Two indigenous Berberis species from Spain were confirmed as alternate hosts of the yellow rust fungus Puccinia striiformis f.sp. tritici

Authors: RODRIGUEZ-ALGABA, JULIAN - Aarhus University; HOVMOLLER, MOGENS - Aarhus University; VILLEGAS, DOLORS - Institute Of Agrifood Research And Technology; CANTERO-MARTINEZ, CARLOS - Universitat De Lleida; Jin, Yue; JUSTESEN, ANNEMARIE - Aarhus University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2021
Publication Date: 10/28/2021
Citation: Rodriguez-Algaba, J., Hovmoller, M.S., Villegas, D., Cantero-Martinez, C., Jin, Y., Justesen, A.F. 2021. Two indigenous Berberis species from Spain were confirmed as alternate hosts of the yellow rust fungus Puccinia striiformis f.sp. tritici. Plant Disease. 105(9):2281-2285. https://doi.org/10.1094/pdis-02-21-0269-sc.
DOI: https://doi.org/10.1094/pdis-02-21-0269-sc

Interpretive Summary: Wheat yellow rust (or stripe rust), caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is an important disease in wheat worldwide. The pathogen uses Berberis and Mahonia species as its alternate hosts to complete its life cycle. To date, more than 50 Berberis spp. have been confirmed susceptible to Pst under natural or experimental conditions. In this study, we investigated whether Berberis vulgaris subsp. seroi and B. vulgaris subsp. australis, which are indigenous in Spain, may serve as alternate hosts for Pst. Seedling plants of the two Berberis subspecies were grown from seeds and inoculated with germinating teliospores of Pst following the protocols previously established by the senior author in studies of Pst life cycle. Pycnia were observed on the adaxial leaf surface from 10 days after inoculation (dai), and aecia were observed on the abaxial leaf surface from 16 dai. Aeciospores were used to inoculate wheat seedlings, producing uredinia 12 dai. Genotypic analysis using 19 Pst simple sequence repeat markers were used to confirm fungal identity through various stages of the life cycle. This study demonstrated that B. vulgaris subsp. seroi and B. vulgaris subsp. australis are susceptible to Pst and may serve as alternate hosts for this important wheat rust pathogen. Although there are no indications of sexual recombination in the contemporary European Pst population, the results stress the importance of rust surveillance in areas where barberry and wheat coexist and appropriate conditions for completion of the sexual cycle of Pst are present. Sexual reproduction could result in novel and unique virulence combinations that can have negative consequences for wheat production. This report provides very important information for agriculturists, plant pathologists and other scientists for detecting and monitoring new virulence in the wheat yellow rust populations.

Technical Abstract: Puccinia striiformis f. sp. tritici (Pst), which causes yellow (or stripe) rust on wheat, is a macrocyclic and heteroecious fungus. To date, more than 50 Berberis spp. have been confirmed susceptible to Pst under natural or experimental conditions. In this study, we investigated whether Berberis vulgaris subsp. seroi and B. vulgaris subsp. australis, which are indigenous in Spain, may serve as alternate hosts for Pst. Seeds of the two subspecies were collected in Spain and species identification of barberry plants were confirmed based on specific morphological characters. The seeds were stratified at 5°C for approximately three months to promote seed germination. Seedlings were inoculated with germinating teliospores of Pst originally collected in Denmark (2019) from wheat cultivar 'Ambition'. Pycnia were observed on the adaxial leaf surface from 10 days after inoculation (dai). Infected plants were regularly sprayed with mist water to facilitate fertilization of pycnia. Aecia were observed on the abaxial leaf surface from 16 dai. The recovery of aeciospores was carried out by exposing wheat seedlings of cultivar 'Morocco' below barberry leaves bearing aecia at 27dai. The wheat seedlings were incubated at 10°C for 24h in darkness, 100% RH, and transferred to spore-proof cabins. Subsequently, uredinia were observed on wheat seedlings from 12 days after aeciospore exposure. The identity of the telia used for the barberry inoculation and the uredinial isolates derived from aeciospores produced on both barberry species were confirmed based on genotypic analysis using 19 Pst simple sequence repeat markers. This study demonstrated that B. vulgaris subsp. seroi and B. vulgaris subsp. australis are susceptible to Pst and may serve as alternate hosts for this important wheat rust pathogen. Although there are no indications of sexual recombination in the contemporary European Pst population, the results stress the importance of rust surveillance in areas where barberry and wheat coexist and appropriate conditions for completion of the sexual cycle of Pst are present. Sexual reproduction could result in novel and unique virulence combinations that can have negative consequences for wheat production.