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N837 deletion in oxysterol binding protein-related protein confers oxathiapiprolin resistance in Phytophthora capsici and P. sojae

Jianqiang Miao: China Agricultural University

<div>Oxathiapiprolin is a novel fungicide which was registered in China in 2015 to control pant-pathogenic oomycetes, such as <em>Phytophthora </em>spp. and downy mildews. In our previous study, point mutation of G770V and G839W in PcORP1 were detected in oxathiapiprolin resistant mutants of <em>P</em>.<em> capsici</em> obtained by fungicide adaption. In the current study, CRISPR/Cas9 system was used to verify the effect of the two-point mutation on characteristics of <em>P</em>. <em>capsici</em> BYA5. Transformants contained heterozygous G770V in PcORP1 showed similar phenotype with wild-type isolate BYA5, including sporangia, zoospores production, cyst germination and pathogenicity. However, two transformants with heterozygous G839W in PcORP1 could not produce sporangia. Three transformants with a new point mutation, <em>Δ</em>N837 in PcORP1, showed high oxathathiapirplin resistance and survival ability. Point mutation, <em>Δ</em>N837 in PsORP1, was also confirmed that it could confer oxathiapiprolin resistance in <em>P</em>. <em>sojae</em> P6497. These <em>P</em>. <em>sojae</em> mutants also showed certain fitness with wild type P6497. PsORP1-<em>Δ</em>N837 with the original promoter was also transferred into P6497, and positive transformants also showed oxathiapiprolin resistance and similar phenotype with P6497. These results showed that G770V, G839W and <em>Δ</em>N837 in ORP1 could confer oxathiapiprolin resistant with no fitness cost. The new information will be useful for the development of series novel OSBPI fungicides.</div>