Resistance to Erysiphe fischeri in two populations of Senecio vulgaris

Abstract

The frequency and distribution of different specific phenotypes for resistance to Erysiphe fischeri was studied in two populations of the annual weed Senecio vulgaris (groundsel) one located in Glasgow, Scotland the other located about 480 km south at Wellesbourne, England. Progeny of individual plants from the two host populations were tested for their response to up to 10 different isolates of E. fischeri, five from each location; each isolate had a different specific virulence phenotype. Most plants in each sample were susceptible to all 10 isolates. The proportion of plants whose progeny were resistant to a particular isolate ranged from 1% to 10% with the exception of resistance to one isolate that occurred with a frequency of 37% at Wellesbourne. Overall, resistance to one or more of the 10 isolates appeared to be more common in the plant population sampled at Wellesbourne than at Glasgow. Of the total number of groundsel line/isolate combinations tested, 10% involving Wellesbourne plants and 2% involving Glasgow plants were incompatible, i.e. resistant/avirulent. Both groundsel populations tended to be dominated by one or two resistance phenotypes but they were nevertheless highly heterogeneous when less frequent resistance phenotypes were considered. This was particularly evident at Wellesbourne where 10 different resistance phenotypes were recorded amongst a total of 75 plants growing within an area of 1 m2.

Testing the Evolution of Increased Competitive Ability (Eica) Hypothesis in a Novel Framework

“…An explanation for this finding may be that resistance to P. lagenophorae is correlated with defense against other enemies (cf. Hallett et al 1990, Hallett and Ayres 1992, Bevan et al 1993b, which are present in the areas where P. lagenophorae was absent and selection for resistance against enemies in general has been maintained. The larger differentiation in resistance among North American populations compared to Europe and Australia could be explained by larger spatial variation in selection by native enemies or by the chronosequence of S. vulgaris introductions leading to variable loss of resistance (Siemann et al 2006).…”

Evolution of host resistance: looking for coevolutionary hotspots at small spatial scales

“…The occurrence of local coevolutionary hotspots and coldspots in host-pathogen interactions is likely to promote the heterogeneity of host resistance that is evident in many natural plant populations (e.g. Dinoor 1970;de Nooij & van Damme 1988;Parker 1988;Bevan et al 1993;Antonovics et al 1994;Thrall et al 2001;Laine 2004). In turn, this heterogeneity will have an impact on fundamental aspects of hostpathogen interactions such as the transmission of local epidemics and the evolution of virulence (Browning & Frey 1969;Wolfe 1985;DiLeone & Mundt 1994;Zhu et al 2000;Thrall et al 2001;Thrall & Burdon 2003).…”

“…Dinoor 1970;de Nooij & van Damme 1988;Parker 1988;Burdon & Jarosz 1991;Bevan et al 1993;Antonovics et al 1994;Thrall et al 2001;Laine 2004). However, empirical data demonstrating adaptive changes in host resistance structure with respect to disease dynamics are scarce.…”

Aspects of the Interactions between Wild Lactuca Spp. and Related Genera and Lettuce Downy Mildew (Bremia Lactucae)

“…There was no evidence for resistance gene pyramiding or plant population heterogeneity as a defence strategy (Crute, 1990), which has been found in some other wild plant pathosystems, e.g. Senecio vulgaris -Erysiphe fischeri (Bevan et al, 1993).…”