<i>Botrytis polygoni</i>, a new species of the genus <i>Botrytis</i> infecting Polygonaceae in Gansu, China

A new species, <i>Botrytis polygoni</i>, was isolated from several species of Polygonaceae in 2011 and 2012 in Tongwei County, Gansu Province, China. The species infects <i>Fagopyrum esculentum, F. tataricum</i>, and <i>Fallopia convolvulus</i>, causing brown leaf spots and large blotches with concentric rings in the field. <i>Botrytis polygoni</i> is morphologically characterized by conidia spherical, unicellular, hyaline to pale brown or brown, (10.2–)14.3–21.4(–23.5) μm; and sclerotia black, spherical to subspherical, allantoid, or irregular-shaped, 0.2–4.1 × 0.1–3.0 mm. Comparison of the nuc rDNA internal transcribed spacer region (ITS1-5.8S-ITS2) sequences confirmed its placement in the genus <i>Botrytis</i>. Phylogenetic analysis based on the protein-coding genes glyceraldehyde 3-phosphate dehydrogenase (<i>G3PDH</i>), heat shock protein 60 (<i>HSP60</i>), and DNA-dependent RNA polymerase subunit II (<i>RPB2</i>) showed that the new species is clustered close but separate from <i>Botrytis pyriformis</i>, which was distant from 37 other <i>Botrytis</i> species and 17 undescribed species. Pathogenicity tests showed that the new species has aggressive pathogenicity to four species of Polygonaceae, specifically <i>Fag. tataricum, Fal. convolvulus, Polygonum sibiricum</i>, and <i>Pol. aviculare</i>, weak pathogenicity to <i>Vicia faba</i> in the Fabaceae, and no pathogenicity to eight other tested plants: <i>Amaranthus retroflexus, Cirsium arvense, Convolvulus arvensis, Kalanchoe blossfeldiana, Lagopsis supine, Mentha canadensis, Plantago asiatica</i>, and <i>Raphanus sativus</i>.