First report of Rhizoctonia zeae on Lolium perenne and Festuca sp. in Hungary

Abstract

In August 2002, brown patches were observed on turf grasses in parks and gardens at four locations in Budapest. Twenty-five samples of Lolium perenne and Festuca sp. showing disease symptoms were collected. The symptoms observed were necrotic lesions on the roots and stems, as well as brown lesions on the leaves. Small pieces of infected tissues were surface sterilized and incubated at 22°C with a 12 h photoperiod on potato dextrose agar. In most cases fast-growing, buff-coloured colonies were observed, with dark brown sclerotia of irregular shape, not differentiated into a rind and medulla, with a size range of 0·2–3·0 mm. These were identified as Rhizoctonia solani (Sneh et al., 1991; Roberts, 1999). Colonies from three samples were colourless to buff-coloured, fast-growing, with small, ball-shaped, reddish-coloured sclerotia 0·5–0·9 mm in diameter. These were identified as Rhizoctonia zeae (Sneh et al., 1991; Roberts, 1999). The hyphae of both types of isolate were multiseptate and multinucleate (confirmed by nuclear staining). The pathogenicity of one R. zeae isolate was determined on a mixture of L. perenne, Festuca rubra and Poa pratensis seedlings. Sterilized barley seeds, colonised with R. zeae and covered with pinkish to orange sclerotia of 0·5–2·5 mm diameter, were used as inoculum. Seeds of test plants were sown in a sandy loam soil admixed with barley seeds previously infected with the pathogen. Pots were then maintained in a glasshouse kept at 16–32°C. Disease symptoms were observed 3 weeks after germination. Brownish lesions were observed on infected seedlings at the base of stems and the lower parts of the leaves. Infected roots showed brown lesions and the leaves, on which orange sclerotia were found, were necrotic. Control plants grown in pots with uninoculated soil did not develop symptoms. Rhizoctonia zeae was reisolated from the diseased tissues. In a host-range study, the isolate proved to be highly pathogenic to germlings of several ornamental and cultivated plants, including Beta vulgaris ssp. vulgaris, Callistephus sinensis, Dahlia variabilis, Daucus carota, Lupinus polyphyllus, Papaver somniferum, Pennisetum glaucum, Phaseolus vulgaris, Sesamum indicum, Solanum melongena, Solanum tuberosum, Sorghum bicolor and Triticum aestivum. The disease caused by R. zeae was described for the first time in Florida, by Voorhees (1934), as sclerotial rot of corn. This fungus is distributed in temperate regions, causing diseases on many plants including species of Agrostis, Beta, Cucumis, Daucus, Festuca, Helianthus, Oryza, Sorghum, Triticum and Zea. This is the first report of R. zeae in Hungary. This work is a part of a study supported by grant NKFP 4/008/2001.