This study was done to investigate biochemical, histological and molecular basis of resistance after a compatible and incompatible interaction between Sorghum varieties andColletotrichum sublineolum. In the susceptible variety, the pathogen invaded all types of tissues but in resistance variety, pathogen invasion was redistricted. Localized cell death was obvious in cortical region of resistant variety that stopped further invasion of pathogen. Epidermis of susceptible variety ruptured shortly after pathogen inoculation and fungal bodies emerged whereas in resistant variety a long delay was noted in occurrence of same event. A steep increase in total phenolics and enzymes related to phenylpropenoid pathway was observed after pathogen challenge in resistant variety as compared to the susceptible one. Histochemical studies revealed heavy deposition of lignin, callose, suberin, phenolics and peroxidases in the resistant variety. These enhanced depositions reduced the pathogen invasion in the host plant. Similarly, RT-PCR analysis revealed higher expression levels of PR protein-genes in the resistant variety. This study presents the nature of a resistant host defense mechanism against a virulent pathogen and made us to integrate defense mechanism for development of resistant varieties in future.
Key words: Sorghum bicolor, Colletotrichum sublineolum, cytological, histochemical, phenolics, lignin, peroxidases, RP genes.
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