Interspecific hybridization involving a rare parental forest pathogen leads to asymmetrical accelerated evolution.

This is the author's final version of the contribution published as:

[Garbelotto M., Lockman B., Sillo F., Gonthier P., 2018. Interspecific hybridization

involving a rare parental forest pathogen leads to asymmetrical accelerated

evolution. Phytopathology 108(10), S184]

The publisher's version is available at:

[https://apsjournals.apsnet.org/doi/10.1094/PHYTO-108-10-S1.1]

When citing, please refer to the published version.

This full text was downloaded from iris-Aperto: https://iris.unito.it/

iris-AperTO

University of Turin’s Institutional Research Information System and Open Access Institutional Repository

Interspecific hybridization involving a rare parental forest pathogen leads to asymmetrical accelerated evolution

M. M. GARBELOTTO1_{, B. Lockman}2_{, F. Sillo}3_{, P. Gonthier}3

(1)_{UC Berkeley, Berkeley, CA, USA;} (2)_{US FS, Portland, OR, USA;} (3)_{University of Torino /}

DISAFA, Grugliasco, ITALY

Hybridization is recognized as a major force in the rapid adaptive evolution of plant pathogens. In a high elevation alpine larch stand in Montana, the dominant pathogenic species Heterobasidion occidentale has hybridized with a rare Eastern North American population of H. irregulare. Based on sequence analyses of five loci, we show that: 1)-Hybridization increased allelic diversity, generating alleles absent from either parental populations; 2)-Hybrid genotypes are viable and consequential in evolutionary terms; 3)-Because H. irregulare is rare, hybrid progeny has been backcrossing with H. occidentale, and thus hybrids carry occidentale mitochondria; 4)-A further consequence of hybrids solely backcrossing with H. occidentale has been the isolation and rapid evolution of the irregulare genome, while the same is not true for the occidentale genome; 5)-Based on phylogenetic, Bayesian assignment, and ordination tests, irregulare alleles in hybrids are clearly distinct from all known irregulare alleles from North America and may represent a new species. This discovery demonstrates that larch can be a universal host favoring hybridization, and that hybridization between one abundant and one rare species can result in asymmetrical accelerated evolution of the nuclear genome of the rare parental species leading to speciation.

iris-AperTO

University of Turin’s Institutional Research Information System and Open Access Institutional Repository