STUDIES ON CITRUS CANKER CAUSED BY Xanthomonas citri subsp citri IN KAGZI LIME (Citrus aurantifolia Swingle)
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Date
2016-09
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University of Horticultural Sciences, Bagalkot
Abstract
The present investigation on “Studies on citrus canker caused by Xanthomonas
citri subsp citri on Kagzi Lime (Citrus aurantifolia Swingle)” was conducted at the
Department of Plant Pathology, College of Horticulture, Bagalkot during 2015-2016.
The causal organism X. citri subsp citri was isolated from infected leaf, branch and
fruit showing typical symptoms of bacterial canker. The pathogenic nature of the
organism was proved by Koch’s postulates and confirmed through 16srRNA
sequencing.
Survey conducted in major lime growing districts of Northern Karnataka
revealed that the disease severity on leaf was highest in Kalaburagi district with 23.11
per cent and on fruit and branch was observed highest in Raichur district with 15.78
and 16.13 per cent. Biochemical characterization revealed that the isolates collected
were Xanthomonas citri subsp citri without any variability.
The antibiotic compounds and chemicals each at three different concentrations
were evaluated for their efficacy against Xanthomonas citri subsp citri by inhibition
zone assay method. Among the different antibiotics, 2-Bromo-2 nitropropane-1,
3-diol showed highest inhibition (14.67, 16.33 and 18.17mm) at 300, 400 and
500ppm. Among the fungicides copper hydroxide recorded highest inhibition (14.33,
15.67 and 17.33 mm) at 1500, 2000 and 2500 ppm respectively.
Thirteen bacterial antagonistic bacterial bioagents were evaluated against
Xanthomonas citri subsp citri under in-vitro condition and observed maximum
inhibition (>90%) from two isolates VK-6B (Lysinibacillus xylanilyticus) and
KK-3A.
The botanicals like plant extracts and different commercial oils were evaluated
for their efficacy against Xanthomonas citri subsp citri. The alcoholic and aqueous
extracts of eleven plant extracts and nine different commercial oils were tested.
Among them Prosopis juliflora (10.83 and 15.21mm) and Garcinia indica (9.50 and
14.00mm) was found to be the most effective botanicals with maximum average
inhibition.
The experiment conducted in nursery showed that 2-Bromo-2 nitropropane-1,
3-diol and Garcinia indica treated plants showed positive result in reduction of
disease. Similarly in field condition 2-Bromo-2 nitropropane-1, 3-diol @ 0.5gm +
COH @ 2.5gm and 2-Bromo-2 nitropropane-1, 3-diol @ 0.5gm + Garcinia indica @
1:5 combination treatment recorded less disease incidence compared to other
treatments.
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