Abstract
ABSTRACT Peach hand thinning improves fruit quality; however, it requires a high demand of labor and increases production costs. The objective of this study was to evaluate the effect of growth regulators applied at post-flowering as an alternative to hand thinning of peaches. The experiment was conducted with peach cultivar Jubileu, in 2012. The treatments consisted of no thinning, hand thinning 45 days after full bloom (DAFB), ethephon (85 and 120 mg L-1), benzyladenine (BA) (400 mg L-1), and BA plus gibberellic acid (GA4 + 7) (400 mg L-1) applied 40 DAFB. BA-treated plants were not different from non-thinned plants, had excessive load, and smaller diameter fruit. Treatment with ethephon at 120 mg L-1 resulted in excessive thinning and decreased yield in comparison with other treatments. Plants treated with 85 mg L-1 ethephon and BA + AG4 + 7 (400 mg L-1) had fruit abscission, crop load, production per plant and fruit diameter similar to hand-thinned plants. In 2013, an increased number of flower buds was observed in treatments with ethephon and also reduction of this trait in BA and BA + GA4 + 7 applications. Ethephon at 85 mg L-1 can be an alternative of chemical thinning in 'Jubileu' peaches, without compromising the return of flower bud numbers in the next crop.
Highlights
The objective of flower or fruit thinning is to reduce fruit number per plant, promoting source-drain balance and reducing competition among fruits for energy, which results in larger fruits with improved flavor and aroma (JR Dennis, 2000; Byers et al, 2003)
Non-thinned trees had a natural abscission of 35% fruit (Table 1)
Ethephon at 85 mg L-1 caused abscission of 79% of the fruit, which was similar to the control with 77% of abscission
Summary
The objective of flower or fruit thinning is to reduce fruit number per plant, promoting source-drain balance and reducing competition among fruits for energy, which results in larger fruits with improved flavor and aroma (JR Dennis, 2000; Byers et al, 2003). Hand thinning is an expensive work and requires high labor demand, raising production costs (Costa & Vizzotto, 2000). Peach chemical thinning is considered promising (Greene & Costa, 2013) and can be performed from the dormant season, reducing the number of buds (Stern & Ben-Aire, 2009), and flower thinning using caustic substances (Yoon et al, 2011), as well as in the postflowering phase (Costa et al, 2006). Among the growth regulators for post-flowering thinning, ethephon has shown thinning effect on peaches from flowering to pit hardening (Byers et al, 2003; Greene & Costa, 2013). The temperature during and after the application is the most important environment factor to be considered, affecting both absorption and degradation of ethylene to ethephon (Yuan, 2007)
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