Fungal colonizers and seed loss in lodgepole pine orchards of British Columbia

Abstract

Lodgepole pine is an important lumber species in Canada and seed orchards are expected to meet the increased demand for seed. However, seed production has been consistently low in the Okanagan region orchards of British Columbia. To determine whether the fungal microbiome contributes to seed loss, histological and molecular approaches were used. Seed production was studied at seven Okanagan orchards, all outside the natural range of lodgepole pine, and at one near Prince George, within its natural range. Seed losses were highest in the Okanagan, compared with Prince George. The role of fungal colonizers in consuming seed during the last stages of maturation is described. Fungal hyphae were frequently observed at all locations in developing seed, particularly once storage substances accumulated. Fungi identified from host tissues using molecular and morphological techniques included Alternaria, Cladosporium, Fusarium, Penicillium, and Sydowia. The opportunistic foliar pathogen Sydowia polyspora, which is known to have a variable biotrophic status, was detected at most orchards within different host tissues (seeds, needles and conelets), in association with pollen and in the air column. Reduced seed viability observed in Okanagan orchards is most likely due to a combination of factors, including the composition of the fungal microbiome. KeywordsMicrobiome, endophyte, Pinus contorta var. latifolia Engelm. ex S. Watson, Sydowia polyspora (Bref. & Tavel) E. Müll. * Significant differences among sites are indicated by differing letters within a single column (Tukey, α = 0.05).

Trees and Insects Have Microbiomes: Consequences for Forest Health and Management

“…The relative importance of their effects on seedling mortality depends on mycorrhizae [199], and may also depend on seed-borne microorganisms. The vertical transmission of the microbiota, which was only recently detected in trees [200][201][202], may play a role in seedling recruitment under herbivory pressure. The initial, maternally transmitted microbiome may indeed affect the assembly trajectory of the microbiome and its composition at the seedling stage, through priority effects [149].…”

Maternal effects shape the seed mycobiome in Quercus petraea

“…Little is known about fungal communities of tree seeds, and in particular about the vertical transmission of fungi from mother trees to their offspring; this transmission could be of importance to the adaptation of forest ecosystems to environmental changes and should be considered in forest tree planting (Vivas et al ., 2020). In previous work, both fungal pathogens and common endophytes were detected in the seeds of some tree species (Ganley & Newcombe, 2006; Qi et al ., 2012; Sarmiento et al ., 2017; de la Bastide et al ., 2019); however, the relative contribution of vertically and horizontally transmitted species to the assembly of the whole fungal community of seeds is not yet known in forest ecosystems. The extent to which fungal species transmitted by the mother tree persist after seed fall is not known either, although this is a prerequisite for their effect on offspring fitness.…”