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Effect of Apical Dominance on Bud Take in Citrus Vegetative Propagation

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Effect of Apical Dominance on Bud Take in Citrus Vegetative Propagation ISSN: 2224-0616 Int. J. Agril. Res. Innov. & Tech. 7 (1): 64-70, June, 2017 Available online at http://www.ijarit.webs.com EFFECT OF APICAL DOMINANCE ON BUD TAKE IN CITRUS VEGETATIVE PROPAGATION 1 1* 1 2 M. Mataa , P. Cheelo , D. Lungu and T. Kinkese Received 30 April 2017, Revised 24 May 2017, Accepted 26 June 2017, Published online 30 June 2017 Abstract The objective of the study was to identify the grafting method, which will have a higher success rate of scion development. The study was conducted at Mount Makulu Central Research station in Chilanga, Zambia (15o33’S / 28o11’E) from April 2010 to November 2011. The study had 4 vegetative propagation methods that varied in the treatment of the rootstock and scion. The four methods were Standard T- budding (STB); Modified T- Budding with decapitation (TBD); T- budding with scion bending (TBB); Crown grafting (CG). Bud take, shoot growth, leaf emergence and Leaf area index were measured up to 11 weeks after treatment (WAT). With CG there was 100 % bud take. STB had a bud take of 58.3 %. TBD had a bud take of 50 %. The lowest bud take percentage was recorded in TBB, which had a bud take of 41.7 %. At 5 weeks the STB and TBB treatment had shoot length of 0.7 and 1.0 cm respectively which were the shortest; this was followed by the CG treatment at 15.3 cm and the modified TBD with apical shoot decapitation (21.7 cm). STB shoots did not start growing until about 5 weeks, which was 2 weeks after the rootstock was cut off. At 5 weeks, the TBB and STB were yet to form leaves. The CG had close to 20 leaves and the TBD had almost 15.2 leaves. At the end of 11 weeks, the TBB had the highest number of leaves. Across the grafting methods; the Leaf area exhibited a pattern similar to leaf number; it kept on doubling every 2 weeks to until the 9th week after which the increase was negligible. At 11 weeks, the highest leaf area was in the TBD followed by the STB and lowest in the CG treatment. Keywords: Apical Dominance, Citrus Fruit, Grafting, Vegetative Propagation 1Department of Plant Sciences, School of Agricultural Sciences, University of Zambia, P.O. Box 32379, Lusaka, Zambia 2University of Cape Town, Faculty of Science, Department of Environment and Geographical Science, African Climate and Development Initiative (ACDI), Private Bag X3, Rondebosch, Cape Town, South Africa *Corresponding author’s email: [email protected] (P. Cheelo) Introduction Citrus fruit production is among the top in the and stock feed (supplying up to 8% crude protein) ranks in terms of the world fruit production Morton and Miami, 1987). The Southern part of (FAO, 2013). The major producers of oranges in Africa has the potential to contribute significantly the world are China, Brazil, the United States of to world citrus production especially the off- America, Mexico and Spain. Citrus farming is season supplier of sweet oranges (Citrus sinensis) being initiated in new zones as production in the (USDA, 2008). Despite the nutritional benefits, old areas is decreasing due to conversion of fruit consumption in developing countries such as agricultural land to human settlements as a result Zambia is still low (Simon, 2014). As a region, of rapid urbanization, emergence of new disease Southern Africa is the world’s leading and indeed and the abandonment of plantations injudiciously dominant supplier of off-season fruits (Jaffee, farmed (Ladaniya, 2008). The prime concern in 1999). Exports from Southern Africa are increasing production is overcoming the various dominated by South Africa followed by problems affecting the production of these citrus Zimbabwe, Swaziland and Mozambique (USDA, depending on the agro climate of that part of the 2008). According to Jaffee (1999), the citrus world (Ladaniya, 2008). subsectors of Zambia and Malawi are insignificant due to production and Citrus fruit has great nutritional and economical comparatively low quality and therefore not importance (Walter, 1992). They are an traded internationally. Among the major important source of carbohydrates, vitamin A, C, problems, limiting production of citrus is lack of and fiber. The fruits are processed into various access to high quality planting material products such as perfume, alcohol manufacture (Makorere, 2014). 64 Mataa et al. (2017) Effect of apical dominance on bud take in citrus vegetative propagation Henceforth, this study was done with the main that trigger initial bud outgrowth remains elusive aim of evaluating the effect of apical dominance (Morris et al., 2005; Loeb, 1918). Moreover, the on bud take using different grafting methods. The transition from dormancy to active growth has specific objective was to help identify the grafting been shown to be modulated by decapitation. method, which will have a higher success rate of scion development. The centrality of decapitation in the transition from dormancy to active growth is important to Historically, the development of nursery plant propagation because most vegetative techniques was aimed at overcoming propagation methods (budding and grafting) environmental constraints (Mudge et al., 2009; involve plant excision or decapitation. However, Melnyk and Meyerowitz, 2015). Nurserymen seek interpreting the mechanisms or responses in to produce large numbers of high quality perennial plants based on observation in annual marketable trees in the shortest possible time plants may be more challenging given the (Melnyk and Meyerowitz, 2015; Hartmann et al., outlined differences in development cycles. Apical 1990). This is made possible by the continued dominance studies have shown the involvement testing and adopting new methods of grafting. of auxins and cytokinins synthesis and Several grafting methods exist with different translocation. Additionally, decapitation has the growth rates of different tree crops grown on effect of disturbing water movement and any different types of root stock (Garner and Saeed, materials transported therein and this may have 1976). more dramatic effects in grafting. This is particularly important in the early stages of Apical dominance has been defined as the control development when the vascular union has not yet exerted by the shoot apex over outgrowth of the occurred. Depending on the climate and season lateral buds (Cline, 1997). Apical dominance vascular connection may take up to 6 weeks after occurs in many plants, for the horticulturist, grafting (Hartmann et al., 1990). manipulating this natural response by processes such as pruning and grafting allows the In this study, we looked at different vegetative horticulturist to determine the shape, size and propagation methods that varied in the treatment productivity of many fruiting trees and bushes of the rootstock and scion and postulated on the (McSteen, 2009; Acquaah, 2009). Apical effects these treatments may have exerted on the dominance is a well-known phenomenon in developing buds with reference to auxins and which it has been traditionally postulated that cytokinins. auxin traveling basipetal from the shoot apex suppresses the outgrowth of axillary buds Materials and Methods (Thimann and Skoog, 1933; Leyser, 2003). If a Location description shoot is decapitated, the axillary buds are activated. If auxin is applied to the cut end of the The study was conducted at Mount Makulu shoot, suppression of buds reoccurs. This is a Central Research station in Chilanga, Zambia classical example of a developmental correlation (15o33’S / 28o11’E) from April 2010 to November where one organ of a plant affects another organ 2011. The research station is located at about (Cline, 1997). However, measurements of the 1300 m above sea level in the agro-ecological speed of translocation of these growth regulators region II of Zambia. The mean annual and detection of the onset of changes in the temperature in this region was 23°C to 25 °C. The activity of the target buds point to the region receives medium annual rainfall of involvement of other more rapid substances or between 800-1000 mm. The meteorological data conditions (Morris et al., 2005). The nature of are shown in Table 1 below. this decapitation-induced long-distance signals Table 1. Climatic data during the grafting period for the experimental site Mt Makulu, Chilanga Zambia. Month July August September October November Maximum Temp (°C) 20.0 24.7 30.7 31.6 27.1 Minimum Temp (°C) 12.0 10.2 15.0 18.1 17.4 Relative Humidity (%) 88.0 57.0 51.4 50.0 68.2 Evaporation 2.9 4.8 7.6 8.5 5.2 Rainfall - - - - 8.8 Plant materials The trees were vigorous and healthy without any history of infectious diseases. The seeds were Rough lemon root stock (Citrus jambiri), the planted in April 2010 and allowed to grow for rootstock commonly used in Zambia for grafting about 1 year. Propagation was done in July 2011 citrus, was used. The seeds for the rootstock were when the stem diameters were about 1.5 cm in obtained from a private grower within the area. diameter. Int. J. Agril. Res. Innov. & Tech. 7 (1): 64-70, June, 2017 65 Mataa et al. (2017) Effect of apical dominance on bud take in citrus vegetative propagation Grafting methods The plants were potted in the same size of pots and exposed to the same kind of environment. Four grafting methods were used; these were Plants were grown in black polyethylene UV Crown grafting (CG), Standard T budding STB), stable sleeves filled with garden soil. The T- budding with bending of the stem (TBB) and polythene sleeves had a volume of 176.71 cm3 T- budding with the decapitation of the apical each. They were bought from Polythene Products bud (TBD). Zambia Ltd., Zambia. Crown grafting A total of 48 one year old rough lemon root stocks The graft was prepared by making two clean cuts- were budded and grafted on the same day the one on each side of the sliced end of the scion scion wood was collected.
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