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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #336835

Research Project: IMPROVED RESISTANCE TO SOYBEAN PATHOGENS AND PESTS

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

Title: Virulence diversity of Phakopsora pachyrhizi isolates from East Africa compared to a geographically diverse collection

Author
item Murithi, Harun - International Institute Of Tropical Agriculture (IITA)
item Haudenshield, James
item Beed, Fenton - Asian Vegetable Research Center
item Mahuku, George - International Institute For Tropical Agriculture
item Joosten, Matthieu - Wageningen Ur
item Hartman, Glen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2017
Publication Date: 4/10/2017
Citation: Murithi, H.M., Haudenshield, J.S., Beed, F., Mahuku, G., Joosten, M., Hartman, G.L. 2017. Virulence diversity of Phakopsora pachyrhizi isolates from East Africa compared to a geographically diverse collection. Plant Disease. 101:1194-1200.

Interpretive Summary: Soybean rust, caused by a fungal pathogen, is a highly destructive disease causing substantial yield losses in many soybean producing regions throughout the world. Knowledge about the virulence of the fungus is needed to guide development and deployment of soybean germplasm with durable resistance against all isolates of the fungus. To assess the virulence diversity of this fungus, 25 isolates from eight countries, including 17 isolates from Africa, were characterized on 11 soybean genotypes. All isolates induced susceptible lesions with abundant sporulation on genotypes without known resistance genes and on genotypes with resistance genes Rpp4 and Rpp5b. The Rpp2 gene caused a resistant reaction to 96% of the isolates. Ten distinct pathotypes were identified in this study, four of which comprised the African isolates representing considerable P. pachyrhizi virulence. Soybean genotypes carrying Rpp1b, Rpp2, Rpp3, and Rpp5 resistance genes and cultivars Hyuuga and UG 5 were found to be resistant against most of the African isolates and therefore may be useful for soybean-breeding programs in Africa or elsewhere. This information is important to pathologists, breeders, and others interested in studying resistance in host-pathogen interactions.

Technical Abstract: Soybean rust, caused by the biotrophic pathogen Phakopsora pachyrhizi, is a highly destructive disease causing substantial yield losses in many soybean producing regions throughout the world. Knowledge about P. pachyrhizi virulence is needed to guide development and deployment of soybean germplasm with durable resistance against all pathogen populations. To assess the virulence diversity of P. pachyrhizi, 25 isolates from eight countries, including 17 isolates from Africa, were characterized on 11 soybean genotypes. All the isolates induced tan lesions with abundant sporulation on genotypes without known resistance genes and on genotypes with resistance genes Rpp4 and Rpp5b. The most durable gene was Rpp2, where 96% of the isolates induced reddish brown lesions with little or no sporulation. Of the African isolates tested, the South African isolate was the most virulent, whereas those from Kenya, Malawi and some of the isolates from Tanzania had the lowest virulence. An Argentinian isolate was virulent on most host differentials, including two cultivars carrying multiple resistance genes. Ten distinct pathotypes were identified in this study, four of which comprised the African isolates representing considerable P. pachyrhizi virulence. Soybean genotypes carrying Rpp1b, Rpp2, Rpp3, and Rpp5 resistance genes and cultivars Hyuuga and UG 5 were found to be resistant against most of the African isolates and therefore may be useful for soybean-breeding programs in Africa or elsewhere.