Association mapping of ectomycorrhizal traits in loblolly pine (Pinus taeda L.).

To understand how diverse mutualisms coevolve and how species adapt to complex environments, a description of the underlying genetic basis of the traits involved must be provided. For example, in diverse coevolving mutualisms, such as the interaction of host plants with a suite of symbiotic mycorrhizal fungi, a key question is whether host plants can coevolve independently with multiple species of symbionts, which depends on whether those interactions are governed independently by separate genes or pleiotropically by shared genes. To provide insight into this question, we employed an association mapping approach in a clonally replicated field experiment of loblolly pine (Pinus taeda L.) to identify genetic components of host traits governing ectomycorrhizal (EM) symbioses (mycorrhizal traits). The relative abundances of different EM fungi as well as the total number of root tips per cm root colonized by EM fungi were analyzed as separate mycorrhizal traits of loblolly pine. Single-nucleotide polymorphisms (SNPs) within candidate genes of loblolly pine were associated with loblolly pine mycorrhizal traits, mapped to the loblolly pine genome, and their putative protein function obtained when available. The results support the hypothesis that ectomycorrhiza formation is governed by host genes of large effect that apparently have independent influences on host interactions with different symbiont species.

Piculell BJ ，José Martínez-García P ，Nelson CD ，Hoeksema JD ... -  《-》

Genetically determined fungal pathogen tolerance and soil variation influence ectomycorrhizal traits of loblolly pine.

Piculell BJ ，Eckhardt LG ，Hoeksema JD 《Ecology and Evolution》

Exome genotyping, linkage disequilibrium and population structure in loblolly pine (Pinus taeda L.).

Lu M ，Krutovsky KV ，Nelson CD ，Koralewski TE ，Byram TD ，Loopstra CA ... -  《BMC GENOMICS》

Benefits provided by four ectomycorrhizal fungi to Pinus taeda under different external potassium availabilities.

Ectomycorrhizal fungi contribute to the nutrition of many woody plants, including those in the Pinaceae family. Loblolly pine (Pinus taeda L.), a native species of the Southeastern USA, can be colonized by multiple species of ectomycorrhizal fungi. The role of these symbionts in P. taeda potassium (K+) nutrition has not been previously investigated. Here, we assessed the contribution of four ectomycorrhizal fungi, Hebeloma cylindrosporum, Paxillus ammoniavirescens, Laccaria bicolor, and Suillus cothurnatus, in P. taeda K+ acquisition under different external K+ availabilities. Using a custom-made two-compartment system, P. taeda seedlings were inoculated with one of the four fungi, or kept non-colonized, and grown under K+-limited or -sufficient conditions for 8 weeks. Only the fungi had access to separate compartments in which rubidium, an analog tracer for K+, was supplied before harvest. Resulting effects of the fungi were recorded, including root colonization, biomass, and nutrient concentrations. We also analyzed the fungal performance in axenic conditions under varying supply of K+ and sodium. Our study revealed that these four ectomycorrhizal fungi are differentially affected by external K+ and sodium variations, that they are not able to provide similar benefits to the host P. taeda in our growing conditions, and that rubidium may be used with some limitations to estimate K+ transport from ectomycorrhizal fungi to colonized plants.

Frank HER ，Garcia K 《-》

Association of loblolly pine xylem development gene expression with single-nucleotide polymorphisms.

Palle SR ，Seeve CM ，Eckert AJ ，Wegrzyn JL ，Neale DB ，Loopstra CA ... -  《-》