Mass rearing of Aphidius gifuensis (Hymenoptera : Aphidiidae) for biological control of Myzus persicae (Homoptera : Aphididae)

The green peach aphid, Myzus persicae, is a major pest of tobacco, Nicotiana tabacum, in Yunnan province, China, where its control still depends on the use of insecticides. In recent years, the local government and farmers have sought to improve the biological control of this tobacco pest. In this paper, we present methods for mass rearing Aphidius gifuensis, a dominant endoparasitoid of M. persicae on tobacco plants in this region. The tobacco cultivar K326 (N. tabacum) was used as the host plant and M. persicae as the host insect. In the greenhouse, we collected tobacco seedlings for about 35 days (i.e., until the six-true-leaf stage), transferred them to 7.5-cm diameter pots, and kept these plants in the greenhouse for another 18 days. These pots were then transferred to an insectary-greenhouse, where the tobacco seedlings were inoculated with five to seven wingless adult M. persicae per pot. After 3 days, the infested seedlings were moved to a second greenhouse to allow the aphid population to increase, and after an additional 4 +/- 1 days when 182 +/- 4.25 aphid adults and nymphs were produced per pot, they were inoculated with A. gifuensis. With this rearing system, we were able to produce 256 +/- 8.8 aphid mummies per pot, with an emergence rate of 95.6 +/- 2.45%; 69% were females. The daily cost of parasite production (recurring costs only) was US$ 0.06 per 1000 aphid mummies. With this technique, we released 109 800 parasitoids in 1998, 196 000 in 1999, 780 000 in 2000, and 5 600 000 in 2001 during a 2-month period each year This production method is discussed with respect to countrywide usage in biological control and integrated control of M. persicae.

The role of glutathione metabolism in tolerance of tobacco BY-2 suspension cells to microcystin-RR

This study was undertaken to investigate the role of the glutathione-involved detoxifying mechanism in defending the tobacco BY-2 suspension cells against microcystin-RR (MC-RR). Analysis showed that exposure of the cells to different concentrations of MC-RR (0.1, 1 and 10 mu g/mL) for 0-6 days resulted in a time and concentration-dependent decrease in cell viability and increase in reactive oxygen species (ROS) content. Reduced glutathione (GSH) and total glutathione (tGSH) content as well as glutathione reductase (GR), glutathione peroxidase (GPX) and glutathione-S-transferase (GST) activities significantly increased after 3-4 days exposure in the highest two concentration treated groups, while decreased until reaching the control values except for GPX at day 6. Oxidized glutathione (GSSG) content markedly increased compared with control in high concentration MC-RR treated group after 6 days exposure. The GSH/GSSG ratio was much higher than control in 10 mu g/mL MC-RR treated group at day 4, but after 6 days exposure, the ratios in all treated groups were lower than that of the control group.