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

Authors: VILLEGAS, DOLORS - Institute De Recerca I Tecnologia Agroalimentaries (IRTA); BARTAULA, RADHIKA - University Of Minnesota; CANTERO-MARTINEZ, CARLOS - Universitat De Lleida; Luster, Douglas - Doug; Szabo, Les; OLIVERA, PABLO - University Of Minnesota; BERLIN, ANNA - Swedish University Of Agricultural Sciences; RODRIGUEZ-ALGABA, JULIAN - Aarhus University; HOVMØLLER, MOGENS - Aarhus University; MCINTOSH, ROBERT - University Of Sydney; Jin, Yue

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2022
Publication Date: 3/9/2022
Citation: Villegas, D., Bartaula, R., Cantero-Martinez, C., Luster, D.G., Szabo, L.J., Olivera, P.D., Berlin, A., Rodriguez-Algaba, J., Hovmøller, M.S., Mcintosh, R., Jin, Y. 2022. Barberry plays an active role as an alternate host of Puccinia graminis in Spain. Plant Pathology. 71:1174-1184. https://doi.org/10.1111/ppa.13540.
DOI: https://doi.org/10.1111/ppa.13540

Interpretive Summary: Stem rust, caused by the fungal pathogen Puccinia graminis, is a destructive group of diseases on cereal crops and grasses. This pathogen uses Berberis spp. as the alternate host upon which the sexual cycle takes place. Genetic recombination through the sexual cycle leads to the occurrence of new virulent strains that can overcome deployed resistance genes in cereal crop cultivars. Thus, investigations in stem rust infections on Berberis species enhance our knowledge on the sources of genetic variations and help to predict where new strains may occur. We investigated the functionality of the indigenous barberries in Spain as alternate hosts of the stem rust pathogen and their associations with cereal production. Rust samples on barberry, cereal crops, and grasses were collected and studied via infection assays and DNA analysis. Berberis hispanica bushes were occasionally found near cereal crops in Albacete province. Berberis garciae was predominant in Huesca and Teruel provinces, often found in close proximity to cereal crop fields. Infection assays using aeciospores resulted in stem rust infections on susceptible genotypes of wheat, barley, rye, and oat, indicating the presence of sexual cycle for several forms of the stem rust pathogen attacking wheat (P. graminis f. sp. tritici), rye (f. sp. secalis), and oat (f. sp. avenae). Sequence analyses from aecial samples corroborated these findings. Infection experiments and DNA analysis concluded that B. garciae provided the primary source of inoculum for stem rust infection of cereal crops and grasses. This study provided the first evidence that indigenous Berberis spp. play an active role in the sexual cycle of P. graminis under natural conditions in Spain. This research will be used by scientists involved in investigating the roles of the alternate hosts in pathogen variations and disease epidemiology.

Technical Abstract: Stem rust, caused by Puccinia graminis Pers., is a destructive group of diseases. The pathogen uses Berberis spp. as alternate host to complete its life cycle. Berberis 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 and uredinial samples on cereal crops and grasses were analyzed via infection assays and DNA analysis. Berberis 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 provided the first evidence that indigenous Berberis spp. play an active role in the sexual cycle of P. graminis under natural conditions in Spain.