Blackpatch of red clover and other legumes caused by Rhizoctonia leguminicola sp. nov.

Abstract

It has also been reported from Wisconsin, Georgia, Tennessee, Illinois, Delaware, and West Virginia. 2. Blackpatch has caused considerable losses during some years to the red clover seed crop in eastern West Virginia. 3. The symptoms of blackpatch on leaves are spreading, zonate lesions which may kill an entire leaf within a few hours. Individual lesions are usually connected by strands of superficial dark mycelium. Stems may show similar zonate lesions or may be encased in a web of superficial mycelium. Flower parts show necrotic lesions from which the mycelium may spread over the entire flower head. Greater damage is done to seed when the head is infected at the early stages of flowering. 4. The fungus causing blackpatch has never been observed to form spores and has remained unnamed. Under some laboratory conditions sclerotia are formed. The name Rhizoctonia leguminicola sp. nov., is proposed for the blackpatch fungus. 5. Many factors may influence sclerotia production; nutritional factors seem to be of major importance. The production of sclerotia by R. leguminicola was favored when the following nitrogen sources were added to a glucose agar medium: asparagine (Difco), peptone (Difco), DL-beta-phenylalanine and potassium nitrate. No sclerotia formed when casein hydrolysate, urea, casamino acids (Difco), ammonium sulfate, ammonium tartrate or ammonium nitrate were used. Over the range of concentrations tried, 0.05 per cent asparagine induced most active production of sclerotia. Numerous sclerotia formed when the sugars D-glucose, D-mannose, D-fructose, maltose and sucrose were used as single carbon sources but few developed in media where D-galactose, D-xylose or lactose were used. Temperatures favoring growth (25°-29°C.) also favored the production of sclerotia. Sclerotia formed best at a pH ranging initially between 5.9 and 7.5. 6. The blackpatch disease has been reported only on legiuninous hosts. In addition to its occurrence on red clover and a number of other common hosts, it has been found in this region on black medick (Medicagu lupulina L.) and Korean lespedeza (Lespedeza stipulacea Maxim). Inoculations have resulted in infections on bush beans (Phaseoliis vulgaris var. humilis) under some greenhouse conditions.

Slaframine toxicosis in Brazilian horses causing excessive salivation

“…In the present report, intoxication occurred after ingestion of alfafa hay but the majority of authors (Crump et al 1963;Hagler and Behlow 1981;Sockett et al 1982;Orsini and Divers 1998;Wijnberg et al 2009) have associated the occurrence of slaframine toxicosis with the consumption of contaminated red clover. It is noteworthy that, in addition to red clover (Trifolium pratense), the fungus may contaminate white clover (Trifolium repens), alfalfa soybean (Glycine max) (Gough and Elliott 1956;Berkenkamp 1977;Broquist 1985), kudzu (Pueraria lobata), cowpea (Vigna unguiculata), blue lupine (Lupinus pilosus), alsike clover (Trifolium hybridum), Korean lespedeza (Lespedeza stipulacea) and black medic (Medicago lupulina) (Wyllie and Morehouse 1978). The physical alterations found in the alfafa hay in this report are similar to those described in the literature (brownish to black patches or concentric circles on the stems or leaves of affected legume forages) caused by contamination with the fungus R. leguminicola (Hintz 1990;Plumlee and Galey 1994;Osweiler 2001).…”

“…A disease in cattle mainly characterised by profuse salivation was described almost 70 years ago (Hagler and Behlow 1981;Croom et al 1995) and years later, Smalley et al (1962) described its relation with the ingestion of forage contaminated with Rhizoctonia leguminicola (R. leguminicola). This fungus was associated with blackpatch (a disease of clovers and other legumes, first described in 1933) by Gough and Elliott in 1956. R. leguminicola is commonly found in soil and is transmitted in seeds (Crump 1973;Plumlee 1997).…”

The Indolizidine Alkaloids, Slaframine and Swainsonine: Contaminants in Animal Forages

“…The cattle were consuming second-cutting red clover hay, and in a similar outbreak of the slobbers in Wisconsin, Smalley et al (52) made the extremely important observation that such forage was infected with the black fungus, Rhizoctonia leguminicola, known to cause black patch of red clover (20). It thus appeared that "the slobber factor" might be a mycotoxin produced by R. leguminicola.…”

“…Using a guinea pig salivation assay the slobber factor, termed slafra mine, (IS, 6S, 8aS)-I-acetoxy-6-aminooctahydroindolizine, was subsequently � �� J IIIOH isolated from R. Leguminicola mycelium (3,44) and microgram quantities were shown to produce excessive salivation in laboratory animals, e. g. rats, guinea pigs, and cats. The slobbers, or excessive salivation, is caused by the consumption of forage (usually red clover, but also white clover, soybean, Kudzu, cow pea, blue lupine, alsike clover, alfalfa, Korean lespedeza, and black medic) that has been infected with R. Leguminicola (20,50). Outbreaks are fairly uncommon but have been reported in the northwestern, midwestern, and southeastern United States.…”

Identification of swainsonine as a probable contributory mycotoxin in moldy forage mycotoxicoses

“…Rhizoctonia leguminicola, a fungus known to cause black spot of red clover (6) and to infest other legumes (see reference 9 for discussion and references), produces at least two indolizidine alkaloids of physiological and toxicological interest: slaframine [(lS,6S,8aS)-1-acetoxy-6-aminooctahydroindolizine (5)] and swainsonine [(1S,2R,8R,8aR)-1,2,8trihydroxyoctahydroindolizine (15)] ( Fig. 1).…”