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Effect of Mild Strain on Severity of Prsv-w Infection

M. F. RAHMAN
Scientific officer (Plant Pathology)
Wheat Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur,

M. A AKANDA
Scientific officer (Plant Pathology)
Wheat Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur,

M. Z. A. SARKAR
Professor, Dept. of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur

Abstract/ Executive Summary:

Studies were conducted to develop mild/avirulent strain of PRSV-W using nitrous acid, sodium azide and UV-radiation for the mutagenic treatments. Among the three mutagens’ sodium azide at 3%, 4%, and 5%, and nitrous acid at 0.1M and 0.125M were proved to be effective in producing mild/avirulent strains of PRSV-W, while UV-radiation was proved to be ineffective. Evaluation on the effectivity of mild/avirulent strains in net house in protecting severe strain of PRSV-W proved that the efficiency of mild/avirulent strain to protect the severe strain of the virus was dependent upon the time gap between the mild strain inoculation and challenge inoculation. The challenge inoculation with the severe strain of PRSV-W after 12 days of mild strain inoculation could confer the cross-protection in about 64% pumpkin plants up to 40 days. The presence of mild/avirulent strains of PRSV-W in the asymptomatic plants challenged with severe strain of PRSV-W was tested by mechanical inoculation of Chenopodium amaranticolor to observe the development of characteristic local lesions of PRSV-W.

Keywords: PRSV, cross protection

Location: Bangabandhu Sheikh Mujibur Rabman Agricultural University (BSMRAU), Gazipur

Start Date: 01-11-2003

End Date: 30-06-2004

Program Area: Pest Management

Commodity: Virus

Objectives:

1. to develop mild/avirulent strains of PRSV-W through mutagenic treatment and 2. to test the effectivity of mild strain of PRSV-W in controlling the virus

Methodology:

The experiment was conducted in the insect proof net house of Plant Pathology Laboratory of Bangabandhu Sheikh Mujibur Rabman Agricultural University (BSMRAU), Gazipur during November 2003 to June 2004. Local pumpkin varieties were used for this experiment. Forty pumpkin seedlings were inoculated with the PRSV-W infected samples and 10 seedlings were maintained as control. After germination, fully expanded cotyledons plants were inoculated. Before inoculation, the cotyledons were dusted with 600- mesh carborundum powder. The samples were prepared by macerating 0.5g preserved leaf samples in 5 ml of 0.05 M sodium phosphate buffer, pH 7.1 The extracted sap was then rubbed on to the cotyledons by finger after rubbing with the sap, the inoculated cotyledons were washed with sterile distilled water. The plants were kept under observation for symptoms development. Similar procedures were followed to inoculate the leaves of Chenopodium amaranticolor, which was used as a local lesion host to check the PRSV-W infection. The samples were selected on the basis of symptoms and the results of DAS-ELISA to develop mild/avirulent strains through mutagenic treatments.The PRSV-W infected samples were collected based on the results of symptomatological study and DAS-ELISA following the method suggested by Noordam (1973). The preserved PRSV-W infected pumpkin samples were inoculated to the cotyledon of healthy pumpkin seedlings for the propagation of the virus according to the method of Noordam (1973). Seedlings of local indigenous variety of pumpkin was raised and maintained as previous. These pumpkin seedlings were used to test the treatment. Solution of sodium azide was prepared and ultraviolet radiation was used for mutagenic treatment following the method of Mowlick (2002). A series of sodium solution i.e., at 4%, 3%, 2%, and 1% were prepared from the 5% solution of sodium azide and preserved separately for use. The exposure times to UV-radiation were I mm, 2 mm, 3 mm, 4 mm, and 5 mm using UV light in the clean bench available in the Laboratory of BSMRAU. A series of nitrous acid solution i.e.. 0.05M, 0.07M, 0.1M, and 0.125M were prepared according to the procedures followed by Yeh et al (1984).The selected mild/avirulent strains were sap inoculated on the cotyledon of each pumpkin seedling and then inoculated with the severe strains of PPSV-W in the in foliate after 4th, 8th, and 12th days of mild strain inoculation called challenge inoculation. The control plants were inoculated at cotyledonery stage with the severe strains of PRSV-W only. All the plants were observed for symptoms development upto 40 days of challenge inoculation with 10 days interval. In all, 14 plants were used for the test.The presence of mild strain in the asymptomatic plants were tested by inoculating Chenopodium amaranticolor with the sap of the symptom less plants to observe the characteristic local lesion development as found in PRSV-W infection. The mechanical inoculation method was employed as described by Noordam (1973).

Source of Information: Bangladesh J. Agril. Res. 35(2) : 279-285, June 2010 ISSN 0258-7122

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The results suggested that among the three mutagens, namely sodium azide, UV-radiation, and nitrous acid, two mutagens-sodium azide at 3%, 4%, and 5%, and nitrous acid at 0.1M and 0.125M were found to be effective in developing mild/avirulent strain of PRSV-W from the severe strain of the virus. UV-radiation was found as ineffective. The time gap between the challenge inoculation with the severe strain after the mild strain inoculation determined the effectiveness of the mild strain in protecting the severe strain. The challenge inoculation by the severe strain of PRSV-W at 12 days of mild strain inoculation conferred cross protection in 64% plants tip to 40 days after challenged in the net house.

Knowledge Management: Journal