An Analysis of the Durability of Resistance to Plant Viruses

Abstract

Genetic resistance often fails because a resistance-breaking (RB) pathogen genotype increases in frequency. On the basis of an analysis of cellular plant pathogens, it was recently proposed that the evolutionary potential of a pathogen is a major determinant of the durability of resistance. We test this hypothesis for plant viruses, which differ substantially from cellular pathogens in the nature, size, and expression of their genomes. Our analysis was based on 29 plant virus species that provide a good representation of the genetic and biological diversity of plant viruses. These 29 viruses were involved in 35 pathosystems, and 50 resistance factors deployed against them were analyzed. Resistance was found to be durable more often than not, in contrast with resistance to cellular plant pathogens. In a third of the analyzed pathosystems RB strains have not been reported, and in another third RB strains have been reported but have not become prevalent in the virus population. The evolutionary potential of the viruses in the 35 pathosystems was evaluated with a compound risk index based on three evolutionary factors: the population of the pathogen, the degree of recombination, and the amount of gene and genotype flow. Our analysis indicates that evolutionary potential may be an important determinant of the durability of resistance against plant viruses.

Evolution and structure of Tomato spotted wilt virus populations: evidence of extensive reassortment and insights into emergence processes

“…The first breakdowns of the Tsw resistance were observed only 1 year after their initial deployment in 1999 in Italy and Spain (García-Arenal & McDonald, 2003). Several factors could be responsible for such low resistance durability.…”

“…For example, the Tsw resistance gene was broken down only a few years after its deployment in pepper crops (Roggero et al, 2002;García-Arenal & McDonald, 2003;Thomas-Carroll & Jones, 2003;Margaria et al, 2004;Sharman & Persley, 2006). The genome of TSWV consists of three ssRNA segments referred to as L, M and S (large, medium and small, respectively) (Whitfield et al, 2005).…”

Mosaics, mixtures, rotations or pyramiding: What is the optimal strategy to deploy major gene resistance?

“…However, once deployed in the field, such resistance has often been quickly overcome, resulting in dramatic epidemics and the need to identify and develop new sources of genetic resistance (García‐Arenal & McDonald, 2003; Johnson, 1984; Lecoq, Moury, Desbiez, Palloix, & Pitrat, 2004; McDonald & Linde, 2002; Parlevliet, 2002). Importantly, novel sources of resistance are not inexhaustible.…”

Phylogenetic analysis of Tomato spotted wilt virus (TSWV) NSs protein demonstrates the isolated emergence of resistance-breaking strains in pepper

“…The application of pepper cultivars bearing Tsw resistance gene triggered the rapid emergence of new RB isolates few years after introducing these resistant Capsicum cultivars. First, reports on resistance breakdown by newly emerged TSWV RB strains were published from the Mediterranean pepper-producing regions, such as Italy and Spain [5][6][7]. Then the appearance of RB isolates was detected in other continents and countries, such as Australia and Hawaii [8,9].…”