IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372. Volume 9, Issue 9 Ver. II (Sep - Oct. 2016), PP 36-41 www.iosrjournals.org DOI: 10.9790/2380-0909023641 www.iosrjournals.org 36 | Page Chitosan Suppresses Antioxidant Enzyme Activities for Mitigating Salt Stress in Mungbean Varieties Shuma Rani Ray * , Muhammad Javidul Haque Bhuiyan, Mohammad Anowar Hossain, Sakil Mahmud, M. Tahjib-Ul-Arif Department of Biochemistry and Molecular Biology, Bangladesh Agricultural University, Mymensingh-2202. Abstract: An experiment was conducted to evaluate the effect of chitosan on the antioxidant enzyme activity and protein content in four Mungbean varieties (BARI Mung3, BARI Mung6, BINA Mung5 & BINA Mung8) under salinity. Each pot having eight kilograms of soil was ready to grow three plants of each variety. The experiment was comprised with four different conditions in triplicates viz. control, saline (40mM Nacl, 25DAS), saline+chitosan (25ppm chitosan, 30DAS on saline condition) and chitosan (25ppm chitosan on control condition). Seed collections was done at 60 DAS followed by data analysis. Protein content (using H 2 SO 4 , CuSO 4 , K 2 SO 4 & selenium in Kjeldahl method), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) (using potassium phosphate buffer, EDTA, H 2 O 2 , ascorbate, guaicol) were measured accordingly. Salinity enhanced antioxidant enzyme [CAT (maximum 2.47 mM/ml in BARI Mung3), POD (maximum 0.406 mM/ml in BARI Mung6) and APX (maximum 11.99mM/ml in BINA Mung8)] activities compare to control groups in all four varieties. On the other hand, the significant reduction in protein content during salt stress was drastically increased with chitosan application. However, chitosan played an outstanding stimulating role to reduce antioxidant enzyme activities by scavenging ROS (Reactive Oxygen Species). Therefore, it is suggested that chitosan could be an effective biostimulator to avoid the salinity stress by scavenging ROS. Keywords: Salinity stress, Chitosan, Antioxidant enzymes, ROS. I. Introduction Pulses are the best dietary source of plant proteins which can play influential role to fulfil the requirements of rapidly increasing population. Mungbean [ Vigna radiate (L.)] is an important short summer season pulse crop which is grown primarily for its protein rich edible seeds. Since it has ability to enhance the physical, chemical and biological soil properties, it is considered as an important component of sustainable agriculture (Yasin et al., 1998). This short duration crop requires less water than other summer crops; therefore, it can be grown in rain-fed areas (Anjum et. al. 2012). However, abiotic stresses severely reduce the productivity of almost all pulse crops including mungbean (Gao et al., 2007). As reported earlier among the most of the known pulse crops mungbean is relatively more sensitive to saline stress (Chakrabarti and Mukherji, 2003). Activities of antioxidant enzymes have been reported to increase in many crops (Mittova et al., 2002; Ashraf, 2009) including mungbean under saline stress. These enhanced activities of antioxidant enzymes (CAT, APX and POD) and non-enzymatic antioxidants (ascorbate, tocopherols and phenolic compounds) help to protect the mungbean plants from damages caused by salt-induced ROS (Yasar et al., 2008). It is now widely accepted that ROS are responsible for various stress-induced damage to macromolecules and ultimately to cellular structure (Moftah and Michel, 1987; Kandpal et al., 1981). So it is necessary to scavenge ROS for maintaining normal growth. APX (EC 1.11.1.11), CAT (EC 1.11.1.6) and POD (EC 1.11.1.7), together with low-molecular mass scavengers such as ascorbate, glutathione and proline, act as the main defense against ROS produced in various parts of plant cells (Apel and Hirt, 2004). Since the adverse effect of salinity causes remarkable loss in yield and quality of crops different techniques like salt resistant variety development, modulation of intercultural operation or application of some bio-stimulators are continuously being practiced by researchers. Application of chitosan (as a biostimulator) could be one of the methods to decrease the negative effect of abiotic stress. Chitosan is a cationic polysaccharide produced by alkaline N-deacetylation of chitin. The beneficial effects of chitosan in enhancing tolerance of plants to biotic and abiotic stresses and its relevance to agriculture have been described earlier (Farouk et al., 2012). Antioxidant activity of chitosan has also been described (Park et al., 2004). Chitosan modulates the plant response to several abiotic stresses including salt and water stress (Ruan and Xue 2002, Dzung et al., 2011). II. Materials And Methods Experimental site and time: The experiment was conducted at the laboratory of the department of Biochemistry and Molecular Biology, Bangladesh Agricultural University, Mymensingh during the period from January to June, 2015.