Introduction
To effectively deploy disease resistance in cultivated crops, it is important that information be obtained regarding the diversity of virulence in the pathogen population. In the Czech Republic and the United States, annual virulence surveys are conducted on the powdery mildew (Blumeria (=Erysiphe) graminis f. sp. hordei) and leaf rust (Puccinia hordei) pathogens of barley, respectively. Recently, the virulence of a powdery mildew population in North Dakota also was analyzed by Dreiseitl and Steffenson (1996). In this study, no isolates were found with virulence for Mla1, Mla6, Mla9, Mla13, or Mlg. In contrast, a high frequency of virulence for Mla3 and Mlp was identified. The proportion of specific virulences in a pathogen population can be affected by corresponding specific resistance genes present in cultivars that are grown in a certain region. To determine whether such a relationship exists in North America, a study was undertaken to postulate powdery mildew resistance genes in barley cultivars from the United States and Canada using tester cultures of B. g. f. sp. hordei with different combinations of virulence genes.
Materials and Methods
The method used for the postulation of powdery mildew resistance genes is based on the gene-for-gene system (Flor 1955). A set of barley cultivars grown in the United States and Canada since 1981 (H. Bockelman, personal communication) and some other cultivars and lines were evaluated in this study (Table 1). Most of the cultivars were provided by the USDA National Small Grains Germplasm Research Facility, Aberdeen, Idaho. The rest of the accessions were from the barley collection at North Dakota State University and from several independent sources. To postulate the resistance genes in barley, pure culture isolates of 12 powdery mildew pathotypes from the working collection at the Agricultural Research Institute in Kromeriz were used (Dreiseitl 1996). Pathotype designations for the pathogen cultures were based on the nomenclatural system of Limpert and Muller (1994). The first nine differential cultivars were selected and arranged according to Limpert and Dreiseitl (1996). The last three differential lines in the set of 12 included P20 (Mlat), P21 (Mlg,Ml(CP) (Kølster et al. 1986), and Borwina (Dreiseitl 1993). The experiments were conducted in a glasshouse without direct solar radiation at 18-22oC. Six to eight seeds per cultivar were sown for each pathogen tester culture in 6-cm-diameter pots. Seedlings were inoculated separately with the selected pathotypes of powdery mildew at DC 11 (Zadoks et al. 1974). Eight days after inoculation, each primary leaf was evaluated for its mildew reaction using the 0-4 scale of Torp et al. (1978). Some cultivars were tested in one replication only due to low amounts of seed. The resistance spectrum for each cultivar (Table 2) was compared with that obtained for the differential host lines carrying known resistance genes. In cases where different reactions were observed within a specific cultivar-pathotype interaction (i.e. the cultivar was heterogeneous for reaction to a mildew pathotype), a plus sign (+) was used between the symbols for the postulated resistance genes present in the cultivar. When the resistance spectrum of a cultivar did not correspond to any known mildew resistance gene, the letter "U" for unknown was used to designate the resistance gene.
Results and Discussion
A total of 139 barley cultivars were tested using 12 selected powdery mildew tester pathotypes. Twenty-nine different resistance spectra were found, 13 of which (and 5 similar subspectra) are given in Table 1.
Spectrum 0 is characteristic of cultivars without any effective resistance genes. All pathotypes produce infection type (IT) 4 on lines with this spectrum. Ninety-five cultivars (66.2% of the total) exhibited this spectrum (Table 2). Components of 12 additional heterogeneous cultivars also displayed spectrum 0. The other component of these 12 cultivars were shown to carry at least one resistance gene.
Spectrum 1 is characteristic of lines carrying Mla1, where compatible reactions (IT 4) are produced in response to pathotypes 5426 and 7532 and incompatible reactions (ITs 0 to 1,0) are produced in response to the other ten pathotypes. Lines CM72, Q21861, UC476, and UC828 exhibited this spectrum. A component of the heterogeneous cultivars Advance and Prato also displayed this spectrum.
Spectrum 2 is characteristic of lines carrying Mla7, where incompatible reactions (IT 1) are produced in response to six of the twelve pathotypes. The differential line P04B possesses this resistance spectrum (Kølster et al. 1986). A component of the heterogeneous cultivar Post exhibited this spectrum.
Spectrum 3 is characteristic of lines carrying Mla12, where incompatible reactions (IT 0-1) are produced in response to eight of the twelve pathotypes. Shyri was the only cultivar tested that exhibited this spectrum.
Spectrum 4 is characteristic of lines carrying Mlat, where incompatible reactions (IT 1-2) are produced in response to ten of the twelve pathotypes. Westbar was the only cultivar tested that exhibited this spectrum.
Spectrum 5 is characteristic of lines carrying Mlg, where incompatible reactions (IT 0) are produced in response to three pathotypes (6000, 4114, and 6040). Cultivars B1202, Crystal, Empress, Harrington and Piroline exhibited this spectrum. Harrington was previously reported to carry Mlg (Steffenson and Kleinhofs 1995). A component of the heterogeneous cultivars Andre, Bearpaw, Bridge, Dawn, and Giza 126 also showed this spectrum.
Spectrum 6 is characteristic of lines carrying Mlk, where incompatible reactions (IT 1-2) are produced in response to six of the twelve pathotypes. Logan exhibited this spectrum in addition to a component of the heterogeneous cultivar Norbert.
Spectrum 7 is characteristic of lines carrying the genes Mlg,Mlk where two different incompatible reactions (ITs 0 and 1-2) are produced in response to selected pathotypes. In this case, spectrum 5 is overlayed with spectrum 6. Line ND13299 was the only accession that exhibited spectrum 7.
Spectrum 8 is characteristic of lines carrying the genes Mla7,Ml(Ab), where two different incompatible reactions (ITs 1 and 2-3) are produced in response to selected pathotypes. Spectrum 8 is similar to spectrum 2; the only difference is the characteristic IT of 2-3 to pathotype 4114 in the former. Only Triumph exhibited spectrum 8. Previously, Triumph was shown to carry Mla7,Ml(Ab),Ml(Tr3) (Brown and Jørgensen 1991). The pathotypes used in this study permitted the identification of the first two resistance genes only.
Spectrum 9 is similar to spectrum 2 and is characteristic of lines carrying the genes Mla7,Ml(Mu2). Pathotype 7532 induces a diagnostic IT 2 on lines carrying these two genes. Such a spectrum is characteristic of the differential line P06 (Kølster et al. 1986). In this study, a component of the heterogeneous cultivar Perry exhibited this spectrum.
Spectrum 10 is suggestive of cultivars carrying the gene Mla1 and an additional unknown gene (U). It is similar to spectrum 1. Cultivars with Mla1,U give a characteristic IT of 1-2 to pathotypes 5426 and 7532. This spectrum was found for the cultivars Sussex and Wysor, both developed from the Virginia Barley Breeding Program. Thus, both cultivars possess Mla1 and another common resistance gene which has not been identified. Cultivars with this resistance spectrum exhibited incompatible reactions to all of the 12 pathotypes tested.
Spectrum 11 is suggestive of cultivars carrying the gene Mla7 and an additional unknown gene (U). Cultivars with this resistance spectrum exhibit incompatible reactions to all pathotypes, except 4523. Ray was the only cultivar tested that exhibited spectrum 11.
Spectrum 12 is suggestive of cultivars carrying the gene Mla12 and an additional unknown gene (U). It is similar to spectrum 3, but is distinguished by its incompatible reaction (ITs 2-3) to pathotype 6662. Line ND14599 exhibited this spectrum.
Sixteen additional resistance spectra were found in this group of North American cultivars, but they did not conform to any of the spectra in known standards. These spectra may be due to unknown resistance genes or perhaps by other factors (particularly the environment). Homogeneous reactions were found in cultivars Beardless, Chinook, Dundy, Hector, Hitchock, Kimberly, Kline, Larker, Maury, Milton, Mollybloom, Mulligan, Norwind, and Stark (Chinook and Larker showed an identical reaction spectrum). Heterogeneous reactions (presence of an unknown resistance spectrum and spectrum 0) were found for cultivars Abee and Surry.
Summary. A set of 139 North American barley cultivars was tested using 12 pathotypes of powdery mildew [Blumeria (=Erysiphe) graminis f. sp. hordei]. Ninety-five cultivars were susceptible to all of the 12 pathotypes. Among the 44 cultivars which showed some resistance to powdery mildew, 12 were heterogeneous being comprised of two components, one with and the other without resistance. Eight known powdery mildew resistance genes (Mla1, Mla7, Mla12, Mlat, Mlg, Mlk, Ml(Ab), Ml(Mu2)) were identified in the studied group. The most common gene identified was Mlg, which was present in five homogeneous and five heterogeneous cultivars. Resistances were not identified (U) in 16 cultivars.
Acknowledgements
We thank H.E. Bockelman, T.G. Fetch and J.D. Franckowiak for providing seed of the barley cultivars. This study was supported by the U.S.-Czech Science and Technology Program (grant No. 95-042) and the Grant Agency of the Czech Republic (No. 521/97/0389).
References
Brown, J.K.M. and Jørgensen, J.H. 1991. In: J.H.Jørgensen (Ed.): Integrated Control of
Cereal Mildews: Virulence and Their Change. Roskilde, Risø National Laboratory: 263-286.
Dreiseitl, A. 1993. Polnohospodarstvo (Agriculture) 39:467-475.
Dreiseitl, A. 1996. Ochr. Rostl. (Plant Protection) 32:313-317.
Dreiseitl, A. and Steffenson B.J.: Cereal Rusts and Powdery Mildews Bulletin (in print).
Gilmour, J. 1973. Nature 246:620.
Flor, H.H. 1955. Phytopathology 45:680-685.
Limpert, E., et al. 1994. J. Phytopathology 140:359-362.
Limpert, E. and Dreiseitl, A. 1996. In: E. Limpert, M. R. Finckh and M. S. Wolfe (Eds.):
Integrated Control of Cereal Mildews and Rusts: Towards Coordination of Research Across Europe.
Limpert, E. and Müller, K. 1994. J. Phytopathology 140:346-358.
Kølster, P., et al. 1986. Crop Science 26:903-907.
Steffenson, B. J. and Kleinhofs, A. 1995. Barley Newsl. 39:89-91.
Torp, J. et al. 1978. Den Kongelige Veterinaerog Landbohojskole. Arsskrift: 75-102.
Zadoks, J.C. 1974. Weed Res. 14:415-421.
Table 1. The resistance of 139 barley cultivars to powdery mildew.
Resistance | Resistance | ||||
Cultivar | Spectrum | genes | Cultivar | Spectrum | genes |
Abee | u+0 | U+none | Glenn | 0 | none |
AC Lacombe | 0 | none | Gus | 0 | none |
Advance | 1+0 | Mla1+none | Harlan II | 0 | none |
Andre | 5+0 | Mlg+none | Harrington | 5 | Mlg |
Anson | 0 | none | Haybet | 0 | none |
Azure | 0 | none | Hazen | 0 | none |
Bartel | 0 | none | Heartland | 0 | none |
Beacon | 0 | none | Hector | u | U |
Beardless | u | U | Hesk | 0 | none |
Bearpaw | 5+0 | Mlg+none | Hitchcock | u | U |
Bedford | 0 | none | Hundred | 0 | none |
Belford | 0 | none | Johnston | 0 | none |
Blazer | 0 | none | Kamiak | 0 | none |
Boone | 0 | none | Karl | 0 | none |
Bowman | 0 | none | Karla | 0 | none |
Boyer | 0 | none | Kimberly | u | U |
Bracken | 0 | none | Klages | 0 | none |
Bridge | 5+0 | Mlg+none | Kline | u | U |
B1202 | 5 | Mlg | Klondike | 0 | none |
B1602 | 0 | none | Kold | 0 | none |
B2601 | 0 | none | Lamont | 0 | none |
B2912 | 0 | none | Larker | u | U |
B3213 | 0 | none | Lewis | 0 | none |
Cason | 0 | none | Logan | 6 | Mlk |
Chinook | u | U | Manker | 0 | none |
Clark | 0 | none | Maranna | 0 | none |
Clemson 100 | 0 | none | Maury | u | U |
CMB643-2A | 0 | none | Milton | u | U |
CM72 | 1 | Mla1 | Mollybloom | u | U |
Colter | 0 | none | Moravian 7559 | 0 | none |
Columbia | 0 | none | Moravian 10107 | 0 | none |
Condor | 0 | none | Moravian III | 0 | none |
Cougbar | 0 | none | Morex | 0 | none |
Cree | 0 | none | Mulligan | u | U |
Crest | 0 | none | ND13299 | 7 | Mlg, Mlk |
Crystal | 5 | Mlg | ND14599 | 12 | Mla12, U |
Dawn | 5+0 | Mlg+none | ND15562 | 0 | none |
Deawn | 0 | none | Nebar | 0 | none |
Diamond | 0 | none | Noble | 0 | none |
Dundy | u | U | Norbert | 6+0 | Mlk+none |
Eight-twelve | 0 | none | Nordic | 0 | none |
Empress | 5 | Mlg | Norwind | u | U |
Ershabet | 0 | none | Odessa | 0 | none |
Excel | 0 | none | Otis | 0 | none |
Foster | 0 | none | Park | 0 | none |
Gallatin | 0 | none | Perkins | 0 | none |
Giza 125 | 0 | none | Perry | 9+0 | Mla7,Ml(M |
Giza 126 | 5+0 | Mlg+none | Surry | u+0 | U+none |
Piroline | 5 | Mlg | Sussex | 10 | Mla1, U |
Post | 2+0 | Mla7+none | Sutter | 0 | none |
Prato | 1+0 | Mla1+none | Tambar 402 | 0 | none |
Preamble | 0 | none | Targhee | 0 | none |
Prilar | 0 | none | Tidewater | 0 | none |
Purcell | 0 | none | Triumph | 8 | Mla7, |
Q21861 | 1 | Mla1 | UC Signal | 0 | none |
Ray | 11 | Mla7, U | UC337 | 0 | none |
Redhill | 0 | none | UC476 | 1 | Mla1 |
Ridawn | 0 | none | UC566 | 0 | none |
Russell | 0 | none | UC828 | 1 | Mla1 |
Samson | 0 | none | Venus | 0 | none |
Schochoh | 0 | none | Virden | 0 | none |
Schuyler | 0 | none | Weal | 0 | none |
Scio | 0 | none | Weskan | 0 | none |
Seco | 0 | none | Westbar | 4 | Mlat |
Shonkin | 0 | none | Willis | 0 | none |
Showin | 0 | none | Wintermalt | 0 | none |
Shyri | 3 | Mla12 | Wocus | 0 | none |
Stander | 0 | none | Wysor | 10 | Mla1, U |
Stark | u | U | |||
Steptoe | 0 | none |
Spec- | Resistance | Powdery mildew isolates | |||||||||||
trum | genes | 4002 | 0106 | 6000 | 4114 | 4047 | 5426 | 4322 | 6662 | 4376 | 6040 | 4523 | 7532 |
0 | none | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
1 | Mla1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
1+0 | Mla1+none | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 0+4 | 4 |
2 | Mla7 | 1 | 4 | 1 | 4 | 1 | 1 | 4 | 1 | 4 | 1 | 4 | 4 |
2+0 | Mla7+none | 1+4 | 1 | 1+4 | 4 | 1+4 | 1+4 | 4 | 1+4 | 4 | 1+4 | 4 | 4 |
3 | Mla12 | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | 4 | 0-1 | 4 | 0-1 | 0-1 | 4 | 4 |
4 | Mlat | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 4 | 1-2 |
5 | Mlg | 4 | 4 | 0 | 0 | 4 | 4 | 4 | 4 | 4 | 0 | 4 | 4 |
5+0 | Mlg+none | 4 | 4 | 0+4 | 0+4 | 4 | 4 | 4 | 4 | 4 | 0+4 | 4 | 4 |
6 | Mlk | 1-2 | 1-2 | 1-2 | 1-2 | 1-2 | 4 | 4 | 4 | 4 | 1-2 | 4 | 4 |
6+0 | Mlk+none | 1+4 | 1+4 | 1+4 | 1+4 | 1+4 | 4 | 4 | 4 | 4 | 1+4 | 4 | 4 |
7 | Mlg, Mlk | 1-2 | 1-2 | 0 | 0 | 1-2 | 4 | 4 | 4 | 4 | 0 | 4 | 4 |
8 | Mla7, Ml(Ab) | 1 | - | 1 | 2-3 | 1 | 1 | 4 | 1 | 4 | 1 | 4 | 4 |
9 | Mla7, Ml(Mu2) | 1 | 4 | 1 | 4 | 1 | 1 | 4 | 1 | 4 | 1 | 4 | 2 |
9+0 | Mla7, Ml(Mu2)+none | 1+4 | 4 | 1+4 | 4 | 1+4 | 1+4 | 4 | 1+4 | 4 | 1+4 | 4 | 2 |
10 | Mla1, U | 0 | 0 | 0 | 0 | 0 | 1-2 | 0 | 0 | 0 | 0 | 0 | 1-2 |
11 | Mla17, U | 1 | 2 | 1 | 2 | 1 | 1 | 2 | 1 | 2 | 1 | 4 | 2 |
12 | Mla12, U | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 | 4 | 0-1 | 2-3 | 0-1 | 0-1 | 4 | - |
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