Effects of cyclanilide on growth and branching characteristics of 1-year old apple plants

Abstract:【Objective】This study investigated the effects of cyclanilide (Cyc) on growth and branching characteristics of the annual grafted apple plants with different scion-rootstock combinations【. Meth- ods】In the experiment, one year old apple trees of four scion-rootstock combinations were used includ- ing Nagafu No.2/M26/Malus prunifolia Borkh., Qincui/M26/M. prunifolia Borkh., Qincui/M26 and Qincui/T337. The axillary buds of these plants were sprayed with 0.2 g·L-1 Cyc added with 1% DMSO for dissolution. Pinching was carried out 3 days before Cyc spraying treatment in Nagafu No.2/M26/M. prunifolia Borkh., and spraying 1% DMSO 3 days after pinching was used as the control. The Cyc treat- ment in Qincui/M26/M. prunifolia Borkh., Qincui/M26 and Qincui/T337 was carried out 4 d after pinching (pinching 4 d + treatment). After elongation growth of the plants had stopped, the related mor- phological indexes such as branching angle, average number of branches, average length of branches, height of the plant and the thickness of the stem were statistically analyzed. In the case of Qincui/M26/Malus prunifolia Borkh. Cyc, the different treatments were divided into two main groups including pinching + regulator treatments and non-pinching + regulator treatments. There are 4 pinching + regula- tor treatments, including NPA spray 4 days after pinching (pinching 4 d + NPA), Cyc spray 4 days after pinching (pinching 4 d + Cyc), 6-BA spray on the day of pinching and Cyc spray 4 days later (pinching +6-BA 4 d + Cyc) , and Cyc spray on the same day of pinching (pinching + Cyc). The concentrations oftheregulatorsusedwere0.2g·L-1,2.9g·L-1,and1.1g·L-1 forCyc,NPAand6-BA,respectively,all added with 1% DMSO. Again pinching +1% DMSO served as the control. The non-pinching treat-ments included sprays with Cyc, 6-BA, and Cyc+6-BA at the concentrations above mentioned, and add- ed with 1% DMSO. After the plants stopped growing, the relevant morphological indexes such as branch angle, average branch number, average branch length, plant height and stem thickness were re- corded【. Results】The results showed that Cyc significantly increased the average branch number and branch angle in Nagafu No.2/M26/M. prunifolia Borkh., and that Cyc significantly increased the aver- age branch number but had no significant effect on the branch angle in the other three scion-rootstock combinations. Cyc had no significant effect on the average branch length in Nagafu No.2/M26/M. prunifolia Borkh. and the other three scion-rootstock combinations and showed different degrees of in- hibition on plant height and stem thickness. Stem thickness in Qincui/M26/M. prunifolia Borkh. was most significantly inhibited. In Qincui/M26/M. prunifolia Borkh., the treatments of pinching 4 d + Cyc and pinching+6-BA 4 d + Cyc, pinching + Cyc increased the average number of branches compared with the control and pinching 4 d + NPA, but the plant height and stem thickness were reduced at different degrees, and their influence on average branch length and branch angle was not significant. The mean effective branches length in pinching + Cyc was the lowest and significantly lower than the control. The comprehensive performance of pinching 4 d + Cyc was the best. In the non-pinching treatments in Qincui/M26/M. prunifolia (wild) Borkh., the inhibitory effect of Cyc treatment on plant height was stronger than that of 6-BA. The average branch number, average effective branch number and average effective branch rate of the plants treated with Cyc and Cyc+6-BA were significantly high- er than those treated by 6-BA. There was no significant difference in stem thickness, branch angle and branch length among the treatments. Comparatively, Cyc had the best overall performance.【Conclusion】Cyc is effective to promote branching and increase the branching angle in Nagafu No.2/M26/M. prunifolia Borkh., and has a potential application in nurseries. Moreover, Cyc has an inhibitory effect on stem thickening and shoot elongation. These results provide valuable reference for the application of Cyc in regulation of apple branches.