Thursday, November 16, 2006 - 9:30 AM

The Effects of Long-Term Tillage and Rotational Treatments on the Presence of Fusarium solani f. sp. glycines Roy in the Rhizosphere of Soybean.

C. E. Ackerman1, T. S. Abney2, F. M. Wanjau3, Sylvie Brouder4, and C. H. Nakatsu1. (1) Purdue University, Dept. Agronomy, 915 W. State St., West Lafayette, IN 47907-2054, (2) USDA-ARS and Dept. Botany & Plant Pathology, Purdue University, 915 W. State St., West Lafayette, IN 47907, (3) American Samoa Community College, P.O. Box 2609, Pago Pago, 96799, American Samoa, (4) Rm 1-300, Purdue University, Dept. Agronomy, Agronomy Dept. 915 W State Street, Purdue University, West Lafayette, IN 47907-2054

Fusarium solani f. sp. glycines Roy (FSG) - (= F. virguliforme O’Donnell), the fungus known to cause Sudden Death Syndrome (SDS) in soybean is of great economic significance due to the potential for severe crop losses as a result of infection. Although Fusarium species are common soil fungi, disease manifestation is often incomplete or altogether absent, suggesting that the presence of FSG does not necessarily lead to infection. Occurrence of SDS may be dependent upon other factors such as plant resistance or agronomic management practices. It is known that the disease generally proliferates under conditions of high rainfall and cooler temperatures. However, current understanding of the effects of different rotational and tillage treatments on the presence of the pathogen is limited. We hypothesized that long-term agronomic management practices will affect the presence of FSG in the rhizosphere of soybean. Our objective was to compare the presence of FSG in soybean rhizosphere over time and under different agronomic treatments. Treatments included: plow-monoculture soybean, plow-soybean rotated with corn, no-till monoculture soybean, and no-till soybean rotated with corn. Soybean plants were collected at specific growth stages throughout their lifecycle for two field seasons. The presence of FSG rhizosphere DNA was determined by nested PCR amplification with an Ascomycete specific primer set followed by amplification with an FSG-specific primer set. Agarose gel electrophoretic analysis of amplicons indicated that the presence of FSG was generally more frequent under the plow-monoculture treatment compared with other treatments. Additionally, the presence of FSG in rhizosphere samples generally increased through time. Ongoing research will confirm these results, providing relevant epidemiological information about the disease with regard to agronomic management practices.