A comparative phenotypic study between bl2 and spl6 mutant wasperformed to characterize spot formation mechanisms of bl2 mutant. Small spots appeared at the seedling stage in bl2 and later it covered large round areas on the leaves whereas, relatively small red spots in parallel line on both leaf surfaces at late tillering stage were observed in spl6. Vegetative and reproductive growth was reduced due to lesion formation at early age in the mutants. Lower growth habit and agronomic trait value was observed in mutants as compared to wild type plants. Genetic segregation data among F2 population revealed that both mutants are recessive in nature. Mesophyll chloroplast was not found in spotted area which demonstrates the damage of chloroplast cell at spotted area due to cell death. Transmission electron microscopy also confirmed the chloroplast damage. Increased level of total chlorophyll and hydrogen peroxide content were observed till 45 days of growth after transplantation under natural environment and dropped at 60 days. Catalase activity was increased until 45 days and decreased at 60 days whereas very slight level difference in protein content was observed. However, increasing level of total ascorbic acid contents were found in spl6 and bl2 as compared with wild type till 60 days after transplantation. Higher expressions of OsPDI and OsGPX1 in bl2 spotted leaves were found whereas OsTPX expression was very low in the spotted leaf. (This research was supported by the National Research foundation of Korea, Grant 0070065).