Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2001
Publication Date: 6/1/2002
Citation: Li, S., Hartman, G.L., Jarvis, B.B., Tak, H. 2002. A stachybotrys chartarum isolate from soybean. Mycopathologia. 154:41-49. Interpretive Summary: Stachybotrys chartarum is a cellulytic saprophytic fungus that normally is not known as a plant pathogen. S. chartarum has been found in soil and on substances rich in cellulose such as hay, straw, cereal grains, plant debris, wood pulp, paper, and cotton. As part of our effort to investigate fungi associated with soybean roots, an isolate of S. chartarum was isolated from soybean root lesions. Identification of S. chartarum from soybean using mycological and molecular approaches provides important information about this toxigenic fungus, its biology, infectivity to plants, and molecular characteristics. This report is of interest to soybean pathologists and mycologists working on toxigenic fungi.
Technical Abstract: Stachybotrys chartarum was isolated from root lesions of soybean. Fungal morphology was examined using light and environmental scanning electron microscopy. Conidia were unicellular, round or ellipsoidal, 5-13 x 4-7 um, initially hyaline with smooth walls then dark brown to black and rough-walled when mature. Pathogenicity was performed using sorghum grain colonized by S. chartarum placed below sown soybean seeds in soil:sand (1:1) steam-pasteurized mix. Three weeks after inoculation, root lesions ranged from 7 to 25 mm long. The fungus was reisolated from soybean root lesions and was reidentified as S. chartarum. Biochemical analysis indicated that this soybean isolate produced satratoxins G and H along with roridin L-2, as well as the spircyclic lactones and lactams in rice culture. The DNA sequence of the ITS region was 100% identical to the S. chartarum strain ATCC 9182, one nucleotide mismatch with S. chartarum strain UAMH 7900, and differed from all published sequences of other Stachybotrys and Memnoniella species in GenBank with genetic divergence ranging from 5.26 to 9.98%. PCR using a S. chartarum-specific primer StacR3 and IT51 amplified a 198-bp DNA fragment from the total genomic DNA. This molecular evidence further supports the identification of S. chartarum isolated from soybean root lesions.