The Henry Doubleday Resfearch Association, National Centre for Organic Gardening, Rytonon Junsmorc, Coventry CVH 1LG, UK.
Variation for virulence in Erysiphe fischeri from Senecio vulgaris
Version of Record online: 5 APR 2007
Volume 42, Issue 4, pages 622–635, August 1993
How to Cite
BEVAN, J. R., CRUTE, I. R. and CLARKE, D. D. (1993), Variation for virulence in Erysiphe fischeri from Senecio vulgaris. Plant Pathology, 42: 622–635. doi: 10.1111/j.1365-3059.1993.tb01543.x
- Issue online: 5 APR 2007
- Version of Record online: 5 APR 2007
Variation for virulence was investigated in two populations of Erysiphe fischeri, the cause of powdery mildew of the common annual weed Senecio vulgaris (groundsel). Infection types were recorded on detached leaf segments from 50 inbred lines of S. vulgaris following inoculation with 24 single-conidial-chain isolates of E. fischeri (12 each from two UK sites; one, at Glasgow, located about 480 km north of the other, at Wellesbourne). Mean infection types for each isolate/line combination were categorized by applying several upper limits below which combinations were considered to be incompatible. Regardless of the limit applied, numerous specific virulence and resistance phenotypes could be discriminated. Virulence phenotypes were complex and all isolates were capable of colonizing and reproducing on the majority of groundsel lines. However, all isolates were completely avirulent (no reproduction) on at least one groundsel line, so no isolate was universally virulent. Plants of several groundsel lines exhibiting different resistance phenotypes were exposed to natural infection at Wellesbourne to act as mildew traps, to examine the virulence characteristics of the pathogen population. Common components of the fungus population colonized groundsel lines exhibiting resistance to only a few or none of the single-conidial-chain isolates. Rarer components of the pathogen population colonized groundsel lines with resistance to the majority or all of the isolates previously tested. These latter components of the fungus population also detected resistance in groundsel lines previously recorded as susceptible to all isolates.