Influence of cultivated landscape composition on variety resistance: an assessment based on wheat leaf rust epidemics

Abstract

Summary• In plant pathology, the idea of designing variety management strategies at the scale of cultivated landscapes is gaining more and more attention. This requires the identification of effects that take place at large scales on host and pathogen populations. Here, we show how the landscape varietal composition influences the resistance level (as measured in the field) of the most grown wheat varieties by altering the structure of the pathogen populations.• For this purpose, we jointly analysed three large datasets describing the wheat leaf rust pathosystem (Puccinia triticina ⁄ Triticum aestivum) at the country scale of France with a Bayesian hierarchical model.• We showed that among all compatible pathotypes, some were preferentially associated with a variety, that the pathotype frequencies on a variety were affected by the landscape varietal composition, and that the observed resistance level of a variety was linked to the frequency of the most aggressive pathotypes among all compatible pathotypes.• This data exploration establishes a link between the observed resistance level of a variety and landscape composition at the national scale. It illustrates that the quantitative aspects of the host-pathogen relationship have to be considered in addition to the major resistance ⁄ virulence factors in landscape epidemiology approaches.

Evolution of Pathogen Specialisation in a Host Metapopulation: Joint Effects of Host and Pathogen Dispersal

“…[50]; but see [51]), this question clearly still requires more investigation. Papaïx et al [52] analysed the pathogenicity structure of leaf rust populations ( Puccinia triticina ) on wheat ( Triticum aestivum ) at the scale of France and found coexistence among qualitative specialists (very restricted host range), quantitative specialists (large host range but transmitted efficiently only by a few of them) and generalists (large host range with roughly equal preference among them). This high diversity of pathogenicity patterns is consistent with the high diversity found here when the host disperses essentially locally.…”

“…Relatively little is known about actual patterns of generalisation and specialisation in natural systems largely because many fewer studies have focused on the pathogenicity structure of pathogen populations [52], [59] than on the resistance structure of their host populations [12]. In general though, assessments of pathogen population structure have found multiple outcomes at the level of individual populations (monomorphic to highly polymorphic) – an observation likely reflecting a number of factors including local adaptation [22], fitness costs associated with pathogenicity [60] and stage in a frequency-dependent cycle of interaction between pathogen and host [61], as well as dispersal capability (isolation-by-distance) and life history features associated with effective local survival.…”

Guiding deployment of resistance in cereals using evolutionary principles

“…Parnell et al 2006), the potential for developing new host resistance management strategies at the landscape scale remains largely unexplored (Plantegenest et al 2007). However, by analysing large datasets describing the interaction between wheat and wheat leaf rust across the whole of France, Papaïx and colleagues (Papaïx et al 2011) established a link between field resistance levels of varieties and varietal composition across the landscape. This suggested the potential for significant impacts on the infectivity structure of pathogen populations in different areas.…”

Meta-modelling of the impacts of regional cropping system scenarios for phoma stem canker control

“…Aubertot et al (2006) showed that preservation of resistance and disease control can be improved by (i) managing pathogen population size (quantitative feature), and (ii) limiting the selection pressure on pathogen populations (qualitative feature). These epidemiological components may be influenced by landscape composition in terms of proportion of host crop (Fitt et al, 2006;Skelsey et al, 2010), of cultivars (e.g., on wheat leaf rust epidemics, Papaïx et al, 2011;on virus in Fabre et al, 2012), including resistance gene deployment (Pink and Puddephat, 1999), and cropping practices (e.g., on phoma stem canker of oilseed rape, Lo-Pelzer et al, 2010). Spatial organization of WOSR fields during successive years also influences resistance sustainability (e.g., Lo-Pelzer et al, 2010).…”