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Leaf Blight Disease Caused by Pseudomonas Syringae Pv. Syringae in the Nurseries of Litchi (litchi Chinensis Sonn.) and Its Management

M.A.H. Khan
On-Farm Research Division, Bangladesh Agricultural Research Institute, Mymensingh

I. Hossain
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh

M.U. Ahmad
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh

M.S.M. Chowdhury
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh

Abstract/ Executive Summary:

Leaf blight of seven varieties of litchi caused by Pseudomonas syringae pv. syringae was surveyed in the nurseries of major litchi growing areas in Bangladesh viz. Rajshahi, Dinajpur, Rangpur, Mymensingh and Khagrachari. The mean level of incidence and severity were 8.58 and 7.88% in Rajshahi, 9.88 and 8.88% in Dinajpur, 8.44 and 7.76% in Rangpur, 6.50 and 6.18% in Mymensingh and 9.00 and 7.98% in Khagrachari. Incidence and severity of bacterial leaf blight disease of litchi varied significantly depending on weather conditions. Correlation studies revealed that bacterial leaf blight disease of litchi seedlings were positively correlated with temperature, rainfall and relative humidity, where temperature and rainfall was the major factor to the variations of both incidence and severity. Antibiotic sensitivity test revealed that among fifteen isolates, most of the isolates of P. syringae pv. syringae collected from litchi were sensitive to Gentamycin and Erythromycin. Under net house condition, six different treatments (i) Gentamycin @ 0.05%, (ii) Erythromycin @ 0.05%, (iii) Doxycycline @ 0.05%,(iv) Copper sulphate @ 0.05%, (v) BAU-Biofungicide @ 2% and (vi) Control were used for controlling bacterial leaf blight of litchi (Variety: China-3). BAU-Biofungicide was found to be superior in controlling bacterial leaf blight of litchi that reduced 33.64% disease incidence and 60.77 % disease severity in 2010-11 and 63.76% disease incidence and 61.40 % disease severity in 2011-12 over control when applied as foliar spray @ 2% followed by Copper sulphate (0.05%) and Erythromycin (0.05%).

Keywords: Antibiotic, BAU-Biofungicide, Litchi, Leaf blight

Location: Rajshahi, Dinajpur, Rangpur, Mymensingh and Khagrachari

Start Date: 10-07-2010

End Date: 10-04-2014

Program Area: Pest Management

Commodity: Diseases

Objectives:

To evaluate some antibiotics, Copper sulphate and BAU-Biofungicide for the management of bacterial leaf blight of litchi.

Methodology:

Survey on the incidence and severity of leaf blight disease of litchi Survey was conducted at different nurseries of five major litchi growing areas of Bangladesh viz. Rajshahi, Dinajpur, Rangpur, Mymensingh and Khagrachari from 10 July 2010 to 10 April 2011 and 10 July 2011 to 10 April 2012. During the survey 30 saplings of litchi for each variety were selected randomly from each location (nursery). In each nursery 30 tagged saplings of each variety were considered for disease incidence and severity. Altogether seven varieties of litchi were surveyed (Table 1). Number of saplings and number of healthy and diseased saplings were recorded from the selected nurseries. Each of the selected saplings was observed carefully and symptoms of leaf blight disease were recorded following the descriptions of Pathak (1980), Burhan (1987), Rawal (1997) and Singh (1998). The disease incidence and severity were evaluated following the formula of Rai and Mamatha (2005), and Johnston (2000), respectively. Meteorological data on temperature, relative humidity and rainfall were collected from weather stations of selected areas to determine the effect of these weather factors on incidence and severity of leaf blight of litchi. Antibiotic sensitivity test of Pseudomonas syringae pv. syringae- Fifteen isolates of P. Syringae pv. syringe were isolated from blighted leaves of litchi then identified and used in this experiment. The isolates were preserved in 10% skimmed milk, kept at -20°C in refrigerator for antibiotic sensitivity test. Sensitivity of P. syringae pv. syringae isolate to different antibiotics was determined in-vitro by employing Kirby-Bauer disc diffusion method (Larkin, 2006). Antimicrobial discs of 0.05% were used for the test. The used antibiotics were Gentamycin, Erythromycin and Doxycycline. With a sterile pipette a drop of test culture of bacteria was poured on NA plate. Sterile glass spreader was used to spread the culture homogenously on the medium. The plate was allowed to sit at room temperature at least 3 to 5 minutes. Then three antibiotic discs were placed aseptically onto the surface of the inoculated plates applying appropriate special arrangement with the help of a sterile forceps. The plates were incubated at 35 ± 2 ?C in the incubator. After 48 hrs of incubation the inhibition zones were measured and recorded. The plates were examined and the diameter of each zone of complete inhibition was measured in millimeter. At the time of measuring zone diameters, always rounded up to the next millimeter. For each antibiotic indicating on the recording sheet the zone size was reported as sensitive (S), intermediate (I), or resistant (R). Management of bacterial leaf blight of litchi- The pot experiment was carried out from July 2012 to June 2013 in the net house, Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, Bangladesh. Three years old saplings of litchi variety China-3 were used and grown in pots. Six different treatments were employed viz. T₁= Gentamycin applied as foliar spray @ 0.05%, T₂= Erithromycin applied as foliar spray @ 0.05%, T₃= Doxycycline applied as foliar spray @ 0.05%, T₄= Copper sulphate applied as foliar spray @ 0.05%, T₅= BAU-Biofungicide applied as foliar spray @ 2% and T₆= Untreated control. The experiment was laid out in Completely Randomized Design (CRD) with three replications. The data were recorded on height of the saplings (cm), total number of branch/sapling, total number of leaves/sapling, number of diseased leaves/sapling and percent leaf area diseased/sapling. The incidence and severity of bacterial leaf blight of litchi was assayed following the formula of Rai and Mamatha (2005), and, Johnston (2000), respectively.

Source of Information: The Agriculturists 15(1): 10-18 (2017)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Bacterial leaf blight (Pseudomonas syringae pv. syringae) of litchi is a great threat for raising quality and healthy saplings in order to get higher fruit production. Most of the isolates of P.syringaepv. syringae were sensitive to Gentamycin and Erythromycin. In net house test, BAU-Biofungicide (2%) was found superior in controlling bacterial leaf blight of litchi followed by Copper sulphate (0.05) and Erythromycin (0.05%) when applied as foliar spray. BAU- Biofungicide may be considered as an alternative means of controlling bacterial leaf blight of litchi in the country.

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