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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (9): 165-172.doi: 10.11707/j.1001-7488.20150921

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Effects of Media and IBA Concentrations on Rooting of Rhododendron fortunei for Cutting Propagation

Wang Shusheng, Shan Wen, Zhang Lehua, Du Youxin, Li Xiaohua, Wang Kaihong   

  1. Lushan Botanical Garden, Jiangxi Province and Chinese Academy of Sciences Lushan 332900
  • Received:2014-07-07 Revised:2014-11-04 Online:2015-09-25 Published:2015-10-16

Abstract:

[Objective] Medium composition and application of exogenous hormones are important factors that influence the rooting of cuttings. As it is hard to root for cutting propagation of Rhododendron fortunei, this study was aimed at investigating different media, indole-3-butyric acid (IBA) concentrations and their interactions on the rooting of cuttings of this species, and to select the optimum combination of rooting medium and IBA concentration, then to provide a theoretical basis for its introduction and domestication, and industrialization. [Method] Using the lignified new terminal branches with leaf buds of R. fortunei as propagating material, and adopting a completely randomized factorial design with two factors, i.e., six types of rooting media: pure river sand, peat + perlite (4:1 by volume), perlite + forest soil (4:1), vermiculite + forest soil (4:1), river sand + forest soil (1:1) and pure forest soil, and four IBA concentrations:100, 200, 400, 800 mg·L-1, we investigated the effects of different combinations of rooting medium and IBA concentration on rooting parameters of R. fortunei, i.e. percentages of callus formation, rotting rate, rooting rate, and retaining rate of old leaves, number of total roots and number of adventitious roots, length of longest adventitious root, width of root system. And then we comprehensively evaluated the effects on rooting of each treatment combination by subordinate function analysis. [Result] The results showed that the effects of rooting medium and IBA concentration were highly significant (P<0.01) for all measured parameters, and the influencing intensity of rooting medium was stronger than that of IBA concentration. The interaction of rooting medium and IBA concentration was highly significant only for four root development parameters including the number of total roots, number of adventitious roots, length of the longest adventitious root and root width. Among the six types of rooting media, the pure river sand medium produced extremely positive effects on most parameters except on length of the longest adventitious root and root width. The peat + perlite (4:1) medium produced the highest callusing percentage, length of the longest adventitious root and root width, with less effect of other parameters than those of pure river sand medium. The rooting effects of the other four media decreased as the proportion of forest soil increased, and the pure forest soil medium showed the worst effect for all parameters. As to the four IBA concentrations, the best callusing and rotting percentages were observed at 100 mg·L-1 treatment, and with increase of IBA concentration, callusing percentage decreased significantly and rotting percentage increased. Rooting rate and retaining rate of old leaves were the highest at 200 mg·L-1 treatment, and decreased gradually as IBA concentration became higher. The number of total roots and adventitious roots, length of longest adventitious root and root width showed no significant difference among 100, 200 and 400 mg·L-1 treatments and all these were better than those at 800 mg·L-1 treatment. Subordinate function analysis showed that, among the 24 treatment combinations, the combination of pure river sand medium with 200 mg·L-1 IBA was the optimal treatment for rooting of R. fortunei, which produced the highest values of rooting rate and retaining rate of old leaves, number of total roots, number of adventitious roots, as well as the lowest rotting percentage in all combinations, followed by the combination of peat + perlite (4:1) medium with 100 mg·L-1 IBA with the highest callusing percentage and good effects on other parameters. The combination of pure forest soil medium with 800 mg·L-1 IBA had the worst rooting effects.[Conclusion] Rooting medium, IBA concentration and their interaction had significant effects on cutting propagation of R. fortunei. The media of pure river sand and peat + perlite (4:1) had better rooting effects than the other four types of media, and they were the preferred medium for cutting propagation of R. fortunei. The pure forest soil medium was not suitable for cutting propagation of the species. The treatment of 200 and 100 mg·L-1 IBA promoted the development of calluses and adventitious roots. And the treatment of 800 mg·L-1 IBA caused rotting of cuttings and it was not good for rooting and the development of root system. The optimum IBA concentration varied in different rooting media. The treatment combinations of pure river sand with 200 mg·L-1 IBA and peat + perlite (4:1) with 100 mg·L-1 IBA were recommended for industrialized propagation of R. fortunei.

Key words: Rhododendron fortunei, cutting propagation, media, IBA concentrations, rooting capacity, root development

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