MORPHOLOGICAL AND BIOCHEMICAL CHARACTERIZATION OF Xanthomonas citri CAUSING CITRUS CANKER AND ITS in-vitro CONTROL WITH BOTANICALS

Abstract

ABSTRACT Xanthomonas citri pv. ctitri (Xcc), causing citrus canker - the most devastating disease of citrus, has been studied through biochemical analysis, morphological characterization and invitro

management by selected botanicals. The laboratory works has been done at Central Laboratory of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh. In biochemical test, the pathogen reacted on Gram Staining and Kovac’s negative but the isolate was positive for KOH. All isolates were found rod shaped, with colony colour ranging from yellow to pale yellow with mucoid surface. Altogether 100 fruits and 300 leaves samples were collected from three markets and four nurseries of Dhaka districts, respectively and pathogenicity of Xanthomonas citri was tested. The isolates showed varied reactions in the symptoms development. In total, eighteen isolates from infected fruits and twenty one isolates from infected leaves were characterized. The isolates viz. Xcc-F-1, Xcc-F-2, Xcc-F-3, Xcc-F-4, Xcc-F-5 and Xcc-F-6 were found highly virulent and produced typical symptoms at the point of inoculation within 13 to 15 days while isolates Xcc-F-1 to Xcc-F-21 developed symptoms within 12 to 15 days in leaves. Six botanical extracts namely, Neem (T 1 ), Tulsi (T 2 ), Ginger (T 3 ), Turmeric (T 4 ), Garlic (T 5 ), and Onion (T 6 ) were evaluated for their efficacy against Xanthomonas citri. Zingiber officinale (Ginger) showed the highest 15.87 ± 0.0 mm and 9.40 ± 0.0 mm diameter inhibition zone against the isolated bacteria in 1:1 (25g) and 1:2 (100g) concentrations, respectively followed by 7.50 ± 0.0 mm diameter recorded in Azadiricta indica in 1:4 concentration. Allium sativum extract showed the lowest 8.0, 6.70 and 5.83 mm diameter of inhibition against the isolated bacteria in all concentrations. The present investigation concludes that there exist pathological and biochemical variations amongst the different isolates of Xanthomonas citri pv. citri and the tested botanicals showed promising performances in control the pathogen in- vitro.