›› 2006, Vol. 49 ›› Issue (3): 393-398.

• RESEARCH PAPERS • Previous Articles     Next Articles

Broomcorn millet grain cultures of the obligate aphid pathogen Zoophthora anhuiensis (Entomophthorales) and their infectivity to Myzus persicae (Hemiptera: Aphididae)

BAO Jia-Sheng, FENG Ming-Guang   

  1. Institute of Microbiology, College of Life Sciences, Zhejiang University
  • Online:2006-07-10 Published:2006-06-20

Abstract:

The obligate aphid pathogen, Zoophthora anhuiensis (Li) Humber (Entomophthorales), is difficult to be propagated in vitro. In this study, the broomcorn millet Panicum miliaceum L. in flasks was used as solid substrate to ease in vitro propagation of the fungal pathogen. Properly steamed millet grains in flasks were mixed with pieces of the fungal colonies grown on the plates of Sabouraud egg yolk-milk agar and then maintained for stationary incubation at the regime of 20℃ and 12L∶12D. The 7-day-old millet cultures produced 13.0×104 conidia/grain and persistently sporulated for up to 6 days. The conidia discharged from the cultured grains were used to inoculate via spore shower the nymphs of the green peach aphid Myzus persicae (Sulzer) on cabbage leaves at nine dosages of 7.9~134.9 conidia/mm2. Data resulted from 7-day observation of the inoculated aphids fit very well to the time-dose-mortality model. Based on time- and dose-effect parameters estimated from the modeling, the LC50 and LC90 of the fungus against M. persicae were 59.8 and 354 conidia/mm2 on day 5 after spore shower, 39.5 and 234 conidia/mm2 on day 6, and 33.5 and 198 conidia/mm2 on day 7, respectively. The LT50 decreased to 4.3 days at the dose of 134.9 conidia/mm2 from 5.1 days at 57.7 conidia/mm2. The results showed that the millet method for propagation of the obligate aphid pathogen was not only easy and convenient but produced desirable millet cultures with each grain sporulating very well and infecting aphids as a natural host cadaver.

Key words: Zoophthora anhuiensis, Myzus persicae, broomcorn millet culture, sporulation capacity, infectivity