The occurrence of Erysiphe trifolii on Lathyrus pratensis in a foothill area of South Bohemia

The occurrence of Erysiphe trifolii on Lathyrus pratensis in a foothill area of South BohemiaThe aim of small-site experiments carried out in the foothills of the Šumava Mts. was to determine the effect of the etiological agent powdery mildew (Erysiphe trifolii) on meadow peavine (Lathyrus pratensis). Over three consecutive years, we observed a whitish to grey-white soft cover of mycelium on the meadow peavine during the vegetation period. This characteristic symptom of the disease was observed on the plants during summer and autumn. In a plot trial with permanent grassland we evaluated the following management systems: i) mulched, ii) fallow, iii) mown stands, and iv) pasture stands grazed by cattle. We evaluated the total number of Lathyrus pratensis plants as well as the number of the plants attacked by Erysiphe trifolii. The three-year investigation of Lathyrus pratensis yielded statistical evidence that the most significant growth of the fungal disease was recorded in fallow stands (68.9%), while the lowest occurrence of the disease (4.4%) was found in the pasture stands grazed by cattle.

Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)

The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii–like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.

Erysiphe trifolii. [Descriptions of Fungi and Bacteria].

A description is provided for Erysiphe trifolii. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On numerous Leguminosae. Common on Trifolium, Lathyrus, Onobrychis. Occasionally on Astragalus, Caragna, Coronilla, Galega, Genista, Lotus, Lupinus, Psoralca, Robinia, Sarothamaus, Tetragonolobus, Wistaria. DISEASE: Powdery mildew of clover. GEOGRAPHICAL DISTRIBUTION: Africa (Rhodesia, Tanzania); Asia (China, Formosa, India, Israel, Japan, U.S.S.R.); Australia; Canada; New Zealand; U.S.A. (Hirata, 1966). TRANSMISSION: Persists on foliage under favourable conditions.