Chemical thinning of 'Forelle' pear with S-abscisic acid and 1-aminocyclopropane-1-carboxylic acid

K.I. Theron, G.F.A. Lötze, J.S. Reynolds
'Forelle' is the second most planted pear cultivar in South Africa. The average fruit size is relatively small, therefore early fruitlet thinning is important. Earlier research with 6-benzyladenine (6-BA) proved to be ineffective as thinner, but recently metamitron was registered as a chemical thinner for 'Forelle' in South Africa. The search for further chemical thinning agents was expanded to S-abscisic acid (S-ABA) and 1-aminocyclopropane-1-carboxylic acid (ACC). During the 2015/16 season S-ABA and ACC were evaluated in two production regions, viz., Warm Bokkeveld (33°18'00.9”S; 19°21'13.8”E) and Elgin (34°10'25.8”S; 10°03'40.3”E), and in the 2016/17 season research was concentrated on the more promising S-ABA, again in the same two regions. S-ABA was evaluated at 100 to 600 mg L-1 and ACC at 75-300 mL L-1 applied at 8-10 mm fruitlet diameter. During the 2015/16 season, ACC significantly reduced fruit set at the Elgin site and improved fruit size when applied at 225-300 mL L-1, but not at the Koue Bokkeveld site. S-ABA significantly thinned 'Forelle' pear fruitlets at both sites and improved fruit size when applied at 200-300 mg L-1. During the 2016/17 season, a linear decrease in fruit set occurred with increasing S-ABA rate at the Warm Bokkeveld site. This resulted in a decrease in yield at the highest S-ABA rate (600 mg L-1). All S-ABA rates increased fruit weight at harvest except the 100 mg L-1 application. At the Elgin site, no significant effect was obtained in fruit set or thinning efficacy, but the two highest rates of S-ABA (400 and 600 mg L-1) increased average fruit weight at harvest. S-ABA at 300 mg L-1 therefore appears to be a promising chemical thinner for 'Forelle' pears, but further research is required to verify this rate.
Theron, K.I., Lötze, G.F.A. and Reynolds, J.S. (2018). Chemical thinning of 'Forelle' pear with S-abscisic acid and 1-aminocyclopropane-1-carboxylic acid. Acta Hortic. 1206, 13-20
DOI: 10.17660/ActaHortic.2018.1206.2
https://doi.org/10.17660/ActaHortic.2018.1206.2
Pyrus communis L., 6-benzyladenine, naphthalene acetic acid, fruit quality, fruit size
English

Acta Horticulturae