Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2007
Publication Date: 6/1/2007
Citation: Miles, M.R., Pastor Corrales, M.A., Hartman, G.L., Frederick, R.D. 2007. Differential response of common bean cultivars to phakopsora pachyrhizi. Plant Disease.91: 698-704
Interpretive Summary: Soybean rust has been a major disease limiting soybean production in the tropical and subtropical areas of Asia and South America where yield losses ranging from 10 to 80% have been reported. However, there is little information on its impact on common bean. A set of 16 common bean cultivars with known genes for resistance to common bean rust, three soybean accessions that were sources of the single gene resistance to the fungus (P. pachyrhizi) that causes soybean rust, and the moderately susceptible soybean ‘Ina’ were evaluated in seedling inoculations with six isolates of the rust pathogen. Resistance to soybean rust was found to be independent of the resistances genes for common bean rust and these common beans were more resistant than the soybeans to the soybean rust isolates used in the study. This research is important to common bean and soybean producers, as it addresses the effect of soybean rust on common bean production.
Technical Abstract: Soybean rust (Phakopsora pachyrhizi H. Sydow & Sydow) has been reported on common beans (Phaseolus vulgaris L.) in Asia, South Africa, and the United States. However, there is little information on the interaction of individual isolates of P. pachyrhizi with common bean germplasm. A set of 16 common bean cultivars with known genes for resistance to Uromyces appendiculatus (Pers.) Unger, three soybean accessions that were sources of the single gene resistance to P. pachyrhizi, and the moderately susceptible soybean "Ina" were evaluated in seedling inoculations with six isolates of P. pachyrhizi. Among the common bean cultivars, "Aurora", "Compuesto Negro Chimaltenango" and "Pinto 114" were the most resistant to all six P. pachyrhizi isolates, with lower severity, less sporulation and consistent reddish-brown (RB) lesions associated with resistance in soybean. A differential response was observed among the common bean cultivars, with a cultivar by isolate interaction for both severity and sporulation levels, as well as the presence or absence of the RB lesion type. This differential response was independent of the known genes that condition resistance to U. appendiculatus, suggesting that resistance to P. pachyrhizi was independent from resistance to U. appendiculatus.