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Variation in Virulence of Isolates of Bipolaris Sorokinana (sacc.in Sorok.)shoemaker on Wheat in Bangladesh

S.K. ADHIKARY
Agrotechnology Discipline, Khulna University, Khulna,

I .H. MIAN
Department of Plant Pathology, Bangabondhu Sheikh Mujibur Rahman Agricultural University, Gazipur

Abstract/ Executive Summary:

One hundred and 22 monoconidial isolates of Bipolaris sorokiniana (Sacc. in Sorok.) Shoemaker were collected from all the major wheat growing areas of Bangladesh. The isolates were tested on a wheat variety "Sonalika" to study the variability among them. Data on seven components of disease development were recorded. The isolates were classified into four clusters based on principal component analysis. The cluster I, II, III and IV contained 22, 8, 14 and 78 isolates, respectively. Eight isolates of cluster II were found to be the most virulent and 78 isolates of cluster IV were the least virulent. Based on the intra-cluster distance, isolates of cluster IV were considered as more homogeneous than others in pathogenicity . On the basis of pathogenicity hierarchy, the isolates were grouped into two clusters at a distance level above 7.0. Cluster level I includes 114 isolates with mild and intermediate virulence and cluster II includes all eight most virulent isolates of cluster II of non-hierarchical clustering.

Keywords: Variability, Bipolaris sorokiniana, Wheat

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Start Date:

End Date:

Program Area: Pest Management

Commodity: Wheat

Objectives:

The present experiment was to ascertain the extent of variability in virulence of B. sorokiniana occur in Bangladesh .

Methodology:

The experiment was conducted during the wheat growing season of 1999-2000 in Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur. A total of 122 virulent isolates of B. sorokiniana collected from 83 upazillas of Bangadesh which include all the major wheat growing areas and a susceptible variety 'Sonalika' was used in the experiment. Three wheat seedlings were raised in polyethylene bags (12.5 cm x 10 cm) containing silty loam soil. Conidial suspension was prepared by collecting conidia from ten-day-old PDA culture. Number of conidia was adjusted to 45 x 10³ conidia/ml by counting under strereo microscope (l5X) using TAKAZA WA counting slide. Ten standard drops of Tween-20 (Polyoxyethelene 20 sorbitan monolaurate) were added to 500 ml suspension of each isolate to enhance dispersion of conidia and to adhere the conidia with the leaf. The experiment was laid out following randomized complete block design. Data were subjected to univariate and multivariate analyses. Simple correlation between pairs of components of disease development was computed. Genetic diversity among the isolates was analyzed following multivariate analysis based on components of disease development. The techniques used in multivariate analysis were: (a) Principal component analysis (PCA), (b) principal coordinate analysis (PCO), (c) cluster analysis (CLSA) and (d) canonical variate analysis (CVA). The univariate and multivariate analyses were performed by using MSTAT-C and GENSTAT (5, 13) computer programmes, respectively.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 31(1): 39-46, June 2005

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

This study provided a clear information about the variability in virulence in B. sorokiniana. The isolates were found randomly distributed in different cluster disregarding their origin from where they were collected. It indicated that diversity among .the isolates was not correlated with the regional origin. If isolates from Wheat Research Centre (DSA86, DSA 110, DSA 111, DSA 112) and isolates from Gobindagonj (GGO1 , GGO11, GG012, GG018, GG030, GG031) are considered as the representatives of two subpopulations then it is apparent that there exists a remarkable genetic variation within each sub-population. The results of the present study also provided similar information and satisfy the theory of gene flow. Diverge origin of wheat varieties cultivated in the same location of Bangladesh may be the other factor of presence of pathogenic variability among the isolates from the same location .

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