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Verification of the Standard Differential Set of Blast Isolates for Bangladesh Condition

Md. Rejwan Bhuiyan
Senior Scientific Officer
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

M A Latif
Principal Scientific Officer
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

MAI Khan
Senior Scientific Officer
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

Md. Ansar Ali
Chief Scientific Officer
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

Abstract/ Executive Summary:

An investigation was carried out to confirm the reaction pattern of selected standard differential blast isolates with blast resistant gene, and to reduce the number of blast isolates for standard differential set of Bangladesh. With the collaboration of JIRCAS, Japan, Plant Pathology Division, BRRI has already selected 25 standard differential blast isolates for blast resistance studies. For confirmation of the pathogenicity of those isolates, need to check again using both Indica and Japonica background Differential Varieties (DVs). Seeds of the DVs were collected from IRRI, Philippines and JIRCAS, Japan, and now multiplying maintaining isolation distance. Depending on the preservation potentiality, rate of sporulation and consistency in reaction, fifteen isolates were confirmed in T. Aman 2014 as stadard differential blast isolates for Bangladesh. But their potentiality in dividing the large scale germplasms according to their genetic bacground are going on, which is the most important characters of differential isolates. Out of fifteen isolates only Ba015; Ba005; and Ba018 are now used in screening purpose. Again, five new isolates collected from Gazipur were also tested against different MLs to detect their virulence reaction. Among the five isolates Ba03 showed 80% resistant requency considering 25 blast resistant gene.

Keywords: Rice, Blast, Verification, Standard differential set, Isolates.

Location: BRRI Gazipur

Start Date: 01-07-2014

End Date: 30-06-2015

Program Area: Pest Management

Commodity: Rice

Objectives:

1. To confirm the reaction pattern of selected standard differential blast isolates with blast resistant genes.

2. To reduce the number of blast isolates for standard differential set of Bangladesh

Methodology:

With the collaboration of JIRCAS, Japan, Plant Pathology Division, BRRI has already selected 25 standard differential blast isolates for blast resistance studies. For confirmation of the pathogenicity of those isolates, need to check again using both Indica and Japonica background Differential Varieties (DVs). Seeds of the DVs were collected from IRRI, Philippines and JIRCAS, Japan, and now multiplying maintaining isolation distance.

Inoculum preparation and inoculation- Stock isolate (paper disc) of single spore culture were sub-cultured on oatmeal agar medium to produce inoculum. After inoculums transfer the plates were incubated at 25 to 28ºC for 12 to 14 days. The culture was scraped with a sterilized tooth brush and the plates were exposed to continuous light for 4-5 days to induce heavy sporulation. Conidia were dislodged by gentile rubbing with a paint brush from incubated plates to sterilize distilled water with 0.01% Tween 20. Spore suspensions were filtered through four layers of gauze mesh and concentration was adjusted to 10⁵ conidia per ml using hemaecytometer. Inoculation of differential varieties both Indica and Japonica background and LTH (universal susceptible check) were carried out following the standard methods. Inoculated seedlings were incubated in a dew chamber at 25ºC for 20 h; then transferred to a greenhouse maintaining 25±1ºC temperature and 70 to 80% relative humidity.

Disease assessment and Data collection- Disease reactions of the inoculated plants were evaluated at 7 days after inoculation using a 0 to 5 scale, where 0 =no evidence of infection; 1= brown specks smaller than 0.5 mm in diameter, no sporulation; 2 = brown specks about 0.5 to 1 mm in diameter, no sporulation; 3 = roundish to elliptical lesions about 1 to 3 mm in diameter with gray center surrounded by brown margins, lesions capable of sporulation; 4 = typical spindle-shaped blast lesions capable of sporulation, 3 mm or longer with necrotic gray centers and water-soaked or reddish brown margins, little or no coalescence of lesions; and 5 = lesions as in 4 but about half of one or two leaf blades killed by coalescence of lesions. The reactions of plant were further categorized as 0 to 2 as resistant (R), whereas 3 to 5 as susceptible (S) in most cases. The scores 2 to 5 were only be categorized as susceptible for the differential variety of IRBL5-M and 4 to 5 for IRBLsh-B and IRBLta2-Pi.

Source of Information: BRRI Annual Report 2014-15.

Article Link (Online Journal):

Funding Source:

1. Government	Budget:
2.	Budget:

Total Budget (Tk.) :

Achievement/Findings:

Depending on the preservation potentiality, rate of sporulation and consistency in reaction, fifteen isolates were confirmed as stadard differential blast isolates for Bangladesh. But their potentiality in dividing the large scale germplasms according to their genetic bacground are going on, which is the most important characters of differential isolates. Out of fifteen isolates only Ba015; Ba005; and Ba018 are now used in screening purpose. Again, five new isolates collected from Gazipur were also tested against different MLs to detect their virulence reaction. Among the five isolates Ba03 showed 80% resistant requency considering 25 blast resistant gene.

Knowledge Management: Report/Proceedings