Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/1995
Publication Date: N/A
Interpretive Summary: Potato tuber dry rot caused by the pathogenic fungus Fusarium sambucinum is the worst postharvest disease of potatoes in the U.S. Although primarily a postharvest disease, infection of the tubers takes place either before or during harvest by fungal spores which are present in the soil. We are currently researching alternatives to the use of synthetic fungicides for the control of soilborne pathogens such as F. sambucinum. One approach which we are exploring is the use of green manure/cover crops which, in addition to increasing soil fertility and preventing soil erosion, reduces soil pathogen levels. We are especially interested in several species in the mustard family which contain high levels of compounds called glucosinolates that break down to volatile antifungal compounds when plants are macerated. We found that the plant's ability to suppress fungal growth was highly correlated to the release of a compound termed allyl isothiocyanate (the compound that gives horseradish its pungent odor). Our research indicates that these plants may be useful as economical and environmentally friendly potato management practice for the control of dry rot.
Technical Abstract: Brassica species were tested for production of volatile fungicidal compounds from macerated green leaf tissue. Tissue (10, 20 and 40 g) of one cultivar each of six Brassica species were assayed for inhibition of Fusarium sambucinum. Only B. nigra and B. juncea cultivars suppressed (>50% inhibition of control) radial growth; radial growth decreased with increasing quantities of tissue. Accessions of B. juncea, B. carinata, B. nigra, and B. napus were screened for suppression of F. sambucinum. Only B. nigra, B. juncea, and B. carinata accessions had suppressive activity, but activity varied among accessions within these species. The concentration of allyl isothiocyanate (AITC), a breakdown product of the glucosinolate sinigrin, was detected in accessions of B. nigra, B. juncea, and B. carinata. Radial growth of F. sambucinum was negatively correlated (p<0.05) with AITC concentration emitted from Brassica leaf tissues. All Brassica accessions with AITC concentrations greater than 0.10 mg/g fresh tissue were suppressive to F. sambucinum in radial growth assays. Growth of five other plant pathogenic fungi was also suppressed by a B. juncea cultivar which contained high concentrations of AITC.