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Oats (Avena sativa L. cv. Joyang), cultivated during June 2023 in experimental fields of Naju County, South Korea, exhibited crown rust symptoms resembling those caused by isolates of Puccinia coronata. Yellow urediniospores measuring 15.3 ± 3.2 × 13.6 ± 3.0 μm were identified through microscopic examination. Multilocus sequence typing of housekeeping genes in the DNA of this fungal isolate showed identity with P. coronata var. avenae f.sp. avenae, a pathogen of oats in South Korea previously lacking in taxonomic classification. This finding raises concerns of escalated crown rust disease in South Korea due to enhanced temperatures and humidity from climate shifts. Addressing these emerging concerns may require proactive strategies to protect oat cultivation in South Korea. [ABSTRACT FROM AUTHOR]

Crown rust is the most harmful disease of oat (Avena sativa L.) around the world. The purpose of this review is to analyze and generalize the available information about DNA markers developed for oat breeding for resistance to crown rust. The review reveals the mechanisms of the A. sativa resistance to the fungus Puccinia coronata Corda f. sp. avenae Erikss. which causes crown rust disease. Special attention is paid to the race-specific resistance caused by the action of Pc genes and the nonspecific resistance controlled mainly by the loci of quantitative traits. Strategies for creating resistant genotypes and the role of molecular markers in oat breeding for crown rust resistance are discussed. Currently, research is focused mainly on the search for and development of molecular markers related to the oat race-specific resistance to P. coronata.The article presents the technological advantages and disadvantages of the existing DNA markers. KASP, TaqMan and HRM markers are currently the most promising technologies for identifying crown rust resistance genes. The validated SCAR and STS markers for the Pc39, Pc68, Pc91, Pc94 genes are recommended as the most available for implementation in practical oat breeding. The results of recent studies on identifying loci of nonspecific resistance to P. coronata are also presented. In general, the use of DNA markers has significant potential for creating oat genotypes resistant to crown rust under present-day conditions. DNA markers of various types are recommended for practical use, in particular for pyramiding genes and increasing the resistance period of new cultivars. Introduction of DNA markers into oat breeding will increase with the growth of molecular genetic data and the improvement of technologies for identifying genes and loci associated with both race-specific and nonspecific resistance of oat to P. coronata.

Molecular mapping of crown rust resistance genes is important to effectively utilize these genes and improve breeding efficiency through marker-assisted selection. Pc45 is a major race-specific crown rust resistance gene initially identified in the wild hexaploid oat Avena sterilis in the early 1970s. This gene was transferred to cultivated oat (Avena sativa) and has been used as a differential for identification of crown rust races since 1974. Previous research identified an association between virulence to Pc45 and PcKM, a crown rust resistance gene in the varieties ‘Kame’ and ‘Morton’. This study was undertaken to reveal the relationship between Pc45 and PcKM. Pc45 was studied in the crosses ‘AC Morgan’/Pc45 and ‘Kasztan’/Pc45, where Pc45 is the differential line carrying Pc45. F2 progenies and F2:3 families of both populations were inoculated with the crown rust isolate CR258 (race NTGG) and single gene segregation ratios were observed. SNP markers for PcKM were tested on these populations and linkage maps were generated. In addition, 17 newly developed SNP markers identified from genotyping-by-sequencing (GBS) data were mapped in these two populations, plus another three populations segregating for Pc45 or PcKM. Pc45 and PcKM mapped to the same location of Mrg08 (chromosome 12D) of the oat chromosome-anchored consensus map. These results strongly suggest that Pc45 and PcKM are the same resistance gene, but allelism (i.e., functionally different alleles of the same gene) or tight linkage (i.e., two tightly linked genes) cannot be ruled out based on the present data.

Spring‐sown oat (Avena sativa L.) is well adapted for forage production in Central Europe; however, environmental conditions make this crop susceptible to crown rust disease (Puccinia coronata) when grown in summer. The objective of this study was to assess oat cultivars sown in late summer, when conditions for crown rust are less favourable, and harvest in autumn for forage with potential use for feeding lactating dairy cows. Three oat cultivars: Berdysz, Zuch and ForagePlus, the first two from Poland and the latter from United States, were sown 1 and 15 August, and 1 September, over three consecutive years, and harvested for forage in late October. The two Polish cultivars had 61% leaf area affected by rust with 1 August sowing, but ForagePlus was not affected by rust with any sowing date. Sowing 15 August significantly reduced crown rust incidence and increased DM yield of the Polish cultivars 21% relative to the 1 August sowing date, but decreased ForagePlus DM yield by 35%. Sowing 1 September resulted in best forage nutritive value, but the lowest DM yields for all cultivars. Calculated milk production per ton of forage for all cultivars was lowest with the 1 August sowing date. Calculated milk production per hectare was greatest for Berdysz sown in mid‐August. Oat can be sown 15 August and harvested in autumn for forage production, avoiding crown rust disease during summer in Poland. Nutritive value of autumn oat forage is adequate to meet forage requirements of lactating dairy cows. [ABSTRACT FROM AUTHOR]

We developed 178 recombinant inbred lines from a southern‐by‐spring oat population designated as "TxH." These lines were genotyped to generate a high‐quality linkage map that resolved 6,902 markers into 21 linkage groups that matched closely with the latest hexaploid oat consensus map. Three major quantitative trait loci (QTLs) affecting heading date were found in locations that are consistent with known QTLs and candidate genes, and two other QTLs affecting heading date were found in novel locations. Five QTLs affecting plant height were found. Both sets of QTLs are responsible for transgressive segregation observed for these two traits. Four QTLs affecting resistance to crown rust, caused by the pathogen Puccinia coronata f. sp. avenae, were identified. Two of these QTLs are consistent with known clusters of rust resistance genes, while two may represent new locations of novel rust resistance genes. A complete set of SNP sequences suitable for generating markers for molecular selection is provided. [ABSTRACT FROM AUTHOR]

Molecular mapping of crown rust resistance genes is important to effectively utilize these genes and improve breeding efficiency through marker-assisted selection. Pc45 is a major race-specific crown rust resistance gene initially identified in the wild hexaploid oat Avena sterilis in the early 1970s. This gene was transferred to cultivated oat (Avena sativa) and has been used as a differential for identification of crown rust races since 1974. Previous research identified an association between virulence to Pc45 and PcKM, a crown rust resistance gene in the varieties 'Kame' and 'Morton'. This study was undertaken to reveal the relationship between Pc45 and PcKM. Pc45 was studied in the crosses 'AC Morgan'/Pc45 and 'Kasztan'/Pc45, where Pc45 is the differential line carrying Pc45. F2 progenies and F2:3 families of both populations were inoculated with the crown rust isolate CR258 (race NTGG) and single gene segregation ratios were observed. SNP markers for PcKM were tested on these populations and linkage maps were generated. In addition, 17 newly developed SNP markers identified from genotyping-by-sequencing (GBS) data were mapped in these two populations, plus another three populations segregating for Pc45 or PcKM. Pc45 and PcKM mapped to the same location of Mrg08 (chromosome 12D) of the oat chromosomeanchored consensus map. These results strongly suggest that Pc45 and PcKM are the same resistance gene, but allelism (i.e., functionally different alleles of the same gene) or tight linkage (i.e., two tightly linked genes) cannot be ruled out based on the present data. [ABSTRACT FROM AUTHOR]

Oat crown rust caused by Puccinia coronata f. sp. avenae is the most destructive foliar disease of cultivated oat. Characterization of genetic factors controlling resistance responses to Puccinia coronata f. sp. avenae in nonhost species could provide new resources for developing disease protection strategies in oat. We examined symptom development and fungal colonization levels of a collection of Brachypodium distcichyon and B. hyhridwn accessions infected with three North American P. coronata f. sp. avenae isolates. Our results demonstrated that colonization phenotypes are dependent on both host and pathogen genotypes, indicating a role for race-specific responses in these interactions. These responses were independent of the accumulation of reactive oxygen species. Expression analysis of several defense-related genes suggested that salicylic acid and ethylene-mediated signaling but not jasmonic acid are components of resistance reaction to P. coronata f. sp. avenae. Our findings provide the basis to conduct a genetic inheritance study to examine whether effector-triggered immunity contributes to nonhost resistance to P. coronata f. sp. avenae in Brachypodium spp. [ABSTRACT FROM AUTHOR]

Accessions of cultivated oat (Avena sativa L.) from the United States Department of Agriculture-Agricultural Research Service Small Grains Collection in Aberdeen. ID were characterized for adult plant resistance (APR) and seedling resistance to crown rust, caused by Puccinia coronata f. sp. avenae. Initially. 607 oat accessions with diverse geographic origins were evaluated in field tests in Baton Rouge. LA. Of those, 97 accessions were not fully susceptible and were tested in the field in St. Paul, MN against a diverse P. coronata f. sp. avenae population. Thirty-six accessions that had some level of resistance in both field tests and mean coefficients of infection of £20 were further evaluated for APR and seedling resistance. Among these, four accessions (PI 193040, PI 194201, PI 237090, and PI 247930) were resistant to eight P. coronata f. sp. avenae races as seedlings. Twenty-nine accessions had resistance to at least one of the P. coronata f. sp. avenae races. Three accessions (Clav 2272, Clav 3390. and PI 285583) were fully susceptible to all eight P. coronata f. sp. avenae races as seedlings. Further evaluation of the three seedling-susceptible accessions at the flag leaf stage in a growth chamber resulted in moderately susceptible to moderately resistant responses. The resistance sources presented here may contain genes not deployed in elite oat varieties, and may be useful for future crown rust resistance breeding. The adult and seedling resistance found in accessions of the cultivated oat species is especially valuable because it avoids problems associated with the transfer of genes from wild species to cultivated oat. [ABSTRACT FROM AUTHOR]

Crown rust (caused by Puccinia coronata) and stem rust (caused by P. graminis) are two common and destructive diseases of turfgrass in the United States. Crown rust has been associated with perennial ryegrass and stem rust with Kentucky bluegrass when identified based solely on fungal morphology. However, recent studies using molecular identification methods have indicated the host-pathogen relationship of rusts on turf to be more complex. Our primary objective was to quickly and accurately identify P. coronata and P. graminis in symptomatic turfgrass leaves over 3 years on turfgrass samples from across the Midwestern United States. Between 2013 and 2015, 413 samples of symptomatic cool-season turfgrass from Wisconsin and surrounding states were screened using real-time polymerase chain reaction. Of these samples, 396 were Kentucky bluegrass and 17% of them contained P. coronata, 69% contained P. graminis, and 13% contained both P. coronata and P. graminis. In addition, both year and location effects were observed on the distribution of Puccinia spp. collected annually from two locations in southern Wisconsin. This research supports previous conclusions that have identified variability among P. graminis and P. coronata host relationships on turfgrass, and further demonstrates that rust fungal populations on Kentucky bluegrass may not be consistent between locations in the same year or over multiple years at the same location. The increasing evidence of variation in the turfgrass rust populations will likely affect future rust management and turfgrass breeding efforts. [ABSTRACT FROM AUTHOR]

Key message: Oat crown rust is one of the most damaging diseases of oat. We identified a new source of resistance and developed KASP and TaqMan markers for selection in breeding programs.Abstract: A new highly effective resistance to oat crown rust (Puccinia coronata f. sp. avenae) was identified in the diploid oat Avena strigosa PI 258731 and introgressed into hexaploid cultivated oat. Young plants with this resistance show moderate susceptibility, whereas older plant tissues and adult plants are resistant with no virulent isolates encountered in over 8 years of testing. Resistance was incorporated into hexaploid oat by embryo rescue, colchicine chromosome doubling followed by backcrosses with a hexaploid parent, and selection for stable transmission of resistance. To mitigate flag leaf and panicle chlorosis/necrosis associated with the resistance, crosses were made with derived resistant lines to breeding lines of divergent parentage followed by selection. Subsequently, two F2 sister lines, termed MNBT1020-1 and MNBT1021-1, were identified in which the chlorosis/necrosis was reduced. These two lines performed well in replicated multi-location state trials in 2015 and 2016 out-yielding all cultivar entries. Segregating F2:3 plants resulting from crosses of MNBT lines to susceptible parents were genotyped with the oat 6K SNP array, and SNP loci with close linkage to the resistance were identified. KASP assays generated from linked SNPs showed accurate discrimination of the resistance in derivatives of the resistant MNBT lines crossed to susceptible breeding lines. A TaqMan marker was developed and correctly identified homozygous resistance in over 95% of 379 F4 plants when rust was scored in F4:5 plants in the field. Thus, a novel highly effective resistance and associated molecular markers are available for use in breeding, genetic analysis, and functional studies. [ABSTRACT FROM AUTHOR]

In order to study the inheritance of resistance to crown rust (Puccinia coronata f. sp. lolii) in perennial ryegrass (Lolium perenne), we crossed a resistant, diploid genotype (A6128/05) with a susceptible genotype of the cultivar Aurora to generate a F1 population. Individuals of the F1 population were screened for their response to three single-pustule isolates (SPI) of crown rust in a detached-leaf segment test under growth chamber conditions. Out of the F1 population, we selected two genotypes (I and II) based on the reaction to SPI of crown rust: genotype I was resistant to SPI A, D and F. Genotype II was resistant to SPI A, but susceptible to SPI D and F. Both genotypes were backcrossed with a second, susceptible Aurora genotype to generate two F2 populations. A resistant genotype out of each of the two F2 populations was used to generate a F3 population by backcrossing with a susceptible Aurora genotype. In the F2 and F3 populations, derived from a cross with the genotype I, a good fit to a segregation ratio of 1R:1S (resistant:susceptible) was observed for the three SPI A, D and F. The frequency of resistant and susceptible plants within the F2 and F3 populations, derived from the genotype II, resulted in a ratio of 1R:1S for SPI A. In contrast, the F2 and F3 progeny was susceptible to SPI D and F. These results provide evidence that at least two different dominant genes for crown rust resistance occur in the resistance donor A6128/05. [ABSTRACT FROM AUTHOR]

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Crown rust (Puccinia coronata f. sp. avenae) can devastate oats (Avena sativa). Plants possessing durable resistance are desirable and they may contain mechanisms that differ from those underlying genes with specific effects. Gathering information about the molecular mechanisms involved, especially those not associated with the hypersensitive reaction, and combining those acting at different infection stages may increase the ability to defeat the pathogen. The cultivar URS 21 has strongly reduced the intensity and growth of crown rust for the last 14 years, demonstrating durable racenonspecific resistance expressed at adult and seedling stages. The main objective of this study was to identify, by deep sequencing, oat transcripts induced by P. coronata in the URS 21 cultivar inoculated at seedling stage. Two important reactions to inoculation, secondary metabolism and the oxidative response, were studied further. The expression of specific genes associated with biosynthesis of secondary metabolites was evaluated in adult plants by RT-PCR, as well as the accumulation of saponins and avenanthramides, found to be important in other pathosystems, and comparisons were made with the susceptible cultivar URS 22. The URS 21 resistance mechanism probably involves several components including the biosynthesis of avenanthramides and steroid saponins; also, several genes related to antioxidative stress were down-regulated. A large number of oat sequences were generated by RNA-seq analysis in this study, which will help in the search for genes involved in the race-nonspecific resistance; they may also be useful in the development of markers to search for QTLs associated with race-nonspecific resistance. [ABSTRACT FROM AUTHOR]

A ferrugem da folha e a helmintosporiose são as principais doenças fúngicas foliares de aveia branca. Em cultivares suscetíveis, o controle químico não considera o limiar de dano econômico (LDE). O objetivo deste trabalho foi obter funções de dano, por modelos de ponto crítico, ao relacionar o dano pela ocorrência simultânea da ferrugem da folha e a helmintosporiose com o rendimento de grãos nas safras de 2006 e 2007, em Lages, Santa Catarina (SC). O gradiente da intensidade das doenças foi gerado por número de aplicações e doses de fungicidas nas cultivares 'UPFA 20' e 'UPFA 22'. Os ensaios consistiram de 10 tratamentos, distribuídos em blocos casualizados, com quatro repetições. As doenças foram avaliadas nos estádios de alongamento, emborrachamento e florescimento. Os modelos de ponto crítico foram obtidos por regressão linear entre rendimento de grãos e incidência (I) e severidade (S). Em 2006, funções significativas foram obtidas para 'UPFA 20' no emborrachamento (R=6.345-22,07I), enquanto para a 'UPFA 22' foi obtida no alongamento (R=5.726-17,96I; R=5.160-541,5S), emborrachamento (R=5.961-21,85I; R=5.433-966,8S) e florescimento (R=6.217-36,41I; R=5.539-1.185S). Em 2007, para 'UPFA 20', no alongamento (R=6.369-55,61I; R=4.965-2.911S), emborrachamento (R=6.620-40,91I; R=5.181-1.702S) e florescimento (R=6.129-32,34I; R=5.252-638,6S), e para 'UPFA 22', no alongamento (R=5.201-41,96I; R=4.977-657,8S), emborrachamento (R=5.329-60,51I; R=4.238-798,1S) e florescimento (R=5.604-32,83I; R=4.680-588,5S). A produção na cultivar 'UPFA 22' foi mais afetada pela ocorrência das doenças, e a intensidade das doenças no estádio de florescimento apresentou maior relação com o rendimento de grãos. As funções geradas permitem obter o coeficiente de dano para uso no cálculo do LDE em patossistema múltiplo ferrugem da folha e helmintosporiose.The leaf rust and helminthosporium blight are the main foliar diseases of white oat. The chemical control in susceptible cultivars does not consider the economic damage threshold (EDT). The objective of this research was to obtain the damage functions by critical-point models to relate damage by simultaneous occurrence of white oat leaf rust and helminthosporium blight with yield grains during 2006/07 crop seasons in Lages, SC, Brazil. The gradient of diseases intensity was generated by number of applications and rates fungicides on cultivars 'UPFA 20' and 'UPFA 22'. The trials consisted by 10 treatments distributed in randomly blocks with four replications. Diseases evaluations were done in the elongation, booting and flowering stages. The critical-point models were obtained by linear regression between grain yield and leaf diseases incidence and severity. In 2006, significant function was obtained for 'UPFA 20' in booting stage (R=6.345-22.07I), with 'UPFA 22'. The significant functions were obtained in elongation (R=5.726-17.96I and R=5.160-541.5S), booting (R=5.961-21.85I; R=5.433-966.8S) and flowering stages (R=6.217-36.41I; R=5.539-1.185S). In 2007, the significant functions were obtained in all growth stages evaluated. To 'UPFA 20', the significant functions were in the elongation (R=6.369-55.61I; R=4.965-2.911S), booting (R=6.620-49.91I; R=5.181-1.702S) and flowering (R=6.129-32.34I; R=5.252-638.6S), while in the 'UPFA 22', were in the elongation (R=5.201-41.96I; R=4.977-657.8S), booting (R=5.329-60.51I; R=4.238-798.1S) and flowering (R=5.604-32.83I; R=4.680-588.5S). The 'UPFA 22' cultivar production was more affected by diseases occurrence and the diseases intensity in the flowering stage showed greater relation with the yield grain. The generated functions allowed obtaining the damage coefficient to use in the EDT in the multiple pathosystem leaf rust and helminthosporium.

Os objetivos deste trabalho foram descrever a variabilidade para resistência parcial à ferrugem da folha em populações segregantes, bem como estudar o controle genético envolvido na expressão da resistência. As avaliações de severidade da doença foram realizadas em 1998, 1999 e 2000, seguindo a escala modificada de Cobb. Os resultados de três anos de estudo evidenciaram que, apesar da grande influência do ambiente na expressão da resistência, as populações segregantes apresentaram grande variabilidade para resistência parcial. A distribuição de freqüências da Área Sob a Curva do Progresso da Doença (ASCPD) em gerações avançadas foi contínua para o caráter, indicando a presença de vários genes de pequeno efeito em seu controle. As estimativas de herdabilidade variaram de moderadas a altas.The objectives of this research were to describe the variability regarding partial resistance to leaf rust in segregating populations and to study genetic control of the resistance expression. The evaluation of disease was done at 1998, 1999 and 2000, according to modified Cobb’s scale. The results of three years studies showed that regardless the great environmental effect on the expression of resistance, the segregating population presented great variability for partial resistance. The frequency distribution of AUDPC for advanced generations, was continuous for this trait, indicating the presence of several genes of small effects controlling the disease. The estimatives of herdability varied from moderate to high.

Rdza koronowa, powodowana przez grzyb Puccinia coronata, jest jedną z najpowszechniej występujących chorób grzybowych owsa w Polsce. Do tej pory u owsa zidentyfikowano ponad 100 genów odporności na ten patogen, jednak są one szybko przełamywane przez nowe patotypy Puccinia coronata. Celem pracy była ocena efektywności genów warunkujących odporność na izolaty Puccinia coronata skolekcjonowane w centralnej i południowo-wschodniej Polsce w latach 2010-2011. W badaniach wykorzystano 31 linii referencyjnych owsa z pojedynczymi genami odporności na rdzę koronową. Analizy przeprowadzono z wykorzystaniem testów żywiciel-patogen w oparciu o 6 izolatów Puccinia coronata. Izolaty pochodzące z różnych rejonów uprawy owsa różniły się między sobą wirulencją w stosunku do 21 z 31 linii referencyjnych. Przeprowadzone badania wykazały, że najbardziej efektywne w stadium siewki są geny Pc14, Pc39, Pc51, Pc52, Pc53, Pc57, Pc60, Pc68, Pc71 i Pc91.

Cereal rusts, caused by obligate and biotrophic fungi in the genus Puccinia, are important diseases that threaten world food security. With the recent discovery of alternate hosts for the stripe rust fungus ( Puccinia striiformis), all cereal rust fungi are now known to be heteroecious, requiring two distinct plant species serving as primary or alternate hosts to complete their sexual life cycle. The roles of the alternate hosts in disease epidemiology and pathogen variation vary greatly from species to species and from region to region because of different climatic and cropping conditions. We focus this review on rust fungi of small grains, mainly stripe rust, stem rust, leaf rust, and crown rust of wheat, barley, oat, rye, and triticale, with emphases on the contributions of alternate hosts to the development and management of rust diseases. [ABSTRACT FROM AUTHOR]

Crown rust, caused by Puccinia coronata Corda f. sp. avenae Eriks., is a serious menace in oats, for which resistance is an effective means of control. Wild diploid oat accessions are a source of novel resistances that first need to be characterised prior to introgression into locally adapted oat cultivars. A genetic analysis of resistance to crown rust was carried out in three diverse diploid oat accessions (CIav6956, CIav9020, PI292226) and two cultivars (Saia and Glabrota) of A. strigosa. A single major gene conditioning resistance to Australian crown rust pathotype (Pt) 0000-2 was identified in each of the three accessions. Allelism tests suggested that these genes are either the same, allelic, or tightly linked with less than 1 % recombination. Similarly, a single gene was identified in Glabrota, and possibly two genes in Saia; both cultivars previously reported to carry two and three crown rust resistance genes, respectively. The identified seedling resistance genes could be deployed in combination with other resistance gene(s) to enhance durability of resistance to crown rust in hexaploid oat. Current diploid and hexaploid linkage maps and molecular anchor markers (simple sequence repeat [SSR] and diversity array technology [DArT] markers) should facilitate their mapping and introgression into hexaploid oat. [ABSTRACT FROM AUTHOR]

Crown rust samples were collected in 2004 on rust infected Italian and perennial ryegrass leaves at 28 sites in 11 European countries. Out of these 28 rust collections, 112 single-pustule isolates were produced to determine virulence frequency and complexity on 32 ryegrass genotypes. A high level of virulence diversity was observed within and between individual sampling sites. In total, 107 pathotypes with different virulence combination were found. Of these, just five combinations occurred twice. All 32 individuals were susceptible to at least two single-pustule isolates using a detached-leaf segment test. In the field, the 32 genotypes differed greatly in their susceptibility to crown rust. Nevertheless, the correlation between mean susceptibility in the field and virulence frequency of the 32 differentials was significant. The three most resistant genotypes in the field were also the genotypes with the lowest virulence frequency. Genetic analysis of resistance to crown rust in three genotypes of perennial ryegrass led to the identification of three dominant resistance genes: Pclol1, Pclol2 and Pclol3. Each of the three genes conferred resistance to a limited number of single-pustule isolates and was ineffective against at least one single-pustule isolate. The patterns of resistance reaction to specific single-pustule isolates provide evidence that the three R-genes represent distinct crown rust resistance genes in ryegrass. Moreover, the data demonstrate clearly the existence of pathotype specificity in crown rust of Lolium species. [ABSTRACT FROM AUTHOR]

Os objetivos deste trabalho foram: determinar o padrão de resistência/suscetibilidade de 20 genótipos de aveia a 40 isolados de Puccinia coronata f. sp. avenae, coletados em três municípios do Rio Grande do Sul; o padrão de virulência/avirulência desses isolados contra os genótipos de aveia; e indicar genitores para a geração de populações com elevada resistência à ferrugem-da-folha. Os padrões de resistência de Puccinia coronata f. sp. avenae e o de virulência/avirulência dos isolados foram determinados pela avaliação da reação desencadeada pela aspersão dos isolados deste fungo em plântulas de genótipos de aveia. A seleção de genitores foi baseada no índice de complementação de cultivares, proposto neste trabalho. Os genótipos que expressaram resistência ao maior número de isolados foram FAPA6, URS20, UPFA20, CFT1 e FAPA5, ao passo que os genótipos UFRGS15, UPF15, UPF18, UPF19 e UPF16 evidenciaram suscetibilidade ao maior número de isolados. Os cruzamentos mais indicados entre os genótipos estudados são: FAPA6 x Albasul, URS22 x FAPA6, CFT1 x URPEL15 e CFT1 x UFRGS19.The objectives of this work were: to determine the resistance/susceptibility pattern of 20 elite oat genotypes to 40 isolates of Puccinia coronata f. sp. avenae; to determine the pattern of virulence/avirulence of isolates collected in three counties of Rio Grande do Sul to the oat genotypes studied; and to indicate potential parents for the generation of populations with high crown rust resistance. The resistance pattern of oat genotypes and the virulence/avirulence of the fungi were determined by the analysis of the reaction incited by the inoculation of Puccinia coronata f. sp. avenae isolates into seedlings of oat genotypes. The selection of genitors was based on the cultivar complementation index proposed in this work. Genotypes expressing resistance to the larger number of isolates were FAPA6, URS20, UPFA20, CFT1 and FAPA5, while UFRGS15, UPF15, UPF18, UPF19 and UPF16 were susceptible to a higher number of isolates. The following crosses are indicated: FAPA6 x Albasul, URS22 x FAPA6, CFT1 x URPEL15 and CFT1 x UFRGS19.

در این بررسی، تاکسونومی Puccinia coronata در ایران با توجه به خصوصیات مورفولوژیک هاگ های مراحل مختلف مورد مطالعه قرار گرفت و چهار واریته درون گونه مذکور تعیین شد که عبارتند از: P. coronata var. coronata, P. coronata var. avenae, P. coronata var. hordei, P. coronata var. golestanica var. nov. در بین آرایه های تعیین نام شده، واریته golestanica برای دنیا و واریته های avenae و hordei برای فلور زنگ های ایران جدید بودند. دامنه میز بانی و خصوصیات مورفولوژیک هر یک از واریته های فوق به اختصار شرح داده شدند و میزبان های جدیدی برای مراحل اسیومی و تلیومی P. coronata شناسایی گردید. همچنین بررسی دامنه ابعاد اسیوسپورهای این گونه بر اساس مطالعه نمونه های ایرانی و خارجی مشخص نمود، تنوع دامنه ابعاد اسیوسپورهای این زنگ بیش از ابعاد ذکر شده برای آنها در منابع مختلف است.

Ryegrasses are important forage species. An important foliar disease in Lolium is crown rust, caused by the fungus Pucciniacoronata. This cosmopolitan biotrophic fungus causes forage and seed losses, and decoloration of amenity grasslands.In breeding towards resistant cultivars, it is important to know the mode of inheritance of crown rust resistance. A paircross between a susceptible and a resistant plant resulted in a F1 population segregating for rust resistance. According tothe segregation data, major genes were assumed to encode for crown rust resistance. In a bulk segregant analysis (BSA)187 primer combinations revealed AFLP markers linked with resistance. Two groups of genetically unlinked markerswere identified, explaining together 35% of the phenotypic variation.

A ferrugem da folha e a helmintosporiose são doenças foliares que afetam o rendimento de grãos e componentes da aveia branca. O objetivo deste trabalho foi quantificar os danos causados pelas duas doenças, considerando um patossistema múltiplo, no rendimento de grãos, massa de mil grãos e peso do hectolitro, bem como determinar a porcentagem de controle destas doenças em resposta ao número (uma duas e quatro) e dose (½, ¾ e dose indicada) de aplicação do fungicida piraclostrobina + epoxiconazole, nas cultivares de aveia branca UPFA 20 Teixeirinha e UPFA 22 Temprana. Os experimentos foram conduzidos na safra agrícola de 2006, em área de rotação de culturas, e na safra de 2007, em área de monocultura. Cada experimento constou de 10 tratamentos, distribuídos em blocos ao acaso, com quatro repetições. A intensidade das doenças foi quantificada entre os estádios fenológicos de início do afilhamento e de grão em massa dura. Os dados de incidência e severidade foliar foram usados para calcular a área abaixo da curva de progresso da doença (AACPD). A doença predominante nas duas safras e em ambas as cultivares até o início do florescimento foi a helmintosporiose. A ferrugem da folha teve sua intensidade aumentada nos estádios subseqüentes. Os danos no rendimento de grãos, massa de mil grãos e peso do hectolitro foram maiores na safra de 2007 para as duas cultivares, com valores percentuais variando, respectivamente, de 5,46% a 50,30%, 3,56% a 32,72%, 1,49% a 7,20% na cultivar UPFA 20, e de 11,10% a 48,45%, 2,08% a 26,01%, 1,88% a 11,51% para cultivar UPFA 22. Os valores de AACPD indicaram maior intensidade das doenças em 2007, possivelmente pela maior disponibilidade de inóculo no sistema de monocultura. A cultivar UPFA 20 foi mais suscetível às doenças. No entanto, apresentou maiores valores dos componentes de rendimento. O controle das doenças foi maior nas duas cultivares na safra 2007, atingindo 86,74% e 85,90% para UPFA 20 e UPFA 22, respectivamente. O maior retorno econômico do controle químico para safra de 2006 nas duas cultivares ocorreu com duas aplicações do fungicida na dose indicada, e na safra de 2007 com quatro aplicações.

O objetivo deste trabalho foi determinar os diferentes níveis de resistência à ferrugem-da-folha em genótipos de aveia, e avaliar seu efeito sobre componentes do rendimento de grãos. Os experimentos foram conduzidos na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, em 1995 e 1996. Foram avaliados dez genótipos de aveia com reações diferenciadas à moléstia. A ferrugem-da-folha causou prejuízos no rendimento de grãos, em diferentes densidades de cultivo da aveia, e o peso de grãos foi o componente mais afetado. Porém, alguns genótipos, como o UFRGS 910906, não foram afetados, apesar de apresentarem níveis intermediários de severidade da moléstia, o que evidencia a possibilidade de combinar resistência parcial e potencial de rendimento num mesmo genótipo.

A ferrugem-da-folha (Puccinia coronata f. sp. avenae) é a principal doença da cultura da aveia (Avena sativa L.), e o uso de cultivares resistentes é o método de controle mais importante. Este trabalho teve por objetivo determinar o controle genético da resistência à ferrugem-da-folha em aveia e identificar fontes de genes diferentes para resistência a esta doença. Foram utilizados três genótipos resistentes (UFRGS 15, UFRGS 881920 e UFRGS 86A1194-2), três genótipos suscetíveis (UFRGS 7, UFRGS 8 e UFRGS 14) e a geração segregante F3 proveniente dos cruzamentos entre estes genótipos. As plantas foram avaliadas individualmente quanto à presença ou ausência da ferrugem-da-folha, sendo os dados destas leituras utilizados numa análise genética em que a hipótese de um ou dois genes de resistência foi testada pelo qui-quadrado. Os resultados evidenciaram um gene dominante de resistência no genótipo UFRGS 881920 e dois genes complementares no genótipo UFRGS 15 quando estes foram cruzados com os suscetíveis. A análise genética feita não permitiu determinar se estes dois genótipos são ou não a mesma fonte genética de resistência.

Barley ( Hordeum vulgare L.) mapping populations have been developed that are useful to study the inheritance of quantitative resistance to adapted and unadapted rust fungi. In a recent host range study, we found that the parents of those mapping populations also differed in their resistance to the crown rust Puccinia coronata ( PcE) of couch grass ( Elymus repens), as well as three isolates of P. striiformis, representing formae speciales hordei ( Psh), tritici ( Pst) and bromi ( Psb). Available mapping populations were phenotyped at the seedling stage to map the genes conferring resistance to these rust isolates. Resistances to PcE, Psb and Pst inherit quantitatively. This contrasted with reports that barley nonhost resistance to unadapted formae speciales of P. striiformis is based on major genes. We mapped QTLs effective against PcE using relative latency period and relative infection frequency. Some QTLs for resistance were contributed by 'Vada' and 'Cebada Capa', others by SusPtrit. One PcE-resistance QTL on 3H, contributed by 'Cebada Capa', co-localised with a QTL effective against four unadapted grass rust species, indicating either a single gene with broad-spectrum effectiveness or a cluster of rather specific genes. Chromosome arm 7HL from Vada seems particularly rich in genes for resistance to rust fungi. Resistance to Pst and Psb, measured as the number of uredinia, tended to co-localise with each other and mapped to 1HS, 2HL and 7HL. The nearly complete resistance of Ethiopian line L94 to Psh was due to a major gene mapped on chromosome 4H. That gene is likely the recessive gene rpsGZ, which was previously reported in the Ethiopian line Grannenlose Zweizeilige. [ABSTRACT FROM AUTHOR]

Crown rust ( Puccinia coronata Corda f.sp. avenae) can devastate oats ( Avena sativa). Oxidative stress is part of the resistance mechanism in several pathosystems, but in the oat-crown rust system, it is unclear, especially regarding partial resistance. We evaluated the effects of P. coronata on oxidative stress in oat cultivars: URS 21 (partially resistant), Leggett (race-specific resistant), URS22 and Clintland 64 (susceptibles). Seedlings and plants were inoculated with P. coronata uredospores. Cultivars were assessed for antioxidant enzyme activity and the reactive oxygen species ( ROS) hydrogen peroxide and superoxide. Due to the importance of the partial resistance of URS21, this cultivar and URS 22 were also appraised for total phenolics and the relative expression of oxidative stress genes. Postinoculation, Leggett and URS 21 showed no increased peroxide levels. The susceptible cultivars increased ROS and ascorbate peroxidase activity. Clintland 64 increased also catalase activity, whereas URS 22 increased glutathione reductase and the expression of genes encoding antioxidant enzymes. URS 21 showed almost no antioxidant enzyme induction. Shortly after inoculation, URS 21 showed increased expression of genes encoding lipoxygenase and peroxidase. Cultivars URS 21 and Leggett accumulated cell wall fluorescent compounds, phenolics being detected in the former. Oxidative stress appears not to cause the hypersensitive response in this pathosystem, but late ROS accumulation did occur in the susceptible cultivars. Cultivar URS 21 may, differently from other known mechanism to date, reduce ROS accumulation by increasing the level of phenolics, resulting in later pathogen and cell death, showing non-specific resistance to races of the pathogen also at seedling stage. [ABSTRACT FROM AUTHOR]

Rusts are destructive fungal diseases that can cause severe thinning and unattractive discoloration of kentucky bluegrass (KBG; Poa pratensis L.). Currently, turfgrass breeding programs rely on field evaluations to screen KBG germplasm for rust resistance; methods that are expensive, labor intensive, and require large turf areas. The availability of a greenhouse-based assay to perform prescreening of KBG germplasm for resistance to rust diseases before field trials would allow breeders to remove the poorest performing plants before field evaluations thus enhancing breeding efficiency. In this study, we set out to develop a reliable, low-cost greenhouse inoculation protocol for the two most common rust pathogens of KBG in temperate growing regions: Puccinia coronata and Puccinia graminis, the causal agents of crown and stem rust, respectively. Using a modified inoculation assay and custom-built plexi-glass chambers adapted from protocols used for cereal rust pathogens, urediniospores of crown and stem rust fungi developed on inoculated plants 10 to 14 days postinoculation. Real-time polymerase chain reaction (PCR) assays, disease symptomology, and morphology of urediniospores confirmed the presence and identity of both rust pathogens from inoculated host tissue. The inoculation protocols described here represent an effective method to accelerate screening of KBG germplasm for resistance to crown and stem rust diseases. Infection of KBG plants in the greenhouse will also allow breeders to maintain populations of crown and stem rust fungi throughout the year, providing a reliable and ongoing source of pathogen inoculum for experimentation and screening in the future. [ABSTRACT FROM AUTHOR]

The cultivar URS Brava, obtained from a simple cross between the line 'UFRGS 995078-2' and the cultivar 'URS 21', shows high grain yield and stability, high grain quality, desirable agronomical traits and partial resistance to crown rust, caused by the fungus Puccinia coronata f. sp. avenae. [ABSTRACT FROM AUTHOR]

Diseases caused by crown rust (Puccinia coronata f. sp. avenae) and powdery mildew (Blumeria graminis f. sp. avenae) are among the most important constraints for the oat crop. Breeding for resistance is one of the most effective, economical, and environmentally friendly means to control these diseases. The purpose of this work was to identify elite alleles for rust and powdery mildew resistance in oat by association mapping to aid selection of resistant plants. To this aim, 177 oat accessions including white and red oat cultivars and landraces were evaluated for disease resistance and further genotyped with 31 simple sequence repeat and 15,000 Diversity ArraysTechnology (DArT) markers to reveal association with disease resistance traits. After data curation, 1712 polymorphic markers were considered for association analysis. Principal component analysis and a Bayesian clustering approach were applied to infer population structure. Five different general and mixed linear models accounting for population structure and/or kinship corrections and two different statistical tests were carried out to reduce false positive. Five markers, two of them highly significant in all models testedwere associated with rust resistance. No strong association between any marker and powdery mildewresistance at the seedling stagewas identified. However, one DArT sequence, oPt-5014, was strongly associated with powdery mildew resistance in adult plants. Overall, the markers showing the strongest association in this study provide ideal candidates for further studies and future inclusion in strategies of marker-assisted selection. [ABSTRACT FROM AUTHOR]

Developing oat cultivars with partial resistance to crown rust would be beneficial and cost-effective for disease management. Two recombinant inbred-line populations were generated by crossing the susceptible cultivar Provena with two partially resistant sources, CDC Boyer and breeding line 94197A1-9-2-2-2-5. A third mapping population was generated by crossing the partially resistant sources to validate the quantitative trait locus (QTL) results. The three populations were evaluated for crown rust severity in the field at Louisiana State University (LSU) in 2009 and 2010 and at the Cereal Disease Laboratory (CDL) in St. Paul, MN, in 2009, 2010, and 2011. An iSelect platform assay containing 5,744 oat single nucleotide polymorphisms was used to genotype the populations. From the 2009 CDL test, linkage analyses revealed two QTLs for partial resistance in the Provena/CDC Boyer population on chromosome 19A. One of the 19A QTLs was also detected in the 2009 LSU test. Another QTL was detected on chromosome 12D in the CDL 2009 test. In the Provena/94197A1-9-2-2-2-5 population, only one QTL was detected, on chromosome 13A, in the CDL 2011 test. The 13A QTL from the Provena/94197A1-9-2-2-2-5 population was validated in the CDC Boyer/94197A1-9-2-2-2-5 population in the CDL 2010 and 2011 tests. Comparative analysis of the significant marker sequences with the rice genome database revealed 15 candidate genes for disease resistance on chromosomes 4 and 6 of rice. These genes could be potential targets for cloning from the two resistant parents. [ABSTRACT FROM AUTHOR]

Key message: Genetic analysis and genome mapping of a major seedling oat crown rust resistance gene, designated PcKM, are described. The chromosomal location of the PcKM gene was identified and linked markers were validated. Abstract: Crown rust ( Puccinia coronata Corda f. sp. avenae Eriks) is the most important foliar disease of oats and can cause considerable yield loss in the absence of appropriate management practices. Utilization of novel resistant genes is the most effective, economic and environmentally sound approach to control the disease. Crown rust resistance present in the cultivar 'Morton' was evaluated in a population developed from the cross OT3019 × 'Morton' to elucidate the genetic basis of resistance. Crown rust reaction evaluated in field nurseries and greenhouse tests demonstrated that resistance provided by 'Morton' was controlled by a single gene, temporarily designated as PcKM. The gene was initially linked to a random amplified polymorphic DNA band and subsequently converted into a sequence characterized amplified region (SCAR) marker. Genotyping with the PcKM SCAR on the 'Kanota' × 'Ogle' population, used to create the first oat chromosome-anchored linkage map, placed the PcKM gene on chromosome 12D. Consensus map markers present in the same region as the PcKM SCAR were tested on the OT3019 × 'Morton' population and two additional phenotyped populations segregating for PcKM to identify other markers useful for marker-assisted selection. Three markers were perfectly linked to the PcKM phenotype from which TaqMan and KBioscience competitive allele-specific PCR assays were developed and validated on a set of 25 oat lines. The assays correctly identified PcKM carriers. The markers developed in this study will facilitate fine mapping of the PcKM gene and simplify selection for this crown rust resistance. [ABSTRACT FROM AUTHOR]

A ferrugem-da-folha (Puccinia coronata f.sp. avenae) foi quantificada em quatro populações F3 de aveia (Avena sativa L.) com o objetivo de estudar a severidade dessa moléstia e seus efeitos sobre seis caracteres da panícula. As populações utilizadas foram UFRGS 881920 x UFRGS 7, UFRGS 881920 x UFRGS 14, UFRGS 15 x UFRGS 7 e UFRGS 15 x UFRGS 14, sendo os genótipos UFRGS 881920 e UFRGS 15 resistentes à moléstia e os demais suscetíveis. A ferrugem-da-folha foi quantificada na época do florescimento, e próximo à maturação foram colhidas, em cada população, 10 plantas ao acaso por nota de ferrugem nas quais foram feitas as seguintes determinações: número de panículas, peso médio de panículas, número de grãos por planta e por panícula, peso de grãos e peso de mil grãos. A variabilidade em relação à severidade da ferrugem-da-folha foi analisada mediante a distribuição de freqüências das notas em cada população. A avaliação dos efeitos da moléstia sobre os caracteres da panícula foi feita pela análise de variância, análise de regressão polinomial e correlações fenotípicas. Os resultados obtidos demonstram haver ampla variação com respeito à severidade da moléstia nas populações estudadas, e os caracteres mais afetados foram o peso médio de panículas e o peso de mil grãos.Crown rust (Puccinia coronata f.sp. avenae) was quantified in four F3 oat (Avena sativa L.) populations with the objective of studying disease severity and its effects on six panicle characters. Populations used were UFRGS 881920 x UFRGS 7, UFRGS 881920 x UFRGS 14, UFRGS 15 x UFRGS 7 and UFRGS 15 x UFRGS 14, with genotypes UFRGS 881920 and UFRGS 15 being resistant and the others susceptible. Crown rust infection was quantified at flowering stage and near grain maturity 10 plants at random were harvested per crown rust score in each population, and the following determinations were made: number of panicles, mean panicle weight, number of grains per plant and per panicle, grain weight and 1,000 grains weight. Variability for crown rust severity was analised through frequency distribution of crown rust scores in each population. Evaluation of crown rust effects on panicle characters was done through analysis of variance, polinomial regression analysis and phenotypic correlations. Results obtained demonstrate great variation for crown rust severity in the populations studied, and the most affected characters by disease occurence were mean panicle weight and 1,000 grains weight.

Background Crown rust, caused by Puccinia coronata f. sp. avenae, is the most important disease of oat worldwide. Adult plant resistance (APR), based upon partial resistance, has proven to be a durable rust management strategy in other cereal rust pathosystems. The crown rust APR in the oat line MN841801 has been effective for more than 30 years. The genetic basis of this APR was studied under field conditions in three recombinant inbred line (RIL) populations: 1) AC Assiniboia/MN841801, 2) AC Medallion/MN841801, and 3) Makuru/MN841801. The populations were evaluated for crown rust resistance with the crown rust isolate CR251 (race BRBB) in multiple environments. The 6 K oat and 90 K wheat Illumina Infinium single nucleotide polymorphism (SNP) arrays were used for genotyping the AC Assiniboia/MN841801 population. KASP assays were designed for selected SNPs and genotyped on the other two populations. Results This study reports a high density genetic linkage map constructed with oat and wheat SNP markers in the AC Assiniboia/MN841801 RIL population. Most wheat SNPs were monomorphic in the oat population. However the polymorphic wheat SNPs could be scored accurately and integrated well into the linkage map. A major quantitative trait locus (QTL) on oat chromosome 14D, designated QPc.crc-14D, explained up to 76% of the APR phenotypic variance. This QTL is flanked by two SNP markers, GMI_GBS_90753 and GMI_ES14_c1439_83. QPc.crc-14D was validated in the populations AC Medallion/MN841801 and Makuru/MN841801. Conclusions We report the first APR QTL in oat with a large and consistent effect. QPc.crc-14D was statistically significant in all environments tested in each of the three oat populations. QPc.crc-14D is a suitable candidate for use in marker-assisted breeding and also an excellent target for map-based cloning. This is also the first study to use the 90 K wheat Infinium SNP array on oat for marker development and comparative mapping. The Infinium SNP array is a useful tool for saturating oat maps with markers. Synteny with wheat suggests that QPc.crc- 14D is orthologous with the stripe rust APR gene Yr16 in wheat. [ABSTRACT FROM AUTHOR]