Prevalence of QoI resistance and mtDNA diversity in the Irish Zymoseptoria tritici population

Abstract

The emergence and spread of Quinone outside Inhibitor (QoI) fungicide resistance in the Irish Zymoseptoria tritici population in the early 2000s had immediate impacts on the efficacy of the entire group of fungicides for the control of septoria tritici blotch. As a result, a dramatic reduction in the quantities applied to winter wheat occurred in the following seasons. Even in the absence of these fungicides, the frequency of the resistance allele, G143A in the pathogens mtDNA has remained exceptionally high (>97%), and as such, it can be anticipated that continued poor efficacy of current QoI fungicides will be observed. Amongst the isolates with G143A, differences in sensitivity to the QoI pyraclostrobin were observed in vitro. The addition of the alternative oxidase (AOX) inhibitor salicylhydroxamic acid increased sensitivity in these isolates, suggesting some continued impairment of respiration by the QoI fungicides, albeit weak. Interestingly, amongst those tested, the strains from a site with a high frequency of inserts in the MFS1 transporter gene known to enhance QoI efflux did not exhibit this increase in sensitivity. A total of 19 mtDNA haplotypes were detected amongst the 2017 strain collection. Phylogenetic analysis confirmed the suggestion of a common ancestry of all the haplotypes, even though three of the haplotypes contained at least one sensitive strain.

Development of a PacBio Long-Read Sequencing Assay for High Throughput Detection of Fungicide Resistance in Zymoseptoria tritici

“…The conformity of the two marker sets demonstrates that the housekeeping gene markers, like SSR markers, are neutral and unlinked to the genes involved in fungicide resistance. The lack of population structure among the three Irish fields agree with previous studies, where little geographic differentiation among Z. tritici populations was found within Ireland (Welch et al, 2018;Kildea et al, 2019a) as well as on a wider geographic scale (Zhan et al, 2003;McDonald and Mundt, 2016) and is suggested to be explained by high gene flow between populations combined with regular sexual recombination. The differences observed in patterns of fungicide sensitivity and haplotype distribution of fungicide resistance genes among locations, despite the high similarity for neutral markers, suggest that the rate of gene flow may not be sufficient to counteract gene frequency changes caused by ongoing local selection for fungicide resistance.…”

“…The number of isolates sequenced varies for the different target genes. d PCR-RFLP used for the detection of the cytochrome b substitution G143A as reported by Kildea et al (2019a). e Sensitivity as determined using in vitro microtitre plate assays as described by Dooley et al (2016b).…”

“…The nucleotide consensus reads from the alignment in Geneious Prime were used to locate SNP markers in the housekeeping genes. Variable nucleotide positions in the Sanger Sequencing of CYP51, SdhB, C, D, and Cytochrome b Genes Amplification, Sanger sequencing and analysis of the CYP51, SdhB, C, and D subunits of the 96 isolates of the three collections were performed as previously described by Dooley et al (2016b) and Kildea et al (2019a), respectively. Due to the low amplification of the SdhC subunit in some isolates, the sequencing assay described by Rehfus et al (2018) was also used.…”

Morphological and Morphometric Analysis of Genus Eriobotrya Lindl. (Rosaceae)

“…In the management of STB, fungicides are generally used. However, fungicide resistance has been oftenly reported (Hayes et al, 2016;Kettles and Kanyuka, 2016;Kildea et al, 2019). Because, STB may overcome fungicides through its genetic variability.…”

Changes in DMI, SDHI, and QoI Fungicide Sensitivity in the Estonian Zymoseptoria tritici Population between 2019 and 2020

“…During the last few years, the frequencies of the CYP51 mutations V136C, A379G, and I381V have been relatively stable across Europe, while a clear pattern of decreasing frequencies of D134G, V136A, and S524T from west to east has been observed [ 4 ]. Due to the continuous accumulation of mutations, a reduction in the field efficacy of tebuconazole, epoxiconazole, and also prothioconazole has been observed in many European countries during the last few years [ 4 , 20 , 21 , 22 , 23 ]. The decline in the efficacy of azoles has started to accelerate, probably due to the appearance of mutation S524T in Zt’s field populations [ 4 , 15 ].…”