Title page for ETD etd-04272011-165903

Type of Document Dissertation
Author Ward, Nicole A
URN etd-04272011-165903
Title Simplicillium lanosoniveum, a Mycoparasite of Phakopsora pachyrhizi and Its Use as a Biological Control Agent
Degree Doctor of Philosophy (Ph.D.)
Department Plant Pathology & Crop Physiology
Advisory Committee
Advisor Name Title
Schneider, Raymond W. Committee Chair
Aime, Mary Catherine Committee Member
Datnoff, Lawrence E. Committee Member
Padgett, Guy Boyd Committee Member
Stout, Michael J. Dean's Representative
  • biocontrol
  • plant pathology
  • soybean
Date of Defense 2011-03-31
Availability unrestricted
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.
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