EFFECT OF POLLENIZER DISTANCE AND SELECTIVE FRUITLET ABSCISSION ON OUTCROSSING RATE AND YIELD IN ATKINS,TOMMY MANGO

Postzygotic self-incompatibility has been reported in several Indian m ango (Mangifera indica L.) commercial cultivars. Floridian cultivars, on the other hand, have been planted in solid blocks and seem to be se lf-fertile. Isozyme analysis enabled us to determine outcrossings rate s at the fruitlet and fruit stages in the Floridian 'Tommy Atkins' ('T ommy'). Two commercial mango orchards consisting of adjacent solid blo cks of 'Maya' and 'Tommy' were studied, This combination offered a uni que opportunity to identify each individual fruitlet or fruit as selfe d or outcrossed by TPI isozyme analysis. A consistent and significant increase in outcrossing rate during fruit development was found: the a verage outcrossing rate increased from 10% and 13% in fruitlets to 66% and 73% in mature fruit in the two 'Tommy' blocks surveyed, This 6-fo ld increase is the result of selective abscission of selfed progeny. A significant inverse correlation was found between the distance of 'To mmy' trees from the 'Maya' block and the outcrossing rate in mature fr uit, No significant correlation between distance from 'Maya', or outcr ossing rate, and yield was observed, suggesting that the practice of p lanting 'Tommy' in solid blocks is sound.