Multiple genotypes within aecial clusters in Puccinia graminis and Puccinia coronata: improved understanding of the biology of cereal rust fungi

Anna Berlin,Björn Andersson,Berit Samils

doi:10.1186/s40694-017-0032-3

Anna Berlin, Björn Andersson + Show 1 more

Open Access

https://doi.org/10.1186/s40694-017-0032-3

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Abstract

BackgroundCereal rust fungi (Puccinia spp.) are among the most economically important plant pathogens. These fungi have a complex life cycle, including five spore stages and two hosts. They infect one grass host on which they reproduce clonally and cause the cereal rust diseases, while the alternate host is required for sexual reproduction. Although previous studies clearly demonstrate the importance of the alternate host in creating genetic diversity in cereal rust fungi, little is known about the amount of novel genotypes created in each successful completion of a sexual reproduction event.ResultsIn this study, single sequence repeat markers were used to study the genotypic diversity within aecial clusters by genotyping individual aecial cups. Two common cereal rusts, Puccinia graminis causing stem rust and Puccinia coronata the causal agent of crown rust were investigated. We showed that under natural conditions, a single aecial cluster usually include several genotypes, either because a single pycnial cluster is fertilized by several different pycniospores, or because aecia within the cluster are derived from more than one fertilized adjoining pycnial cluster, or a combination of both.ConclusionOur results imply that although sexual events in cereal rust fungi in most regions of the world are relatively rare, the events that occur may still significantly contribute to the genetic variation within the pathogen populations.

Highlights

Cereal rust fungi (Puccinia spp.) are among the most economically important plant pathogens
In total, the eight single sequence repeat (SSR) markers used to analyze the aecial collections of P. graminis identified 46 alleles, and the ten SSR markers used in the aecial collections of P. coronata identified 40 alleles (Table 1)
In total 22 aecial clusters were analyzed; 12 representing P. coronata, where 7 were excised from R. cathartica and 5 from F. alnus, and 10 representing P. graminis which were all excised from B. vulgaris (Table 2, Additional file 1: Table S1 and Additional file 2: Table S2)

Summary

Introduction

Cereal rust fungi (Puccinia spp.) are among the most economically important plant pathogens. These fungi have a complex life cycle, including five spore stages and two hosts. They infect one grass host on which they reproduce clonally and cause the cereal rust diseases, while the alternate host is required for sexual reproduction. Cereal rust fungi (Puccinia spp.) are among the most studied plant disease-causing agents, as they affect cereals and grasses in all parts of the world, potentially causing devastating yield losses. The spore stage causing disease on cereals and other grasses is the uredinial stage, where clonally propagated dikaryotic urediniospores re-infect the gramineous hosts in several

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