Source: SEAMEO BIOTROP's Research Grant | 2021
Abstract:
Acacia tree is one of the fastest growing forest species and provides advantages such as good wood quality, tolerance for various types of soil and environment. The wood of Acacia can be used as the main raw material for paper pulp. Acacia is one of the trees that is used as greenery in urban areas. The production of Acacia wood can be done through agricultural extensification efforts which can be carried out by expanding the Acacia plantation area on saline land. Currently, there are stands of Acacia mangium generation M1 which is mutated from 13 years old A. mangium mutations planted in the SEAMEO BIOTROP experimental garden. Seed yields from the M1 generation plants need to be tested for germination and sterility as the M2 generation. However, the M1 and M2 generation trees must also be propagated vegetatively. Vegetative propagation for the M1 and M2 A. mangium generations has never been done. Therefore, this study was aimed at seeking the right technology for vegetative propagation of the M1 and M2 generations of A. mangium. Results of direct observation showed that around the planting area of A. mangium M1 generation there were no growth of A. mangium saplings. Consequently, the seeds were taken from the M1 generation of A. mangium, which is called the M2 generation of A. mangium. To prove the existence of M2 generation, it is necessary to carry out seed germination as a test for seed sterility. Germination is an important activity from dormant seeds to growing seedlings depending on seed viability, suitable environment and in some plants depending on the seeds’ efforts to break dormancy. Therefore, it is necessary to conduct seed testing to determine the seeds’ viability or the ability of seeds to grow into seedlings under optimum environmental conditions. This study was conducted to prove the infertility of the M1 generation seeds of A. mangium obtained from mutation breeding techniques. This study is the first step in the conservation effort for A. mangium which aimed to prove the initial hypothesis that A. mangium seeds are sterile. The objective of this research were to: (i). determine the sterility of the M2 generation seeds of A. mangium; (ii) propagate A. mangium by means of shoot cuttings and grafts using materials from mature trees (M1) and from germinating M2 seeds, and (iii) obtain sterilization technique and the approriate media composition for micropropagation of A. mangium. Five treatments were applied to germinate the seeds of A. mangium Willd, namely: (A) without treatment (control); (B) cutting the cotyledons of the seeds; (C) sanding the seeds in the hylum section; (D) soaking in water for 24 hours in plain water (room temperature); (E) immersion treatment for 30 seconds in 90 oC water. This study provided information on preliminary treatment for A. mangium seeds to be used by the general public in terms of cost effeciency, time and easiness for field application. Four methods of sterilization were used to sterilize the explant of A. mangium i.e., treatment 1: 10% concentration of NaOCl for 10 minutes; treatment 2: 10% concentration of NaOCl for 15 minutes; treatment 3: 15% concentration of NaOCl for 10 minutes; and treatment 4: 15% concentration of NaOCl for 15 minutes. The explant was planted on modified MS medium. Experimental study on micropropagation technique was conducted using a Factorial Completely Randomized Design (CRD) with two factors and three replicates. The first factor was BAP (0 mg/L, 1 mg/L, 2 mg/L, and 3 mg/L), the second factor was NAA (0 mg/L, 0.1 mg/L, 0,2 mg L). , so there are 12 treatment.
The results of this study showed that each treatment provided different results on the percentage of A. mangium seed germination, i.e., treatment A with a percentage value of 6%,
treatment B with a percentage value of 91%, treatment C with a percentage value of 88%, treatment D with percentage value of 4%, and treatment E with a percentage value of 94%. Overall, the best treatment for germinating A. mangium seeds was treatments B, C and E. Germination of A. mangium seeds in treatments B, C and E was above 80%. This is categorized as high seed germination, thus proving that A. mangium seeds are not sterile. Meanwhile, the smallest percentage of seed germination occurred in treatments A (control) and D (soaking the seeds in water for 24 hours). The highest germination rate of A. mangium seeds with treatment E was 2.27% / day. Germination growth of A. mangium seeds carried out in each treatment reached a growth point of 0 on the 15th to the 20th days. The highest germination value was produced by seeds with treatment E, which was 0.64% / day, while the lowest was in treatment D, which was 0.0047% / day. The characteristic of Acacia seeds is having hard outer skin surface, so the seeds require pre-treatment to increase their germination. However, these Acasia seeds are not sterile.
The best and most effective sterilization method was explants immersion with treatment 3 (5.25% NaOCl solution 15% concentration for 10 minutes) capable of producing 84.52% sterile explants. The results of the micropropagation study showed that the best medium for propagating A. mangium explants were by tissue culture in MS medium with the addition of 1 mg/L BAP and 0.1 mg/L NAA. Micropropagation is an effort to produce considerable amounts of A. mangium explants. The multiplication rate varied from 1 to 7 depending on the growth regulator used. Cytoxines and auxin in plant are very closely related to the process of cell division and morphogenesis that direcly influence the formation of shoots and bud extention. The optimal condition of media for maximum shoot production will differ according to the physiological age of the plant. The 0.1 mg/L NAA and 1 mg/L BAP concentrations at 8 WAP provided 16 mm plant height.
Propagation of shoot cuttings using materials from old trees (M1) and from germinated seeds (M2) can produce cuttings that are capable of rooting. Cuttings from M2 germinated seedlings showed signs of root growth. Meanwhile, adult tree cuttings experienced rooting difficulty because the cells have aged so that the percentage of rooting on the cuttings decreases with the age of the tree.
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