Corn and sorghum represent a major portion of the cereal crops grown in Texas as well as in the United States. Significantly, corn and sorghum are distinguished from other cereal crops by the broad range of diseases caused by a number of highly variable pathogens. In addition, all parts of the plants are vulnerable to pathogens, which makes it more difficult to establish effective management strategies. The most efficient and economic means of controlling corn and sorghum diseases is the use of disease-resistant hybrids. In addition, cultural practices and the use of chemicals enhance the effectiveness of disease management. Nonetheless, understanding the genetic, biochemical and molecular bases of fungal pathogenesis and recognizing pathogen variability in the field are critical for the development of more diverse, effective, long-term strategies to improve plant disease management.

My laboratory is focused on studying the biology of fungal pathogens of corn and sorghum, particularly that of Fusarium verticillioides and Cercospora zeae-maydis. F. verticillioides is a major pathogen of corn causing ear rot and stalk rot and produces fumonisins, a group of carcinogenic mycotoxins, on infested ears. C. zeae-maydis, causal agent of gray leaf spot of corn and sorghum, produces cercosporin, a phytotoxin suggested to be a virulence factor. Our goal is to identify and characterize genes that are involved in fungal secondary metabolism (fumonisin and cercosporin), fungal differentiation, and plant pathogenesis. Characterization of these genes and pathways will further our understanding of the mechanisms involved in disease development. We are also interested in establishing the profiles of variability in the pathogen populations related to corn and sorghum diseases in Texas. Genetic and molecular techniques as well as classical mycological and plant pathological methods will be used to investigate the variability in key pathogens. These profiles will help us understand the dynamic relationship between pathogen population and host crops, and more importantly, can be used to better evaluate and select for resistance in the field.

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Uma Shankar Sagaram, Brian D. Shaw, and Won-Bo Shim. 2007. Fusarium verticillioides GAP1, a gene encoding a putative glycolipid-anchored surface protein, participates in conidiation and cell wall structure but not virulence. Microbiology 153: 2850-2861.

Xiquan Gao, Won-Bo Shim, Cornelia Göbel, Susan Kunze, Ivo Feussner, Robert Meeley, and Michael Kolomiets. 2007. Disruption of a maize 9-lipoxygenase results in increased resistance to fungal pathogens and reduced levels of contamination with mycotoxin fumonisin. Molecular Plant-Microbe Interactions 20: 922-933.

Uma Shankar Sagaram and Won-Bo Shim. 2007. Fusarium verticillioides GBB1, a gene encoding heterotrimeric G protein ß subunit, is associated with fumonisin B1 biosynthesis and hyphal development but not with fungal virulence. Molecular Plant Pathology 8: 375-384.

Jung-Eun Kim, Kilseon Myong, Won-Bo Shim, Sung-Hwan Yun, and Yin-Won Lee. 2007. Functional characterization of acetylglutamate synthase and phosphoribosylamine-glycine ligase genes in Gibberella zeae. Current Genetics 51: 99-108.

Uma Shankar Sagaram, Mike Kolomiets, and Won-Bo Shim, 2006. Regulation of Fumonisin Biosynthesis in Fusarium verticillioides-Maize System. The Plant Pathology Journal 22: 203-210.

Uma Shankar Sagaram, Robert A. E. Butchko, and Won-Bo Shim. 2006. GBP1, a putative monomeric G-protein, is negatively associated with fumonisin B1 production in Fusarium verticillioides. Molecular Plant Pathology 7: 381-389.

Won-Bo Shim, Uma Shankar Sagaram, Yoon-E Choi, Jinny So, Heather H. Wilkinson, and Yin-Won Lee. 2006. FSR1 is essential for virulence and female fertility in Fusarium verticillioides and F. graminearum. Molecular Plant-Microbe Interactions 19: 725-733.

Won-Bo Shim and Larry D. Dunkle, 2005. Malazy, a degenerate, species-specific transposable element in Cercospora zeae-maydis. Mycologia 97: 349-355.

Won-Bo Shim, Joseph Flaherty, and Charles Woloshuk. 2003. Comparison of fumonisin B1 biosynthesis in germ and degermed kernels of maize by Fusarium verticillioides. Journal of Food Protection 66: 2116-2122.

Won-Bo Shim and Larry D. Dunkle. 2003. CZK3, a MAP kinase kinase kinase homolog in Cercospora zeae-maydis, regulates cercosporin biosynthesis, fungal development, and pathogenesis. Molecular Plant-Microbe Interactions 16: 760-768.