|Pastor Corrales, Marcial - Talo|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2007
Publication Date: 1/4/2007
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: The Asian soybean rust, caused by a fungus known as Phakopsora pachyrhizi, is a major disease that reduces soybean production in Asia, Africa and Latin America. This pathogen also attacks some 90 other leguminous crops including dry and snap beans, collectively known as the common bean. Although the occurrence of the Asian soybean rust on common bean has been reported in South Africa, and the U.S., there is little information about the reaction of different common bean cultivars react to different strains of the Asian soybean rust pathogen. Thus, the objectives of this research was to compare the reaction of a selected group of common bean and soybean cultivars to six isolates of the Asian soybean rust fungus from Asia, Africa and Latin America under greenhouse conditions. As a group, the common bean cultivars evaluated in this study were more resistant to the six isolates of the soybean rust pathogens than soybeans. None of the common bean cultivars were immune but some cultivars had low severity to all six isolates of the Asian soybean rust pathogen while others were more susceptible. Based on these and other results, the threat of soybean rust does not appear to be as severe in common bean as it is with soybean production. The gene or genes in common beans that control the resistance to the Asian soybean rust can be utilized to develop resistant common beans through traditional breeding and possibly to develop resistant soybeans using genetic engineering methods.
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.