Discovery and Deployment of Molecular Markers Linked to Fusarium Head Blight Resistance: An Integrated System for Wheat and Barley

the USA, the responsibility to address the challenge of rapid gene discovery and deployment falls primarily on Fusarium head blight (FHB), caused by Fusarium graminearum the public sector scientists in Land Grant institutions Schwabe [teleomorph Gibberella zeae (Schwein.)], is a devastating disease that reduces yield, quality and economic value of wheat (Tritiand the USDA. Breeding programs have been provided cum aestivum L.) and barley (Hordeum vulgare L.). The quantitative funding to address local breeding efforts and there are nature of resistance and tremendous expense of phenotypic screening coordinated germplasm screening systems in place. indicate that the identification of resistant genotypes in breeding popuHowever, given that most programs are working with lations might be expedited by molecular markers. The markers must the same resistance sources and given that DNA markbe polymorphic and informative across populations for them to be ers for these resistance genes are emerging, a centralized used by breeders. Worldwide, several groups are mapping genes for laboratory that provides low cost genotyping services FHB resistance in wheat and barley and marker discovery is underway. for major resistance QTL may speed the development Although these markers may be validated and made breeder-friendly of resistant cultivars. by the laboratories that developed them, the urgency of the FHB situation in North America and worldwide requires efforts to accelerAn example of the potential utility of a centralized ate this process. To take advantage of economies of scale and accelersystem can be found in two scenarios, one actual and ate information sharing, we propose the establishment of a National the other hypothetical. Despite lacking complete resisGenotyping Center (NGC) for barley and wheat. The immediate tance to FHB, the Chinese cultivar Sumai 3 and its objective of the NGC would be to identify and deploy breeder-friendly derivatives are considered the most effective sources of markers linked to FHB resistance quantitative trait loci (QTL). Over resistance discovered so far and have been widely used time, we propose that several regional genotyping centers will be in crosses (Bai and Shaner, 1994). One could argue that established to correspond to regional and market class needs. The the first step in a rapid deployment of resistance genes NGC would provide the regional centers with high throughput marker should be the creation of a set of commercially viable systems that would be used to genotype plants in breeding populations submitted by plant breeders. For the long term, we expect that the wheat cultivars containing the Sumai 3 resistance for focus of the NGC will extend beyond FHB resistance, and that a key every market class vulnerable to FHB. While this is objective will be the development of new technologies to enhance plant contrary to the conventional wisdom about genetic unibreeding efforts. formity, all FHB-threatened farmers desire access to the best possible resistance. In the hypothetical scenario, consider a malting barley which is resistant to the production of the FHB-induced H scab, or Fusarium head blight of wheat and toxin deoxynivalenol (DON), for which there is a zero barley is a significant disease with devastating ecotolerance in the malting industry. In recent years, maltnomic consequences. Losses in the USA during the ing barley production has severely declined in North 1990s approached $3000 million (Windels, 2000). As a Dakota and Minnesota as DON levels and yield losses result, in 1997 the U.S. Wheat and Barley Scab Initiative reduced its comparative advantage. Growers whose livewas established. In fiscal year 1999, $3.5 million was aplihood depends on malting barley production would find propriated by Congress for research directed towards solvit imperative that the resistant cultivars be available as ing the problems caused by FHB (http://www.scabusa. soon as possible. Clearly, the urgency of the situation org; verified January 15, 2001). One of the key objectives facing farmers hard hit by the disease requires a compreof the Scab Initiative is the rapid development of resishensive, coordinated approach using any available techtant cultivars. Among wheat and barley researchers in nology. One technology that could facilitate the rapid introDavid Van Sanford, Dep. of Agronomy, Univ. of Kentucky, Lexinggression of FHB resistance genes is marker-assisted ton, KY 40546-0091; James Anderson, Dep. of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108; Kimberly Camp(MAS) or marker-based selection (MBS). Several bell, USDA-ARS, Pullman, WA 99164; Josè Costa, NRSL Dep., Univ. groups are mapping genes for FHB resistance in wheat of Maryland, College Park, MD 20742; Perry Cregan, USDA-ARS, and barley and a number of markers have been discovSoybean and Alfalfa Research Lab., Beltsville, MD 20705; Carl ered (Kolb et al., 2001). These markers may be eventuGriffey, Dep. of Crop & Soil Env. Sciences, Virginia Tech Univ., Blacksburg, VA 24061; Patrick Hayes, Dep. of Crop and Soil Sci., ally validated in diverse populations and made breeder Oregon State Univ., Corvallis, OR 97331; Richard Ward, Crop and friendly by the laboratories that developed them. HowSoil Sciences Dep., Michigan State Univ., East Lansing, MI 48824. The investigation reported in this paper (00-06-75) is in connection Abbreviations: FHB, Fusarium head blight; NGC, national genotyping with a project of the Kentucky Agric. Exp. Stn. and is published with center; MAS, marker-assisted selection; MBS, marker-based selection; the approval of the director. Received 15 April 2000. *Corresponding QTL, quantitative trait locus; DH, doubled haploid; DON, deoxyniauthor (agr038@pop.uky.edu). valenol; SSR, simple sequence repeat; SNP, single nucleotide polymorphism. Published in Crop Sci. 41:638–644 (2001).