Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2001
Publication Date: 9/20/2001
Citation: BUJOLD, I., PAULITZ, T.C., CARISSE, O. EFFECTS OF MICROSPHAEROPSIS SP. ON THE PRODUCTION OF PERITHECIA AND ASCOSPORES OF GIBBERELLA ZEAE. PLANT DISEASE. 85: 977-984. 2001. Interpretive Summary: Microsphaeropsis sp. (isolate P130A) is an antagonist of Venturia inaequalis, the causal agent of apple scab. It prevents the formation of fruiting bodies on the fallen apple leaves. We tested it for the ability to prevent the formation of fruiting bodies (perithecia) of Gibberella zeae on wheat straw. Gibberella zeae is the causal agent of Fusarium head blight, an important disease of wheat that produces mycotoxins in the grain. Microsphaeropsis reduced the formation of perithecia in both lab and field tests.
Technical Abstract: The potential of Microsphaeropis sp. (isolate P130A) as an antagonist of Gibberella zeae was tested under in vitro and field conditions. Firstly, an in vitro method of ascospore production was developed on wheat and corn residues. The plant type (corn and wheat), residue type (straw/stalk or grain), and incubation conditions (closed or open) had a significant effect on ascospore production. Perithecia were more abundant on wheat and corn grain incubated under open conditions. On these two substrates, the application of microsphaeropis sp. significantly reduced ascospore production. On wheat, the antagonist had a significant effect when applied 2 weeks before (-2), at the same time (0), and 4 weeks after (+4) inoculation with G. zae, with 1.73, 0.31, 1.11, and 1.36 log ascospores per cm2 for the control, -2, 0, and +4 weeks treatments, respectively. On corn, Microsphaeropsis sp. had a significant effect when applid 2 weeks before, at the same time, 4 weeks after and 6 weeks after inoculation with G. zeae with 3.02, 0.23, 1.29, 2.35, and 2.22 log ascospores per cm2 for the control, -2, 0, +4, and +6 weeks treatments, respectively. When applied to crop residues in the field as postharvest or preplanting applications, Microsphaeropis sp. had no effect on the pattern of perithecia maturation, but significantly reduced the number of perithecia produced on two sampling dates, May 1998 and July 1999. There is a potential to biologically reduce the initial inoculum of G. zeae; however, more work is needed to optimize the efficacy of the biocontrol agent.