Abstract: Rice blast fungus is one of the most important rice pathogens， whose pathogenicity on rice can be enhanced through several ways. Successive inoculation can make their virulence improved， which is called adaptive variation. In order to understand the molecular mechanisms related to adaptive mutation， a suppression subtracted hybridization library was constructed using the original strain and the fourth generation strain after successive inoculation on rice. After verification by PCR and sequence analysis， total of 168 nonredundant EST sequences were obtained. Alignment analysis led to 110 Unigenes. BLASTX analysis against different databases was used to reveal the functions of these proteins deduced from EST sequences， which were obtained from sequence analysis of the suppression subtracted hybridization library. KEGG analysis showed that 20 Unigenes can be classified into metabolic pathways. Annotation of the proteins showed that these proteins were primarily associated with the synthesis and signal transduction. GO analysis revealed that the proteins involved in many aspects of life activities， but mainly in cell growth， nucleic acid binding and the perception of external stimuli and signal transduction.

Key words: Magnaporthe grisea, adaptive variation, suppression subtracted hybridization, EST, pathogenicity