Improvement of salt-tolerance of the rain tree (Samanea saman Merr.) using colchicine treatment
2002
Kirdmanee, C.(National Science and Technology Development Agency, Bangkok (Thailand). National Center for Genetic Engineering and Biotechnology)
Saline soil has become a serious problem for plant growth. Reforestation is the most practical and effective strategy to solve this problem. However, the lack of salt-tolerant species is a limiting factor. The Rain tree (Samanea saman Merr.) is a plant that can grow quickly and can expand its roots and branches and so is suitable to solve the saline soil problem. The aim of this research is to improve the salt-tolerance of the Rain tree by using colchicines treatment. Seven clones of the Rain tree from a salt-tolerance selection program were selected to use as plant material for improving salt-tolerance. Seeds were sterilized and the seed coats wee excised before soaking in 0, 1.5, 3.0, 6.0 and 9.0 mM colchicines solution in MS liquid medium. The seedlings were transferred to 90 mM sucrose solidified-MS medium and cultured for 6 months, with subculturing at 2 month intervals. The LD sub(50) of colchicines treatment was 3.0 mM. However, plantlets derived from this treatment significantly showed the biggest leaf area and stomatal size as well as the highest DNA content and chlorophyll content, which were 1.3, 1.4, 1.5 and 1.8 times higher, respectively than those of control plantlets (0 mM colchicines). The plantlets were transferred to photoautotrophic conditions for 6 weeks. The culture medium was adjusted to 0, 171, 342, 684 and 1026 mM NaCl. Net-photosynthetic rate (NPR) in each treatment was measured and then the salt-tolerance index (STI) was calculated using the equation, STI=NPR at 1026 mM NaCl/NPR at 0 mM NaCl. The plantlets treated with colchicines had a significantly higher the salt-tolerance level than did the control plantlets. Plantlets derived from 3.0 mM colchicines treatment in each clone of Rain tree showed the STI values under salt-stress condition of 1.1-1.2. Colchicine treatment should be used to induce clone mutations so that salt-tolerance of the Rain tree.
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