1-Methylcyclopropene (1-MCP) has been found to inhibit ethylene action and thus it can delay the fruit ripening process. The effects of 1-MCP (90 ppb for 12 h) on softening related changes were determined through physiological changes, fruit firmness and activities of the cell wall degrading enzymes including α-galactosidase, β-galactosidase, pectin methylesterase (PME) and xylanase during ripening in papaya (Carica papaya L. cv Sekaki). In this study, fruits were treated with 90 ppb concentration of 1-MCP gaseous vapors for 12 h in airtight container maintained at 28oC. After the treatment fruits were placed at ambient temperature (28oC). Papaya treated with 1-MCP experienced a significant delayed in skin color development, weight loss and reduced firmness loss compared with the fruit without 1-MCP treatment. As softening progressed, activity of the cell wall degrading enzymes in fruit without 1-MCP treatment increased significantly coincident with a rapid decline in fruit firmness. With 1-MCP application, fruit experienced a delay in activity of cell wall degrading enzymes but continued to increase until later stage of ripening. Thus it may be suggested that 1-MCP treatment may aid in delaying softening-related process and thereby extended the postharvest life and maintained the quality of the ‘Sekaki’ papaya fruit.
The aim of this study was to establish an effective protocol for callus induction from the seed explants of Solanum dubium and to investigate the callus extract ability in milk clotting activity. The effects of growth regulator, basal media strength and sucrose were studied using different concentrations (0.5, 1.0, 1.5, and 2.0 mg/L) of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthalene acetic acid (NAA) and 2,4-dichlorophenoxy-acetic acid (2,4-D) alone or in combination with 0.5 mg/L of 6-benzylamino purine (BAP). For milk clotting activity, about 50 or 100 μL extracts of seed callus was mixed with 2 mL 50% milk held at 55°C for 5 and 10 min until milk clotting occurred. The results showed that NAA alone or in combination with BAP gave a higher callusing percentage (80 to100%) compared to the other plant growth regulators at the same concentrations. When an auxin was supplied in combination with BAP, a significant increase in callusing percentage or degree of callusing was observed. The time required for callus to be developed was shortened and the quality of the induced callus improved. An increase in callus growth in low sucrose (10 g/L) concentration was found be comparable (88%) to high sucrose concentration (30 g/L; 60%). Crude extracts obtained from S. dubium callus were shown to exhibit milk clotting activity.