Study on characteristics of the mycelial growth and conidia germination of Ustilaginoidea virens

The mycelial growth and conidia germination were tested in different culture media,temperature and pH,respectively.The results showed that PSA(potato sucrose agar) was suitable for pathogen growth.The range of temperature of mycelial growth and conidia germination was 15-30 ℃,with the optimum of 28 ℃.The favorable pH was 4-11,with the optimum of pH 6.There were highest dry weight of mycelia(16.48 mg·mL-1) and number of conidia(4.19×106 conidia·mL-1) after pathogen cultured in liquid culture of PSB(potato sucrose broth) for 13 d and 9 d,respectively.However,with the prolong of culture period,the dry weight of mycelia,number of conidia,and pH obviously decreased in PSB,which exhibited inhibition to germination of rice seeds.The conidia germination rate were 81.79% and 44.20% when exposed to temperature range of 15-33 ℃ and 13-23 ℃ for 48 h under natural condition,respectively,but the conidia germination rate decreased 43.38% during 28 ℃ for 48 h after they exposed to 4 ℃ for 168 h,and no conidia germination was found after they exposed to 40 ℃ for 6 h.The 2% extract of panicle at booting stage and preliminary stage of the grout in rice varieties 'Liangyoupeijiu','Shanyou63' and 'Yongyou6' could significantly promote conidia germination,the effect was better than PSA,2% sucrose and 2% glucose solid media,with over 94% of germination rate during 24 h.