Population Dynamics ofPhytophthora infestansin the Netherlands Reveals Expansion and Spread of Dominant Clonal Lineages and Virulence in Sexual Offspring

Abstract

For a comprehensive survey of the structure and dynamics of the Dutch Phytophthora infestans population, 652 P. infestans isolates were collected from commercial potato fields in the Netherlands during the 10-year period 2000–2009. Genotyping was performed using 12 highly informative microsatellite markers and mitochondrial haplotypes. In addition, for each isolate, the mating type was determined. STRUCTURE analysis grouped the 322 identified genotypes in three clusters. Cluster 1 consists of a single clonal lineage NL-001, known as “Blue_13”; all isolates in this cluster have the A2 mating type and the Ia mitochondrial haplotype. Clusters 2 and 3 display a more elaborate substructure containing many unique genotypes. In Cluster 3, several distinct clonal lineages were also identified. This survey witnesses that the Dutch population underwent dramatic changes in the 10 years under study. The most notable change was the emergence and spread of A2 mating type strain NL-001 (or “Blue_13”). The results emphasize the importance of the sexual cycle in generating genetic diversity and the importance of the asexual cycle as the propagation and dispersal mechanism for successful genotypes. Isolates were also screened for absence of the Avrblb1/ipiO class I gene, which is indicative for virulence on Rpi-blb1. This is also the first report of Rpi-blb1 breakers in the Netherlands. Superimposing the virulence screening on the SSR genetic backbone indicates that lack the Avrblb1/ipiO class I gene only occurred in sexual progeny. So far, the asexual spread of the virulent isolates identified has been limited.

Large subclonal variation in Phytophthora infestans populations associated with Ecuadorian potato landraces

“…The genotyping data and isolate information can be found in Li et al . (). In addition the Shannon index and the evenness were calculated using the frequency data in Nicaragua reported by Blandón‐Díaz ().…”

Durable Resistance of Crops to Disease: A Darwinian Perspective

“…A recent example is the use of Rpi-blb1 against potato late blight (Phytophthora infestans), which was effective against all known races of P. infestans (124,139). Virulence to Rpi-blb1 has now been discovered in P. infestans from Mexico (31) and field samples in the Netherlands (88). Although Rpi-blb1 is still effective against most isolates and is being used in potato breeding (88), its durability depends on the cost of virulence.…”

“…Virulence to Rpi-blb1 has now been discovered in P. infestans from Mexico (31) and field samples in the Netherlands (88). Although Rpi-blb1 is still effective against most isolates and is being used in potato breeding (88), its durability depends on the cost of virulence. These coevolutionary predictions relate to a GFG system in which there is variation in the pathogen.…”

Genetic Variation within Clonal Lineages of Phytophthora infestans Revealed through Genotyping-By-Sequencing, and Implications for Late Blight Epidemiology

“…This allows for genetic recombination via sexual reproduction followed by rapid proliferation of the fittest individuals via asexual reproduction and dispersal via airborne sporangia or movement on infected plant tissue. The resulting clonal lineages, which are comprised of clonal descendants of one unique individual, then dominate a geographic region until a more fit individual displaces them [6,7]. In the United States, where sexual reproduction is not common but has been indirectly observed twice [8,9], novel-genotypes are presumed to emerge through migration [10–12].…”

“…The 12 microsatellite markers currently used to genotype isolates of P . infestans have sufficient resolution to distinguish clonal lineages, and have also been used to investigate diversity within lineages [6,14,27]. Several studies have identified phenotypic variability among asexual P .…”