Study Of Genetic Variation Of Bipolaris Species, The Causal Agent Of Rice Brown Spot Disease In Guilan Province Based On PCR-RFLP
2007
Safari Motlagh, M. R., Associated Prof, of Plant Pathology, College of Agriculture, Azad Univ., Rasht. | Nikkhah, M.J., Associated Prof. of Plant Pathology., College of Agriculture. Tehran Univ., Karaj.
Brown spot is one of the most important seedborne diseases of rice . Two species of fungus including B. oryzae and B. victoriae were previously record as the causal agent of disease in Guilan province. The study on 342 isolates of its fungus collected from rice fields of Guilan, revealed that besides the above species two other species including B. indica and B. bicolor, were reported as causal agent of the disease. The basis of identification, was morphological characteristics such as color of the colonies, shape, color and size of conidia and conidiophores, the process of conidium formation and pattern of conidium germination. B. victoriae was the most abundant species in Guilan, and B. oryzae, B. bicolor and B. indica were the subsequent species, respectively. Pathogenicity test on these four species was applied on seedlings of rice in dessicator, which revealed the pathogenicity of the species and their ability to cause brown spot on rice. 180 isolates of 342 isolates were studied by PCR-RFLP . In order to do PCR-RFLP, two groups of primers and three restriction enzyme were applied .At first, the DNA of all isolates was isolated, and was amplified in thermocycler. Cluster analysis using UPGMA method gaved four DNA fingerprinting groups in relation to B. victoriae, B. oryzae, B. bicolor and B. indica with the abundance of 85%, 10%, 3% and 2%, respectively. Levels of polymorphism was observed between DNA of different isolates as this polymorphism was observed either between or within species. The pattern of DNA bands couldn’t show the direct correlation between polymorphism and climates or geographical areas. Therefore, application PCR-RFLP is useful for identification of the fungi at the species level and can provide good results for further studies including introduction of resistant varieties.
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