In vitro budding capability of Aquilaria crassna Pierre
Ta Minh Hoa – Research subject manager
Nguyen Thi Hien – Collaborator
Summary.
Propagation of Aquilaria crassna has been carried out from leading and axillary shoots of A.crassna by in vitro method. The multiplication of the shoots has been done with leading shoots in MS medium containing BA 0.2mg/l; Kinetin 0.2 mg/l and Adenin 0.1mg/l. The growth of the shoots (containing shoot meristem or axillary shoots) takes place in MS without hormone, from the sections with 1-2 nodes (dormant axillary buds). The role of plant regulators (Auxin Cytokinin and Adenin), Auxin/Cytokinin ratio, the position of axillary shoots on the stem and the development of shoots are matters need consideration. Following are results of the project “Improved propagation of Aquilaria crassna through tissue and plant cells culture technology “carried out by the Forest Products Research Centre.
Introduction
Aquilaria crassna is one of the tree species yielding valuable non-timber forest products. In recent years a number of foreign enterprises, private companies and households in many localities in the country have invested in planting A.crassna in concentrated plantations. Thus the planting stock supply met with difficulties as a large part of A.crassna plantations was raised from seedlings, the seed sources were of poor quality. In this research we investigate the capability of production of A.crassna shoots from the shoot meristem by in vitro method and the development of the shoots at different positions on the stem of Acrassna trees many years of age and at the same time initially make a collection of A.crassna clones in vitro culture condition.
Materials
Axillary shoots of 8 – year old A.crassna trees planted in the Forest Products Research Centre garden and sections of leading shoots of 5-6 month old seedlings were used for comparison.
Method
Axillary and leading shoots of A.crassna are made into in vitro collection. Cutting axillary shoots on A.crassna stem and leading shoots of seedlings, tops of axillary shoots are cut apart and the remaining of the shoots are cut into sections (each usually contains 1-2 nodes); sterilization with HgCl2 1% and kept apart in 1/2 MS medium (Murashige Skoog 1962). Observation was made of the shoot development 15 days after the beginning of the culture in the conditions: light intensity 2500 ± 500 lux; temperature 25 ± 20C, humidity 55±5%. Observation and comparison on the variation between stem sections of axillary shoots and leading shoots of seedlings.
In vitro culture:
The culture of axillary shoot stem sections and leading shoot sections was done with MS medium containing BA 0.2 mg/l; Kinetin 0.2 mg/l and Adenin 0.1mg/l. The development of clusters of shoots 40-45 days after the beginning of the culture in the conditions: light intensity 2500±500 lux; temperature 25±20C, humidity 55±5%.
Capability of budding of samples in in vitro culture. With medium 1/2MS, variation was found in both ratio of budding samples and the quality of the buds, 15 days after the beginning of the culture. Budding of the axillary shoot stem sections is strong with high speed and good quality buds. (Figure 1).
Section samples | Number of samples | Ratio of budding samples | Budding speed | Quality |
Axillary shoot stem sections | 20 | 15/20 | high | Strong buds, stout, dark green. |
Tops of axillary shoot | 20 | 8/20 | low | Weak buds |
Leading shoots | 20 | 12/20 | average | Young buds, slender, yellowish – green leaf |
In vitro bud development
40-45 days after the beginning of the culture, no bud development was noticed in the media MS, MS with 1,3 or 5 mg/l BA.
With MS medium containing BA 0.2 mg/l; Kinetin 0.2 mg/l and Adenin 0.1 mg/l there occurred the elongation of the bud tops and about 3-4 axillary buds were found on the initial bud top. These buds made the bud top longer and at each axil there appeared an axillary bud. 45 days after the beginning of the culture the total number of the shoots was about 15-20 (Figure 2).
Discussion.
The culture of the axillary shoots of old – aged trees in sterilized medium can easily creating a collection of A.crasna clones in vitro. The variation of growth of the plants in vitro among different section samples testifies the capability of budding of old-aged trees, contributing to the conservation process of the valuable gene sources of A.crassna.
Results of the study reveals the budding capability of the stem sections of auxiliary shoots in medium 1/2 MS; the growth of the axllary buds already present on the shoots in vitro culture and the appearance of new axillary buds on the elongated shoots in medium with BA 0.2 mg/l; Kinetin 0.2 mg/l and Adenin 0.1 mg/l. The presence of the combination of Kinetin and BAP/Kinetin ratio in the medium do affect the capability of the creation of clusters of shoots and the development of axillary buds on the clusters of shoots. The approximation of BAP/Kinetin ratio to 1, i.e the balance state, the number of shoots in vitro is greater.
Conclusion.
From the results obtained, conclusion can be drawn as follows:
1. A collection of A.crassna clones in vitro can be created through the culture of axillary shoots of old – aged trees.
2. Stem sections of axillary shoots are capable of strongest budding as compared with other shoots in vitro culture. Stem sections of axillary shoots of old-aged trees give stronger budding than stem sections of seedlings.
3. The appearance of the clusters of shoots is due to the growth of the axillary buds already present on the leading shoots in vitro, new axillary buds are created in the elongation of the shoot tops in vitro in medium MS added with 0.2 mg/l BA; 0.2 mg/l Kinetin and 0.1 mg/l Adenin.
In this study we just only deal with the budding and creation of clusters of buds of old-aged trees and seedlings. We continue increasing the number of A.crassna clones of the in vitro collection at the same time studying the rooting capability of the plants from in vitro culture to obtain complete plants for planting out in the nursery.
In the future we shall conduct feasibility study on the budding capability in vitro of A.crassna trees already having scent resin to investigate the possibility of selection and conservation of gene sources of the A.crassna trees already producing scent resin.
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