Doctor of Philosophy (PhD)


Plant Pathology and Crop Physiology

Document Type



In 2007, a filamentous fungus was recovered from sori of soybean rust (SBR), caused by Phakopsora pachyrhizi, collected from Louisiana and Florida. This fungus was identified as Simplicillium lanosoniveum on the basis of ITS sequence data and morphological traits. Simplicillium lanosoniveum was found coiling within sori and around urediniospores and showed a trophic attraction to rust sori, extending from sorus to sorus. In co-inoculated soybean leaves, the fungus did not grow or establish on leaf surfaces until sori erupted. Similarly, S. lanosoniveum colonized within 3 days and sporulated within 4 days on leaves showing disease symptoms. In field studies, when soybean leaves were inoculated with S. lanosoniveum during the latent stages of infection of SBR, disease progression was significantly limited. Additionally, sori became increasingly red-brown, which appeared to represent accelerated aging of sori. In the presence of S. lanosoniveum, urediniospores turned brown and failed to germinate. To examine the mode of action by which S. lanosoniveum antagonized urediniospores, we used scanning and transmission electron microscopy as well as confocal microscopy to characterize the interaction. Putative penetration points were observed over germ pores, and hyphae penetrated urediniospores through germ pores within the first 24 hours. By the third day, hyphae exited urediniospores and sporulated on the surface of colonized urediniospores. These studies provide evidence of a mycoparasitic interaction between S. lanosoniveum and P. pachyrhizi. Implications of this mycoparasitic relationship include potential use of S. lanosoniveum as a component of an integrated pest management program or as a biological control agent in organic soybean production.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Schneider, Raymond W.