Duarte, I., Thon, M.R. and Sukno, S.A. 2006. MANRRS 21st Annual Career Fair and Training Conference, St. Louis, Missouri. March 30- April 1, 2006.
The filamentus fungus Colletotrichum graminicola causes the disease anthracnose leaf blight and anthracnose stalk rot on corn (Zea mays). Anthracnose has become a major problem in the United States, affecting many corn fields in the Midwest, but is also of worldwide importance. During infection of susceptible corn varieties, C. graminicola, develops a series of specialized infection structures including germ tubes, appresoria, penetration pegs, primary hyphae, and secondary hyphae that allow colonization of the host tissue. In an attempt to understand the genetic basis of pathogenicity in C. graminicola, a series of mutants were constructed and screened for defects in pathogenicity. We found that mutant 87-7 had reduced virulence on corn leaves. We have compared the virulence of mutant 87-7 with that of the wild-type strain M1001 by quantitatively measuring the rate of disease development in corn leaves using pathogenicity assays. Rates of in vitro and in planta spore germination, appresorium formation, growth rate, as well as size of lesions in planta were measured and compared to that of the wild-type strain. We found that 87-7 made smaller and fewer lesions than M1001 in vitro and also produced fewer spores. Our findings show that 87-7 is less virulent than the wild-type strain and that reduced virulence may be due to defects in penetration or post-penetration events.
KEY WORDS- Colletotrichum graminicola, pathogenicity, mutant characterization