Characterisation of Fusarium isolates infecting roots of ragwort (Jacobaea vulgaris syn. Senecio jacobaea) and an assessment of their potential as a biological control agents

• Main Author: Pearson, Karen Aileen
• Published: University of Aberdeen 2011
• Subjects: 579.5; Weeds : Tansy ragwort : Biological control systems
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540464

Ragwort (Jacobaea vulgaris syn. Senecio jacobaea), a common weed of pasture and poorly managed land worldwide, is toxic to livestock and horses. There is no fully satisfactory control option available. The aim of the work described in this thesis was to assess the potential of root infecting pathogens to cause disease in ragwort, and to examine the possibility of using them as biological control agents against this weed. Thirty-six root infecting isolates were obtained from ragwort roots, collected from a nationwide postal survey where Pony Club adult leaders were asked to provide samples. Twenty-one of these were identified as Fusarium spp. by morphological identification and tested for the ability to cause disease on aseptically raised ragwort seedlings. Twelve isolates demonstrated virulence towards ragwort when measured by disease score over a 14 day period. These isolates were identified by molecular means using the internal transcribed spacer and translation elongation factor genes, as either Fusarium avenaceum or F. acuminatum while isolates of F. solani, F. redolens, F. cerealis or F. culmorum did not exhibit virulence except one isolate of F. culmorum which was weakly virulent. To investigate the biological control potential of virulent isolates, a representative of F. avenaceum and F. acuminatum plus the one weakly virulent F. culmorum isolate, were tested against plants of agricultural importance in grasslands. Six grasses (crested dogs tail, Cynosurus cristatus; Timothy, Phleum pratense; red fescue Festuca rubra; Italian ryegrass, Lolium multiflorum; and two varieties of perennial ryegrass, L. perenne) were unaffected by inoculation with any of the isolates. There was no significant difference between the symptoms caused by F. avenaceum and F. acuminatum on ragwort, red clover (Trifolium pratense) and white clover (T. repens). F. culmorum was more virulent towards white clover than either red clover or ragwort. This suggests that although high concentrations of pure PA may inhibit fungal growth, the range of other nutrients in the plants can counteract this negative effect.