Effect of Chemical Thinning Season Using Metamitron on Peaches ‘Sensação’ Quality

Aims: The objective of this study was to evaluate peach fruits quality after chemical thinning using metamitron at different times in the South of Brazil.

Study Design: The experimental design was in randomized blocks, with five replications of three plants, fruits were harvested and evaluated the central plant in the plot, and twenty fruits were evaluated in each replicate.

Place and Duration of Study: The experiment was conducted in a commercial peach orchard ‘Sensação’, in the city of Morro Redondo, Rio Grande do Sul, Brazil, in the years 2015 and 2016.

Methodology: Treatments were composed of metamitron application (200 mg L-1) at 20, 30, 40, 50 and 60 days after full bloom (DAFB) and manual thinning performed at 50 DAFB. The epiderms color, pulp firmness, ripening index, soluble solids, titratable acidity, pH, total phenolic compounds and antioxidant activity were evaluated.

Results: The manual and chemical thinning at 20 and 30 DAFB contributed to the epidermis greenish-yellow fruits coloration in the year 2015. The lowest maturation indices were verified in fruits submitted to chemical thinning at 20 and 30 DAFB during the two years evaluated. The firmness of fruit pulp increased when peach trees were submitted to chemical thinning at 30 and 60 DAFB in the year 2015. The phenols and antioxidant activity of fruits presented higher concentrations of these compounds in manual thinning during the two years evaluated.

Conclusion: Peaches quality was altered according to the thinning methods and the application time of the metamitron performed in the trees. The use of metamitron in peach chemical thinning did not affect the fruits soluble solids content in relation to manual thinning. Thinned fruits quality presented differences in relation to the cycles evaluated for epidermis color, firmness and soluble solids.