Growth and development of durian fruit cv. Monthong and the effect of ethephon preharvest treatment

Study on fruit growth and development of 'Monthong' durian was carried out using durians from an orchard in Chumporn during July-October 1995 and from Chanthaburi during January-May 1996. The growth and development period of whole fruit and different parts of fruit from anthesis to its maturity was 120-127 days. Its growth pattern was found to be simple sigmoid curve. The lag phase was from fruit set to 57 days old, the log phase was between 57-85 and 57-92 days in Chumporn and Chanthaburi respectively. The stationary phase was after 85-92 days. Dry weight and lipid content in durian pulp rapidly increased from the end of the log phase to the early stationary phase. The pulp was pale yellow at 99 days and became obviously yellow at 113-127 days, moderately related to beta-carotene content. TNC and total sugar content were high in the young fruit, decreased to the lowest level at the beginning of the stationary phase and then increased again to the peak level at 127 days in both provinces. Soluble solids content followed the pattern of the TNC content. 'Monthong' durian harvested at 120 and 127 days from Chanthaburi, stored at room temperature, ripened in 6-9 and 4-6 days respectively. The husk of ripened fruits turned slightly yellow while the pulp and seed coat became more yellow or brown respectively. Beta-carotene, TNC, SS and total sugar content in durian pulp increased througthout the storage time and related to taste panel analysis. However, dry weight and lipid contents of durian pulp were rather constant. When 500 milligram/liter ethephon was applied to the fruit of 'Monthong' durian grown in Chumporn for 3 times at 78, 85 and 92 days after anthesis, the fruit became small and poorly developed. The peel was brown in appearance while the pulp was pale yellow. The pulp of 500 milligram/liter ethephon treated fruits, harvested at 127 days and kept of another 4 days, was still firm. However, beta-carotene, TNC, SS and lipid contents were not different from untreated fruits. For 1,000 milligram/liter ethephon treatment, applied to durian fruit 3 times at 106, 113 and 120 days after anthesis, the pulp was more yellow than untreated fruit. Total sugar content was also higher. The treated fruit could be easily dehusked using only a force of 105-141 newton. For the untreated and 500 milligram/liter ethephon treated fruits, more than 196 newton was required.