Genes for resistance to powdery mildew in European winter barley cultivars registered in the Czech Republic and Slovakia to 2010

In central Europe, winter barley is infected by a broader spectrum of pathogens than spring barley. However, the dominant disease on susceptible cultivars is powdery mildew. The objective of this contribution was to postulate resistance genes in cultivars registered in the Czech Republic and Slovakia from 1993 to 2010 using a set of 40 isolates of the barley powdery mildew pathogen. Seedlings of 42 European cultivars were tested, and 15 known resistance genes were postulated namely, Mla6, Mla7, Mla12, Mla13, MlaRu4, Mlg, Mlh, MlLa, Mlra, Ml(Ch), Ml(Dr2), Ml(IM9), Ml(Lo), Ml(Ru2) and Ml(St). Two unknown resistances were detected, one in cultivars Gilberta, Mirko and Polana, and another in Ricus. Three cultivars (Campanile, Carrero and Mirko) were heterogeneous for mildew response. The most frequent genes were Mlra and Mlh, which were found in 25 and 14 cultivars, respectively. Genes located at the Mla locus were present in 14 cultivars; 11 of these cultivars carried Mla6. No resistance gene was detected in Hanna. Previously unknown resistances will be further characterized.     

Race-Specific Resistance Genes Against Erysiphe graminis f. sp. hordei in Old and Recent French Barley Accessions

Leaf segments from seedlings of 68 old barley varieties and 38 more recent cultivars of past or current importance in France were infected with 6—9 powdery mildew isolates in order to identify race-specific resistance genes. No resistance gene was apparent in the 21 old winter varieties, 43 of 47 old spring varieties, 10 recent winter and 3 recent spring cultivars. Two old spring varieties (‘Colmar S 142’ and ‘Johanna’) were postulated to have Mlg and Ml(CP), and two others (‘Pontrieux’ and ‘Finistère 62-5’) had an unidentified, weakly effective gene. Mlg, Ml(CP), Mlb, Mla6 and Mlal3 were the only genes detected in recent winter cultivars. Recent spring cultivars presented the greatest diversity; the presence of one or several genes among Mlal, Mla6, Mla9, Mla12, Mlg, Ml(CP), Ml(La), Mlk and mlo was postulated in several lines.     

Powdery mildew resistance in Czech and Slovak barley cultivars

Fifteen powdery mildew resistance genes and the gene MlaN81 derived from ‘Nepal 81’were found in 76 Czech and Slovak spring and winter barley cultivars when tested for reaction to a set of powdery mildew isolates. Nine cultivars (‘Donum’, ‘Expres’, ‘Jubilant’, ‘Orbit’, ‘Primus’, ‘Progres’, ‘Stabil’, ‘Vladan’ and ‘Zlatan’) are composed of lines with different resistance genes. The Mlat gene is present in nine cultivars and was transferred from the Anatolian landrace ‘A‐516′. The resistances derived from ‘KM‐1192’and ‘CI 7672’were identical and designated Ml(Kr). Five winter barley cultivars possess the Ml(Bw) resistance. The winter barley line ‘KM‐2099’carries the mlo gene. The parental cultivar ‘Palestine 10’was also tested in which the genes Mlk1, MlLa were identified. The German cultivar ‘Salome’, a parent of seven cultivars tested, probably carries the gene MlLa in addition to mlo and Mla7. The gene mlo6 may be present in the cultivar ‘Heris’. Most of the results were confirmed by the pedigrees of the cultivars.     

Postulation of genes for resistance to powdery mildew in spring barley cultivars registered in the Czech Republic from 1996 to 2010

Powdery mildew caused by the airborne biotrophic fungus Blumeria graminis f. sp. hordei is a common disease of barley. Although it can be controlled by fungicide applications, genetic resistance is an efficient and more environmentally acceptable way of limiting its effect on yield and quality. Spring barley is the second largest cereal crop in the Czech Republic and seventy spring barley cultivars (cvs.) were registered from 1996 to 2010. Seedlings of 43 cvs. were tested for reaction to selected isolates of the pathogen and resistance genes were identified using the postulation method. The following 12 known resistance genes were postulated namely, mlo, Mla6, Mla8, Mla12, Mla13, MlaRu4, MlaN81, Mlg, MlLa, Ml(Ab), Ml(Ro) and Ml(St) and two unknown resistances were found in Paulis and Prosa. Four cvs. (Azit, Paulis, Respekt and Tocada) were heterogeneous for mildew response. The most frequently found gene was mlo, which was present in 29 cvs. In nine of 15 cvs. without mlo, Mlg occurred and in seven cvs. genes located in the Mla locus were postulated. A newly identified resistance in Prosa will be further characterised. This report demonstrates that resistance gene postulation from multi-race tests remains an essential research tool for postulating genes for resistance to plant pathogens.     

Powdery Mildew Resistance Genes in 127 Northwest European Spring Barley Varieties

One hundred and twenty-seven spring barley varieties grown in Denmark since 1979 were characterized for resistance genes using 30 powdery mildew isolates. The resistance genes are traced in the pedigrees to verify the results. Eleven named genes, 12 tentatively named genes/resistances and six unknown resistances were found. Resistance in many varieties was based on combinations of either known genes or of known and new factors. The following five new or relatively new resistance genes more or less effective against the present powdery mildew populations were detected: the ‘Mlo’ resistance conferred by the recessive mlo gene with the characteristic infection type 0/(4), ‘Ricardo’ and ‘Turkish’ sources having gene Mla3 in common and ‘Turkish’ with Ml(Tu2) in addition. In three varieties the new resistance Ml(IM9) was found in combination with different Mia alleles. Variety ‘Jarek’ has two new unidentified resistances.     

Inheritance of the Powdery Mildew Resistance Mlk in Wheat

The inheritance of the Mlk powdery mildew resistance originating from ‘Heine 2174.50’ was analyzed by crossing the Mlk resistant cultivar ‘Ralle’× cv. ‘Amor’ (highly susceptible) and vice versa and by observing the reactions of F₁- and F₂-plants after inoculation with two different Mlk avirulent powdery mildew isolates. In all cases, a 3 (resistant): I (susceptible) segregation was found in F₂. The reactions of the F₂plants against the two powdery mildew isolates were identical in each case. Therefore, it is supposed that one dominant resistant gene is responsible for the resistant reactions against these two isolates. These results support the earlier assumption of Heun and Fischbeck (1987b) that the whole Mlk resistance pattern is controlled by a single gene.     

Identification of Powdery Mildew Resistance Genes in Common Wheat (Triticum aestivum L.)

Major genes for resistance to powdery mildew were analysed in 24 Czechoslovakian wheat cultivars and, in part, in their parents. For this purpose individual isolates of the pathogen, able to differentiate host lines with known resistance genes, were selected. Eight of nineteen winter wheat cultivars do not possess any major resistance gene. Three cultivars have one and seven have two genes. One cultivar carries a combination of three genes (Pm2, Pm4b, Pm8). The most common resistance genes are Pm4b, Pm5 and Pm8. Pm2 is once combined with Pm6. Only one of five spring cultivars lacked a major resistance gene. Mlk is once present alone and twice combined with Pm5. There is one spring cultivar with a novel combination of three genes: Pm1, Pm5 and another gene needing further characterization. The observations are discussed with additional results of parent lines and further information on pedigrees.     

A novel resistance against powdery mildew found in winter barley cultivars

Barley powdery mildew caused by Blumeria graminis f. sp. hordei can be effectively controlled using genetic resistance. Moreover, specific resistances are also important for characterizing cultivars and verifying their origin, purity and authenticity. Winter barley is distinguished by several specific resistances, which are usually absent in spring barley. Besides responses caused by known genes, many cultivars showed a response suggesting the presence of an unknown resistance. Therefore, the aim of this research was firstly, to test winter barley cultivars, suspected to carry an unknown resistance gene, using a large collection of pathogen isolates for their expression of this specific response and to characterise the corresponding resistance. A set of 16 winter barley accessions originating from four gene banks was studied where each accession was represented by five single plant progenies. For resistance tests, 56 isolates of the pathogen were used. A new resistance with a proposed designation of Lu was found in all 16 selected accessions. Apart from Lu, eight well‐known Ml genes (a6, a8, a12, g, h, Lo, ra and Ru2) were postulated. Two accessions of cv. 'Borwina' originating from different gene banks were found to differ in their set of resistance genes.     

Race Specific Powdery Mildew Resistance in 31 Northwest European Wheat Cultivars

Race specific powdery mildew resistance in 23 winter wheat cultivars, eight spring wheat cultivars, and 14 lines/cultivars possessing known powdery mildew resistance genes, has been studied by analyzing host/pathogen interactions. The cultivars were tested as intact seedlings, and as detached primary leaf segments on water agar; both methods revealed reproducible and concordant results. The 45 cultivars/lines were divided into 24 resistance spectra according to the patterns of reaction to the powdery mildew isolates used. Of the 31 cultivars investigated, eight did not possess any of the resistance genes detected, and the remaining 23 were divided in 16 resistance spectra. The race specific resistance of nine cultivars was conferred by the single resistance genes Pm2, Pm4b, Pm5/Ml-i: or Pm6, while the race specific resistance of 14 cultivars was conferred by 2, 3, 4 or 5 genes in combination.     

Genes for resistance to powdery mildew in European barley cultivars registered in the Czech Republic from 2011 to 2015

Barley (Hordeum vulgare) is cultivated on 49.1 million hectares worldwide with 50.2% of the area located in Europe. Powdery mildew, caused by Blumeria graminis f. sp. hordei (Bgh), occurs wherever barley is grown. Cultivar resistance plays an important role in global barley production, especially in parts of Europe where high concentrations of both spring and winter types are grown. The aim of this report was to postulate specific resistance genes in barleys from nine European countries registered in the Czech Republic from 2011 to 2015. Thirty‐five spring cultivars and 27 winter barleys were tested with 56 diverse Bgh isolates. Twenty‐five known resistance genes were postulated, and unknown genes were detected in Sandra, Saturn and Zeppelin. Unidentified specific resistance genes were also present in winter hybrids Hobbit and Wootan. Spring cultivars Arthur and Francin consisted of three and two genotypes, respectively. Resistance gene mlo was present in 26 spring cultivars, and the proportion of cultivars with this gene increased from 62.9% in 2006–2010 to 75.7% in 2011–2015. The gene Mlp1 was identified for the first time in German winter cultivar Saturn. Five spring cultivars registered in Slovakia were included in the tests. All the cultivars that were tested contained one or more specific resistance genes to powdery mildew. Adaptability of the pathogen and possibilities for breeding winter barleys are discussed.     

Effectiveness and environmental stability of quantitative powdery mildew (Blumeria graminis) resistance among winter wheat cultivars

Powdery mildew in wheat (Blumeria graminis f. sp. tritici) is a major disease in Northern and Central Europe. The aim of the study was to analyse the effectiveness and environmental stability of quantitative powdery mildew resistance under high epidemic pressure in the field across years in the absence/presence of ineffective race‐specific resistances. Cultivars with and without Pm (major) genes were inoculated in three experiments with a genetically broad mildew population with all matching virulences. Resistance was measured three times by assessing the percentage of leaf area covered by powdery mildew on a plot basis (0–100%). Mean powdery mildew severity of the highly susceptible cv. ‘Kanzler’ varied across 10 years from 24% to 66% (Exp. 1). Means of three cultivars without Pm genes, ‘Ramiro’, ‘Miras’ and ‘Zentos’, and several cultivars with ineffective Pm genes varied quantitatively from 4% to 13%. Environmental stability of the quantitative resistances was on average higher than that of susceptible genotypes, as revealed by a regression approach. In the second experiment, all groups of cultivars with ineffective Pm gene(s) contained a large proportion of entries with a similar low mildew rating as the quantitatively resistant standard ‘Miras’. Mildew severity of pairs of cultivars with the same Pm gene(s) was significantly different across 6 years (Exp. 3) indicating the presence of additional quantitative resistances in some of these cultivars. In the analysis of variance, genotypic variance had a high impact (P < 0.01) with low importance of genotype × environment interaction. Consequently, heritabilites were high (0.95–0.97). In conclusion, breeders have already accumulated effective minor genes for powdery mildew resistance in many of the released German winter wheat cultivars. These quantitative resistances are long lasting, environmentally stable and provide a high level of protection to powdery mildew.     

Resistance to powdery mildew in selections from Moroccan barley landraces

Seventy-five barley landraces from Morocco were tested for resistance to powdery mildew and a number of different resistance genes were detected. Thirty-five isolates of Blumeria graminis f. sp. hordei and the Pallas isoline differential set were used. Isolates used in the experiment had virulences corresponding to all major resistance genes used in Europe. Forty-four of the tested landraces showed resistant reactions. From each of these landraces, one to five resistant plants were selected and 92 single plant lines were created. Six lines selected from 3landraces were assumed to carry the mlo gene but they were discarded after microscopic investigation. Seventeen lines were tested in the seedling stage with 17isolates and another 69 lines were tested with 23 differential isolates. These lines showed 71 reaction spectra to isolates of powdery mildew. Eight lines (9%), 255-3-3, 282-3-4, 286-1-1, 294-2-3,294-2-4, 295-1-2, 308-1-2 and 327-2-1, selected from 7 landraces showed resistance to all isolates. Seventy-eight lines (90%) showed a resistant infection type 2with more than 50% of the isolates used. In most of the selected lines (86%) unknown genes, alone or in combination with known specific resistance genes, were detected. Four different resistance alleles (Mlat, Mla6, Mla14 and Mla1) were postulated to be present in the tested lines. The most common was Mlat, which was postulated in 35 (41%) lines. The use of newly identified sources of powdery mildew resistance in barley breeding is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genes for Powdery Mildew Resistance in Cultivars of Spring Wheat

Twenty-three cultivars of spring wheat were inoculated with nineteen different powdery mildew isolates; their ruction patterns hive been compared with those of twenty-two cultivars/lines carrying identified powdery mildew resistance genes. Applying the gene-for-gene hypothesis, it is evident that three cultivars have none of the resistance genes used, seven others (including ‘Solo’) may carry Pm4b, only. The resistance pattern of ‘Selpek’ is identical to A/-1 resistant cultivars of winter wheat and may be explained by the presence of Pm5. The resistance pattern of Pm5 (Mt-i) cultivars is very different from a number of ‘Kolibri’-related cultivars of spring wheat. Since either all or nothing of that specific pattern has been transferred to all cross progenies of ‘Kolibri’, a single gene is assumed to oe responsible for it, preliminarily designated as Ml-k. The cultivar ‘Mephisto’ carries the ‘Normandie’ resistance (Pwl 2, 9). In five cultivars to spring wheat the combined effects of at least two of the above-mentioned sources have been found. Despite the fact that ‘Normandie’ and ‘Sappo’ are not closely related. ‘Sappo’ shows the complete ‘Normandie’ resistance pattern plus that of Pm4b. The same is true for ‘Planet’ and ‘Walter’.     

Powdery mildew resistance in winter barley cultivars

Powdery mildew is the most common disease of barley in the Czech Republic and winter barley plays a crucial role in the winter survival and reproduction of the pathogen. This study was aimed at identifying resistance genes in winter barley cultivars grown in the Czech Republic from 1971 to 2005 by using the method of postulation. Forty-one cultivars and a parental line were tested at the seedling stage for their reaction to 32 selected isolates of Blumeria graminis f. sp. hordei . In total, 26 resistance spectra were detected and the following 18 resistance genes were found: Mla6 , Mla7 , Mla8 , Mla13 , Mla14 , MlaMu2 , MlaNo3 , MlaRu4 , Mlg , Mlh , MlLa , Mlra , Ml ( Bw ), Ml ( Ch ), Ml ( Dr2 ), Ml ( Dt5 ), Ml ( IM9 ) and Ml ( St ). Two cultivars ('Kiruna' and 'Sorna') exhibited heterogeneity for mildew resistance. Another source of Mla13 and a possible centre of origin of Ml ( Bw ) are discussed.     

Isolation, chromosomal location, and expression analysis of putative powdery mildew resistance genes in wheat (Triticum aestivum L.)

Special and degenerate primers are designed according to the conservative sequence of barley powdery mildew resistance genes Mla1, Mla6, and Mla13. Two wheat Mla-like orthologs, TaMla-2 and TaMla-3 are cloned and sequenced from the cDNA of wheat resistant-powdery mildew line TAM104R by RT-PCR method. TaMla-2 and TaMla-3 encode distinct but highly related coiled-coil nucleotide-binding site leucine-rich repeat type (NBS-LRR) resistant disease proteins and both reveal about 74 and 81% identity with amino acid sequence of Mla1, respectively. They are multiple copies in wheat genomes, one copy of them is mapped on wheat chromosome 1AL and two on 1BL using Chinese Spring nulli-tetra-somic lines and ditelosomic lines of 1A, 1B and 1D in southern analysis. This result suggests that may be the two Mla-like genes originated from the two diploid ancestral genomes, respectively. The expression pattern analysis of semi-quantitative PCR shows the TaMla genes are mainly expressed in leaf and sheath, and expression level is enhanced in organs infected by Erysiphe graminis, suggesting that TaMla-2 and TaMla-3 are powdery mildew resistance related-genes in wheat. Electronic Supplementary Material Supplementary material is available for this article at     

Two unnecessary powdery mildew resistance genes in a synthetic rye population are neutral on fitness

A synthetic winter rye population was produced with two race-specific powdery mildew resistance genes, one dominant (Rm1) and the other (rm2) recessive, each at a frequency of about 0.50. The population was advanced by open-pollination in an isolated plot under mildew-free conditions for eight years. Samples of generations Syn-0 through Syn-7 were inoculated in the laboratory with two mildew isolates, one avirulent to either resistance gene, the other virulent to Rm1 and avirulent to rm2, to discriminate resistant and susceptible phenotypes. From the proportions of resistant plants, frequencies of Rm1 and rm2 were calculated and the fitness of carriers of resistance alleles was estimated in relation to carriers of susceptibility alleles at the two loci using continuous models and linear regression analyses. Frequencies of the two resistance genes oscillated only weakly over the eight generations. Coefficients of selection against Rm1-and rm2rm2 genotypes were –0.04 and –0.02, respectively, and not significantly different from zero. Thus the two resistance genes were selectively neutral. It is concluded that pyramiding of major powdery mildew resistance genes in rye varieties should not reduce their yield potential in the absence of mildew.     

Identification of Wheat Powdery Mildew Resistance Genes by Analysing Host-Pathogen Interactions

Fifty-nine winter wheat cultivars and thirteen lines possessing known powdery mildew resistance genes were inoculated with eleven different isolates. By comparing their resistance patterns the responsible major resistance genes of the above-mentioned cultivars have been determined. The so-called “Blaukorn” resistance is conditioned by gent Pm4b. The resistance patterns of Ml-i and Pm5 being similar, the relationship between them has to be analysed by segregating populations.     

Search for novel genes for resistance to powdery mildew (Sphaerotheca fuliginae) in cucumber (Cucumis sativus)

Summary The current powdery mildew (Sphaerotheca fuligninea) resistant cucumber varieties suffer from leaf chlorosis during autumn, winter and early spring cultivation in the Netherlands. Therefore screening was carried out for novel powdery mildew resistance genes. From 177 accessions, derived from different sources, 108 accessions proved to be partially resistant to S. fuliginea. Crosses were made with 53 resistant accessions to distinguish the presence of novel genes. It is likely that the accessions C. sativus 2145, C. sativus LV 41, PI 188807, Vladivostokij, White and Yellow 1 have one or more recessive powdery mildew resistance genes, different from powdery mildew resistance genes of the line NPI, which was used for variety breeding. Powdery mildew resistance tests with S. fuliginea give similar results in different regions of the world.Abbreviations pmr powdery mildew resistance     

New molecular markers linked to qualitative and quantitative powdery mildew and scald resistance genes in barley for dry areas

A partial genetic linkage map was constructed on 71 doubled-haploid lines derived from a cross between the barley lines Tadmor and WI2291 with 181 molecular markers. The segregating population was used to detect markers linked to the gene Mlg conferring resistance to powdery mildew (Erysiphe graminis f. sp. hordei) and to genes for quantitative resistance to scald (Rhynchosporium secalis). The gene Mlg on chromosome 4H was flanked by two AFLP markers at a distance of 2.0 and 2.4 cM, respectively. QTLs for resistance to scald were detected on chromosomes 2H and 3H. This association of molecular markers with qualitative and quantitative disease resistance loci represents a valuable starting-point for marker-assisted selection. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of the Powdery Mildew Resistance Gene Pm9 in Relation to Pm1 and Pm2 of Wheat

The inheritance of the powdery mildew resistance gene Pm9 originating from the hexaploid spring wheat cultivar ‘Normandie’ was analyzed in relation to Pm1 and Pm2. Two leaf segments of individual P_1?, P_2?, F_1? and F₂-plants of the cross ‘Normandie’ (Pm1, 2, 9) בFederation’ (no known Pm gene) were inoculated separately with two powdery mildew isolates. Using powdery mildew isolate No. 6 virulent for Pm1 and Pm2 but avirulent for Pm9, a 1 resistant (r): 3 susceptible (s) F₂-segregation was found for the Pm9 gene. Using powdery mildew isolate No. 3 virulent for Pm1 and Pm9 but avirulent for Pm2, a 3 (r): 1 (s) F₂-segregation was found for the Pm2 gene. Combining the data of both experiments (leaf segments of identical plants had been used), a 9 (sr): 3 (ss): 3 (rr): 1 (rs) segregation resulted for the F₂ of this cross: therefore, independent inheritance of the genes Pm2 and Pm9 can be concluded. Similarly, the cross ‘Mephisto’ (Pm1, 2, 9) בAmor’ (no known Pm gene) was analyzed. The Pm9 gene again showed a monogenically recessive inheritance, whereas Pm1 showed a monogenically intermediate segregation upon inoculation with powdery mildew isolate No. 9a virulent for Pm2 and Pm9 but avirulent for Pm1. Combining the single gene segregations, linkage between both genes was found among the progenies. A distance of 8.5 cM was calculated. Analyzing a set of spring wheat cultivars with seven defined powdery mildew isolates, the presence of Pm1, Pm2 and Pm9 in these lines was verified; in most cases, Pm1 occurred together with Pm9.