Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2002
Publication Date: 12/15/2002
Citation: MEADOR, C.B., MELOUK, H.A. SCREENING OF WEED SPECIES FOR REACTION TO SCLEROTINIA MINOR AND SCLEROTIUM ROLFSII. PROCEEDINGS, AMERICAN PEANUT RESEARCH AND EDUCATION SOCIETY. 2002. V. 34. ABSTRACT P. 36-37.
Technical Abstract: Sclerotium rolfsii and Sclerotinia minor have wide host ranges including 500 and 222 plant species, respectively. Three-week-old plants of sixteen weed species (Citronmelon, Crownbeard, Cypressvine morningglory, Eclipta, Hemp sesbania, Ivyleaf morningglory, Jimsonweed, Kochia, Pitted morningglory, Red root pigweed, Sicklepod, Smallflower morningglory, Spurred anoda, Tall morningglory, Velvetleaf, and Venice mallow) from six families (Amaranthaceae, Asteraceae, Convovulvaceae, Leguminaceae, Malvaceae, and Solanaceae) and Okrun, a susceptible variety of peanut, were inoculated with S. minor and S. rolfsii in separate experiments. Plants were grown in the greenhouse and then placed in a 100% relative humidity chamber for inoculation (maintained at 24-49 deg C) in both tests. At three days post inoculation, lesion measurements were taken daily for three days. Plants were left in the humidity chambers for seven days for sclerotia formation. Number of sclerotia/5-cm of stem was determined. Sclerotial viability was determined by germination on potato dextrose agar medium containing 100 micro grams of streptomycin sulfate/ml. A 5-mm diameter agar plug, containing mycelia from a two-day old culture of S. minor, was placed on the stem in a leaf axil at approximately two-thirds of the height of the plant. Stems of Sicklepod and Crownbeard were totally invaded and colonized with S. minor at 5 days post inoculation, producing an average of 26 and 20 viable sclerotia/5-cm of stem, respectively. Ivyleaf morningglory, Smallflower morningglory, Spurred anoda, Velvetleaf, and Venice mallow all showed little response to S. minor developing only small lesions (<25-mm) and forming no sclerotia. In the test with S. rolfsii, filter paper was placed on the soil surface around the base of each plant for inoculation with two sclerotia of S. rolfsii adjacent to the plant stem. S. rolfsii caused less response on most weeds tested. Jimsonweed and Crownbread showed the greatest response, producing 7 and 2 viable sclerotia/5-cm of stem respectively. All other plants had less than one viable sclerotia/5-cm of stem in response to S. rolfsii. Eclipta, Ivyleaf morningglory, Smallflower morningglory, Tall morningglory, and Venice mallow all developed small lesions (<25-mm) but no sclerotia were formed when inoculated with S. rolfsii. This study suggests that some weed species could serve as hosts in maintaining pathogen population in the soil.