Barberry plays an active role as an alternate host of Puccinia graminis in Spain

Stem rust, caused by Puccinia graminis, is a destructive group of diseases. The patho - gen uses Berberis species as alternate hosts to complete its life cycle. B. vulgaris and the endemic species B. hispanica and B. garciae are present in Spain. The objective of this study was to investigate the functionality of the indigenous barberry as alternate hosts. Field surveys were conducted in 2018 and 2019 in Huesca, Teruel and Albacete provinces of Spain. Aecial samples on barberry were analysed via infection assays and DNA analysis. B. garciae was predominant in Huesca and Teruel provinces, often found in the field margins of cereal crops. Aecial infections on B. garciae were ob- served in May and uredinial infections on cereal crops in June. Scattered B. hispanica bushes were occasionally found near cereal crops in Albacete, where aecial infections on B. hispanica were observed in June when most cereal crops were mature. Infection assays using aeciospores resulted in stem rust infections on susceptible genotypes of wheat, barley, rye and oat, indicating the presence of the sexual cycle for P. graminis f. sp. tritici, f. sp. secalis and f. sp. avenae. Sequence analyses from aecial samples sup- ported this finding as well as the presence of Puccinia brachypodii. This study provides the first evidence that indigenous Berberis species play an active role in the sexual cycle of P. graminis under natural conditions in SpainThe research was supported by the United States Department of Agriculture‐Agricultural Research Service, the Bill and Melinda Gates Foundation and the United Kingdom Department for International Development managed by Cornell University, USA, grant number: DGGW‐OPP1133199, and the State Research Agency (AEI), Spain, project PID2020‐118650RR‐C31. Thanks to Dr Fanny Álvaro for the initial observation and sampling of aecial infection on barberry. The assistance of Dr Joan Pedrol and Dr Rosario Fanlo (University of Lleida, Spain) in grass species identification is gratefully acknowledged. We thank the assistance of Amparo López Olmeda (Teruel Plant Health Service), Gloria Herrero Sánchez (Cereales Teruel Sociedad Cooperativa) and Vicente Lozano Herrera (farmer cereal producer). Meteorological data from the El Ballestero site (Albacete province) were kindly provided by Manuel Fernández. Data from surface cropping area of Aragón have been provided by Sección de estadística del Departamento de Agricultura, Ganadería y Medio Ambiente del Gobierno de Aragón (Silvia Quílez‐Domingo). The support of Daniel Gómez and Alberto Pastoriza (Herbarium curators in the Pyrenean Institute of Ecology, IPE‐CSIC, Jaca) is thankfully acknowledged. Technical assistance of Melissa Carter, Jerry Johnson and Kim‐Phuong Nguyen from USDA‐ARS is acknowledged. Dr Villegas acknowledges the contribution of the CERCA program (Generalitat de Catalunya, Spain)

Barberry plays an active role as an alternate host of Puccinia graminis in Spain

Stem rust, caused by Puccinia graminis, is a destructive group of diseases. The pathogen uses Berberis species as alternate hosts to complete its life cycle. B. vulgaris and the endemic species B. hispanica and B. garciae are present in Spain. The objective of this study was to investigate the functionality of the indigenous barberry as alternate hosts. Field surveys were conducted in 2018 and 2019 in Huesca, Teruel and Albacete provinces of Spain. Aecial samples on barberry were analysed via infection assays and DNA analysis. B. garciae was predominant in Huesca and Teruel provinces, often found in the field margins of cereal crops. Aecial infections on B. garciae were observed in May and uredinial infections on cereal crops in June. Scattered B. hispanica bushes were occasionally found near cereal crops in Albacete, where aecial infections on B. hispanica were observed in June when most cereal crops were mature. Infection assays using aeciospores resulted in stem rust infections on susceptible genotypes of wheat, barley, rye and oat, indicating the presence of the sexual cycle for P. graminis f. sp. tritici, f. sp. secalis and f. sp. avenae. Sequence analyses from aecial samples supported this finding as well as the presence of Puccinia brachypodii. This study provides the first evidence that indigenous Berberis species play an active role in the sexual cycle of P. graminis under natural conditions in Spain.info:eu-repo/semantics/publishedVersio

Diversity of thermal aptitude of Middle Eastern and Mediterranean Puccinia striiformis f. sp. tritici isolates from different altitude zones

The worldwide spread of wheat yellow rust lineage PstS1/S2 adapted to higher temperatures prompted us to investigate how diverse temperature responses of this lineage are in the Middle East, where diversity was previously observed within this lineage for pathotypes and genotypes. Here we highlight the diversity of response to temperature within a PstS1/S2 population. Twenty-six isolates from eight countries and different altitudes, which were tested under four combinations of cold and warm incubation and postincubation temperature conditions, showed diversity for infection efficiency (IE) and latency period (LP). IE of the various isolates ranged from 5.8% to 13.7% under cold (5°C) and 0.04% to 1% under warm (20°C) incubation temperatures. LP varied from 10.2 days under warm to 4.43 days under cold incubation. LP of isolates from the same country could differ by 2 days. Significant differences in thermal aptitudes of the isolates were observed between and within countries. IE and LP diversity was not related to altitude origin of the isolates on the whole; however, a trade-off between IE and LP was observed for isolates from low altitude (<400 m) under a warm regime. We showed diversity for thermal aptitude for IE and LP of isolates belonging to the same PstS1/S2 lineage. Understanding Pst temperature aptitude among geographically distant isolates of the same clonal lineage may help to identify the geographic range of pathogens and also to improve forecast models or breeding programmes

Molecular markers for tracking the origin and worldwide distribution of invasive strains of <i>Puccinia striiformis</i>

Investigating the origin and dispersal pathways is instrumental to mitigate threats and economic and environmental consequences of invasive crop pathogens. In the case of Puccinia striiformis causing yellow rust on wheat, a number of economically important invasions have been reported, e.g., the spreading of two aggressive and high temperature adapted strains to three continents since 2000. The combination of sequence-characterized amplified region (SCAR) markers, which were developed from two specific AFLP fragments, differentiated the two invasive strains, PstS1 and PstS2 from all other P. striiformis strains investigated at a worldwide level. The application of the SCAR markers on 566 isolates showed that PstS1 was present in East Africa in the early 1980s and then detected in the Americas in 2000 and in Australia in 2002. PstS2 which evolved from PstS1 became widespread in the Middle East and Central Asia. In 2000, PstS2 was detected in Europe, where it never became prevalent. Additional SSR genotyping and virulence phenotyping revealed 10 and six variants, respectively, within PstS1 and PstS2, demonstrating the evolutionary potential of the pathogen. Overall, the results suggested East Africa as the most plausible origin of the two invasive strains. The SCAR markers developed in the present study provide a rapid, inexpensive, and efficient tool to track the distribution of P. striiformis invasive strains, PstS1 and PstS2

Potential for re-emergence of wheat stem rust in the United Kingdom

Wheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogen Puccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-late twentieth century. However, isolated outbreaks have occurred in recent years. Here we investigate whether a lack of resistance in modern European varieties, increased presence of its alternate host barberry and changes in climatic conditions could be facilitating its resurgence. We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years, with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25 years also suggest increasingly conducive conditions for infection. Furthermore, we document the first occurrence in decades of P. graminis on barberry in the UK. Our data illustrate that wheat stem rust does occur in the UK and, when climatic conditions are conducive, could severely harm wheat and barley production.</p

The European barley powdery mildew virulence survey and disease nursery 1993-1999

National barley powdery mildew virulence surveys were co-ordinated through COST817 on a European scale from 1993 to 1999 to allow comparison of results across national borders. The frequencies of virulence matching resistance genes Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlk, MlLa and Mlg were moderate to high in most years and countries. Several additional sources of resistance were matched by virulence frequencies below 5% . Generally, no increase in aggressiveness against Mlo-resistance was detected, but change may be under way as particular isolates of British origin gave higher infection levels on Mlo-resistant varieties than did other groups of isolates. Therefore, it is important in the future to focus on virulence matching the new sources of resistance and Mlo. Multi-location field trials were established in 1998 and 1999 in order to study powdery mildew resistance in barley genotypes in different environments. The trials showed large interactions of location and phenotypic expression of the resistance. A continued exchange of ideas, methodology and plant material between national survey programmes, and a rapid dissemination of results to farmers and plant breeders across Europe is vital.Étude des virulences dans les populations d'oïdium de l'orge et évaluation des variétés pour leurs résistances partielles à l'échelle européenne de 1993 à 1999. Les suivis nationaux de virulences chez l'oïdium de l'orge ont été coordonnés à l'échelle européenne de 1993 à 1999 dans le cadre de l'action COST817. L'objectif était de comparer les résultats au-delà des frontières nationales. Les fréquences de virulences correspondant aux gènes de résistance Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlk, MlLa et Mlg étaient modérées à fortes pour la plupart des années et des pays. Pour plusieurs sources de résistance supplémentaires, les fréquences de virulences étaient inférieures à 5 % . En général, aucune augmentation d'agressivité vis-à-vis de la résistance Mlo n'a été détectée, mais des changements pourraient être en cours puisque des isolats particuliers d'origine britannique inoculés sur des variétés possédant la résistance Mlo ont présenté des niveaux d'infection plus élevés que d'autres groupes d'isolats. Par conséquent, il est important dans le futur d'étudier avec attention les virulences correspondant aux nouvelles sources de résistance et à la résistance Mlo. Des essais au champ multilocaux ont été mis en place en 1998 et 1999 pour étudier la résistance à l'oïdium des génotypes d'orge dans différents environnements. Ces essais ont montré de grandes interactions entre lieu et expression phénotypique de la résistance. Il est primordial de poursuivre les échanges d'idées, de méthodologie et de matériel végétal entre programmes de suivis nationaux, et de distribuer rapidement les résultats aux agriculteurs et aux sélectionneurs à travers l'Europe

Erratum. The European barley powdery mildew virulence survey and disease nursery 1993-1999

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The European barley powdery mildew virulence survey and disease nursery 1993-1999

National barley powdery mildew virulence surveys were co-ordinated through COST817 on a European scale from 1993 to 1999 to allow comparison of results across national borders. The frequencies of virulence matching resistance genes Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlk, MlLa and Mlg were moderate to high in most years and countries. Several additional sources of resistance were matched by virulence frequencies below 5% . Generally, no increase in aggressiveness against Mlo-resistance was detected, but change may be under way as particular isolates of British origin gave higher infection levels on Mlo-resistant varieties than did other groups of isolates. Therefore, it is important in the future to focus on virulence matching the new sources of resistance and Mlo. Multi-location field trials were established in 1998 and 1999 in order to study powdery mildew resistance in barley genotypes in different environments. The trials showed large interactions of location and phenotypic expression of the resistance. A continued exchange of ideas, methodology and plant material between national survey programmes, and a rapid dissemination of results to farmers and plant breeders across Europe is vital.Étude des virulences dans les populations d'oïdium de l'orge et évaluation des variétés pour leurs résistances partielles à l'échelle européenne de 1993 à 1999. Les suivis nationaux de virulences chez l'oïdium de l'orge ont été coordonnés à l'échelle européenne de 1993 à 1999 dans le cadre de l'action COST817. L'objectif était de comparer les résultats au-delà des frontières nationales. Les fréquences de virulences correspondant aux gènes de résistance Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlk, MlLa et Mlg étaient modérées à fortes pour la plupart des années et des pays. Pour plusieurs sources de résistance supplémentaires, les fréquences de virulences étaient inférieures à 5 % . En général, aucune augmentation d'agressivité vis-à-vis de la résistance Mlo n'a été détectée, mais des changements pourraient être en cours puisque des isolats particuliers d'origine britannique inoculés sur des variétés possédant la résistance Mlo ont présenté des niveaux d'infection plus élevés que d'autres groupes d'isolats. Par conséquent, il est important dans le futur d'étudier avec attention les virulences correspondant aux nouvelles sources de résistance et à la résistance Mlo. Des essais au champ multilocaux ont été mis en place en 1998 et 1999 pour étudier la résistance à l'oïdium des génotypes d'orge dans différents environnements. Ces essais ont montré de grandes interactions entre lieu et expression phénotypique de la résistance. Il est primordial de poursuivre les échanges d'idées, de méthodologie et de matériel végétal entre programmes de suivis nationaux, et de distribuer rapidement les résultats aux agriculteurs et aux sélectionneurs à travers l'Europe