Evidence of Coevolution Between Cronartium harknessii Lineages and Their Corresponding Hosts, Lodgepole Pine and Jack Pine.

Variation in rate of infection and susceptibility of Pinus spp. to the fungus Cronartium harknessii (syn. Endocronartium harknessii), the causative agent of western gall rust, has been well documented. To test the hypothesis that there is a coevolutionary relationship between C. harknessii and its hosts, we examined genetic structure and virulence of C. harknessii associated with lodgepole pine (P. contorta var. latifolia), jack pine (P. banksiana), and their hybrids. A secondary objective was to improve assessment and diagnosis of infection in hosts. Using 18 microsatellites, we assessed genetic structure of C. harknessii from 90 sites within the ranges of lodgepole pine and jack pine. We identified two lineages (East and West, FST = 0.677) associated with host genetic structure (r = 0.81, P = 0.001), with East comprising three sublineages. In parallel, we conducted a factorial experiment in which lodgepole pine, jack pine, and hybrid seedlings were inoculated with spores from the two primary genetic lineages. With this experiment, we refined the phenotypic categories associated with infection and demonstrated that stem width can be used as a quantitative measure of host response to infection. Overall, each host responded differentially to the fungal lineages, with jack pine exhibiting more resiliency to infection than lodgepole pine and hybrids exhibiting intermediate resiliency. Taken together, the shared genetic structure between fungus and host species, and the differential interaction of the fungal species with the hosts, supports a coevolutionary relationship between host and pathogen.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Signatures of Post-Glacial Genetic Isolation and Human-Driven Migration in the Dothistroma Needle Blight Pathogen in Western Canada.

Many current tree improvement programs are incorporating assisted gene flow strategies to match reforestation efforts with future climates. This is the case for the lodgepole pine (Pinus contorta var. latifolia), the most extensively planted tree in western Canada. Knowledge of the structure and origin of pathogen populations associated with this tree would help improve the breeding effort. Recent outbreaks of the Dothistroma needle blight (DNB) pathogen Dothistroma septosporum on lodgepole pine in British Columbia and its discovery in Alberta plantations raised questions about the diversity and population structure of this pathogen in western Canada. Using genotyping-by-sequencing on 119 D. septosporum isolates from 16 natural pine populations and plantations from this area, we identified four genetic lineages, all distinct from the other DNB lineages from outside of North America. Modeling of the population history indicated that these lineages diverged between 31.4 and 7.2 thousand years ago, coinciding with the last glacial maximum and the postglacial recolonization of lodgepole pine in western North America. The lineage found in the Kispiox Valley from British Columbia, where an unprecedented DNB epidemic occurred in the 1990s, was close to demographic equilibrium and displayed a high level of haplotypic diversity. Two lineages found in Alberta and Prince George (British Columbia) showed departure from random mating and contemporary gene flow, likely resulting from pine breeding activities and material exchanges in these areas. The increased movement of planting material could have some major consequences by facilitating secondary contact between genetically isolated DNB lineages, possibly resulting in new epidemics.

Ectomycorrhizal species associated with Pinus radiata in New Zealand including novel associations determined by molecular analysis.

Ectomycorrhizal (ECM) associates of the exotic plantation species Pinus radiata were investigated above and below ground over two years in the North Island of New Zealand. ECM species were identified using morphological and molecular (restriction fragment length polymorphism and DNA sequencing) analysis. Eighteen ECM species were observed fruiting above ground; 19 ECM species were identified below ground. In the above ground study, Wilcoxina mikolae, Rhizopogon pseudoroseolus and Inocybe sindonia were noted for the first time as ECM associates of P. radiata in New Zealand. Below ground, the species W. mikolae, R. pseudoroseolus, Rhizopogon luteorubescens, Pseudotomentella sp., Pseudotomentella tristis and Tomentella sp. were found as new associates of P. radiata in New Zealand. Additionally, six ECM types were found that could not be identified with molecular analysis. The putative ECM taxa Tricholoma pessundatum, Laccaria laccata and Hebeloma crustuliniforme were examined by molecular analysis, and species identifications were proposed to be changed to Tricholoma sp., L. laccata and Hebeloma sp. for specimens associated with P. radiata in New Zealand. The species identity of I. sindonia, previously unidentified to species level, was determined with direct sequencing.