Dual mycorrhizal symbiosis: an asset for eucalypts out of Australia?

Abstract

The dual symbiotic habit of the genus Eucalyptus is well documented: while arbuscular mycorrhizae are always dominant in seedlings and young trees, they are replaced by ectomycorrhizae in older trees. Here, the mycorrhizal status of eucalypts of different ages was assessed over the year in three plantations in the humid Mediterranean climate zone of Algeria (using morphological, anatomical, and histological criteria) and quantified in the dry and wet seasons over three years (using the grid-line intersect method of Giovannetti and Mosse (1980, New Phytol. 84: 489–500, doi: 10.1111/j.1469-8137.1980.tb04556.x ) on randomized fine root segments). Unexpectedly, the results revealed the persistence of arbuscular mycorrhizae in old trees and their dominance over ectomycorrhizae during the dry season, while the opposite pattern was observed in the wet season. Composite mycorrhizae displaying intimately mixed arbuscular mycorrhizae and ectomycorrhizae anatomical structures also occurred and were more frequent during the dry season. Eucalypts were clearly able to form a wide diversity of symbiotic associations with arbuscular mycorrhizal and ectomycorrhizal fungi locally associated with native trees, shrubs, and herbaceous plants. Therefore, the mycorrhizal status should not be a limiting factor to the silviculture of eucalypts in this area of Algeria because the dual symbiotic habit provides complementary benefits in a poor soil and in an alien environment.

Dual‐mycorrhizal plants: their ecology and relevance

“…In extreme cases, seedlings are completely AM early in life (Bellei et al ., ; Chen et al ., ) and then simply lose AM associations and become almost completely EM after 1 yr, particularly when growing after severe site disturbance or as exotics in plantations. These shifts from AM‐ to EM‐dominated seedlings in Eucalyptus (Lapeyrie & Chilvers, ) have also been reported in alien ranges such as Algeria and Brazil (dos Santos et al ., ; Adjoud‐Sadadou & Halli‐Hargas, ). Here, we show this clear switching with seedling age in seven Eucalyptus species from two studies that provided sufficient data to calculate a mycorrhizal‐type dominance ratio (Fig.…”

Rhizobium Presence and Functions in Microbiomes of Non-leguminous Plants

“…It is considered, even more than 25% of alien ectomycorrhizal fungal species have been introduced with Myrtaceae (mostly Eucalyptus; Vellinga et al 2009). However, the seedlings of Eucalyptus are rapidly colonized by arbuscular mycorrhizal fungi, being replaced by ectomycorrhizal fungi along with tree age (dos Santos et al 2001;Adjoud-Sadadou and Halli-Hargas 2017), what is thought to be a major contributory factor of Eucalyptus success outside its native range (aforementioned studies; Teste et al 2019).…”

Mixing planting with native tree species reshapes soil fungal community diversity and structure in multi-generational eucalypt plantations in southern China

“…However, ECM fungi can transfer N sources (e.g., chitin and protein) from OM, which is an important process in the mitigation of drought and nutrient stress (Read and Perez-Moreno, 2003). Eucalypt species have a dual mycorrhizal symbiosis mode (ECM and AM), and changes in soil nutrients and hosts as a result of plantation transformation may upset the balance between symbiotic fungi and hosts (Adjoud-Sadadou and Halli-Hargas, 2017). Soil saprophytic fungi are preferred to decompose recalcitrant plant residues and soil OM, with a significantly positive correlation between their relative abundance and soil fertility (Kyaschenko et al, 2017;Castano et al, 2019).…”