Metamitron and Different Plant Growth Regulators Combinations in the Chemical Thinning of ‘Eva’ Apple Trees
Carolina Goulart *
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
Suélen Braga de Andrade
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
Angelica Bender
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
Andressa Vighi Schiavon
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
Gabriel Almeida Aguiar
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
Marcelo Barbosa Malgarim
Department of Phytotechnology, Faculty of Agronomy ‘Eliseu Maciel’, Federal University of Pelotas, Pelotas, Brazil.
*Author to whom correspondence should be addressed.
Abstract
Aims: The objective of this study was to evaluate the effect of the application of Metamitron and the combinations of NAA + BA and Promalin + BA on the fruit thinning of the Eva cultivar apple tree in southern Brazil.
Study Design: The experimental design used was a randomized complete block design, with four replications, with two plants per treatment in each block, following a one-step scheme with 10 treatments for the thinning factor.
Place and Duration of Study: The experiment was carried out in the agricultural year of 2013/2014 in a commercial orchard located in the municipality of Morro Redondo, RS, Brazil (Lat. 31º 40’ 60” S and Long. 52º 34” 50” W).
Methodology: Spraying of Metamitron was carried out at doses of 300, 350 and 400 mg L-1 and combinations of 5 mg L-1 of NAA + BA at doses 50, 75 and 100 mg L-1 and 0.5 ml L-1 of Promalin® + BA at doses of 50, 75 and 100 mg L-1. Only the doses of Promalin® were applied in full bloom, the other sprayings were carried out in fruiting with 5-8 mm in diameter. The variables analyzed were: number of fruits per trunk section area, number of fruits per plant, yield per plant, mean fruit mass, pulp firmness, fruit shape and diameter, fruit length, length/diameter ratio and soluble solids.
Results: A reduction in harvest load by Metamitron was only observed with the 300 mg L-1 dose. The combination of NAA 5 mg L-1 + BA 75 mg L-1 showed the highest fruit reduction, with a low fruit density per cm-2 and the highest average fruit mass. For the combinations of Promalin® + BA, as the increment of the dose of BA increased, there was a reduction of the number of fruits and consequently an increase in their size.
Conclusion: It was concluded that the Metamitron at the dose of 300 mg L-1 was able to cause thinning when applied in the fruit formation phase (5-8 mm). And the combinations of NAA 5 mg L-1 + BA 75 mg L-1and Promalin® 0.5 ml L-1 + BA 100 mg L-1 were able to reduce harvest load and increase the fruit size.
Keywords: Malus domestica (Borkh.), inhibitor of photosystem II, plant growth regulators, concentration, fruit set; fruit production