Use of plant growth regulators in 'Clapp's Favourite' pears

The objective of the present study was to evaluate the effect of different plant growth regulators in the flowering and production of ‘Clapp’s Favourite’ pears. The experiment consisted of applying prohexadione-calcium (PCa 2400.00 mg L^‑1), gibberellin (GA₃ 10.00 mg L^‑1), cytokinin combined with gibberellins (6-BA 16.92 mg L^‑1 + GA₄₊₇ 16.92 mg L^‑1), its combinations (PCa 2400.00 mg L^‑1 + GA₃ 10.00 mg L^‑1 + 6-BA 16.92 mg L^‑1+ GA₄₊₇ 16.92 mg L^‑1) and control (water) in an orchard of ‘Clapp’s Favourite’ pears cultivated in São Francisco de Paula city (29°05’50”S; 50°50’14”W, altitude 892 m), Rio Grande do Sul State, Brazil. The treatments were applied at early petal fall and about 30 days after the first application. The number of flowers and inflorescences produced per branch, fruit set, stem diameter, tree leader length and annual shoot extension growth were monitored. At harvest, production, fruit weight, diameter, epidermis colour, flesh firmness, soluble solids, pH, and acidity were evaluated. The fecundity and tendency of the occurrence of parthenocarpy were estimated by seeds produced. The use of growth regulators tested at the early petal fall and one month later did not increase fruit set and yield of ‘Clapp’s Favourite’. Application of prohexadione-calcium caused lower fruit weight since the first harvest. Reapplication of different sources of gibberellic acid prompted parthenocarpy production. The floral induction was jeopardized by the combination of the three growth regulators, totally inhibiting the floral differentiation and consequently the production in the third consecutive year of application.