First Report of Pythium myriotylum Causing Stem and Root Rot of Kidney Bean in Taiwan

Abstract

HomePlant DiseaseVol. 107, No. 3First Report of Pythium myriotylum Causing Stem and Root Rot of Kidney Bean in Taiwan PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Pythium myriotylum Causing Stem and Root Rot of Kidney Bean in TaiwanY. R. Liang and F. C. LiaoY. R. Liang†Corresponding author: Y. R. Liang; E-mail Address: [email protected]https://orcid.org/0000-0002-9232-3936Taiwan Agricultural Chemicals and Toxic Substances Research Institute, Taichung 41358, TaiwanSearch for more papers by this author and F. C. LiaoTaiwan Agricultural Chemicals and Toxic Substances Research Institute, Taichung 41358, TaiwanSearch for more papers by this authorAffiliationsAuthors and Affiliations Y. R. Liang † F. C. Liao Taiwan Agricultural Chemicals and Toxic Substances Research Institute, Taichung 41358, Taiwan Published Online:14 Feb 2023https://doi.org/10.1094/PDIS-06-22-1464-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleKidney beans (Phaseolus vulgaris Linn.) are widely grown in central and southern Taiwan. In June 2021, kidney beans showing stem and root rot symptoms were observed in a 3,000 m2 plot in Xinyi Township, Nantou County, Taiwan (23.62°N, 120.87°E; with around 600 plants). About 15% of the plants on site displayed similar symptoms with stem and root rot. Small pieces (3 to 4 mm) of affected tissue were surface disinfected by immersion in 0.6% sodium hypochlorite for 5 min, rinsed twice in sterile distilled water, and placed on a V8 agar plate. Plates were incubated at 28°C for 24 h in the dark. A Pythium-like organism was consistently isolated. Genomic DNA was extracted from one of the isolates using a DNA extraction kit (Kaneka Easy DNA Extraction Kit version 2; Takasago, Japan). The identities were confirmed by the internal transcribed spacer (ITS) sequence (accession no. MZ994503), which had 100% homology with KY019264.1; and the cytochrome c oxidase subunit I (COI) (Robideau et al. 2011) sequence (accession no. OK513021), which had 100% homology with MT222434.1. For morphological characterization, the pathogen was cultured on V8 agar to produce oogonia (24 to 27 μm), lobulate sporangia, and zoospores. Isolates were identified as P. myriotylum based on morphological characteristics (Watanabe 2002) and ITS and COI sequences. Koch’s postulates were completed in the greenhouse on kidney beans at the four- to five-leaf stage. Six plants were inoculated with a 3-mm mycelial plug of 3-day-old V8 plates and the plugs were placed beside the collar of these plants without wounding. Four control plants were inoculated with a 3-mm water agar plug using the same method. All plants were kept in wet plastic bags (near 100% relative humidity) at 25 ± 2°C for 48 h and maintained in a growth chamber with a 12-h photoperiod. The experiment was repeated twice. Two days after inoculation, symptoms similar to the original were observed on the inoculated plants. Koch’s postulates were confirmed by reisolating the same pathogen from diseased plants and sequencing the same ITS region. Control plants remained symptomless. P. myriotylum has previously been described as infecting a wide range of plants in temperate and tropical regions (Perneel et al. 2006). It has been described occurring on ginger (Zingiber officinale), peanut (Arachis hypogaea), rape (Brassica rapa var. rapa), lettuce (Lactuca sp.), tobacco (Nicotiana tabacum L.), and royal paulownia (Paulownia tomentosa Steud.) in Taiwan. To our knowledge, this is the first report of root rot on kidney bean caused by P. myriotylum in Taiwan.The author(s) declare no conflict of interest.