新蚜虫疠霉连续液体培养的菌丝生物量、产孢量及杀蚜毒力

BIOMASS, SPORULATION AND APHID-INFECTING VIRULENCE OF PANDORA NEOAPHIDIS MYCELIA PRODUCED IN REPEATED LIQUID CULTURE 

继代培养常被疑为虫霉菌种毒力下降或某些生物学性状发生改变的原因之一。从研究新蚜虫疠霉 (Pandoraneoaphidis)固体平板菌落的液体培养获得的初始菌液出发 ,连续 6次继代液培 ,测定了其在萨氏营养液中继代培养生产的菌丝生物量、产孢量及其对桃蚜 (Myzuspersicae)的毒力。在初始菌液的生物量 8 8mg mL和产孢量 7 2× 1 0 5孢子 mg的条件下 ,以三种转接比 (种液 营养液 ,v v)连续 6次继代培养 ,在 1 2 0转接比下的菌丝生物量和产孢量分别为 6 4～ 1 0 0mg mL和 7 3× 1 0 5～ 1 0 8× 1 0 5孢子 mg,在 2 2 0下为 5 7～ 8 5mg mL和 1 0 0× 1 0 5～ 1 2 1× 1 0 5孢子 mg ,在 4 2 0下为 5 5～ 1 0 9mg mL和 6 4× 1 0 5～ 1 0 9× 1 0 5孢子 mg。方差分析表明 ,继代培养对生物量和产孢量均无显著影响 (P <0 0 5)。用初始菌液和 1 2 0转接比下继代培养的菌液制备而成的接种体对桃蚜进行两组毒力测定 ,每一组测定的接种体为所有 7批菌丝体产生的分生孢子 ,第二组测定只包括初始菌液、第 3及第 6次继代培养物。十批接种体在接种后第 3～ 7d对桃蚜的LD50 依次为 2 2 8～ 1 62 0、4 7～ 49 4、2 8～ 1 6 7、2 3～9 5和 1 8～ 5 2个孢子 mm2 ,其中第 7d的LD50

Repeated culture of entomophthoraceous isolates is a suspectable factor leading to their virulence decline of biological variation. In the present study, an isolate of \%Pandora neoaphidis\%,F98028,was repeatedly cultured six times at the regime of 20℃ and 80 r/min in Sabouraud dextrose broth(SDB) at three inoculation ratio of 1/20,2/20, and 4/20 (seed culture over fresh SDB). Mycelial biomass(MB), sporulation capacity(SC), and virulence to the green peach aphid, \%Myzus persicae\%,were assessed for each of the subcultures. The repeated liquid cultures, initiating from seed culture with MB 8.84 mg/mL ad SC 7.22×10 5 conidia/mg, yielded MB and SC in a range of 6\^4～10\^0?mg/mL and 7\^3×10 5～10\^8×10 5 conidia/mg at the ratio of 1/20(72h culture), 5\^7～8\^5 mg/mL and 10\^0×10 5～12\^1×10 5 condia/mg at 2/20(60?h culture), and 5\^5～10\^9 mg/mL and 6\^4×10 5～10\^9×10 5 conidia/mg at 4/20(48?h culture), respectively. There was no significant difference in both MB and SC among the cultures(\%F=0\^299,P=0\^903)\% or the three inoculation ratios (\%F=0\^561,P=0\^587)\%. Inocula from each of the cultures at the inoculation ratio of 1/20 were repeatedly bioassayed on the second and third instar colonies of \%M.periscae.\% Based on time\|dose\|mortality analysis, the estimates of LD\-\{50\}s for all batches of the inocula were 22\^8～162,4\^7～49\^4,2\^8～16\^7,2\^3～9\^5,and 1\^8～5\^2 conidia/mm\+2 3～7 d after inoculation, respectively. All the estimates for the repeated cultures fell within a range previously reported. Thus, the method used for repeated liquid culture in this study did not cause a visible decline in the virulence of \%P.neoaphidis\% F98028.