Plant Growth Regulators in Flowering Alternation of the Fuji Suprema Apple Tree

Abstract

Aims: Research on alternate bearing in apple trees is usually focused on chemical thinning techniques, but in recent decades synthetic bioregulators have proven to be effective in promoting or inhibiting floral induction in apple trees. However, the results can be variable since some cultivars are prone to alternation, as Fuji and its clones. The objective of the present study was to observe the effect of naphthalene acetic acid (NAA), Ethephon, and their combinations in the formation of flowering buds avoiding flowering alternation, in Cv, Fuji Suprema.
 Place and Duration of Study: The experiments were carried out in southern Brazil, municipality of Caçador / SC, during the cycles from 2014 to 2019, in the cultivar Fuji Suprema / Marubakaido / M9, with 12 years old.
 Methodology: Several variables were evaluated such as flowering return, fruit set, yield, number of fruits per plant, average fresh fruit mass, and biennial bearing index (BBI).
 Results: The results were variable and showed that NAA and Ethephon had little effect on reducing flowering alternation when applied during the vegetative phase of the Fuji Suprema apple tree. After years of high productivity, there was a decrease in the yield, even in the treatments of NAA and Ethephon. Ethephon or its combination with NAA has a thinning effect, but without influence on the return of flowering.