Effect of pollenizer distance and selective fruitlet abscission on outcrossing rate and yield in 'Tommy Atkins' mango

Abstract

Postzygotic self-incompatibility has been reported in several Indian mango (Mangifera indica L.) commercial cultivars. Floridian cultivars, on the other hand, have been planted in solid blocks and seem to be self-fertile. Isozyme analysis enabled us to determine outcrossings rates at the fruitlet and fruit stages in the Floridian 'Tommy Atkins' ('Tommy'). Two commercial mango orchards consisting of adjacent solid blocks of 'Maya' and 'Tommy' were studied. This combination offered a unique opportunity to identify each individual fruitlet or fruit as selfed or outcrossed by TPI isozyme analysis. A consistent and significant increase in outcrossing rate during fruit development was found: the average outcrossing rate increased from 10% and 13% in fruitlets to 66% and 73% in mature fruit in the two 'Tommy' blocks surveyed. This 6-fold increase is the result of selective abscission of selfed progeny. A significant inverse correlation was found between the distance of 'Tommy' trees from the 'Maya' block and the outcrossing rate in mature fruit. No significant correlation between distance from 'Maya', or outcrossing rate, and yield was observed, suggesting that the practice of planting 'Tommy' in solid blocks is sound.