Great pathotype diversity and reduced virulence complexity in a Central European population of Blumeria graminis f. sp. hordei in 2015–2017
Powdery mildew caused by the airborne fungus Blumeria graminis f. sp. hordei is one of the main diseases of barley (Hordeum vulgare) throughout the world. In Europe spring and winter barley is widely grown under high-input management and with European-bred varieties containing resistance genes to B. graminis f. sp. hordei. The pathogen is wind-borne and in Central Europe spores can be blown in from any direction. Thus, in this region directional selection can maintain and expand virulences arising from local mutations or introduced from other parts of the continent. In this paper, 309 isolates were studied and, based on the reaction to 32 differential varieties, assigned to 279 pathotypes (Simple index = 0.903). Complexity ranged from 5 to 18 virulences, where the most frequent (56) were isolates characterized by nine virulences. In 2016 and 2017, eight additional differential varieties revealed that the population was highly diverse and 226 isolates were represented by 224 pathotypes (Simple index = 0.982). This illustrates the importance of genetic recombination in the formation of this pathogen population. There was a gradual decrease in virulence frequencies to some resistances resulting in a reduced average virulence complexity from 11.30 in 2015 to 9.26 in 2017. The cause might be attributed to a decreased area of varieties with the particular resistances leading to a weakening of directional selection. New virulences to resistances contained in Camilla, Sara and E-388/01 were detected over the same period.
KeywordsBarley Hordeum vulgare Powdery mildew Resistance genes Virulence frequency
The excellent technical assistance of Mrs. Dagmar Krejčířová is greatly appreciated. This study was funded by grand no. RO1117 supported by the Ministry of Agriculture of the Czech Republic.
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Conflict of interest
The author declares that he has no conflict of interest.
Human and animals rights
Research do not involve human participants nor animals.
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