Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 3/1/2007
Citation: Monteros, M.J., Missaoui, A., Phillips, D.V., Walker, D.R., Boerma, H.R. 2007. Mapping and confirmation of the ‘Hyuuga’ red-brown lesion resistance gene for Asian soybean rust. Crop Science.47(2):829-836 Mar-Apr 2007 Interpretive Summary: Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is one of the most destructive foliar diseases of soybean. The development of ASR-resistant cultivars will be an important approach to management of the disease and the economic losses it can cause. One type of resistance is characterized by the development of red-brown (RB) lesions instead of the tan lesions associated with most susceptible hosts. A gene from the Japanese cultivar Hyuuga that conditions resistance to ASR isolates from Georgia was mapped, confirmed, and tagged using DNA markers. This will allow soybean breeders to select for the Hyuuga gene in segregating breeding populations without having to test plants for ASR resistance in every generation, even if only one copy of the gene is present. This should be particularly useful to breeders from the northern US, where local screening for ASR resistance at the whole plant level will be difficult or impossible. Being able to track inheritance of the Hyuuga gene with markers will also make it easier to combine the gene with other ASR resistance genes to enhance the durability of the resistance.
Technical Abstract: Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is a widespread disease of soybean [Glycine max (L.) Merr.], and has the potential to cause serious economic losses. The objectives of this study were to genetically map red-brown lesion type resistance from the Japanese cultivar Hyuuga. A population of 117 recombinant inbred lines (RILs) from the cross of ‘Dillon’ (tan lesion type) × Hyuuga (red-brown lesion type, RB) was planted in the field at Attapulgus, GA, and fingerprinted using simple sequence repeat (SSR) markers. The RB resistance gene was mapped close to Satt460 on linkage group (LG) -C2. The Dillon × Hyuuga RILs were also planted in the greenhouse to confirm the RB-lesion phenotype. Using the greenhouse phenotypic data, the resistance gene was mapped between Satt460 and Satt307 on LG-C2. When field severity rating and lesion density in the greenhouse were mapped as quantitative traits, the Rpp?(Hyuuga) locus explained 22% and 15% of the variation, respectively (P < 0.0001). The RB lesion type was associated with fewer lesions and reduced sporulation when compared to the tan lesion type. A population of F5:6 lines from the cross of ‘Benning’ × Hyuuga was screened with SSR markers in a 4 cM region on LG-C2 flanked by Satt134 and Satt460, and genotype at these markers was used to predict lesion type when the plants were exposed to P. pachyrhizi isolates from the southeastern U.S. All of the lines were selected for the Hyuuga markers in this interval. F5:6 lines with the RB lesion type had on average approximately 50% fewer lesions compared to F5:6 lines with tan lesions, and sporulation could only be detected in 6% of the RB lines compared with 100% in the tan lines. SSR markers associated with lesion type can be used by soybean breeders for marker-assisted selection to develop breeding material with the Rpp?(Hyuuga) gene for resistance to soybean rust isolates already established in the U.S.