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Abstract Using UV mutant breeding method for improving the herbicidal activity of HGE which was evaluated as a potential bioherbicide for biological Echinochloa species control in rice, we screened one mutant strain M1 which might be utilized as the industrial strain in liquid fermentation. It was clearly observed that the morphological characteristics of M1 were obviously different from the wild strain HGE that included M1 colony color was gray to white but HGE was dark green. Furthermore the mycelia growth rate of M1 was faster than wild strain HGE and inhibition rate of fermentation liquid to barnyardgrass radicle and plumule was also superior to HGE. After pass-generation tests for 7 times, M1 still showed fairly excellent genetic stability. Further RAPD-PCR analysis DNA of M1 and HGE suggested that their genetic substance had been actually varied. For a mass of mycelia yield and metabolized toxin products of mycoherbicide, the optimal liquid fermentation technics was confirmed with submerged culture experiments. The highest mycelial yield was up to 14.37g/L when cultured in No. 3 medium at pH7, 150r/min and 24℃ for 6 days. The optimal fermentation technics of toxin products was obtained as following instance: stationary culturing in No. 4 medium at pH7 and 24℃ for 2 weeks.
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Received: 13 September 2006
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