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.
Description:
A Thesis
Submitted to the Faculty of Agriculture, Dept. of Plant Pathology
Sher-e-Bangla Agricultural University, Dhaka
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE (MS)
IN
PLANT PATHOLOGY
SEMESTER: JANUARY-JUNE, 2021
