First Report of Powdery Mildew on Zinnia elegans Caused by Podosphaera xanthii in Northeast China.

Abstract

HomePlant DiseaseVol. 106, No. 3First Report of Powdery Mildew on Zinnia elegans Caused by Podosphaera xanthii in Northeast China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Powdery Mildew on Zinnia elegans Caused by Podosphaera xanthii in Northeast ChinaChao Fan, Miao Liu, Wei Li, Yongcai Lai, Lili Tang, and Yingdong BiChao Fanhttps://orcid.org/0000-0001-6307-7951Institute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, ChinaHeilongjiang Academy of Agricultural Sciences Postdoctoral Program, Harbin, Heilongjiang 150086, ChinaSearch for more papers by this author, Miao LiuInstitute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, ChinaSearch for more papers by this author, Wei LiInstitute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, ChinaSearch for more papers by this author, Yongcai LaiInstitute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, ChinaSearch for more papers by this author, Lili TangHeilongjiang Academy of Agricultural Sciences Postdoctoral Program, Harbin, Heilongjiang 150086, ChinaInstitute of Cash Crops, Heilongjiang Academy of Agricultural Sciences, Harbin, ChinaSearch for more papers by this author, and Yingdong Bi†Corresponding author: Y. D. Bi; E-mail Address: [email protected]Institute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations Chao Fan1 2 Miao Liu1 Wei Li1 Yongcai Lai1 Lili Tang2 3 Yingdong Bi1 † 1Institute of Crop Cultivation and Tillage, Heilongjiang Academy of Agricultural Sciences, Heilongjiang 150086, Harbin, China 2Heilongjiang Academy of Agricultural Sciences Postdoctoral Program, Harbin, Heilongjiang 150086, China 3Institute of Cash Crops, Heilongjiang Academy of Agricultural Sciences, Harbin, China Published Online:17 Jan 2022https://doi.org/10.1094/PDIS-06-21-1218-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleZinnia (Zinnia elegans L.) is a common garden flowering plant in China, which can also grow well in the cold regions of northeast China. In August 2020, powdery mildew on zinnia was observed in the garden of the International Agricultural Science and Technology Innovation Center of Heilongjiang Province (126°30′ N, 45°47′ E), Harbin, Heilongjiang Province, China. More than 95% of plants were affected in the garden. Powdery mildew colonies began as small white spots on the upper surface of the older leaves and then spread to entire leaves. Subsequently, younger leaves developed rapid symptoms, resulting in premature senescence of the plants. Conidia collected from infected plant tissues were ellipsoid-ovoid to barrel-shaped, with distinct fibrosin bodies visible in their cytoplasm, and measured 20 to 28 × 14 to 19 μm with a length/width ratio of 1.5 to 2.0. Conidiophores were unbranched, straight, 95 to 230 × 9 to 16 μm in size, and produced four to six immature conidia in chains. Foot cells of conidiophores were cylindrical and 35 to 70 μm long, with light constriction at the basal septum, and followed by one to three short cells. Fungal hyphae were septate, branched, flexuous to straight, and up to 5 μm wide with indistinct to slightly nipple-shaped appressoria. Chasmothecia were absent in the collected infected samples. Partial sequence of small subunit ribosomal RNA gene, internal transcribed spacer 1 (ITS1), 58S ribosomal RNA gene, internal transcribed spacer 2 (ITS2), and partial sequence of large subunit ribosomal RNA gene were amplified from conidia collected from infected leaves of four individual plants using primers ITS1/ITS4, respectively (White et al. 1990). Four ITS region sequences were deposited in GenBank (accession no. MW142496 [538 bp], MZ348457 [538 bp], MZ348458 [540 bp], and MZ348459 [540 bp]). All the amplicons exhibited more than 99% sequence identity (MW142496 [536/538], MZ348457 [536/538], MZ348458 [538/540], MZ348459 [537/540]) with those sequences of P. xanthii isolates (accessions no. MT568609 to MT568611) on Z. elegans in Taiwan (Xiao et al. 2021). Based on these morphological characteristics and molecular analysis, this pathogen was identified as P. xanthii (Braun and Cook 2012). The phylogenetic trees were constructed using the neighbor-joining method in MEGA 7.0. Based on the ITS rDNA phylogenetic tree, the sequences retrieved from the specimens clustered within a strongly supported clade with P. xanthii (MT704550, MT864007, MN818562, and MW692364), confirming the identity A pathogenicity test was performed by dusting conidia from an infected leaf onto young leaves of five healthy plants in the greenhouse with five noninoculated plants as a control. Powdery mildew symptoms were observed on inoculated leaves after 5 days of inoculation at 18/25°C (night/day) and 75% relative humidity, whereas control plants remained asymptomatic. The fungus on inoculated leaves was morphologically identified as that observed on the original diseased leaves. Powdery mildew on zinnia caused by P. xanthii has been identified in Taiwan (Xiao et al. 2021), and by Golovinomyces cichoracearum in Turkey (Soylu et al. 2011). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on Z. elegans in northeastern China.The author(s) declare no conflict of interest.