Tolerance is a virus-specific defence in plants

Viruses are important pathogens of plants, thus the need to understand the defences of the host. Tolerance is the ability of the host to reduce the negative effects of virus infection on its fitness, an under explored and under-exploited defence of plants to viruses. Theoretical predictions assert that tolerance to low virulence pathogens would be achieved through resource reallocation from growth to reproduction. Tolerance to Cucumber mosaic virus (CMV) in Arabidopsis thaliana accords to these predictions. To address if resource reallocation is a non-specific response to the stress of infection or a virus-specific defence, and to understand responses to high virulent pathogens, six A. thaliana wild genotypes, having long or short life-cycle length, were challenged with five viruses with different genomic structures, life histories and transmission modes. The results indicated that, in A. thaliana, tolerance to virus infection is a genotype-specific response and effective tolerance attained through modification of resource allocation is a specific, narrow-spectrum response, as it was observed only in response to one out of the five viruses tested. When the assayed A. thaliana genotypes are clustered according to their life cycle length, long life-cycle genotypes are tolerant to CMV infection, while short life cycle genotypes suffered more severely from CMV infection. At odds with theoretical predictions, tolerance was linked to longer pre-reproductive periods. This study contributes to the understanding of plant-virus interaction.