Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/1997
Publication Date: N/A
Interpretive Summary: An epidemic of Fusarium oxysporum f. sp. erythroxyli is presently occurring in the coca-growing region of the Huallaga Valley in Peru. Analysis of isolates of the pathogen using DNA fingerprinting was undertaken to elucidate the genetic complexity of the disease and to identify a specific DNA fingerprint for the pathogen. The isolates could be grouped into two subpopulations based on DNA fingerprint analysis. Both subpopulations showed widespread distribution, and both were present in the central Huallaga Valley where the epidemic was first reported. Fusarium oxysporum f. sp. erythroxyli could be distinguished from nonpathogenic isolates of F. oxysporum, other form species of F. oxysporum, and other species of Fusarium. Hence, a specific DNA fingerprint has been established for the pathogen that can be used for its identification in the field. The results are significant for understanding the nature of the epidemic and for considering its future application as a biocontrol agent.
Technical Abstract: An epidemic of vascular wilt caused by Fusarium oxysporum f. sp. erythroxyli is presently occurring in the coca-growing regions of the Huallaga Valley of Peru. RAPD analysis of isolates of the pathogen was undertaken to elucidate its genetic complexity and origin, as well as to identify a specific DNA fingerprint for the pathogen. Two hundred isolates of Fusarium were collected from ten coca-growing regions in Peru. Of these, 187 were confirmed to be F. oxysporum, and 143 were shown to be pathogens of coca by a root dip pathogenicity test. The pathogens could be grouped into two subpopulations based on RAPD analysis, and no polymorphism in RAPD pattern was observed among isolates of either subpopulation. Both subpopulations were present in the central Huallaga Valley where earliest reports of the epidemic occurred. Subpopulation I was present in all regions except the southernmost regions, whereas Subpopulation II was absent from the northern regions. The isolates of F. oxysporum f. sp. erythroxyli could be easily distinguished from nonpathogenic isolates of F. oxysporum, other form species of F. oxysporum, and other species of Fusarium by RAPD analysis, indicating its utility in DNA fingerprinting.