|
Descripción
|
|
|---|---|
| Plant pathogens may cause epidemics in crops with effects in human health and welfare comparable to those caused by human pathogens. Viruses are the second group of plant pathogens according to the number and relevance of the diseases they cause, which often decrease plant production by 80% at the local or regional scales. A major reason of the importance of viral diseases of crops is that available control strategies are few, being limited to reducing the amount and dispersion of inocula and to the use of genetically resistant crop varieties. Particularly harmful are crop diseases caused by emergent pathogens and, as is the case for humans and domestic or wild animals, viruses make the largest fraction of emergent pathogens of plants, accounting for about 47% of emergence events. Virus emergence in the population of a new host is a complex process. Among the ecological and evolutionary factors favouring emergence ecosystem simplification and host range have been underscored. Indeed, the host range of a pathogen is central to predicting disease risk, which is not independent of ecosystem simplification. Current hypotheses for disease risk ? host diversity relationships are contradictory, with high host diversity predicting both increases and decreases in disease risk, and focus on specialist associations despite the widespread phenomenon of generalism. Our analyses of multi-host ? multi-pathogen systems demonstrate how plant viruses with broad host ranges respond to host diversity in different communities within agricultural landscapes in a scale-dependent manner, and show habitat-specific host specialisation, i.e. facultative generalism. Host specialisation may involve adaptation to different hosts, which may be hindered by across-host fitness trade-offs. Across-hosts trade-offs have been well documented, and the underlying mechanisms have been identified, in experimental systems. However, information on the role that across-host fitness trade-offs play in host-range evolution in nature, and on how this role is modulated by ecology, is scant. We have analysed the role of across-host fitness trade-offs in host range evolution in a specific case of emergence: the appearance and fixation in virus populations of genotypes overcoming the genetic resistance of host plants. Resistance breaking is a serious problem affecting the sustainability of plant disease control. Our studies have focussed on the tobamoviruses that infect pepper crops, usually controlled by resistance alleles at the L locus of Capsicum spp., bred into pepper cultivars. The tobamovirus-pepper interaction is according to a gene-for-gene model, so that resistance-breaking results in the expansion of the virus host range. Long term epidemiological studies, and experiments with field isolates, showed that L-gene resistance-breaking may be hindered by penalties in within-host virus multiplication. Analyses of resistance-breaking mutants derived from infectious cDNA clones showed pleiotropic effects of resistance-breaking mutations on virus multiplication. The magnitude and sign of such pleiotropìc effects was modulated by external factors, e.g., the specific genotype of susceptible hosts and the type, single or mixed with other virus genotypes, of the infection. Resistance-breaking mutations had also pleiotropic effects on virus particle stability and survival in the environment, a life-history trait independent of the virus-host interaction that is not often considered in the study of host range evolution. | |
|
Internacional
|
No |
|
ISSN o ISBN
|
000-00--0000-000-0 |
|
Entidad relacionada
|
Sociedad Española de Virología |
|
Nacionalidad Entidad
|
Sin nacionalidad |
|
Lugar del congreso
|
Cádiz |