Plant performance of enhancing licorice with dual inoculating dark septate endophytes and Trichoderma viride mediated via effects on root development

Abstract

Background: This study aimed to assess whether licorice (Glycyrrhiza uralensis) can benefit from dual inoculation by Trichoderma viride and dark septate endophytes (DSE) isolated from other medicinal plants. Methods: First, we isolated and identified three DSE (Paraboeremia putaminum, Scytalidium lignicola, and Phoma herbarum) and Trichoderma viride from medicinal plants growing in farmland of China. Second, we investigated the influences of these three DSE on the performance of licorice at different T. viride densities (1 × 10 6 , 1 × 10 7 , and 1 × 10 8 CFU/mL) under sterilised condition in a growth chamber. Results: Three DSE strains could colonize the roots of licorice, and they established a positive symbiosis with host plants depending on DSE species and T. viride densities. Inoculation of P. putaminum increased the root biomass, length, surface area, and root:shoot ratio. S. lignicola increased the root length, diameter and surface area and decreased the root:shoot ratio. P. herbarum increased the root biomass and surface area. T. viride increased the root biomass, length, and surface area. Structural equation model (SEM) analysis showed that DSE associated with T. viride augmented plant biomass and height, shoot branching, and root surface area. Variations in root morphology and biomass were attributed to differences in DSE species and T. viride density among treatments. P. putaminum or P. herbarum with low-or medium T. viride density and S. lignicola with low-or high T. viride density improved licorice root morphology and biomass. Conclusions: DSE isolated from other medicinal plants enhanced the root growth of licorice plants under different densities T. viride conditions and may also be used to promote the cultivation of medicinal plants.

Synergistic and Offset Effects of Fungal Species Combinations on Plant Performance

“…A series of single- and dual-inoculation experiments indicated that greater performance of plants were potentially obtained in multi-species than in single-species contexts ( Figure 2 ). This result, itself, is consistent with previous reports of enhanced plant growth by specific pairs of bacteria/fungi ( Han and Lee, 2006 ; Wang et al, 2011 ; Ważny et al, 2018 ; He et al, 2020 ). Meanwhile, our experiments on 78 combinations of fungi systematically suggested that pairs of microbes, each of which had greatly positive impacts on plant growth in single inoculations, could show minor effects on plants under multi-species conditions.…”

“…One of the major challenges in utilizing plant-associated microbial functions is to design sets of microbial species/isolates ( Vorholt et al, 2017 ; Paredes et al, 2018 ; Toju et al, 2018a ; Wei et al, 2019 ). While a single microbial species or isolate can have specific functions in promoting plant growth, broader ranges of positive effects on plants are potentially obtained by introducing multiple microbial species/isolates ( Wang et al, 2011 ; Ważny et al, 2018 ; He et al, 2020 ). For example, a fungal species degrading organic nitrogen ( Newsham, 2011 ) and another fungus suppressing soil pathogens ( Vinale et al, 2008 ) may collectively provide plants with a broader spectrum of physiological functions than each of them alone, potentially having additive or synergistic effects on the growth of their hosts.…”

“…Thus, knowledge of the prevalence and intensity of such synergistic and offset effects is essential in synthetic microbiome studies. Nonetheless, although there have been studies reporting synergistic/offset effects of multiple plant-associated microbes ( Han and Lee, 2006 ; Wang et al, 2011 ; Ważny et al, 2018 ; He et al, 2020 ), experimental studies systematically evaluating the commonness of those effects are scarce.…”

Synergistic and offset effects of fungal species combinations on plant performance

“…2). This result, itself, is consistent with previous reports of enhanced plant growth by specific pairs of bacteria/fungi (Han and Lee, 2006;Wang et al, 2011;Ważny et al, 2018;He et al, 2020).…”

“…One of the major challenges in utilizing plant-associated microbiome functions is to design sets of microbial species/isolates (Vorholt et al, 2017;Paredes et al, 2018;Toju et al, 2018a;Wei et al, 2019). While a single microbial species or isolate can have specific functions in promoting plant growth, broader ranges of positive effects on plants are potentially obtained by introducing multiple microbial species/isolates (Wang et al, 2011;Ważny et al, 2018;He et al, 2020). For example, a fungal species degrading organic nitrogen (Newsham, 2011) and that suppressing soil pathogens (Vinale et al, 2008) may provide plants with a broader spectrum of physiological functions than each of them alone, potentially having additive or synergistic effects on the growth of their hosts.…”