Ericoid mycorrhizal fungus enhances microcutting rooting of Rhododendron fortunei and subsequent growth

Abstract

Adventitious root (AR) formation is a unique feature of plant reproduction and plays a vital role in crop production as many horticultural and forestry plants are propagated through cuttings. A growing number of reports have shown that microbes, particularly mycorrhizal fungi are able to promote AR formation, but the underlying mechanisms remain largely unclear. This study established an in vitro culture system and investigated AR formation in microcuttings of Rhododendron fortunei Lindl. inoculated with Oidiodendron maius Barron Om19, an ericoid mycorrhizal fungus strain. Hormones and precursors involved in the biosynthesis of indole-3-acetic acid (IAA) in Om19 mycelium were analyzed. Om19 was able to produce a large quantity of tryptophan (Trp) and also indole-3-pyruvate (IPA) and IAA, indicating that IAA biosynthesis in Om19 could be through a Trp-dependent pathway. After inoculation of Om19, ARs were quickly formed in microcuttings. Symbiosis related genes were activated in ARs, and Om19 effectively colonized the roots. YUC3, a key gene in plant biosynthesis of IAA and genes involved in nitrogen (N) uptake and metabolism, phosphorus (P) uptake were highly upregulated. Plants absorbed significantly greater quantity of mineral nutrients, and their growth was substantially enhanced compared to the control plants without Om19 inoculation. A working model for Om19 enhanced AR formation was proposed. The rapid formation of ARs in cuttings could be due in part to the induction of IAA biosynthesized by Om19 and also attributed to Trp catalyzed biosynthesis of IAA in plants. AR formation, in turn, provided Om19 preferred sites for colonization. Our study suggested that in addition to promoting AR formation, Om19 could potentially be used as a new biofertilizer for enhancing production of ericaceous plants, such as blueberry, cranberry, and rhododendron.

Lingonberry (Vaccinium vitis-idaea L.) Interact With Lachnum pygmaeum to Mitigate Drought and Promote Growth

“…It is exciting that under drought stress, Lp ZL6 inoculation can significantly increase the growth of lingonberry roots, up to 1157.6% ( Figure 6B ). This result is consistent with in Rhododendron fortunei ; ErM fungi can significantly increase root biomass ( Wei et al, 2020 ).…”

“…The mechanism is that Oidiodendron maius fungi can produce high concentrations of Trp (tryptophan) for IAA synthesis through IPA (indole-3-pyruvate) and IAA to promote mycelium growth. IAA may also induce adventitious root formation in micro-cutting and promote IAA production in plants ( Wei et al, 2020 ). Our results showed that Om FC and Lp ZL6 colonized the roots of lingonberry and formed mycorrhizal structures ( Figure 3E ).…”

“…Ascomycota is the main fungus involved in the formation of ErM. Oidiodendron maius is a member of Leotiomycetes and has been isolated from Rhododendron fortunei ( Wei et al, 2020 ). Rhododendron fortunei seedlings inoculated with the Oidiodendron maius strain produced abundant roots ( Wei et al, 2016a ), and significantly increased root and stem biomass ( Wei et al, 2016b ).…”

Arbuscular mycorrhizal fungi improve the growth and drought tolerance of Cinnamomum migao by enhancing physio‐biochemical responses

“…The effect of AMF colonization on host plants depends on many factors, including the host specificity and local diversity of AMF, the selectivity of host plants for AMF, and the adaptability of fungal strains to different environmental conditions, which affect inoculation effectiveness (Wei et al, 2020; Yang et al, 2012; Zhang et al, 2011). In this study, the inoculation of Cl.…”

Table_2.DOCX

“…The mechanism is that Oidiodendron maius fungi can produce high concentrations of Trp (tryptophan) for IAA synthesis through IPA (indole-3-pyruvate) and IAA to promote mycelium growth. IAA may also induce adventitious root formation in microcutting and promote IAA production in plants (Wei et al, 2020). Our results showed that OmFC and LpZL6 colonized the roots of lingonberry and formed mycorrhizal structures (Figure 3E).…”