Recessive Genes for Resistance to Puccinia striiformis f. sp. hordei in Barley

ABSTRACT Barley genotypes Abyssinian 14, BBA 2890, Grannelose Zweizeilige, PI 548708, PI 548734, PI 548747, and Stauffers Obersulzer are resistant to all races of Puccinia striiformis f. sp. hordei identified thus far in North America. Astrix, BBA 809, Bigo, Cambrinus, Emir, Heils Franken, Hiproly, I5, Mazurka, Trumpf, and Varunda have specific resistance to certain races, whereas Topper and Steptoe are susceptible to all races. Seedlings of parents and F(1), F(2), and F(3) progeny from crosses of resistant genotypes with Topper and Steptoe were tested for resistance to North American P. striiformis f. sp. hordei races PSH-1, PSH-4, PSH-10, PSH-13, and PSH-20. When tested with PSH-1, one recessive gene was detected in BBA 809, BBA 2890, Bigo, Hiproly, and Grannelose Zweizeilige; two recessive genes were detected in Emir, I5, PI 548708, PI 548734, PI 548747, Varunda, and Astrix; and one dominant gene and one recessive gene were detected in Abyssinian 14 and Stauffers Obersulzer. In tests with PSH-4, one recessive gene was detected in BBA 809, two recessive genes were detected in Trumpf, and two partially recessive genes were detected in Astrix. In tests with PSH-13, one recessive gene was detected in BBA 2890, Grannelose Zweizeilige, I5, and PI 548708 and two recessive genes were detected in Abyssinian 14, Hiproly, PI 548734, and PI 548747. In tests with PSH-20, one recessive gene was detected in Bigo and a recessive gene and a dominant gene were detected in Heils Franken. A gene in Cambrinus for resistance to PSH-10 and a gene in Mazurka for resistance to PSH-20 were dominant on the basis of the response of the first seedling leaf but recessive on the basis of the response of the second leaf. Four different types of epistasis were detected. Information on the number of genes, mode of inheritance, and nonallelic gene interactions should be useful in understanding the host-pathogen interaction and in breeding barley for resistance to stripe rust.     

Specificity of Prehaustorial Resistance to Puccinia hordei and to Two Inappropriate Rust Fungi in Barley

ABSTRACT To elucidate the specificity of prehaustorial resistance to inappropriate rust fungi, we studied two populations of recombinant inbred lines of barley that segregated for partial resistance (PR) to Puccinia hordei and for the resistance to the inappropriate rust species P. recondita f. sp. tritici and P. hordei-murini. PR to P. hordei is prehaustorial and nonhypersensitive, and its level can be assessed accurately by measuring the latent period of the fungus. The resistance to the inappropriate rust species is a combination of prehaustorial (nonhypersensitive) and posthaustorial (hypersensitive) mechanisms. The amount of nonhypersensitive, early abortion of P. recondita f. sp. tritici and P. hordei-murini sporelings reflects the degree of prehaustorial defense to the two inappropriate rust species. All lines showing a long latent period of P. hordei also had a relatively high level of early abortion of the growth of P. recondita f. sp. tritici and P. hordei-murini. This indicates that genes for PR to P. hordei are also effective against these two inappropriate rust species. The reverse was not necessarily true; some lines showing a high level of early abortion of P. recondita f. sp. tritici and P. hordei-murini had a low level of PR to P. hordei. Moreover, lines with a similar level of prehaustorial resistance to P. recondita f. sp. tritici could differ considerably in their prehaustorial resistance to P. hordei-murini. This indicates that genes for prehaustorial resistance may exhibit rust species specificity.     

Resistance of some barley cultivars to leaf rust,Puccinia hordei; polygenic,partial resistance hidden by monogenic hypersensitivity

Three cultivars, all carrying the Pa7 gene for low infection type were crossed with ‘L94’, a cultivar assumed to carry no genes for partial resistance. The latent period (LP), the most important component determining partial resistance, was measured on 111 F₂ plants not carrying the Pa7 gene and on four cultivars representing the known range in LP. Of 20 F₃ lines the LP was evaluated, too. The F₂ showed a continuous segregation for LP from nearly as short as ‘L94’ to as long as ‘Vada’. This was substantiated by the F₃ data. The cultivars possessing the Pa7 gene are assumed to carry a series of minor genes, covered by Pa7, which govern a LP at least as long as that of ‘Vada’, a cultivar with a very high level of partial resistance and a long LP.     

Virulence spectrum of Puccinia hordei in barley production systems in Ethiopia

Barley leaf rust caused by Puccinia hordei is an important disease of barley in Ethiopia. In the 2003 and 2004 cropping seasons, surveys of P. hordei were conducted on fields in the main rainy, residual moisture and short rainy season-barley production systems. A total of 381 isolates were analysed on 12 barley differential hosts carrying different Rph resistance genes ( Rph1 – Rph12 ). Based on infection phenotypes on leaf rust ( Rph ) resistance genes, seven pathotypes were identified, namely ETPh7611, ETPh7631, ETPh6611, ETPh7651, ETPh7671, ETPh7653 and ETPh7633, with frequencies of 63·0, 21·5, 6·8, 2·9, 2·6, 2·1 and 1·2%, respectively. ETPh7611 and ETPh7631 were the most common pathotypes found in all the surveyed areas of the three production systems. ETPh7653 was found in the small rainy season production system only. ETPh7671, ETPh7653 and ETPh7633 were the most virulent, but the least frequent, pathotypes. All isolates were virulent on resistance genes Rph1 , Rph4 , Rph8 , Rph9 , Rph11 and Rph12 . Virulence against Rph3 and Rph7 was absent. Genes Rph2 , Rph6+2 , Rph5 and Rph10 were effective against 96·3, 88·9, 65 and 2·4% of the rust isolates tested, respectively.     

Race-specific aspects of polygenic resistance of barley to leaf rust,Puccinia hordei

Partial resistance of barley to leaf rust,Puccinia hordei, is characterized by a reduced rate of epidemic development in spite of a susceptible infection type. Barley cultivars vary greatly for partial resistance and its components. In a test for interaction between host cultivars and pathogen isolates most variation was of a horizontal nature. However, in the combination between Julia and the rust isolate 18, a differential interaction (vertical effect) occured; Julia had lost a small part of its partial resistance. The same interaction was found for latent period (LP), the most important component of partial resistance. Julia showed a shortened LP for isolate 18. Genetic analyses revealed, that Julia carries a polygene for longer LP not present in the other cultivars. The effect of this polygene appears to be broken by isolate 18 indicative for a gene-for-isolate relation, and even for a gene-forgene relation.Samenvatting Partiële resistantie van gerst voor dwergroest,Puccinia hordei, is gekenmerkt door een vertraagde epidemie-opbouw ondanks een vatbaar infectietype. Gerstrassen variëren sterk in partiële resistentie en haar componenten. In een toets ter bestudering van de interactie tussen waardplant en pathogeenisolaat bleek de meeste variatie horizontaal van aard te zijn. In de combinatie van Julia met isolaat 18 werd echter een differentiële interactie waargenomen; Julia had een klein deel van zijn partiële resistentie verloren. Dezelfde interactie werd waargenomen voor de belangrijkste component van partiële resistentie, de latentieperiode (LP); Julia had een iets verkorte LP voor isolaat 18. Genetische analyses toonden aan, dat Julia een polygen voor langere LP bevat; dit gen is niet aanwezig in de andere bestudeerde rassen. Er wordt verondersteld dat het effect van dit polygen door isolaat 18 is doorbroken. Dit wijst op een gen-om-isolaat en zelfs op een gen-om-gen-relatie.     

Diversity and Complexity of Erysiphe graminis f.sp. hordei Collected from Barley Cultivar Mixtures or Barley Plots Treated with a Resistance Elicitor

Powdery mildew populations were analysed to determine the effects of a resistance elicitor and cultivar mixtures on genetic complexity and diversity. Isolations were made from a range of spring barley monocultures and mixtures in a field trial, and characterised for virulence and RAPD profile. In a second trial, isolates were taken from a single mixture from untreated and resistance elicitor-treated areas and from the components of the mixture in monoculture. The mildew population was not only highly heterogeneous for virulence characteristics, but also proved heterogeneous within pathotypes for molecular markers, indicating the major impact of sexual recombination on population structure and the lack of clonal dominance. Various diversity measurements were compared and the value of dissimilarity measurement for revealing genetic distance within a population was highlighted. There was a trend towards increasing complexity as the season progressed, but there was no consistent relationship between cultivar or mixture, disease control treatment, fertiliser treatment, replicate or position in trial, and pathogen genotype. Whilst the resistance elicitor did reduce mildew by 78% in the first trial, and there was no interaction with fertiliser level in its expression, control was substantially less in the second trial. There were no differences between mildew isolates from elicitor and control treatments. It was felt that more effective and consistent resistance elicitors need to be developed before it can be stated that they are unlikely to be eroded by selecting resistant or adapted mildew genotypes.     

Resistance in Australian barley (Hordeum vulgare) germplasm to the exotic pathogen Puccinia striiformis f. sp. hordei,causal agent of stripe rust

Eighty‐eight Australian and 10 international barley cultivars were assessed for resistance to the barley stripe (yellow) rust pathogen, Puccinia striiformis f. sp. hordei (Psh). All cultivars were tested for seedling resistance to two UK‐derived isolates of Psh (11.01 and 83.39) that were shown to differ in virulence based on responses on 16 differential barley genotypes. The 98 barley cultivars differed substantially in stripe rust response; 45% were susceptible to Psh 11.01, 53% to Psh 83.39 and 44% to both isolates. The observed diverse infection types (ITs) suggest the presence of both known and uncharacterized resistance. However, further multipathotype tests are required for accurate gene postulation. The Yerong × Franklin (Y×F) doubled haploid (DH) population was phenotypically assessed as seedlings using both Psh isolates. Yerong and Franklin were immune and highly resistant, respectively, to both isolates used in this study. Marker‐trait and QTL mapping identified a major effect on the long arm of chromosome 7H contributed by Franklin in response to all isolates. The resistance of Yerong was mapped to 113·96 and 169·38 cM on chromosome 5HL in response to Psh 11.01 and 83.39, respectively. The Psh resistance sources identified in this study can be used for further genetic analysis and introgression for varietal improvement.     

Relationship Among Genes Conferring Partial Resistance to Leaf Rust (Puccinia triticina) in Wheat Lines CI 13227 and L-574-1

ABSTRACT This study describes the segregation of genes for resistance to the fungus Puccinia triticina in a cross between partially resistant wheat lines L-574-1 and CI 13227 with two and four genes for resistance, respectively. The objectives of this study were to use parental, F(1), F(2), and backcross populations to quantify maternal effects, degree of dominance, and transgressive segregation, and to determine whether CI 13227 and L-574-1 share any resistance genes for long latent period or small uredinia. In two experiments conducted in the greenhouse, the uppermost leaf of adult wheat plants was inoculated prior to heading with P. triticina. On days 6 to 21 after inoculation, the number of uredinia that erupted from the leaf surface was counted and used to calculate the mean latent period (MLP). The length and width of five arbitrarily selected uredinia were measured and used to calculate uredinium area. Midparent values, degree of dominance, and broad-sense heritability were calculated for MLP and uredinium area. For experiment A, MLP values for CI 13227, L-574-1, F(1), and F(2) generations were 12.2, 10.5, 10.2, and 10.6 days, respectively. For experiment B, MLP values for CI 13227, L-574-1, F(1), F(2), backcross to CI 13227, and backcross to L-574-1 were 12.3, 10.0, 10.6, 10.8, 11.1, and 10.0 days, respectively. The inheritance of long latent period was partially recessive, and no maternal effect was present (P = 0.62 to 0.87 for the comparison of means in reciprocal crosses). Broad-sense heritability for MLP ranged from 0.72 to 0.74, and there was transgressive segregation in the F(2) and backcross populations. Uredinia of the F(1) generation were slightly larger than uredinia for CI 13227. The inheritance of uredinium size was partially dominant, and no maternal effect was present (P = 0.5 to 0.63). Broad-sense heritability for uredinium area ranged from 0.36 to 0.73 and transgressive segregation was present in the F(2) and backcross populations. The results for MLP indicate that lines CI 13227 and L-574 likely share one gene for resistance (based on F(1) values) but not two genes (based on the presence of transgressive segregation). CI 13227 and L 574-1 appear to have at least one gene difference for uredinium area. The linear relationship between uredinium area regressed onto MLP was significant (P < 0.001) and r(2) values ranged from 0.14 to 0.26. These results indicate that the resistance in CI 13227 and L-574-1 could be combined to create wheat cultivars with greater partial resistance than that possessed by either parent based on MLP or uredinium size.     

Chromosomal Location of Genes for Resistance to Puccinia striiformis in the Wheat Line TP1295 Selected from the Cross of Soissonais-Desprez with Lemhi

Crosses of a wheat line TP1295 with the cultivar Chinese Spring monosomic series were used to locate, on chromosome 1D, a major gene for resistance to isolate WYR 85-22 of race 6E0 of Puccinia striiformis. The gene is designated as Yr25 and is probably present in several of the cultivars currently widely used for differentiating races of this pathogen. The expression of the gene was modified by the environment and by at least one minor gene which may be located on chromosome 6A. In F2 and F3 generations from a cross between TP1295 and euploid Chinese Spring, a wide range of variation in infection type (IT) was observed. This precluded the classification of the plants as either resistant or susceptible, so they were assigned to 6 classes and analyzed by factorial correspondence analysis and non-hierarchical classification. When all F3 plants in a family were fully resistant, like TP1295 itself (IT ;), both Yr25 and the modifying gene were assumed to be present and homozygous. In environments favourable to expression of the gene, families thought to carry Yr25 alone had a distribution of ITs from fully resistant (IT ;) to intermediate (IT 2, rarely 3 or 3+). This F3 analysis indicated that use of IT data alone, in the monosomic analysis, would not reveal the chromosomal location of the genes and that chromosome counting of numerous plants was necessary. As well as indicating the chromosomes carrying the genes for resistance to isolate WYR 85-22, the data showed that plants monosomic for chromosomes 5B and 5D were more resistant than the corresponding disomics, indicating that these chromosomes promote susceptibility and supporting other evidence of the effects of these chromosomes on yellow rust resistance.     

Heredity of Heterodera avenae Resistance Originating from two Barley Cultivars and one Spring Wheat Cultivar1

Two spring barley cultivars Bajo Aragon-1-1 and Martin 403-2 from the cyst nematode test assortment were each crossed with a susceptible, a pathotype-11 -resistant, and a pathotype-11 and 12-resistant cultivar, as well as with each other. A spring wheat cultivar, AUS 10894, from the cyst nematode test assortment was crossed with a susceptible and a resistant cultivar. From these crosses F! and F₂ single plants were tested against pathotype 12 and/or pathotype 11 of Heterodera avenae in Denmark. Some plants of the spring barley cultivar Bajo Aragon-1-1 have two resistance genes, which probably are both dominant, but it is not out of the question that one might be recessive. Each gene is inherited independently of the other or with low linkage frequency. Neither gene is the same as or allelic to the resistance gene in the cultivar Ortolan, but one gene is allelic to or the same as the 191 gene in the cultivar Siri. The spring barley cv. Martin 403-2 has one dominant resistance gene which is not allelic to or the same as the resistance gene in Ortolan but is the same as or allelic to the 191 gene in the cultivar Siri. It is possible that there is one more gene, which might be recessive against pathotype 11. The spring wheat cv. AUS 10894 has one dominant resistance gene which might be the same as or allelic to the Loros gene.     

Genetic analysis and molecular mapping of resistance to Puccinia striiformis f. sp. pseudo‐hordei in common wheat

This is the first genetic study reporting on the interaction and molecular mapping of resistance to the barley grass stripe rust pathogen (Puccinia striiformis f. sp. pseudo‐hordei, Psph) in common wheat. Seedlings of 638 wheat accessions were tested and it was determined that wheat is a near‐nonhost to Psph based on rare susceptibility observed in <2% of commercial cultivars and <5% of wheat landraces. As previously observed for P. striiformis f. sp. tritici (Pst), the Australian cultivar Teal was highly susceptible to Psph. In contrast, a selection of cv. Avocet carrying complementary resistance genes Yr73 and Yr74 (Avocet R; AvR) was resistant. The Teal × AvR (T/A) doubled haploid (DH) population was used to map resistance in AvR to Psph. Infection types on the T/A DH lines inoculated with Psph and Pst indicated that all DH lines carrying both Yr73 and Yr74 were also resistant to Psph; however, fewer DH lines were susceptible to Psph than expected, suggesting the resistance was more complex. QTL analysis using 9053 DArT‐Seq markers determined that resistance to Psph was polygenically inherited and mapped to chromosomes 3A, 3D, 4A and 5B. The 3DL and 5BL markers co‐located with Yr73 and Yr74, suggesting an overlap between host and non‐host resistance mechanisms.     

Polymerase Chain Reaction Detection of Ustilago hordei in Leaves of Susceptible and Resistant Barley Varieties

ABSTRACT Although Ustilago hordei infects barley seedlings, symptoms of the disease covered smut are not visible until heading. Natural or artificial inoculation usually results in inconsistent infection, even in highly susceptible lines. Thus, breeding for resistance to covered smut is time consuming and difficult. The ribosomal DNA internal transcribed spacer (ITS) regions of U. hordei were sequenced and a primer pair was developed for polymerase chain reaction (PCR). These primers amplified a 574-bp fragment from DNA of Ustilago spp., but did not amplify DNA from barley or other common barley pathogens. DNA extracted from as few as four U. hordei sporidia was detected by this method. U. hordei DNA was amplified from leaf tissue of inoculated susceptible and resistant plants at different stages of plant development in differential varieties. Growth of the fungus in different leaves of an individual plant was variable. Several highly resistant varieties were shown to contain U. hordei DNA in the first three to four leaves, but not in later leaves. Thus, although the fungus can infect many resistant plants, the plants remain symptomless. Detection of U. hordei prior to heading should assist efforts for breeding for resistance and provide clues concerning the mechanisms of resistance employed by different resistance genes.     

Resistance to Striga hermonthica in Wild Accessions of the Primary Gene Pool of Pennisetum glaucum

ABSTRACT Resistance to Striga hermonthica in 274 wild Pennisetum glaucum subsp. monodii and stenostachyum accessions was evaluated at Samanko, Mali in 1997 and 1998, and at Cinzana, Mali and Sadoré, Niger in 1998. Data recorded included number of striga plants per plot at least three times during the season, date of striga emergence, number of Pennisetum plants, Pennisetum anthesis date, and downy mildew incidence (caused by Sclerospora graminicola). Across trials, the average maximum number of striga per host plant ranged from 0.9 to 8.3. Average days to striga emergence ranged from 54 to 68 days across trials, and was negatively correlated (P < 0.01) with maximum striga within trials. Days to Pennisetum flowering ranged from 54 to 74 days across trials. Host flowering was correlated (P 相似文献   

Genes for race-specific resistance to yellow rust (Puccinia striiformis) in Indian wheat cultivars

Seedlings of Indian wheat cultivars (Kalyansona, Sonalika, WL711 and eight others released commercially) were tested with 13 British and four alien races of Puccinia striiformis. The data indicated the probable presence of the resistance gene Yr2 in the three cultivars named above and in six of the others. Reactions of the remaining two cultivars, PWB12 and WL2265, were consistent with the presence of the gene 177. The presence of Yr2 in Kalyansona, Sonalika and WL711 was supported by evidence from crosses between them and with Heines VII, which is known to carry Yr2. In crosses of Sonalika with a susceptible cultivar, Kharchia Local and also with WL711, tests of F1, F2 and F3 generations indicated that, in addition to Yr2 , Sonalika possesses at least two other genes. Both these genes were difficult to detect but the F3 data supported the hypothesis that there is a single partially recessive gene giving resistance to alien race 6E16 and a different, possibly complementary, gene system effective against another alien race, 39E134. The presence of resistance in addition to Yr2 was also detected in WL711 and HD2329.     

小麦条锈病菌非亲和性小种诱发小麦抗锈性研究

 在水源11、洛夫林10等7个品种上分别选择小麦条锈菌CY17、CY28等9个生理小种中非亲和小种进行诱发接种,亲和小种为挑战小种。观察发病后的病情指数并与单独接种诱发小种和单独接种挑战小种处理的病情指数进行比较。证明诱发抗病现象是比较普遍的,但表现程度因小麦品种、诱发小种和挑战小种而不同。诱发抗病性的表达时间可持续8 d,以诱发接种后1~2 d表达最强。诱发接种量与诱发抗病性表达呈指数函数关系,也间接证明这种诱发抗性是局部的。作者认为:诱发抗病性在品种、诱发和挑战小种不同组合之间的差异在小种动态中会起一定的作用。     

Quantitative Trait Loci Associated with Seedling Resistance to Isolates of Puccinia coronata in Oat

ABSTRACT In our previous report, quantitative trait loci (QTL) for field adult plant resistance to crown rust were identified in an oat population of 152 F(5:6) recombinant inbred lines from the cross of 'Ogle' (susceptible)/MAM17-5 (resistant). The objectives of the present study were to identify in the same population, the number, genomic location, and effect of QTL and digenic QTL epistasis associated with greenhouse seedling resistance to isolates of Puccinia coronata to determine if the QTL detected are isolate-specific and to compare them with previously detected QTL for field resistance. Reaction type was scored on greenhouse seedlings inoculated with three isolates. Composite interval mapping was conducted to identify genomic regions associated with resistance using a framework map of 272 molecular markers. Two QTL, Pcq1 and Pcq2, were identified for resistance to each of the three isolates. Pcq1, the major QTL controlling field resistance, did not confer detectable greenhouse seedling resistance when present singly; however, Pcq1 did serve as an enhancer of seedling resistance when it was combined with Pcq2. The final model explained 76.5, 77.9, and 79.3% of total phenotypic variation for resistance to isolates MNB248, MNB249, and MNB251, respectively. Race-specificity of quantitative resistance remains to be further examined.     

Gene Action and Linkage of Avirulence Genes to DNA Markers in the Rust Fungus Puccinia graminis

ABSTRACT Two strains of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, were crossed on barberry, and a single F(1) progeny strain was selfed. The parents, F(1), and 81 F(2) progeny were examined for virulence phenotypes on wheat differential cultivars carrying stem rust resistance (Sr) genes. For eight Sr differentials, phenotypic ratios are suggestive of single dominant avirulence genes AvrT6, AvrT8a, AvrT9a, AvrT10, AvrT21, AvrT28, AvrT30, and AvrTU. Avirulence on the Sr; (Sr 'fleck') differential showed phenotypic ratios of approximately 15:1, indicating epistatic interaction of two genes dominant for avirulence. Avirulence on Sr9d favored a 3:13 over a 1:3 ratio, possibly indicating two segregating genes-one dominant for avirulence and one dominant for avirulence inhibition. Linkage analysis of eight single dominant avirulence genes and 970 DNA markers identified DNA markers linked to each of these avirulence genes. The closest linkages between AvrT genes and DNA markers were between AvrT6 and the random amplified polymorphic DNA marker crl34-155 (6 centimorgans [cM]) AvrT8a and the amplified fragment length polymorphism marker eAC/mCT-197 (6 cM) and between AvrT9a and the amplified fragment length polymorphism marker eAC/mCT-184 (6 cM). AvrT10 and AvrTU are linked at distance of 9 cM.