Pre-treatment with 1-methylcyclopropene alleviates methyl bromide-induced decay, softening and wall degradation in blueberry

Abstract

Methyl bromide (MeBr) fumigation is the most common quarantine treatment used to con-trol fruit flies in blueberry. Recent studies suggest that these treatments can increase decay and sof-tening during transport, distribution and retail. We evaluated whether the ethylene action inhibitor 1-methylcyclopropene (1-MCP) could counteract the detrimental effects caused by MeBr. ´Jewel´ and ´Emerald´ blueberries with 100 % surface blue color were harvested and treated with 1-MCP (1 µL L-1 12 h, 2 ºC), MeBr (32 g m-3, 3 h, 21 ºC), or 1-MCP followed by MeBr. Untreated berries were used as a control. Fruit was stored for 0, 7 or 14 d at 2 ºC and decay, internal breakdown, firmness, respiration, weight loss, color, soluble solids, acidity and the total ascorbic acid (AsA), anthocyanin and glutathione (GSH) concentrations were determined. We also assessed pectin solu-bility by sequential cell wall extraction and neutral sugar composition. MeBr exposure exacerbated internal breakdown and respiration after long-term storage. These effects were significantly reduced by pre-treatment with 1-MCP, indicating that MeBr-induced damage requires ethylene action. 1-MCP application prior to MeBr fumigation also prevented berry softening by delaying solubilization of cell wall uronic acids and galactose. The combination of 1-MCP + followed by MeBr caused no detrimental effects on fruit surface color, anthocyanin, weight loss, soluble solids or acidity. MeBr fumigation reduced total AsA and GSH concentrations regardless of 1-MCP, indicating that the improved quality retention cannot be attributed to changes in AsA or GSH and were more likely due to inhibition of ethylene-dependent over-ripening and senescence symptoms. Pre-treatment with 1-MCP may be useful to alleviate MeBr-induced deterioration in blueberry.