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

Abstract

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. graminisf. 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.

Stem rust on barberry species in Europe: Host specificities and genetic diversity

“…Although it could also be that the resulting stem rust infections were a result of different special forms and/or subspecies infecting other grass hosts as P. graminis is able to infect multiple grass species ( Anikster, 1984 ). Accessory hosts such as wild cereals and grasses may play a crucial role in the epidemiology of stem rust as these could function as an important source of inoculum to maintain stem rust populations in the absence of cereal crops ( Villegas et al, 2022 ). Host specificity analysis by cross-infection studies using a panel of different grasses and fungal strains, could help to obtain novel insights into host specialization and to evaluate the potential risk of stem rust spreading between different cereal and grass hosts.…”

“…Line E, Hiproly, and Prolific), and Pga (var. Marvelous) ( Villegas et al, 2022 ). Additionally, wheat varieties Cartago and Morocco were also included as these are considered as “universal” susceptible varieties for the yellow/stripe wheat rust fungus, P. striiformis f.sp.…”

“…seroi and B. vulgaris subsp . australis in Spain ( López González, 1986 ) and B. aetnensis in Italy ( Ahrendt, 1961 ), and interspecific hybrids, are present in Europe and may potentially play a role in the epidemiology of cereal rust fungi ( Villegas et al, 2022 ).…”

“…However, less attention has been put to characterize the aecial structures formed on barberry species and infer in the rust species that may undergo sexual reproduction. To date, only a few studies have reported on the Puccinia species and/or genera infecting barberry species in local areas in Europe ( Berlin et al, 2013a ; Lewis et al, 2018 ; Villegas et al, 2022 ).…”

Global dispersal and diversity of rust fungi in the context of plant health

“…The immediate source areas for LDD events involving rust fungi have often been dominated by clonal populations, with the exception of the incursions of yellow rust PstS7/PstS8 from the near-Himalayan region into Europe [38] and stem rust Clade III-B into Europe, first detected in a recombining population in the Caucasian region [7,43]. However, sexual recombination, which in the case of rust fungi often requires an alternate host, as well as somatic hybridization events should not be underestimated as drivers of evolution of new variants [45][46][47][48].…”