THE INFLUENCE OF BORON ON FRUIT SET IN AVOCADO
Poor fruit set is often a serious problem among avocado cultivars in some regions of Southern Africa. Although boron has been found to improve fruit and seed set in various plant species, very little information is available on the optimal requirements for optimal fruit set. In this study we report on the boron uptake by avocado flowers and the relationship between boron concentration of the flowers and pollen germination and pollen tube growth. Semi vivo experiments were conducted on flowers obtained from trees growing on the experimental farm at the University of Pretoria and boron-sprayed and unsprayed trees from orchards at Westfalia Estate, Duiwelskloof. A parabolic relationship was found between boron concentration of the medium and that of the flowers after 24h incubation. Best pollen tube growth occurred where the boron concentration of the flowers was between 50mg kg-1 and 75mg kg-1. A leaf spray with Solubor (1000 mg dm-3) and a soil application (3kg h-1) increased the boron concentration of the leaves significantly, but not sufficiently for optimal pollen tube growth and fruit set. These results are discussed in relation to information obtained from experiments conducted on beans, tomatoes and petunias under controlled laboratory conditions.
Robbertse, P.J., Coetzer, L.A., Swart, N.G.N., Bezuidenhout, J.J. and Vorster, L. (1990). THE INFLUENCE OF BORON ON FRUIT SET IN AVOCADO. Acta Hortic. 275, 587-594