Effect of a Single Defoliation and Fruit Thinning on Papaya Fruit Production and Quality

Abstract

The effect of defoliation and fruit thinning on papaya fruit set, growth, and ripe fruit quality was determined. Three defoliation levels (0%, 50%, 75%) and two defoliation methods (75% leaf cut off from the oldest to the youngest vs. 75% leaves removed in a spiral from the oldest) was compared with fruit thinning experiment on `Sunset' papaya during the warm season. Removal of 75% of the leaves significantly reduced new flower and fruit set, and decreased TSS level in ripe fruit. There was no significant difference between 0% and 50% defoliation in new fruit set, or ripe fruit TSS levels. Removal of leaves in a spiral reduced the number of new flower and fruit set more than the defoliation from the bottom to top. Defoliation of the `Kapoho' variety increased ripe fruit number and significantly reduced ripe fruit TSS and sugar level, dry mass persentage 2 weeks after defoliation. There was no significant difference between defoliated and non-defoliated treatment in fruit production, average fruit mass, and percentage of fruit flesh and seed, seed mass ratio, and seed dry mass during the test period. Fruit thinning increased new fruit set and increased ripe fruit TSS level in Line-8 and `Sunset', but not in `Kapoho'. However, average ripe fruit mass increased in fruit thinning experiment in `Kapoho' but not `Sunset' and Line-8 varieties. Fruit thinning also increased remaining young fruit TSS and sugar levels on the remaining fruit on plants compared to same-aged fruit on control and defoliated plants in Line-8. There was no effect on `Kapoho' young fruit TSS and sugar levels of defoliation. Ripe fruit TSS varied with weather conditions, plant growth conditions, and cultivars. These results indicated that although different cultivars had different responses to artificial defoliation and fruit thinning, source–sink balance and the ratio of fruit to leaf was an important factor in controlling potential fruit production and final fruit quality.