Randy Molina

Arbutus menziesii (Ericaceae) facilitates regeneration dynamics in mixed evergreen forests by promoting mycorrhizal fungal diversity and host connectivity

UNLABELLED PREMISE OF STUDY In the mixed evergreen forests in the western United States, Arbutus menziesii is able to quickly resprout following disturbance and, as such, act as a nurse tree during forest regeneration. The mechanism for this nurse tree effect has frequently been ascribed to mycorrhizal fungi, but no detailed molecular-based studies of the mycorrhizal fungal communities associated with A. menziesii roots have yet been conducted. • METHODS We examined the structure of the mycorrhizal fungal communities associated with A. menziesii in varying forest types and seasons and assessed the potential for common mycelial networks between A. menziesii and Pinaceae hosts, particularly Pseudotsuga menziesii. Study sites were located in the Klamath-Siskyou region in southern Oregon, United States. Molecular approaches were used to identify the mycorrhizal fungi (ITS rDNA) and plant hosts (trnL cDNA). • KEY RESULTS Arbutus menziesii hosts a highly diverse mycorrhizal fungal community with similar composition to communities found on other angiosperm and Pinaceae hosts. Phylogenetic analyses of the mycorrhizal genus Piloderma revealed that host species and geographic location had little effect on fungal taxon relatedness. Multihost fungal taxa were significantly more frequent and abundant than single-host fungal taxa, and there was high potential for the formation of common mycelial networks with P. menziesii. • CONCLUSIONS Our results suggest A. menziesii is a major hub of mycorrhizal fungal diversity and connectivity in mixed evergreen forests and plays an important role in forest regeneration by enhancing belowground resilience to disturbance.

Mycorrhiza Specificity: Its Role in the Development and Function of Common Mycelial Networks

The establishment of common mycelial networks by mycorrhizal fungi shared between host plants depends on the ability of neighboring plants to enter into mycorrhizal associations with compatible fungal species. Such compatibility is governed by the potential mycorrhiza specificities of the symbionts. Mycorrhiza specificities exist along a continuum from low specificity (association with multiple partners) to high specificity (association with one or few partners). Although the ability of symbionts to form mycorrhizas may be largely governed by host-fungus gene interactions as influenced by co-evolutionary events, mycorrhizal associations in natural ecosystems can also be influenced by environmental factors (e.g. soil) and biological factors (e.g. different neighboring host species), phenomena referred to as “ecological specificity.” For example, in natural settings, mycorrhizal fungi often express “host preference” wherein fungi may be more common on a particular host in mixed-host settings than would be expected by random species assemblage within the fungal and plant communities. Mycorrhiza specificity phenomena significantly influence plant community dynamics, particularly plant succession. Early seral plants can positively affect the establishment of later-seral plants by maintaining commonly shared mycorrhizal fungi, and thus affecting the function of common mycelial networks over time. Such knowledge provides guidance for ecosystem managers to maintain “legacy” early -seral plants that benefit later-seral plants via shared mycorrhizal fungus species. Understanding specificity phenomena is also crucial for predicting the successful migration of plants and compatible mycorrhizal fungi during climate change. We review mycorrhiza specificity terminology and types of specificity phenomena, and suggest use of common terms to provide consistency in addressing this research topic. We also provide extensive examples from diverse ecosystems on the ability (or inability) of neighboring plants to develop common mycelial networks.

Tuber 2013: scientific advances in sustainable truffle culture.

Since the 3rd International Truffle Conference in Spoleto (2008), researchers have made considerable progress in advancing understanding of the biology and ecology of Tuber species and in improving the sustainable productivity of these valuable fungi. Publication of the black truffle, Tuber melanosporum Vittad., genome (Martin et al. 2010) has opened new possibilities to explore gene functions and population dynamics of black truffles. Newmolecular technologies provide valuable tools to monitor black truffle development (Parlade et al. 2013) and allow researchers and managers to monitor the success of new truffle plantations and the effects of cultivation treatments on truffle productivity. Given the significant impact of truffle plantations on local economies, the regional government of Aragon, together with other institutes and truffle grower groups (see “Acknowledgments”), organized the 1st International Congress of Trufficulture in Teruel on March 5–8, 2013. The province of Teruel (Aragon region, Spain) produces almost 20 % of the global truffle market and hosts 11 % of the world’s black truffle plantations. The main objective of the congress was to promote the sustainable productivity of truffles by highlighting and exchanging the latest scientific advances in truffle biology, ecology, and truffle plantation management among researchers, students, truffle hunters, truffle growers, forest managers, land-use planners, and rural entrepreneurs from around the world. The conference brought together 270 participants from 23 countries of Europe, North and South America, Australia, and New Zealand. More than 100 presentations, of which, 54 oral and the remaining posters, covered many aspects of truffle biology, genetics, taxonomy, ecology, cultivation, and commercialization. The congress also included market displays by regional truffle entrepreneurs and a local field trip to productive truffle plantations, seedling nurseries, and a truffle processing facility. Congress attendees thus experienced firsthand the many aspects of the region’s practicing truffle culture. The trip culminated with a delightful banquet where all enjoyed the essence of truffle cuisine.