Microplot Comparison of Rate-Reducing and Race-Specific Resistance toPhytophthora megaspermaf. sp.glycineain Soybean

Publisher Website
Google Scholar
Abstract
Microplots were artifically infested with races 1, 3, and 4 of Phytophthora megasperma f. sp. glycinea alone and in all posisble combinations. Five soybean (Glycine max) cultivars containing different levels of rate-reducing resistance alone or in combination with race-specific resistance to P. m. f. sp. glycinea were grown in microplots for 3 yr in succession. Cultivars with high levels of rate-reducing resistance sustained low disease levels regardless of the race or race combination of P. m. f. sp. glycinea. In microplots infested with incompatible races of the fungus, specific resistance was not significantly more effective than a high level of rate-reducing resistance in all 3 yr. Also, race-specific resitance was ineffective in the presence of race combinations that contained a proportion of compatible races of P. m. f. sp. glycinea. Since diverse races of the pathogen now exist over wide areas, our results indicate that a high level of rate-reducing resistance offers the best means of stable, long-term control of soybean root and stem rot.