First Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in Illinois

Abstract

HomePlant DiseaseVol. 103, No. 7First Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in Illinois PreviousNext DISEASE NOTESFirst Report of Red Crown Rot of Soybeans Caused by Calonectria ilicicola (Anamorph: Cylindrocladium parasiticum) in IllinoisN. Kleczewski, D. Plewa, C. Kangas, E. Phillippi, and V. KleczewskiN. Kleczewski†Corresponding author: N. Kleczewski; E-mail Address: nathank@illinois.eduhttp://orcid.org/0000-0001-5671-6727University of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, D. PlewaUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, C. KangasUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, E. PhillippiUniversity of Illinois, Department of Crop Sciences, Urbana, IL 61801Search for more papers by this author, and V. KleczewskiGrowmark Inc., Bloomington, IL 61701Search for more papers by this authorAffiliationsAuthors and Affiliations N. Kleczewski1 † D. Plewa1 C. Kangas1 E. Phillippi1 V. Kleczewski2 1University of Illinois, Department of Crop Sciences, Urbana, IL 61801 2Growmark Inc., Bloomington, IL 61701 Published Online:7 May 2019https://doi.org/10.1094/PDIS-01-19-0105-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In September 2018 soybean (Glycine max) disease was observed in a commercial field located near Pittsfield, Illinois. Signs and symptoms resembled those of red crown rot, caused by Calonectria ilicicola (Hartman et al. 2015). Red to brown lesions were observed at the stem base, and red, raised perithecia were observed on the lesion surface. The root systems of affected plants were black and severely rotted, often with only taproots remaining after removal from the soil. The inner pith of the lower stem was light gray in appearance. Foliar symptoms included interveinal chlorosis and defoliation. Disease incidence was estimated at 75%, and yield loss was estimated at approximately 25%. Affected plants were harvested, placed in a cooler on ice, and transported to the University of Illinois. Stems were surface sterilized in 10% bleach (30 s), 75% ethanol (30 s), followed by two rinses in sterile distilled water bleach, and allowed to air dry under a biosecurity cabinet. Isolations were made from sections of symptomatic stems on Petri plates containing half-strength potato dextrose agar placed under a light bank equipped with cool fluorescent lights set on a 12-h light/dark cycle at 20°C. Fungi were isolated from 100% of sections plated, and individual isolates were collected via hyphal tip technique. Isolated colonies initially produced white, aerial mycelia that later turned burnt red to brown with age. Conidia were hyaline, cylindrical with zero to three septae, and measured 28.5 to 87.1 × 3.9 to 7.6 μm. Perithecia were reddish orange, oval to globose, 202.6 to 424.7 μm tall, and 100.3 to 353.8 μm in width. Asci were hyaline and clavate and measured 111.0 to 206.1 × 10.5 to 28.6 μm, and each contained eight falcate ascospores with one to two septa. Morphological characteristics identified this organism as C. ilicicola (anamorph: Cylindrocladium parasiticum [Hartman et al. 2015]). A 600-bp fragment of the β-tubulin gene was amplified using the T1 (O’Donnell and Cigelnik 1997) and Bt2b (Glass and Donaldson 1995) primers. Thermocycler conditions were as follows: initial denaturation for 10 min at 96°C followed by 30 cycles of 96°C for 15 s, 55°C for 35 s, and 75°C for 35 s, with a final elongation step of 75°C for 2 min (Crous et al. 1999). Polymerase chain reaction products were purified and sequenced at the Roy J. Carver Biotechnology Center at the University of Illinois at Urbana-Champaign. A sequence of the representative isolate 3A was submitted to GenBank (MK370992). Comparisons with GenBank showed 99% similarity with multiple sequences of C. ilicicola (top match JX0693831.1, bit score 1,107, E = 0.0, 607/610 bp). Pathogenicity was confirmed by inoculating 3-week-old seedlings of soybean cultivar Pioneer 93Y25 grown in in 15-cm-diameter pots containing autoclaved greenhouse potting media. Six plants were present in each pot, and three pots were used per treatment. Inoculation was conducted by drenching with a 105 conidia/ml suspension acquired from 14-day-old, single-spore fungal isolates. Three unamended pots were used as controls. Plants were watered daily and maintained in a greenhouse set to 23°C and a 14-h/10-h light/dark cycle. After 14 days, inoculated plants showed similar basal stem symptoms and after 30 days developed interveinal chlorosis on leaves. C. ilicicola was reisolated from diseased plants and confirmed through microscopy. This pathogen may pose a threat to >440,000,000 ha of soybean in Illinois, not including surrounding states. Our understanding of impact and management under Midwest production practices is currently unknown.The author(s) declare no conflict of interest.