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.     

Identification of powdery-mildew-resistance genes in common wheat (Triticum aestivum L.). VI. Wheat cultivars grown in China

A total of 26 common wheat cultivars and advanced breeding lines grown in China were tested with a set of 11 differential powdery-mildew isolates. Seven cultivars were susceptible. Another seven cultivars showed the response pattern of resistance gene Pm2, either individually or in combination with genes Pm3d or Pm4a. Five cultivars expressed the resistance of gene Pm4b singly or in combination with Pm6. Another four cultivars exhibited the response patterns of genes Pm5, Pm6 and Pm8, respectively. Three cultivars, which included one breeding line with a pair of substituted chromosomes from Haynaldia villosa, presumably carrying the resistance gene Pm21, showed resistance-response patterns to all the isolates tested.     

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’.     

Identification of powdery-mildew-resistance genes in common wheat (Triticum aestivum L. em. Thell.). V. Old German cultivars and cultivars released in the former GDR

A total of 59 old wheat cultivars grown in Germany prior to 1960 were tested for mildew response using a collection of 12 differential isolates of Erysiphe graminis DC f. sp. tritici Marchal (Blumeria graminis (DC) Speer f. sp. tritici). Nineteen cultivars did not possess any major resistance gene and 25 were characterized by susceptible or intermediate responses. Fifteen cultivars revealed isolate-specific response patterns that could not be attributed to known major resistance genes or gene combinations. Many of the old German cultivars inherited a mildew-resistance gene from the Canadian cultivar ‘Garnet’ which is tentatively designated M1-Ga. Cultivars ‘Bretonischer Bartweizen’ (designated M1-Br) and ‘Adlungs Alemannen’ (designated M1-Ad) appeared to carry unknown resistance genes. Among 18 winter wheat cultivars released in the former GDR. eight showed susceptibility to all isolates used. Cv. “Borenos” carries resistance gene Pm3c. Five cultivars possess gene Pm4b. two cultivars gene pm5 and one cultivar a combination of genes Pm2 and Pm4b. Cultivar ‘Zentos’ was resistant to almost all isolates used. Its resistance might be conditioned by different unknown major resistance genes.     

Identification of powdery mildew resistance genes in common wheat (Triticum aestivum L. em Thell.). IX. Cultivars, land races and breeding lines grown in China

The objective of the study was to provide information about the occurrence and distribution of resistance genes in wheat cultivars, including old cultivars, land races and advanced breeding lines grown in China. Ninety-four accessions were analysed with a set of 11 differential powdery mildew isolates. Forty-four cultivars did not possess any major mildew resistance genes. Thirty cultivars revealed the response pattern of individual resistance genes. The most frequently encountered gene was Pm8, which occurred singly in 11 cultivars, combined either with Pm4a in three cultivars or with Pm4b in another three cultivars. However, 12 cultivars possessing the wheat-rye translocated chromosome pair T1BL-1RS did not express Pm8. Gene Pm2 was found in four cultivars and in combination with Pm6 in one cultivar. Genes Pm4a and Pm4b were observed in four and five cultivars, respectively. Another six cultivars carried Pm5. A gene combination of Pm2+Pm4b+Pm6 was found in one cultivar. Twelve cultivars and breeding lines exhibited a response pattern that could not be assigned to resistance genes or gene combinations present in the differential cultivars. Five out of these 12 cultivars/lines showed resistance to all the isolates tested. There is an urgent need to search for novel sources of mildew resistance in order to sustain resistance to existing and emerging powdery mildew pathogens.     

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.     

An STS marker distinguishing the rye-derived powdery mildew resistance alleles at the Pm8/Pm17 locus of common wheat

A sequence‐tagged site marker has been developed from restriction fragment length polymorphism marker probe IAG95 for the rye‐derived powdery mildew resistance Pm8/Pm17 locus of common wheat. This polymerase chain reaction marker enables the amplification of DNA fragments with different sizes from T1AL.1RS and T1BL.1RS wheat‐rye translocation cultivars with chromatin from ‘Insave’ and ‘Petkus’ rye, respectively, and therefore will be very useful in distinguishing Pm8‐carrying cultivars from Pm17‐carrying cultivars. Results obtained with that marker were compared with resistance tests performed on detached primary leaves of 29 wheat lines from two populations derived from doubled haploid production. The molecular assay corresponded well with the resistance tests in all the lines, and therefore will be helpful for the identification of Pm17 in lines in which other Pm genes or quantitative trait loci are present.     

Chromosomal location of powdery mildew resistance gene Pm16 in wheat using SSR marker analysis

The use of resistant cultivars is a most economical way to control powdery mildew (Blumeria graminis f.sp. tritici) in wheat (Triticum aestivum L.). Identification of molecular markers closely linked to resistance genes can greatly increase the efficiency of pyramiding resistance genes in wheat cultivars. The objective of this study was to identify molecular markers closely linked lo the powdery mildew resistance gene Pm16. An F₂ population with 156 progeny was produced from the cross‘Chancellor’(susceptible) ב70281’ (resistant), A total of 45 SSR markers on chromosomes 4A and 5B of wheat and 15 SSRs on chromosome 3 of rice was used lo lest the parents, as well as the resistant and susceptible bulks: the resulting polymorphic markers were used to genotype the F₂ progeny. Results indicated that the SSR marker Xgwm159, located on the short arm of chromosome 5B, is closely linked to Pm16 (genetic distance: 5.3 CM). The cytogenetical data presented in an original report, in combination with this molecular analysis, suggests that Pm16 may he located on a translocated 4A.5BS chromosome.     

12个小麦品种(系)白粉病抗性的遗传分析

利用17个不同来源和毒力的白粉菌菌株对12个小麦品种(系)进行苗期抗性鉴定和抗病性遗传分析,同时利用Pm2和Pm8基因的特异分子标记检测了相应基因。供试的12个品种至少能够抗11个白粉菌菌株。用E09、E20和Bg2菌株接种F₂群体,抗感植株分离比例和适合性测验证明这12个品种对不同白粉菌菌株的抗性均受1对显性基因控制。抗谱分析和基因紧密连锁分子标记(Xcfd81)分析表明良星66很可能含有Pm2或其等位基因。ω-黑麦碱基因(1RS染色体)和Glu-B1基因(1BS染色体)特异分子标记分析结果证明,山农20和郑麦9962含有T1BL·1RS易位染色体,即可能携带Pm8基因。由于Pm8基因对大多数菌株表现感病,所以这2个品种除Pm8外,还具有其他抗病基因。偃展4110与天民668对参试菌株的反应型表现一致,其他材料对不同菌株的反应型表现不同。     

Occurrence of 1BL.1RS wheat-rye chromosome translocation and of <Emphasis Type="Italic">Sr36/Pm6</Emphasis> resistance gene cluster in wheat cultivars registered in Hungary

The 1BL.1RS wheat-rye translocation and a wheat-Triticum timopheevii chromosomal introgression carry the Sr31, Lr26, Yr9 and Pm8 genes and the Sr36/Pm6 gene cluster, respectively. The objective of this study was to determine the distribution and impact of these two translocations in 220 wheat varieties registered in Hungary in the last 35 years until 2005. The 1BL.1RS translocation was introduced into Hungary via wheat cultivars ‘Avrora’ and ‘Kavkaz’, which were registered in 1970. New 1BL.1RS cultivars developed in Hungary first appeared in 1982. After reaching a maximum frequency of 50.0% among cultivars registered in Hungary in 1994, their presence declined steadily to 13.3% by 2005. The Sr36/Pm6 cultivars first appeared in 1980. Their frequency quickly reached 31.8% (1983–1984), but then dropped to between 9.6 and 18.5% (1990–2005). The two main Hungarian breeding programs showed opposing trends in the exploitation of these two translocations. In Martonvásár, 1BL.1RS played a dominant role, being present from 1993 to 1997 in ca. 95% of the released cultivars, while at the same time the use of Sr36/Pm6 was marginal. Conversely, among the Szeged cultivars, Sr36/Pm6 was present at high frequency (44.7% in 2002) with a low share of 1BL.1RS. In artificial field inoculation tests (1985–2003) both of the stem rust resistance genes provided significant resistance in all the years, though Sr36 proved more effective than Sr31. While Pm8 was not effective, except for the last 2 years, Pm6 exhibited significant resistance against powdery mildew in most of the 18 years tested. These data may help breeders to assess the usefulness of wheat-rye 1BL.1RS chromosome translocations and the Sr36/Pm6 resistance gene clusters in their future wheat improvement programs.     

Evidence of allelism between genes Pm8 and Pm17 and chromosomal location of powdery mildew and leaf rust resistance genes in the common wheat cultivar'Amigo'

TIBL-1RS wheat-rye translocation cultivars utilized in wheat programmes worldwide carry powdery mildew resistance gene Pm8. Cultivar‘Amigo’possesses resistance gene Pm17 on its TIAL-1RS translocated chromosome. To be able to use Pm17efficiently in breeding programmes, this gene was transferred to a TIBL-1RS translocation in line Helami-105, and allelism between Pm8 and Pm17was studied. The progenies of the hybrids in the F₂ generation and F₃ families provided evidence that the two genes are allelic. Genetic studies using monosomic analyses confirmed that in cultivar‘Amigo', Pm17 and leaf rust resistance gene Lr24 are located on a translocated chromosome involving 1 A and 1B, respectively.     

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.     

Identification of a microsatellite marker associated with Pm3 resistance alleles to powdery mildew in wheat

The Pm3 resistance locus, located on chromosome 1A in wheat, confers race‐specific resistance to the obligate biotrophic fungus Blumeria graminis (DC) E.O. Speer f. sp. tritici, the causal agent of powdery mildew. Several Pm3 alleles are still effective in controlling the disease in Europe. A genetic map was constructed to map the Pm3g allele in the recombinant inbred line progeny from the cross ‘RE9001’ (susceptible) בCourtot’ (resistant). Two microsatellite markers were closely mapped to Pm3g. The PSP2999 marker, which cosegregates with this allele, was shown to detect the presence of the Pm3g resistance allele in other cultivars. A collection of 56 wheat cultivars or advanced lines carrying one Pm3 allele was used to assess the allele‐specific amplification of the PSP2999 marker. The same amplification pattern was obtained for lines with Pm3a, Pm3b, Pm3e, Pm3f and Pm3g alleles. Twenty genotypes carrying Pm3d showed a specific amplification pattern. This marker allowed the detection of the Pm3d allele in highly resistant lines whose resistance gene combinations were unknown. It was concluded that PSP2999 is a useful marker to detect Pm3 alleles in parents and to manage them in breeding programmes.     

Chromosome location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L.) 1. Mlk and other alleles at the Pm3 locus

Summary Several wheat cultivars/lines were inoculated with isolates of Erysiphe graminis tritici to identify new genes/alleles for resistance. The wheats were tested with 13 isolates that had been characterized from responses on differential lines with known resistance genes. Gene Mlk which occurs in cultivars Kolibri, Syros, Ralle and several other European common wheats was found to be an allele at the Pm3 locus and is now designated Pm3d. The mildew resistance in an old Australian wheat, W150, is conferred by a single gene also allelic to Pm3 and now designated Pm3e. The near-isogenic line Michigan Amber/8^*Cc possesses another allele now designated Pm3f. A Syrian land variety of common wheat shows mildew resistance that is conditioned by the combination of genes Pm1 and Pm3a. Finally, two accessions of Triticum aestivum ssp. sphaerococcum appeared to possess the Pm3c allele.     

Temperature and resistance gene interactions in the expression of resistance to Blumeria Graminis f. sp. Tritici

The influence of temperature on the resistance to powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal, was evaluated on six wheat cultivars/lines, Axminster/8^* Chancellor (Cc) (Pm1), Chul/8^*Cc (Pm3b), Yuma/8^*Cc (Pm4a), VPM1 (Pm4b), Kavkaz (Pm8), and Chancellor, at two temperatures of 25EC and 15EC with two isolates of powdery mildew. Resistance, based on the components of latency period, infection type, colony number per unit leaf area, per cent infected leaf area, and AUDPC, was much less effective at 15EC than at 25EC for VPM1 and Yuma/8^*Cc, but no resistance shift was observed for Kavkaz and Axminster/8^*Cc, indicating the difference of temperature-sensitivity among Pm genes or among the interactions of individual host genes with corresponding powdery mildew pathogen genes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and characterization of a new 1BL.1RS translocation line with resistance to stripe rust and powdery mildew of wheat

The 1BL.1RS wheat-rye translocation from Petkus rye has contributed substantially to the world wheat production. However, following the breakdown of disease resistance genes in 1RS, its importance for wheat improvement decreased. We have developed a new 1BL.1RS line, R14, by means of crossing rye inbred line L155, selected from Petkus rye to several wheat cultivars. One new gene each, for stripe rust and powdery mildew resistance, located on 1RS of the line R14, are tentatively named YrCn17 and PmCn17. YrCn17 and PmCn17 confer resistance to Puccinia striiformis f. sp. tritici pathotypes that are virulent on Yr9, and Blumeria graminis f. sp. tritici pathotypes virulent on Pm8. These two new resistances, YrCn17 and PmCn17, are now available for wheat improvement programs. The present study indicates that rye cultivars may carry yet untapped variations as potential sources of resistance.     

Genetic linkage of the Yr1 and Pm4 genes for stripe rust and powdery mildew resistances in wheat

Summary Genes Yr1 for resistance to stripe rust and Pm4a for resistance to powdery mildew showed linkage of 2.0±0.6 cM. Close repulsion linkage probably accounts for the absence in European wheats of genes Yr1 and Pm4b in combination.     

Genetic analysis of powdery-mildew resistance of a winter-wheat line, RE714, and identification of a new specific-resistance gene

The winter-wheat line RE714, resulting from an intergeneric cross between Aegilops squarrosa and Triticum dicoccum, and implying a sister line of ‘Roazon’ (VM4) in its genealogy, was obtained in order to increase the genetic diversity for disease resistance. The aim of this study was to identify and characterize the powdery-mildew-resistance gene(s) present in this line at the seedling stage on detached leaves. The comparison of the reaction of the RE714 line and of differential hosts to 24 Erysiphe graminis. f.sp. tritici isolates indicated that only Pm4a, Pm4b and/or Mlar genes could be present and that a new resistance factor, different from all known mildew-resistance genes, was present in this line. The powdery-mildew reactions of segregating F₂ populations produced evidence that RE714 carries the Pm4b allelic form and a recessive new resistance gene, tentatively designated mlre. While Ae. squarrosa was resistant to most isolates, T. dicoccum was specifically attacked by REV 14-virulent isolates and was therefore assumed to be the donor of mire. The VM4 parent was confirmed as the Pm4b donor.     

Molecular detection of rye (Secale cereale L.) chromatin in wheat line 07jian126 (Triticum aestivum L.) and its association to wheat powdery mildew resistance

Powdery mildew (Pm), caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most serious diseases for common wheat in many regions around the world. Seeking for new resistance source is urgently required to meet the challenge of the rapid loss of resistance due to the co-evolution of the pathogen’s virulence. Wheat line 07jian126 (Triticum aestivum L.) is highly resistant to the Pm disease prevailing in Sichuan province of China. Previous study showed that a SSR marker Xbarc183 was linked to the Pm resistance in 07jian126, which might be controlled by a single dominant gene, designated as Pm07J126. In this study, two additional F₂ populations were used to confirm the linkage between Pm07J126 and Xbarc183. Furthermore, rye chromatin was detected in 07jian126 by molecular analysis of a rye-specific SCAR marker O5 which co-segregated with Pm07J126. This result indicated that Pm07J126 might originate from rye. The reaction patterns to 21 Bgt isolates and molecular marker analysis implied that Pm07J126 might be different from the known rye-derived Pm genes Pm7, Pm8, Pm17 and PmJZHM2RL. Chromosome observation, molecular marker, and A-PAGE analysis suggested that 07jian126 might be a rye introgression line and neither contain 1RS translocation nor secalins gene. Consequently, 07jian126 could be considered as a valuable resource for Pm resistance development of wheat. Besides, the molecular markers Xbarc183 and O5 are useful in marker-assisted selection of Pm07J126 in wheat breeding programs.     

Dynamics of changes in the races and virulence of wheat powdery mildew in Hungary between 1971 and 1999

Important microevolutional processes have taken place in the wheatpowdery mildew population over the last thirty years. There has been aconsiderable change in the race composition of the pathogen populationand in the prevalent races. Of the 78 races identified, only eleven have`lived' for more than 15 years. Many races were only isolated in one ortwo years. The number of virulence genes rose from 2.03 in 1973 to 5.63in 1993. On the basis of race composition and virulence the wheatpowdery mildew population between 1971 and 1999 can be divided intofour distinct groups. A large proportion of the powdery mildew isolates arevirulent to most resistance genes. Complete resistance is provided byresistance genes Pm4a (Khapli) and partial resistance by Pm2 + Mld (Halle st. 13471), Pm4b+ (TP 315/2) and Pm1 + 2 + 9 (Normandie). The majority of cultivated varieties carry theresistance gene Pm8 due to the presence of the 1B/1R translocation.