HOST RANGE AND PERSISTENCE OF THIELAVIOPSIS BASICOLA IN TOBACCO SOIL

Abstract

Thielaviopsis basicola was recovered from roots of tobacco (Nicotiana tabacum L.), lamb’s-quarters (Chenopodium album L.), black medick (Medicago lupulina L.), redroot pigweed (Amaranthus retroflexus L.), horsetail (Equisetum arvense L.), and round-leaved mallow (Malva neglecta Wallr.) growing in highly to moderately infested tobacco fields. No infection was observed on the rotation crops of rye (Secale cereale L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and corn (Zea mays L.), either in naturally infested fields or in soil artificially infested with T. basicola at a rate up to 50,000 endoconidia per g soil. In artificially infested soil, tobacco cultivar Hicks Broadleaf was less susceptible than cowpsa (Vigna sinensis Endl.) and bean (Phaseolus vulgaris L.). T. basicola was recovered from decomposing residues of tobacco and cereal plants. Under humid conditions the fungus penetrated and sporulated on shoot fragments of these plants, cowpsa, and bean. The implications of these results on the possible build-up of T. basicola and increase of its virulence in tobacco fields over the years is discussed.