Studies on the significance of the microflora of wilt affected clover plants.

Field, laboratory, and greenhouse investigations were conducted on wilt and root rot of red clover. Repeated isolations from tissues in various stages of disease yielded 3 important fungi:- Verticillium albo-atrum, Fusarium avenaceum, and Sclerotinia trifoliorum. Temperature and pH relationships of these fungi in pure culture are reported. Substances produced by the fungi in a liquid medium were shown to be toxic to red clover. Inoculation experiments vTith the 3 fungi were performed. Each was found pathogenic under certain conditions

Occurence of Verticillium dahliae on sunflower (Helianthus annus ) in the UK

In August 1994 verticilliosis-like symptoms were noticed in a maturing crop of sunflower at IACR-Rothamsted. Wilting plants with chlorotic areas on some leaves, and dark areas of microsclerotia at the base of stems, were first observed on 11 August. As the plants matured, dark stripes were also observed on the stems. Many stems became brittle and later collapsed. Infected xylem showed a brown discolouration, later turning to black, and microsclerotia developed. Verticillium dahliae was isolated from an parts of the plant. In general, once symptoms were present, the incidence of verticilliosis-affected plants increased, and the disease developed, more rapidly in early maturing varieties than in the later maturing types. At harvest, incidence ranged between 24.5% and 89.8%, depending on variety. Early maturing varieties appeared to be more susceptible than later maturing types. Isolates of V. dahliae were cultured in the laboratory. Sunflower plants were artificially inoculated with these isolates and developed verticilliosis symptoms when grown under controlled environmental conditions