Fruit set in ‘Ortanique’ tangor in response to pollination and different environmental stress situations

Abstract

Environmental stress factors and pollination effects on final fruit set of self-incompatible ‘Ortanique’ tangor were studied. Two factors were evaluated: ‘shadding’ (‘M’: 35 % flat shade nets and ‘SM’: without shadding) and ‘irrigation’(‘SR’: no irrigation and ‘R’: drip irrigation) under field conditions. From full bloom to the end of physiological drop, fruit set was evaluated. Additionally, in each situation, 120 leafy single flowered shoots were tagged, and three treatments were applied: a) control; b) emasculated and bagged flowers; and c) emasculated and hand pollinated flowers with ‘Nova’ mandarin. Leaf and stem water potential (ψ_F and ψ_X) were measured periodically and stomatal conductance (g_s ) and leaf temperature (TH) in two dates. Shadded trees registered significantly higher final fruit set (0.52 % M vs. 0.21 % SM), while irrigation treatments had no significant effect. Fruit set proportion showed a significant and negative correlation with TH and positive with ψ_F and ψ_X and g_s . Under shadded conditions, hand pollination significantly increased fruit set percentage. Control had higher final fruit set than emasculated treatment, suggesting that this cultivar presents stimulative parthenocarpy. Results and their implications over productivity of this cultivar are discussed.