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Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects.

ABSTRACT: Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to Pca in Avena have been designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of Pca in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between wild oat communities and oat crops. Efforts to develop cultivars with genetic resistance to Pca began in the 1950s. Based almost solely on all all-stage resistance, this has had temporary benefits but very limited success. The inability to eradicate wild oats, and their common occurrence in many oat growing regions, means that future strategies to control Pca must be based on the assumption of a large and variable prevailing pathogen population with high evolutionary potential, even if cultivars with durable resistance are deployed and grown widely. The presence of minor gene, additive APR to Pca in hexaploid oat germplasm opens the possibility of pyramiding several such genes to give high levels of resistance. The recent availability of reference genomes for diploid and hexaploid oat will undoubtedly accelerate efforts to discover, characterise and develop high throughput diagnostic markers to introgress and pyramid resistance to Pca in high yielding adapted oat germplasm.

SUBMITTER: Park RF

PROVIDER: S-EPMC9729147 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects.

Park R F RF Boshoff W H P WHP Cabral A L AL Chong J J Martinelli J A JA McMullen M S MS Fetch J W Mitchell JWM Paczos-Grzęda E E Prats E E Roake J J Sowa S S Ziems L L Singh D D

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik 20220604 11

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to Pca in Avena have been designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of Pca in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between ...[more]

PMID: 35665827

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Project description:Oat crown rust, caused by the fungus Pucinnia coronata f. sp. avenae, is a devastating disease that impacts worldwide oat production. For much of its life cycle, P. coronata f. sp. avenae is dikaryotic, with two separate haploid nuclei that may vary in virulence genotype, highlighting the importance of understanding haplotype diversity in this species. We generated highly contiguous de novo genome assemblies of two P. coronata f. sp. avenae isolates, 12SD80 and 12NC29, from long-read sequences. In total, we assembled 603 primary contigs for 12SD80, for a total assembly length of 99.16 Mbp, and 777 primary contigs for 12NC29, for a total length of 105.25 Mbp; approximately 52% of each genome was assembled into alternate haplotypes. This revealed structural variation between haplotypes in each isolate equivalent to more than 2% of the genome size, in addition to about 260,000 and 380,000 heterozygous single-nucleotide polymorphisms in 12SD80 and 12NC29, respectively. Transcript-based annotation identified 26,796 and 28,801 coding sequences for isolates 12SD80 and 12NC29, respectively, including about 7,000 allele pairs in haplotype-phased regions. Furthermore, expression profiling revealed clusters of coexpressed secreted effector candidates, and the majority of orthologous effectors between isolates showed conservation of expression patterns. However, a small subset of orthologs showed divergence in expression, which may contribute to differences in virulence between 12SD80 and 12NC29. This study provides the first haplotype-phased reference genome for a dikaryotic rust fungus as a foundation for future studies into virulence mechanisms in P. coronata f. sp. avenaeIMPORTANCE Disease management strategies for oat crown rust are challenged by the rapid evolution of Puccinia coronata f. sp. avenae, which renders resistance genes in oat varieties ineffective. Despite the economic importance of understanding P. coronata f. sp. avenae, resources to study the molecular mechanisms underpinning pathogenicity and the emergence of new virulence traits are lacking. Such limitations are partly due to the obligate biotrophic lifestyle of P. coronata f. sp. avenae as well as the dikaryotic nature of the genome, features that are also shared with other important rust pathogens. This study reports the first release of a haplotype-phased genome assembly for a dikaryotic fungal species and demonstrates the amenability of using emerging technologies to investigate genetic diversity in populations of P. coronata f. sp. avenae.

Project description:Puccinia coronata f. sp. avenae (Pca) causes crown rust disease in cultivated and wild oat (Avena spp.). The significant yield losses inflicted by this pathogen make crown rust the most devastating disease in the oat industry. Pca is a basidiomycete fungus with an obligate biotrophic lifestyle, and is classified as a typical macrocyclic and heteroecious fungus. The asexual phase in the life cycle of Pca occurs in oat, whereas the sexual phase takes place primarily in Rhamnus species as the alternative host. Epidemics of crown rust happens in areas with warm temperatures (20-25 °C) and high humidity. Infection by the pathogen leads to plant lodging and shrivelled grain of poor quality. Disease symptoms: Infection of susceptible oat varieties gives rise to orange-yellow round to oblong uredinia (pustules) containing newly formed urediniospores. Pustules vary in size and can be larger than 5 mm in length. Infection occurs primarily on the surfaces of leaves, although occasional symptoms develop in the oat leaf sheaths and/or floral structures, such as awns. Symptoms in resistant oat varieties vary from flecks to small pustules, typically accompanied by chlorotic halos and/or necrosis. The pycnial and aecial stages are mostly present in the leaves of Rhamnus species, but occasionally symptoms can also be observed in petioles, young stems and floral structures. Aecial structures display a characteristic hypertrophy and can differ in size, occasionally reaching more than 5 mm in diameter. Taxonomy: Pca belongs to the kingdom Fungi, phylum Basidiomycota, class Pucciniomycetes, order Pucciniales and family Pucciniaceae. Host range: Puccinia coronata sensu lato can infect 290 species of grass hosts. Pca is prevalent in all oat-growing regions and, compared with other cereal rusts, displays a broad telial host range. The most common grass hosts of Pca include cultivated hexaploid oat (Avena sativa) and wild relatives, such as bluejoint grass, perennial ryegrass and fescue. Alternative hosts include several species of Rhamnus, with R. cathartica (common buckthorn) as the most important alternative host in Europe and North America.ControlMost crown rust management strategies involve the use of rust-resistant crop varieties and the application of fungicides. The attainment of the durability of resistance against Pca is difficult as it is a highly variable pathogen with a great propensity to overcome the genetic resistance of varieties. Thus, adult plant resistance is often exploited in oat breeding programmes to develop new crown rust-resistant varieties. Useful website: https://www.ars.usda.gov/midwest-area/st-paul-mn/cereal-disease-lab/docs/cereal-rusts/race-surveys/.

Dataset Information

Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects.

Publications

Breeding oat for resistance to the crown rust pathogen Puccinia coronata f. sp. avenae: achievements and prospects.

Similar Datasets

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