SELECTION OF IN VITRO TECHNIQUE FOR PATHOGENICITY AND SCREENING OF WHEAT CULTIVARS AGAINST BIPOLARIS SOROKINIANA

Bipolaris sorokiniana (Cochliobolus sativus) is a seed and soil borne pathogen causing leaf blight or spot blotch of wheat worldwide. In Pakistan the pathogen was identified as predominant leaf spot causing fungus in wheat growing areas during 2004 – 2006. A lab based technique has been standardized to study the pathogenic nature of the pathogen, its variability/ aggressiveness and preliminary screening of cultivars/ germplasm before going to explore the sources of resistance under natural conditions. The purpose of this study was to adopt a time and cost effective methodology which can be referred as In-vitro technique. Five methods were used to select the best one and later that method was standardized. This may be used for pathogenicity test, to check the Pathogen variability/ aggressiveness of the pathogen and preliminary screening of varieties/ germplasm against the pathogen. These methods include pot and test tube experiments by application of inoculum and seed in soil simultaneously, by dipping roots in spore suspension before planting in soil, by foliage spray with spore suspension, seed coating with spore suspension before planting in test tube with cotton swab method. Out of these five procedures the test tube with cotton swab method has been found the most appropriate and effective for the study of B. sorokiniana.