Ectomycorrhizal compatibility of Lactarius quieticolor and Tuber floridanum with Pinus elliottii and Pinus taeda.

Abstract

This study evaluated ectomycorrhizal compatibility, functional effects, and the inoculum-dose response of Lactarius quieticolor and Tuber floridanum in Pinus elliottii and Pinus taeda, aiming to understand the role of fungus-host specificity in the expression of growth and physiological responses. Basidiomes of Lactarius spp. used as the inoculum source were identified through morphological and molecular analyses, confirming the identity as L. quieticolor. The symbiont L. quieticolor formed ectomycorrhizae on both Pinus species, whereas T. floridanum established an association only with P. elliottii, representing the first experimental record of this interaction. In P. elliottii, both fungi elicited integrated responses regardless of dose, with increases in growth, root biomass and electron transport rate, while L. quieticolor also increased root length, phosphorus content and modulated initial chlorophyll fluorescence. In P. taeda, effects were more limited and dose-dependent: increases in shoot nitrogen content, electron transport rate and root colonization were observed only at the highest inoculum concentrations. Multivariate analyses revealed a clear separation between control and inoculated plants even as the fungal treatments, indicating specific functional signatures. Altogether, the results demonstrate that ectomycorrhizal compatibility is not universal among congeneric Pinus species and highlight the potential of L. quieticolor and T. floridanum as functional ectomycorrhizal symbionts, with implications for seedling production and the ecology of forest systems.