Effects of plant growth regulators applications on induction of lateral branching in Oregon Spur apple nursery trees

Abstract

The study presents the influence of 6-benzayladenine alone and in combination with gibberellic acid on growth and lateral branching of one-year-old ‘Oregon Spur’ apple nursery trees grafted on MM-106 rootstock. Different concentrations of BA and BA+GA3 (200, 300, 400, 500, 600 and 700 ppm) were applied three times at one week interval during second vegetative growth. Investigation reveal that Oregon Spur have strong apical dominance and plant applied with growth regulators resulted in a significant increase in number of feathers (0.58 to 6.18 per tree) compared to untreated control (0.18 per tree). However, BA alone has more significant effect on number of feathers (1.45 to 6.18 per tree) than BA+GA3 (0.58 to 4.35 per tree). Maximum number of feathers (6.18 per tree) has been obtained with 500 ppm BA treatment. This treatment also resulted in more uniform feather length (2.58 short and 2.55 medium length lateral branches per tree) and correct distribution of feathers along the trunk (20.63 cm branching zone) with appropriate average feathers crotch angle (54.74° from vertical). Furthermore, this treatment resulted in 100 per cent feathered trees compared to none in control and 2.88 trunk and mean feather diameter ratio compared to 1.54 in control. Some treatments with BA had a negative influence on the tree height. Whereas, most treatments increased trunk diameter and crotch angle compared to control.