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. 2016 Sep 23:153:10.
doi: 10.1186/s41065-016-0014-0. eCollection 2016.

Genetic diversity and occurrence of the F129L substitutions among isolates of Alternaria solani in south-eastern Sweden

Firuz Odilbekov  1 , Eva Edin  2 , Larisa Garkava-Gustavsson  3 , Helena Persson Hovmalm  3 , Erland Liljeroth  1
Affiliations

Genetic diversity and occurrence of the F129L substitutions among isolates of Alternaria solani in south-eastern Sweden

Firuz Odilbekov et al. Hereditas. .

Abstract

Background: Early blight, caused by the fungus Alternaria solani, occurs on potato mainly in the south-eastern part of Sweden, but also in other parts of the country. The aim of this study was to investigate the genetic diversity of A. solani populations from different potato growing regions in south-eastern Sweden using AFLP marker analysis. In addition, the cultured isolates were examined for substitutions in the gene encoding cytochrome b, associated with loss of sensitivity against QoI fungicides.

Results: Nei's gene diversity index for the Swedish populations of A. solani revealed a gene diversity of up to 0.20. Also genetic differentiation was observed among populations of A. solani from different locations in south-eastern Sweden. The mitochondrial genotype of the isolates of A. solani was determined and both known genotypes, GI (genotype 1) and GII (genotype 2), were found among the isolates. The occurrence of the F129L substitution associated with a loss of sensitivity to strobilurins was confirmed among the GII isolates. In vitro conidial germination tests verified that isolates containing the F129L substitution had reduced sensitivity to azoxystrobin and, at a lower extent, to pyraclostrobin.

Conclusions: Genetic diversity was relatively high among isolates of A. solani in south-eastern part of Sweden. F129L substitutions, leading to reduced sensitivity to strobilurins, have been established in field populations, which may have implications for the future efficacy of QoI fungicides.

Keywords: AFLP; Early blight; Potato; Sensitivity; Strobilurin.

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Figures

Fig. 1
Fig. 1
Map of southern Sweden showing the location where the isolates of Alternaria solani were sampled
Fig. 2
Fig. 2
Dendrogram from cluster analysis (UPGMA) based on Dice genetic similarity for Alternaria solani isolates from Sweden. The values at the branches are the bootstrap values generated by 1000 re-samplings. The colour shows different locations where the samples were collected. GI = genotype I, GII = genotype II, GII* = genotype II with F129L substitution. A few A. alternata isolates were included as an outgroup
Fig. 3
Fig. 3
Principal coordinate analysis (PCoA) of 52 isolates of Alternaria solani from five locations in Sweden based on AFLP data. * = GII with F129L mutation
Fig. 4
Fig. 4
Mean of EC50 values for wild type (GI) (n = 5, 2011) and F129L substitution isolates (GII) (n = 5, 2011 and n = 10, 2014) of Alternaria solani obtained from in vitro sensitivity tests of azoxystrobin and pyraclostrobin after 5 h incubation. * = significantly different from wild type 2011 (p < 0.05) according to two sample t-tests using Minitab 16.2.4 statistical software
See this image and copyright information in PMC

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