~ 1567 ~    Journal of Pharmacognosy and Phytochemistry 2017; 6(5): 1567-1571 E-ISSN: 2278-4136 P-ISSN: 2349-8234 JPP 2017; 6(5): 1567-1571 Received: 20-07-2017 Accepted: 21-08-2017 Md Saroar Jahan Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh SM Zia Hasan Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Rizwoana Sharmin Lia Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Md Faruk Hasan Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Md Asadul Islam Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Biswanath Sikdar Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Md Khalekuzzaman Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Correspondence Md Khalekuzzaman Department of Genetic Engineering and Biotechnology, Faculty of Life and Earth Sciences, University of Rajshahi, Rajshahi-6205, Bangladesh Biochemical characterization and biological control measures of citrus variegated chlorosis (CVC) bacteria Md Saroar Jahan, SM Zia Hasan, Rizwoana Sharmin Lia, Md Faruk Hasan, Md Asadul Islam, Biswanath Sikdar and Md Khalekuzzaman Abstract The present investigation was undertaken to isolate and characterize citrus variegated chlorosis (CVC) bacteria as well as evaluation of its control measures through standard antibiotics and medicinally important plant extracts. The isolated bacteria was characterized by different morphological and biochemical test methods. Standard antibiotics and antibacterial sensitivity of plant extracts were tested against the isolated bacteria using disc diffusion method. In biochemical tests isolated bacteria was found to be positive in carbohydrate fermenting, catalase, Simmons Citrate, Methyl red, Kligler Iron Agar test, tween 80 test and potassium hydroxide test, while it showed urease test negative. The extract of Allium sativum showed highest antibacterial activity with 10±.5mm diameter of zone of inhibition. Erythromycin showed highest antibiotic activity with 32±0.5mm diameter of zone of inhibition against isolated bacteria. The present investigation would be helpful for further detection and biological management of CVC disease caused by Xylella fastidiosa pathogen. Keywords: Citrus spp., Citrus Variegated Chlorosis (CVC), Xylella fastidiosa, Biochemical test, Biological control Introduction The present investigation was undertaken to isolate and characterize citrus variegated chlorosis bacteria as well as evaluation of its control measures through standard antibiotics and medicinally important plant extracts. Citrus species are evergreen, subtropical important fruit crops all over the world, belonging to the family of Rutaceae. It was originated in tropical and subtropical Southeast Asia. Citrus lemon is most important fruit in all over world (Mohanapriya et al., 2013; Chaturvedi et al., 2016) [1, 2] . Citrus fruit contain zero saturated fats or cholesterol, but are good source of vitamin and dietary fiber (7.36% of RDA). It is cultivated mainly for its alkaloids, which are having anticancer activities and the antibacterial potential in crude extracts of different parts (viz., leaves, stem, root and flower) against clinically significant bacterial strains (Kawaii et al., 2000) [3] . Citrus flavonoids have a large spectrum of biological activity including antibacterial, antifungal, antidiabetic, anticancer and antiviral activities (Burt, 2004; Ortuno et al., 2006) [4, 5] . Xylella fastidiosa is a xylem-limited gram negative bacterium, which affects a large number of species, including monocotyledon and dicotyledon woody plants (Chagas et al., 1992) [6] . The development of CVC disease affects the host plant metabolism and induces morphological alterations in leaves and fruits (Silva Stenico et al., 2009) [7] . These younger trees become systemically affected by X. fastidiosa. Affected trees show foliar chlorosis resembling zinc deficiency with interveinal chlorosis. The chlorosis appears on young leaf as they mature and may also occur on older leaves and fruit size is greatly reduced. It is well known that citrus plants have been infected by Xylella fastidiosa display nutritional deficiencies, probably caused by production of extracellular polymers by the bacteria that block normal nutrient flow through the xylem. It can spread rapidly and results in significant economic losses. There are many reports on citrus plant diseases like citrus canker (Mubeen et al., 2015) [8] , citrus greening (Hosokawaa et al,. 2015) [9] and others. As far we know, there is no suitable report on this devastating disease detection and their control management. That is why, thepresent research work was aimed to characterize the CVC bacteria through different morphological and biochemical test and to evaluate its biological control measures by different antibiotics and some medicinally important plant extracts. Material and methods Collection of plant materials The present investigation was conducted during the period of 2015-2016 at Professor Joarder