Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2021
Publication Date: 8/2/2021
Citation: Detranaltes, C.E., Cai, G. 2021. Report of Mycoleptodiscus terrestris as a new soybean root rot pathogen in Indiana. American Phytopathological Society Abstracts. Plant Health. 2-6 Aug 2021 (Virtual).
Technical Abstract: Screenings of soybean (Glycine max L.) seedlings grown at Purdue’s ACRE farm were conducted in the summers of 2019 and 2020. Four isolates of Mycoleptodiscus terrestris (Gerd.) Ostaz. were recovered from seedlings showing reddish-brown girdled lesions on the crown, root rot, and discolored vascular tissue. Fungal cultures were obtained from surface sterilized root tissue on water agar then semi-selective media and purified by hyphal tipping. Morphological examinations of the cultures were consistent with species descriptions of M. terrestris. The ITS region and TEF1-a gene were sequenced and matched 99-100% to accessions of M. terrestris in GenBank. To complete Koch’s postulates, modified cotton seed meal broth was inoculated with plugs of a 7-day old isolate on PDA or sterile plugs of PDA and incubated for two weeks. Soybean seeds (cv. Williams) were grown for one week before being inoculated by root dip in each treatment for 30 minutes and replanted under indoor light racks. After 7 days, all seedlings dipped in the infested broth showed symptoms of root rot consistent with field symptoms while controls were healthy. M. terrestris was recovered from infected plants but not controls and identified as above. This is the first report of M. terrestris infecting soybean in the state of Indiana. Mycoleptodiscus terrestris has been studied and developed for biocontrol of invasive aquatic weeds, however introduction of this pathogen into soybean production areas may increase disease risk.