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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #90441
Title: CHARACATERIZATION OF A GROUP I INTRON IN THE NUCLEAR RDNA DIFFERENTIATING PHIALOPHORA GREGATA F. SP. ADZUKICOLA FROM P. G. F. SP. SOJAE

Author
item CHEN, WEIDONG - UNIVERSITY OF ILLINOIS
item Gray, Lynn
item GRAU, CRAIG - UNIVERSITY OF ILLINOIS

Submitted to: Mycoscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phialophora gregata is a fungal pathogen that causes a vascular disease of soybean and adzuki bean plants. The individuals (called isolates) that cause a disease on soybean do not cause a disease on adzuki bean plants and individuals that cause a disease on adzuki bean plants do not cause a disease on soybean plants. However, microscopically the fungal isolates all look the same. The only way to distinguish these isolates is to conduct greenhouse pathogenicity tests that takes six to eight weeks. From ongoing molecular studies, a unique fragment of DNA was identified that is only present in DNA samples of Phialophora isolates that cause disease on adzuki bean plants. Nucleotide sequence data was obtained for this piece of DNA. From this information, a pair of what are called DNA primers were designed that when used with a molecular technique called the polymerase chain reaction allows the production of a piece of DNA from samples from only the adzuki bean Phialophora isolates. This procedure is very fast and can be used for the rapid identification of adzuki bean Phialophora isolates. This new information can be used by plant pathologists and mycologists to rapidly identify which particular fungal isolate they are working with rather than using pathogenicity tests that require a lot of time to obtain useful results.

Technical Abstract: An insertion sequence was detected near the 3' end of the nuclear small subunit rDNA in isolates of Phialophora gregata f. sp. adzukicola, the causal agent of the brown stem rot disease of adzuki bean. This insertion sequence was absent in isolates of P. g. f. sp. sojae which causes brown stem rot of soybean. The insertion sequence is 304 bp long and contains all the characteristics of group I introns. These characteristics include the four conserved sequence elements (P, Q, R, and S), the presence of a U at the 5' splice site of the exon, a G at the 3' splice site of the intron, a putative internal guiding sequence, and the sequence fit a secondary structure model for group I introns. Similar to most group I introns found in nuclear small subunit rDNA, the intron was located at a highly conserved region conserved region and is devoid of long open reading frames. This intron provides a convenient marker for use in conventional PCR to separate P. g. f. sp. adzukicola from P. g. f. sp. sojae.