To investigate the changes in polygalacturonase (PG) and pectin methyl esterase (PME) activity of dudaim melon (Cucumis melo Group Dudaim), the plants of three cultivars, ‘Zangi-Abad’, ‘Kermanshah’ and ‘Kangavar’, were planted in open-field. Female flowers were labeled at anthesis, and fruits were harvested at two maturity stages corresponding to 21 and 28 days after anthesis (DAA). Harvested fruits were stored at 5 or 13 °C for three weeks and firmness, ethylene production, and PG and PME activities were assayed during storage. In all three cultivars at most times during storage, PME activity of early-harvested fruits (21 DAA) was greater than in late-harvested fruits (28 DAA). Conversely, in late-harvested fruits this parameter did not fluctuate significantly during storage. In early-harvested fruits, PME activity decreased, whereas in some treatments (e.g., early-harvested ‘Zangi-Abad’ fruits stored at 13 °C) the activity of this enzyme increased. In general, PG activity in early-harvested fruits increased up to the 14th day (in ‘Zangi-Abad’ and ‘Kermanshah’) or 7th day (in ‘Kangavar’) of storage and then decreased until the end of storage. ‘Kangavar’ fruits behaved differently compared to the other two cultivars in the activity of the two enzymes measured. According to the results of this study, in dudaim fruits, PG and PME activities depend on the time of fruit harvest (i.e., number of days after anthesis), storage temperature, and storage duration.
Keywords: Cucumis melo, enzyme activity, ripening; firmness, anthesis