that were sealed and injected with 20μLL−1 1-MCP. After 12h, samples of intercellular atmosphere were removed and analyzed for 1-MCP concentration. Accumulation of internal gaseous 1-MCP varied markedly among cultivars, ranging from 0.14±0.06, 0.22±0.03, and 0.77±0.30 in ‘Redcort’, ‘McIntosh’, and ‘Empire’, respectively, to 2.10±0.28, 3.33±0.13, and 6.93±0.35μLL−1 in ‘Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively. Accumulation of gaseous 1-MCP was reduced an average of 51% in fruit treated with Sta-Fresh 8711 fruit wax. The role of the epidermis in modulating 1-MCP ingress was determined by measuring gaseous 1-MCP accumulation in fresh-cut tissue. Fresh-cut cortical tissue rapidly depleted headspace 1-MCP (>95%) over a 1-h exposure yet accumulated negligible quantities of internal gaseous 1-MCP. By contrast, cortical tissue treated with ascorbic acid or hypotaurine, or aged for several hours prior to exposure to 1-MCP, showed reduced consumption of headspace 1-MCP and high accumulation of internal gaseous 1-MCP. Levels of internal 1-MCP in cortical tissue from the cultivars generally paralleled those for intact fruit, ranging from 0.23±0.07, 0.37±0.18 and 1.09±0.14μLL−1 in ‘Empire’, ‘McIntosh’ and ‘Redcort’, respectively, to 2.40±0.71, 4.55±0.15, and 6.24±0.85 in Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively. Although commercial fruit wax influences gaseous 1-MCP accumulation, the comparable accumulation patterns in unwaxed whole and fresh-cut apple fruit suggest that epidermal tissue/native waxes alone do not account for cultivar differences.