6. Genetical variability among the Alternaria solani isolates causing early blight of tomato in South Western Region of Bangladesh using RAPD analysis

Assessment of the genetic diversity of pathogenic fungi provides a basis for future resistant crop variety development. An experiment with twelve Alternaria solani isolates was conducted during the year 2019 in Plant Pathology Laboratory, Khulna University Khulna. To determine the genetic variability among the twelve Alternaria solani isolates. Isolates were isolated from infected tomato leaves collected from different locations in the Khulna district. A total of six arbitrary RAPD primers were used. Among six RAPD primers, four primers generated clearly visible banding patterns. Among twelve isolates 100% genetic similarity was observed among As4, As5, As9, As10, and As11. The lowest genetic similarity was 60% between As1 and As7 and also between As2 and As7.  From cluster analysis two distinct clusters were visible. Clusters I and II were further subdivided into two sub-clusters. Cluster I contains only three isolates and cluster II contained nine isolates. According to the PCA, the first principal component (Isolate No. 1 or As1) accounted for about 87.06% of the total variation for all genetic traits and exhibited a high correlation among the characteristics analyzed. From the eigenvectors, it was found that cumulatively first six components create 99.66% of the variation in genetic traits. A degree of variability exists among the Aalternaria solani isolates that originated in the same location. 

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