Abscission and Ethylene Production in Mango (mangifera Indica L) Fruit Cv. Tommy Atkins1

Rates of fruit drop and remaining fruited pan icles were monitored in the field for 96 days beginning on April 1, 1983. More than 90% of total fruit drop occurred within the first 4 wk, and final fruit set was 0.61%. Per centage of fruited panicles remained constant for the first 3 wk, decreasing sharply to 40% by the 6th week, and ending at 11.7% at harvest. Of the fruit which reached maturity, 42% were seedless. Samples of seeded and seedless fruit collected during the high drop period showed different ab scission patterns in the laboratory. All seeded fruit separated within 72 hr after harvest, where as 22% of the seedless fruit were still attached 95 hr after harvest. Abscission of seeded fruit was accompanied by a rise in ethylene production, while parthenocarpic fruit abscised without an increase in the iFlorida Agricultural Experiment Stations Journal Series No. 5171. From a dissertation submitted by the senior author in partial fulfill ment of the requirements for the M.S. degree of the Fruit Crops Dept. of the University of Florida. Proc. Fla. State Hort. Soc. 96: 1983. level of this hormone. In the field, the observation that seed less and seeded fruit are shed throughout the entire period of fruit development indicates that physiological factors oc curring after pollination and/or ovule fertilization are in volved in fruit abscission and consequently affect the final yield in mango. The mango is a tropical fruit crop which has a pro nounced tendency to shed fruit at all stages of development until harvest (12). Monoembryonic types show this behavior more intensely than polyembryonic ones, a fact attributed to the development of nucellar embryos which apparently influence a greater retention of fruit (15). The problem of low fruit set by mango trees has been well documented through the years. In Florida, the monoembryonic cultivar, 'Edward', had 3.8% fruit set in an 18-wk study of 160 panicles (15). The 'Haden' mango of Florida is well known for its high unfruitfulness and erratic bearing habits. Young (17) showed that only a small fraction of the perfect flowers normally set and mature fruit, which is at tributed to a high percentage of fruitlets that drop early in the season due to abortion of ovules. In a study by Naik and Rao (8), mango panicles produced 2000 to 4000 flowers, with only 1 to 35% being hermaphroditic. Furthermore, 13 to 28% set fruit and only 0.1 to 0.25% reached maturity. Some cultivars have been noted to develop one fruit to maturity of 150 apparently fertilized flowers, particularly with a heavy fruit set (7).