The Effects of Ethyl Methanesulphonate and Sodium Azide on Plant Growth in Azalea (Rhododendron)

Mutagens have become an important tool in generating new variability that can be used to improve yield and quality in many crops and ornamental plants. The main objective of the experiment is to determine the effectiveness and optimum doses of chemical mutagens to induce the changes of growth and physiology responses in azalea by evaluating buds survivability (visual damage rating score), the height of new growth, new leaf number, leaf area, and chlorophyll content at different rates of Ethyl Methanesulphonate (EMS) and Sodium Azide (SA). The buds (wrapped by the absorbent cotton) of ‘G.G.Gerbing’ azalea plants were treated with EMS at rate of 0 (water), 30 mM, 60 mM, 90 mM,120mM and 150 mM for 1d, 2d, and 3d, and with SA at rate of 0 (water), 2 mM, 4 mM, 6 mM,8 mM and 10 mM for 1d, 2d, and 3d. The treatment solution was applied in a closed frame covered with plastic film and black shade cloth. After each treatment time, the cotton was removed and all buds were washed under running water for 2 minutes to remove traces of mutagens adhering to the buds surface. Plants were then placed outside in a completely randomized block design (CRBD) for evaluation. Ethyl Methanesulphonate had lower buds survival rate and new leaf number than those caused by SA. In EMS, plants treated with 90, 120, 150 mM had the highest visual damage rating score, ranging from 9.6 to 10.0, while plant treated with 0 mM EMS had the lowest visual damage rating score, followed by those treated with 30 mM (4.6) and 60 mM EMS (7.2). There was no significant difference of chlorophyll content among 0, 30, and 60 mM EMS treatment solution. In SA, plants treated with 10 mM had the highest visual damage rating score (5.8), followed by 8 mM (4.1) and 6 Mm (3.9), 4 mM (2.7), 2 mM (1.4), and 0 mM (0.2). There was no significant difference of chlorophyll content among all SA treatment solution. In both mutagens, plant treated for 3d had the lowest buds survival rate and chlorophyll content. In summary, plants can be tested with EMS at rates between 60 and 90 mM for 2d, and with SA at rates higher than 10 mM for 3d in future research.