Effect of Gibberellin on Delayed Harvesting of Mango cv. Kaew in the Upper North

Abstract

The rainfed  production sites in the Upper North are naturally the late-harvesting area of Kaew mango in the country. Because of climatic and environmental advantages, increased value of Kaew mango for fresh consumption by the more delayed harvesting is expected. The objective of this study was to determine the effect of gibberellin (GA₃) on the delayed harvesting of Kaew mango trees. A Factorial in a Completely Randomized Design with 3 replicates was established,  1 tree was assigned as 1 replicate, consisting of two factors : five levels of gibberellin (GA₃) concentrations (0, 50, 100, 150 and 200 ppm) and two number of applications (one and two times), at 80 days after full bloom stage and one week later. Thirty 12 year old mango trees cv. Kaew trees planted with a spacing of 6 m X 6 m, grown in the farmer ’s field, the Chom Tong Land Reform Project Area, Doi Lor district, Chiang Mai, were tested during December 2000 -May 2001.  The results indicate that all the treatments of GA₃ concentrations and times of GA₃ applications had no effect on the delayed harvesting, size, weight of fruit and seed, fruit drop, fruit stalk toughness, fruit firmness, soluble solids (SS) and titratable acidity (TA). The application time of GA₃ had only a significant effect on the L value of the peel ’s color. Double applications gave a significant higher L value of green peel color than a single application. The relatively high rate of GA₃ at 200 ppm gave also a significantly lower L value of flesh color than the others. Further studies are needed to determine the appropriate application time of GA₃ for delaying the Kaew mangos harvesting in the Upper North.