Vegetative propagation of Acacia nilotica (L) subspecies nilotica. Brenan by stem cuttings

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1 Vegetative propagation of Acacia nilotica (L) subspecies nilotica. Brenan by stem cuttings Yahia H. A. Elbasheer 1 and Sayadat El-Tigani 2 Abstract Vegetative propagation of Acacia nilotica was studied using stem cuttings treated with indole-3-butyric acid. The concentrations at 10, 20, 50 and 100 mg/l significantly enhanced the rooting ability of nursery stock and mature cuttings. Cuttings from nursery stock plants treated with 10 and 100 mg/l IBA, during summer, gave 39.2 and 10 rooting percentages for the two concentrations, respectively. In winter 50 mg/l IBA gave 30%; while, the lower concentrations, 10 and 20 mg/l gave 10 and 20 percent. The100 mg/l gave only 10 percent rotted cuttings Keywords: Acacia spp. A. nilotica, vegetative propagation, stem cuttings Introduction Acacia nilotica is found on the silt banks of the river Nile from the southern Central Sudan extending northwards to the Egyptian borders (El-Amin, 1990). A. nilotica is used mainly for railway sleepers, construction and round poles, fuel-wood, tannin production from the bark, pods and leaves for tanneries and traditional medicinal drugs. In addition it contributes to of the total production of sown wood and building poles (Abdelazim et al., 2006) Most forest tree species are known to have long life cycles and often display changes with time in growth rate and morphological features that are reflected in characteristics such as, stem form, volume and yield. It has been reported that maturation-related changes in performance are developmental changes triggered by programmed activation or inactivation of different sets of genes (Libby and Rauter, 1984). Vegetative propagation techniques were introduced in tree planting to overcome most of the problems that prevent successful efficient propagation of important economic forest tree species Rooted cuttings in tree improvement programme were preferred than other methods (Libby and Rauter, 1984). Vegetative propagation aspects were well documented and published (Hartman and Kester, 1983; Longman and Jenik, 1990). The success of rooting of cuttings was more or less affected by a number of factors as, age, early selection of desired characters and interaction with the environment (Ali and El-Tigani, 2003). Work on rooting cuttings of fruit trees and of some forest trees showed that; the degree of lignifications in the primary phloem affects the rooting ability of cuttings from trees by hindering the root primordia tissue to develop root initials (El-Tigani, 2003). However it is time to propose cloning in forestry as a viable alternative to conventional seedling-based forestry for such forest trees (Ali and El-Tigani, 2003). Nevertheless A. nilotica riverbanks plantation was recorded to suffer from the phenomenon of die-back that affect its production and plantations. The cause is still debatable after some experimental works on effects of precipitations, insects and fungal attacks. However work is needed including physiological, biochemical and biotechnological to detect effects of phenol compounds that were reported to be one of the factors of die-back (Zobel, et al.,. 1987), then selection and propagation of healthy individuals is needed. 1 Forestry Research Centre, P.O. Box 13391, Soba, Khartoum, Sudan. 2 Botany Department, Faculty of Sciences, University of Khartoum. 1

2 The main objectives are to investigate the propagation of Acacia nilotica by stem cuttings taken from nursery stock and mature plants to determine suitable concentration of indole-3- butyric acid (IBA) and propagation conditions. Materials and Methods The experiments was carried out during the seasons winter (December-February), Summer (May-September) and Autumn (October-January) in the Botany Garden Nursery at the University of Khartoum. Two types of stem cuttings were taken from nursery stock plants (6-12 month-old) grown in polyethylene bags (20 30 cm) and from mature plants (10-20 year-old) from Al-Mogran Forest in Khartoum State. The cuttings were about cm in diameters and cm in length defoliated leaving 3-5 pairs of leaves with protected axillary buds by leaving small part of the petiole of the leaf intact. The culture medium was course sand prepared by sieving in sieve No.3. The rooting hormone used was Indole-3-butyric acid (IBA) from Sigma Chemical Co. Ltd. The concentrations of 0, 10, 20, 50, and 100 mg/l were applied by the dilute dip method (Ali, 1997). They were prepared by dissolving the specified concentrations in few drops of ethanol (80%) and then made up to the required volume. Cuttings from each group were dipped vertically to a depth of about 3-5 cm from the distal in glass containers, covered with perforated polythene bags to reduce evaporation. Treatment time was hours, and the sets were places in a laboratory room at 25 ± 2 C, thereafter the cuttings were washed under running tap water, wiped and planted early morning in moist course sand medium in perforated polyethylene bags (20 30cm), one cutting per bag, Humidity was maintained by water spraying every three hours while watering was done early morning and afternoon. The cuttings were kept under diffused light. Four sets each of 20 cuttings each in three replicates from each type (nursery stock and mature trees) and each treatment (0, 10, 100 mg/l IBA) were arranged in a randomized block design in the shaded house. Observations and data were taken weekly during the experimental periods (4 months) where cuttings were carefully lifted for record of number of rooted cuttings, total length of lateral roots and main roots length were measured. The data were subjected to analysis of variances by using JMP where the statistical differences were based on arcsine transformed value of percentage rooting cuttings. Results Indole-butyric acid at concentrations 0, 10, 20, and 100 mg/l significantly affects rooting of both types of stem cuttings of Acacia nilotica during winter. 50 mg/l IBA significantly affected only cuttings of nursery plants and gave 33.2 percent rooting. During summer 10 mg/l IBA gave 39.2% and 18.4% rooting with 100mg/l only with nursery plants cuttings. No significant effects were obtained with other concentrations on rooting of both types of cuttings. During autumn all concentrations of IBA had no significant effect on rooting of both types of cuttings. This suggests that rooting of stem cuttings of A. nilotica seems to respond to a different stimulus other than the hormonal treatment. This is shown by the probability levels for significant differences in the three seasons which vary with IBA concentrations. The rooting percentages significantly affected by IBA treatments (Table 1). The result showed that winter season significantly affects both types of cuttings irrespective to IBA concentration. Hence nursery plants rooted during summer with 10 and 100mg.l IBA giving 39.2 and 18.4 percent respectively. But in winter with 50 mg/l IBA it gave 30 percent; whereas, the concentrations 10 and 20 mg/l gave 18.4 and

3 percent; while 100 mg/l gave 18.4 rooting percent. Figure 1 shows clearly rooting of stem cuttings of mature Acacia nilotica with IBA concentrations. 3

4 Discussion A successful propagation of nursery stock and mature plants of Acacia nilotica was obtained. From the experiment it seems that the persistence of physiologically active leaves and the development of buds into branches are prominent signs of rooting of cuttings. In winter and summer all cuttings formed adventitious roots with 10 mg/l and 100 mg/l Indole-3-butyric acid (IBA). This means that stem cuttings of A. nilotica plants responded to low as well as to high IBA concentrations. The low rooting ability was probably indicated the slowing down of growth in shoots as shown by the low percentage of rooting of cuttings. Similarly Leakey et al., (1990) related the rooting ability of stem cuttings to the morphological status of the parent plant. Presumably these variations are attributed to the hormonal contents of the shoots from which cuttings were obtained. Therefore it could be concluded that the formation of adventitious roots is probably initiated by a reaction between the pericycle cells and the hormone that travels from the developed shoots. Moreover, El-Tigani (2003) discussed the relation of the degree of lignifications of the primary phloem cells with rooting. The conclusion reached could be that, as the propagation ability of the cuttings falls, the continuation of lignified tissue increases ending with a lignified ring. But in this experiment all plants cuttings and their varying percentages may indicate that the lignified elements has do not prevent primordial growth to form adventitious roots initials as reported by Ali (1997) on rooting of A. senegal plant. Treated and untreated stem cuttings with exogenous auxins such as IBA exhibited seasonal variations in their rooting response where the use of exogenous auxins enhanced rooting in some seasons. The effectiveness of auxins for root formation may also be related to changes in the level of contents of internal nutrient such as phenols and carbohydrates compounds in the stem cuttings that was supported by the work of Ali (1986). It seems therefore that A. nilotica shoots contain appropriate ratios of these complex compounds that help in the production of cuttings which root readily. Hence better rooting occurs during the winter after bud sprouting, development and formation of branches. In contrast during autumn these inhibitors such as the phenol compounds might be accumulated in toxic levels that inhibited the formation and initiation of adventitious roots. It is concluded that vegetative propagation of nursery plants and mature ones of Acacia nilotica subs niltica is successful by stem cuttings with use of 50 mg/l IBA and 10 mg/l IBA during winter and summer. Rooted cuttings can be used successfully in establish seed orchards and large-scale production plantations. But, commercial production work needs continunity to quantify the optimum environmental conditions that maximize rooting of A. nilotica cuttings. Recommendation According to the results; it is recommended that: vegetative propagation of Acacia nilotica subs nilotica is through cuttings of lengths cm and cm diameter with use of the following: a) For nursery stock plants 50 mg/l IBA in winter and 10 mg/l IBA in summer. b) Four mature cuttings, 10 mg/l IBA in winter. The IBA should be applied by the dilute dip method for 18 hours placed in germination room. 4

5 References Abdelazim, Y. A; Daf Alla, M., and Mahmoud, A. E. (2006). A Research Note on Variability of Mechanical Properties of Acacia nilotica Wood in Abukouk Forest. Sudan Silva 12 (1): Ali, Y. H. (1986). Vegetative Propagation of some Forest Trees: Structural, Physiological and Biochemical Aspects. M Sc. Thesis University of Khartoum Sudan Ali, Y. H. (1997). Physiological and Biochemical Factors Affecting the Propagation of Acacia senegal (Willd.). PhD Thesis, University of Khartoum Sudan Ali, Y.H., and El-Tigani, S. (2003). Vegetative Propagation of Acacia senegal (Willd.) by Stem Cuttings. Sudan Silva 9 (2): El-Amin, H. M. (1990). Trees and Shrubs of the Sudan; Ithaca Press. P El-Tigani, S. (2003). Comparative Anatomy of Stem Explants Used in Vegetative Propagation of some Acacia species. Sudan Journal of Basic Sciences. Series B: Biological Science: Sudan Institute for Natural Sciences Hartman, H. T., and Kester, D. E. (1983). Plant propagation: Principles and practices (Fourth Ed.) Prentice Hall. Inc. New Jersey. 662pp. Libby, W. J. And Rauter, R. M. (1984). Advantages of Clone Forestry. Scientific and Technical Articles. The Forestry Chronicle Leakey, R. R. B.; Chapman, U.R. and Longman K.A.(1990). Physiological studies for tropical improvement and conservation.: Factors affecting root initiation in cuttings of Triplochiton scleroxylon. K. Scham. Forest Ecology and Management. 4: Longman, K. A., and Jenik, J. J. (1990). Tropical Forest and its Environment (2nd ed.) Co- Published in the United States with John Wiley and sons Inc., New York. Zobel, B.J. van Wry, G. and Per Stahl. (1987) Growing Exotic Forests. A Wiley-inter-science publication, John Wiley and Sons; New York chi Chester Birchen Toronto Singapore 508pp Table1. Test of significance differences of Indole-3-butyric acid (IBA) mg/l and season's on % rooting cuttings of Acacia nilotica at a) nursery plants cuttings; and b) mature plants cuttings. a) Nursery plants cuttings Season Concentration of Indole-3-butyric acid (mg/l) Winter Summer Autumn Probability b) Mature plants cuttings Probability Season Concentration of Indole-3-butyric acid (mg/l) Probability Winter Summer Autumn Probability Statistical significance difference of percentage rooting of cuttings was based on arcsine-transformed values using Tukey-Kramer at 0.05% 5

6 mg/l IBA Figure 1. Rooting of stemss cuttings of mature Acacia nilotica trees at various concentrations of IBA 6