Virulence patterns of barley yellow rust and effective resistance genes to Puccinia striiformis in three parts of Iran

Stripe rust of barley (Hordeum vulgare L.), caused by Puccinia striiformis f. sp. hordei, is a serious problem of barley production in many parts of the world. Monitoring of the pathogen virulence factors and their changes provides basic information for development of an early warning system to breeders and researchers. To monitor the regular virulence changes, trap nurseries comprising of 12 barley differential sets were planted at different parts of Iran in six consecutive years 2007–2012. When the infection and severity under natural infection on susceptible cultivar Afzal as the check was high, then the response of each line was assessed using modified Cobbs scale. Results revealed that no virulence was observed on plants with resistance genes rpsEm1, rpsEm2, rpsHF, Rps4, rpsVa1, rpsVa2 and rpsAst. Therefore, these genes were considered effective genes and can be used to pyramid with those for race-non-specific resistance genes to achieve more durable and highly effective resistance to stripe rust. The plants with the resistance genes rps2, Rps1.b, Rps3 and rpsI5 showed susceptible reaction and virulence was observed on them, thus their resistance genes were considered ineffective.     

Mapping genes for resistance to barley stripe rust (Puccinia striiformis f. sp. hordei)

Two genes conferring resistance to the barley stripe rust found in Mexico and South America, previously identified as race 24, were mapped to the M arms of barley chromosomes 7 and 4 in a doubled haploid population using molecular markers and the quantitative trait loci (QTL) mapping approach. The resistance gene on chromosome 7 had a major effect, accounting for 57% of the variation in disease severity. The resistance gene on chromosome 4 had a minor effect, accounting for 10% of the variation in trait expression. Two pairs of restriction fragment length polymorphism markers are being used to introgress the resistance genes to North American spring barley using molecular marker-assisted backcrossing.Ore. Agric Exp Stn J no. 10283     

Isolate-specific QTLs for partial resistance to Puccinia hordei in barley

By using a high-density AFLP marker linkage map, six QTLs for partial resistance to barley leaf rust (Puccinia hordei) isolate 1.2.1. have been identified in the RIL offspring of a cross between the partially resistant cultivar ’Vada’ and the susceptible line L94. Three QTLs were effective at the seedling stage, and five QTLs were effective at the adult plant stage. To study possible isolate specificity of the resistance, seedlings and adult plants of the 103 RILs from the cross L94×’Vada’ were also inoculated with another leaf rust isolate, isolate 24. In addition to the two QTLs that were effective against isolate 1.2.1. at the seedling stage, an additional QTL for seedling resistance to isolate 24 was identified on the long arm of chromosome 7. Of the eight detected QTLs effective at the adult plant stage, three were effective in both isolates and five were effective in only one of the two isolates. Only one QTL had a substantial effect at both the seedling and the adult plant stages. The expression of the other QTLs was developmental-stage specific. The isolate specificity of the QTLs supports the hypothesis of Parlevliet and Zadoks (1977) that partial resistance may be based on a minor-gene-for-minor-gene interaction. Received: 16 February 1999 / Accepted: 20 February 1999     

Genetic analysis of resistance to Puccinia striiformis f.sp. tritici in cv. Aflak at adult plant stage

In order to investigate heritability and gene action for yellow rust resistance in wheat, a resistance yellow rust cultivar Aflak was crossed to susceptible cultivar Avocet‘s’. Parents, F₁, F₂ and F₃ generations were cultured according to randomised complete block design with two replications in the research station of Gharakhil, Iran. Parents and other generations were inoculated with 70E0A+ race. Traits including severity and infection type were recorded and then coefficient of infection was calculated. For this trait, generations mean and variance analysis were performed and results showed that there were significant differences among generations for coefficient of infection. Results showed that in addition to additive and dominance effects, at least one kind of epistasis interaction (additive × additive) control this trait. Although additive and dominance effects control this trait, but with attention to generations variance analysis, the results showed that additive variance had important role to control this trait.     

Inheritance and molecular mapping of a gene conferring seedling resistance against Puccinia hordei in the barley cultivar Ricardo

Genetic studies were undertaken to determine the inheritance and genomic location of uncharacterised seedling resistance to leaf rust, caused by Puccinia hordei, in the barley cultivar Ricardo. The resistance was shown to be conferred by a single dominant gene, which was tentatively designated RphRic. Bulk segregant analysis (BSA) and genetic mapping of an F₃ mapping population using multiplex-ready SSR genotyping and Illumina GoldenGate SNP assay located RphRic in chromosome 4H. Given that this is the first gene for leaf rust resistance mapped on chromosome 4H, it was designated Rph21. The presence of an additional gene, Rph2, in Ricardo, was confirmed by the test of allelism. The seedling gene Rph21 has shown effectiveness against all Australian pathotypes of P. hordei tested since at least 1992 and hence represents a new and useful source of resistance to this pathogen.     

Characterisation of wheat germplasm for slow rust resistance against Puccinia striiformis

Thirty-seven wheat germplasm were screened under artificial epiphytotic conditions against stripe rust of wheat at University Research Farm, Chatha, during Rabi, 2013–2014 and 2014–2015. On the basis of final rust severity (FRS), AURPC (Area Under Rust Progress Curve) and CI (Coefficient of Infection), 8 genotypes ((DWR 16, HD2281, VL616, K65, UP2121, HD2329, HD2307 and Lal Bahadur) exhibited partial resistance against the disease. PCR profiles revealed co-dominant pattern with distinct fragment of 150 bp in 14 germplasm, showing the presence of Yr18 gene and 229 bp band in 16 germplasm exhibited absence of Yr18.     

Genetic control of durable resistance to yellow rust (Puccinia striiformis) in the wheat cultivar Hybride de Bersée

The wheat cultivar Hybride de Bersee is described as possessing durable resistance to yellow rust. Some races of Puccinia striiformis can infect it at the seedling stage but not severely in the field. Using euploid and aneuploid stocks of Bersee it was shown that a large part of this resistance was controlled by chromosome 5BS-7BS, the effect being detectable in seedlings and at later growth stages. Measurements of spore production from infected seedlings showed that the line ditelosomic for the 5BS arm of the chromosome was more resistant than the line ditelosomic for the 7BS arm under environments favouring high spore production, but more susceptible under environments favouring low spore production. Thus both arms of the chromosome could contribute to resistance in appropriate environments. Chromosome 5BS-7BS did not carry the factors controlling the race-specific resistance to race 37 E132 of P. striiformis. The possibility of exploiting the resistance carried by chromosome 5BS-7BS in wheat breeding programmes is discussed.     

Association mapping of resistance to Puccinia hordei in Australian barley breeding germplasm

Key message

“To find stable resistance using association mapping tools, QTL with major and minor effects on leaf rust reactions were identified in barley breeding lines by assessing seedlings and adult plants.”

Abstract

Three hundred and sixty (360) elite barley (Hordeum vulgare L.) breeding lines from the Northern Region Barley Breeding Program in Australia were genotyped with 3,244 polymorphic diversity arrays technology markers and the results used to map quantitative trait loci (QTL) conferring a reaction to leaf rust (Puccinia hordei Otth). The F_3:5 (Stage 2) lines were derived or sourced from different geographic origins or hubs of international barley breeding ventures representing two breeding cycles (2009 and 2011 trials) and were evaluated across eight environments for infection type at both seedling and adult plant stages. Association mapping was performed using mean scores for disease reaction, accounting for family effects using the eigenvalues from a matrix of genotype correlations. In this study, 15 QTL were detected; 5 QTL co-located with catalogued leaf rust resistance genes (Rph1, Rph3/19, Rph8/14/15, Rph20, Rph21), 6 QTL aligned with previously reported genomic regions and 4 QTL (3 on chromosome 1H and 1 on 7H) were novel. The adult plant resistance gene Rph20 was identified across the majority of environments and pathotypes. The QTL detected in this study offer opportunities for breeding for more durable resistance to leaf rust through pyramiding multiple genomic regions via marker-assisted selection.     

Identification of additional sources of resistance to Puccinia striiformis f. sp. hordei (PSH) in a collection of barley genotypes adapted to the high input condition

A total of 336 barley genotypes consisting of released cultivars, advanced lines, differentials and local landraces from the ICARDA barley breeding programme were screened for seedling and adult‐plant resistances to barley stripe rust pathogen (Puccinia striiformis f. sp. hordei [PSH]). Seedling resistance tests were undertaken at Shimla, India by inoculating 336 barley genotypes with five prevalent PSH races [Q (5S0), 24 (0S0‐1), 57 (0S0), M (1S0) and G (4S0)] in India. Barley genotypes were also evaluated at the adult‐plant stage for stripe rust resistance at Durgapura (Rajasthan, India) in 2013 and 2014, and at Karnal (Haryana, India) in 2014 under artificial PSH infection in fields, using a mixture of the five races. Twelve barley genotypes (ARAMIR/COSSACK, Astrix, C8806, C9430, CLE 202, Gold, Gull, Isaria, Lechtaler, Piroline, Stirling, and Trumpf) were resistant to all five PSH races at the seedling and adult‐plant stages. Two of these genotypes, Astrix and Trumpf, were part of international differentials and reveal that five races were avirulent to genes Rps4 (yr4), rpsAst, rpsTr1 and rpsTr2. These genes were highly effective against PSH races prevalent in India. The virulence/avirulence formula reported in this study helped to determine the effectiveness of PSH resistance genes against Indian races. Forty‐five genotypes showed adult‐stage plant resistance (APR) in the field. The identified PSH resistant genotypes may possess novel resistance genes and might serve as potential donors of PSH resistance at seedling and APR in the future. Further research is needed to determine the nature of resistance genes through allelic studies and mapping of these genes.     

The detection and molecular mapping of a major gene for non-specific adult-plant disease resistance against stripe rust (Puccinia striiformis) in wheat

A major gene determining non-specific adult-plant disease resistance against stripe rust (Puccinia striiformis) designated Yrns-B1 was mapped by using a cross between ’Lgst.79–74’ (resistant) and ’Winzi’ (susceptible). Analyzing F₃ lines of two consecutive experimental years contrary modes of inheritance were observed due to the intermediate character of the gene and the difference in the disease pressure during the seasons. Using the disease scoring data of both experimental years independently two maps were constructed detecting Yrns-B1 20.5 and 21.7 cM, respectively, proximal to the wheat microsatellite (WMS) marker Xgwm493 on the short arm of chromosome 3BS. The genetic relationships to other major genes or to quantitative trait loci controlling adult plant disease resistance against rusts in wheat are discussed. Received: 27 May 1999 / Accepted: 28 September 1999     

Quantitative resistance of some Elite wheat lines to Puccinia striiformis f. sp. tritici

Host resistance is the most economical way to manage wheat stripe rust caused by Puccinia striiformis f. sp. tritici. Slow rusting, a type of quantitative resistance, has been reported to last for a long time. Quantitative resistance, in terms of slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC) and coefficient of infection (CI), was evaluated in a set of 29 wheat genotypes along with susceptible control during 2008–2009 and 2009–2010 cropping seasons. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran) under natural infection conditions with two times artificial inoculation. Artificial inoculation was carried out by yellow rust inoculum having virulent genes against Yr2, Yr6, Yr7, Yr9, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, YrA and YrSU. Results of mean comparison for resistance parameters showed that lines C-86-1, C-86-2, C-87-1 and C-87-3 along with susceptible had the highest values of FRS, CI, r and rAUDPC, therefore were selected as susceptible lines. The lines C-86-3, C-86-9, C-87-2, C-87-6, C-87-8, C-87-11 and C-87-18 were susceptible at the seedling stage and had low level infection at adult plant stage. Consequently, these lines with low different parameters most probably have slow rusting resistance. The remaining lines had no infection or were at low level of infection. Thus, they were selected as resistant or moderately resistant lines. In this study, correlation coefficient between different parameters of slow rusting was significantly high (r = 0.92–0.99).     

Mapping Rph20: a gene conferring adult plant resistance to Puccinia hordei in barley

A doubled haploid (DH) barley (Hordeum vulgare L.) population of 334 lines (ND24260?×?Flagship) genotyped with DArT markers was used to map genes for adult plant resistance (APR) to leaf rust (Puccinia hordei Otth) under field conditions in Australia and Uruguay. The Australian barley cultivar Flagship carries an APR gene (qRphFlag) derived from the cultivar Vada. Association analysis and composite interval mapping identified two genes conferring APR in this DH population. qRphFlag was mapped to the short arm of chromosome 5H (5HS), accounting for 64?C85% of the phenotypic variation across four field environments and 56% under controlled environmental conditions (CEC). A second quantitative trait locus (QTL) from ND24260 (qRphND) with smaller effect was mapped to chromosome 6HL. In the absence of qRphFlag, qRphND conferred only a low level of resistance. DH lines displaying the highest level of APR carried both genes. Sequence information for the critical DArT marker bPb-0837 (positioned at 21.2?cM on chromosome 5HS) was used to develop bPb-0837-PCR, a simple PCR-based marker for qRphFlag. The 245?bp fragment for bPb-0837-PCR was detected in a range of barley cultivars known to possess APR, which was consistent with previous tests of allelism, demonstrating that the qRphFlag resistant allele is common in leaf rust resistant cultivars derived from Vada and Emir. qRphFlag has been designated Rph20, the first gene conferring APR to P. hordei to be characterised in barley. The PCR marker will likely be effective in marker-assisted selection for Rph20.     

Early molecular diagnosis and detection of Puccinia striiformis f. sp. tritici in China

Aims: Wheat stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is the most important foliar disease on wheat in China. Early molecular diagnosis and detection of stripe rust will provide a useful aid to the accurate forecast and seasonal control of this destructive disease. Our objective was to develop PCR assays for the rapid identification and detection of P. striiformis. Methods and Results: The genomic DNA of P. striiformis and P. triticina were amplified by a pair of primers derived from conserved β‐tubulin gene sequence. A 235‐bp specific DNA fragment of P. striiformis was isolated and purified. Based on its sequence, another two primer sets were designed successfully to obtain new sequence‐characterized amplified region (SCAR) markers of P. striiformis, which could be amplified in all test isolates of P. striiformis, whereas no DNA fragment was obtained in other nontarget wheat pathogens. The detection limit of the primer set YR (f)/YR (r1) was 2·20 pg μl^?1. The new SCAR markers of P. striiformis can also be detected in Pst‐infected wheat leaves postinoculated for 2 days. Conclusions: Our assays are significantly faster than the conventional methods used in the identification of P. striiformis. Significance and Impact of the Study: Development of a simple, high‐throughput assay kit for the rapid diagnosis and detection of wheat stripe rust would be anticipated in a further study.     

小麦条锈菌分子生态学研究进展

小麦条锈病是危害最严重的小麦流行性病害之一,小麦条锈菌的生态学研究对制定合理的防治策略和抗锈育种具有重要意义.近十几年来,DNA分子标记技术被应用于小麦条锈菌的群体遗传学研究,推动了小麦条锈菌分子生态学研究的快速发展,为揭示小麦条锈菌的群体生态特性开辟了一个新的途径.本文系统介绍小麦条锈菌分子生态学研究的主要进展,并就我国当前研究的局限性和发展趋势进行了分析.     

Genetic analyses of rDNA spacer-length variation in barley

Summary The genetic mechanism controlling the inheritance of single and multiple spacer-length variant (slv) phenotypes in barley was investigated in six F₂ segregating populations. The results indicated that two independently assorting loci, each with co-dominant alleles, govern genetic variability for rDNA in barley regardless of the number of bands expressed by a given phenotype. The following chromosomal locations are proposed: sl variants 1, 4, 5, 6, and 7 on chromosome 7, and sl variants 7, 8, 9, 12, and 13 on chromosome 6; sl variant 7 is thus located on both of the chromosomes.     

UDP-N-Acetylglucosamine and Uridine Pools in Puccinia striiformis Infected Wheat

The uridine diphosphate sugar pools were analyzed in young wheat plants at the three leaf stage in which the distal half of the second leaf was uniformly infected with Puccinia striiformis. Whereas UDP-glucose did not change significantly, UDP-N-acetylglucosamine, the precursor of fungal chitin synthesis, was very low in the control and the healthy proximal part of the infected second leaf but increased markedly (250 nmol per g dry weight) in the infected distal half. Of the nucleosides only uridine increased in the infected distal half which was interpreted to indicate a recycling of the UDP moiety of the chitin precursor. Inorganic phosphate determinations showed a strong accumulation not only in the infected distal half but also in the healthy proximal part of the infected second leaf.     

条形柄锈菌33号生理小种的分子标记

采用RAPD-SCAR分子标记技术,从300条RAPD随机引物中筛选到了对条形柄锈菌Puccinia striiformis f. sp. tritici 33号生理小种特异的2条引物,将特异性片段回收、克隆和测序后（GenBank注册号为AB914691和AB914692）,依据其序列设计出了2对引物S261F33/S261R33和S300F33/S300R33,能够特异性地从33号生理小种基因组DNA及发病小麦叶片总DNA中分别扩增出247bp和763bp的片段,其结果与采用常规的鉴别寄主法鉴定的结果一致。因此,这2对引物都可用于条形柄锈菌33号生理小种的快速鉴定与监测。