Fereshteh Kamiab - Department of Horticultural Science, Rafsanjan Branch, Islamic Azad University, Rafsanjan, Iran
Iraj Tavassolian - Department of Horticultural Science and Landscape Design, Shirvan Faculty of Agriculture, University of Bojnord, Bojnord, Iran
Mehdi Hosseinifarahi - Department of Horticultural Science, Yasuj Branch, Islamic Azad University, Yasuj, Iran

Purpose: Barberry has been used for many centuries due to its highly nutritious benefits, ornamental value, and medicinal properties. Iran is the largest producer of seedless barberry and this has been growing in various regions with dry climates, poor soil conditions and severe water shortages. Alternative bearing is a frequent problem in seedless barberry production. To avoid it, thinning has been employed as a common cultural practice in orchard management. Research method: In this study, three chemical thinners including gibberellic acid (GA۳) at ۷۵, ۱۰۰ and ۱۵۰ mg/L, naphthalene acetic acid (NAA) at ۱۰, ۲۰ and ۴۰ mg/L and ethephon at ۵۰, ۱۰۰ and ۲۰۰ mg/L, and hand thinning (۲۰%) were applied in a commercial orchard in Birjand, Iran, one week after petal fall. Thinning rate, quantitative and qualitative traits were investigated in comparison to the control in the split plot arrangement in a randomized complete block design during ۲۰۱۵ and ۲۰۱۶. Findings: Results showed that NAA at ۱۰ mg/L caused the highest fruit abscission. Vegetative traits such as shoot length, number of leaves per shoot and leaf area showed significant increases under the treatments while shoot diameter had no significant difference with control. Chemical thinning remarkably enhanced the starch and sugar of the shoots, especially in “on” year (۲۰۱۵). The minimum chlorophyll content in “off” year was observed in control and the highest by NAA at ۱۰ ppm. All the treatments increased seedless barberry shrub yield in the “off” year (۲۰۱۶). Biochemical traits such as ascorbic acid, total soluble solids, titratable acidity and anthocyanin improved in most treatments. Research limitations: No limitations were encountered. Originality/Value: To avoid alternative bearing in seedless barberry shrubs, thinning has been employed as a common cultural practice in orchard management. So, the application of NAA ۱۰ mg/l is recommended for control of alternative bearing and also better fruit quality.

barberry, Berry yield, Ethephon, Gibberellic acid, Naphthalene acetic acid