Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2000
Publication Date: 2/1/2001
Citation: Li, S., Hartman, G.L. 2001. First report of stachybotrys chartarum causing soybean root rot. Plant Disease. 84:100.
Interpretive Summary: Rotted soybean roots were examined to determine the cause of the rot. A fungus was isolated from surface-disinfested soybean roots. The fungus was purified and the morphology examined. Stachybotrys chartarum, a fungus known to produce toxins, was identified. The fungus was inoculated to healthy soybean plants under greenhouse and growth chamber conditions. All soybean plants inoculated with S. chartarum had root-rot symptoms. Based on DNA sequences, molecular evidence supported the identification of S. chartarum. This is the first report of S. chartarum causing soybean root rot. This report impacts other soybean researchers who also may find and work with this fungus and disease in the future to determine if it is a significant disease.
Technical Abstract: Stachybotrys chartarum (Ehrenb. ex Link) Hughes was isolated from surface-disinfested soybean [Glycine max (L.) Merr] root lesions. The fungus was cultured on potato dextrose agar and the morphology was examined using light and an environmental scanning electron microscopy. Conidiophores were determinate, macronematous, solitary or in groups, and simple or irregularly branched. The phialides occurred in whorls and were obovate or ellipsoidal. Conidia were unicellular, round or ellipsoidal, 5-13 x 4-7 um, initially hyaline, smooth-walled, then turning dark brown to black and rough-walled when mature. A pure culture obtained from infected soybean roots was used to test pathogenicity under greenhouse and growth chamber conditions. S. chartarum was grown on sterilized sorghum grain for 2 weeks and placed in soil 2 to 3 cm below sown soybean seeds. Non-infested sorghum grain was used as a control. All soybean plants inoculated with S. chartarum had root-rot symptoms with lesions ranging from 7 to 25 mm 21 days after sowing, while control plants did not have any measurable root rot. The DNA sequence of the ITS region was 100% identical to the S. chartarum strain ATCC 9182 (1), but differed from all published sequences of other Stachybotrys and Memnoniella species in GenBank (1). PCR using the S. chartarum-specific primer StacR3 and IT51 (1) amplified a 198-bp DNA fragment from the total genomic DNA. This molecular evidence further supports the identification of S. chartarum isolated from soybean. This is the first report of S. chartarum causing soybean root rot.