Effect of Cultivar on Endogenous Ethylene Evolution and its Relationship to Increases of Soluble Protein in Peach Mesocarp Tissue

Abstract

Differences in ethylene evolution rate among ‘Biscoe,’ ‘Belle of Georgia,’ ‘Loring,’ and ‘Redskin peach’ ( Prunus persicaL.) and ‘Fantasia’ nectarine ( Prunus persicaL., v nuciperscia) fruits were investigated. The effect of cultivar on ethylene evolution rate was highly significant. The mean ethylene evolution rate in ‘Belle of Georgia’ peach fruits was higher than in any other cultivar. The lowest mean ethylene evolution rate was observed in ‘Loring’ peach fruits. Ethylene evolution rates were compared with ripening associated changes in accumulation of soluble mesocarp proteins. The soluble protein fraction extracted from fruits at three time points during ripening were resolved by denaturing polyacrylamide gel electrophoresis. Protein band density was determined by scanning laser microdensitometry. Cultivar and ethylene evolution rate were related to protein density and significant gel protein band by cultivar interactions were observed. Analysis of band variance tested the effect of cultivar on protein accumulation during maturation. Sixteen bands showed significant differences and five bands showed no significant differences among cultivars. For ‘Belle of Georgia’ fruits, the ethylene evolution rate was related to increased accumulation of two proteins with estimated molecular masses of 39.0 and 56.5 kDa. No increased accumulation of 39.0 or 56.5 kDa protein was observed in the three remaining Prunuscultivars with suppressed ethylene evolution rates, or in ripening ‘Loring’ fruits treated with (2-chloroethyl)phosphonic acid (ethephon).