Dark Septate Endophytic Fungi Help Tomato to Acquire Nutrients from Ground Plant Material.

Carlos Vergara,Karla E C Araujo,Peter S Medeiros,Leandro A Santos,Segundo Urquiaga,Nivaldo Schultz,Jerri E Zilli,Gustavo R Xavier,Fabiano De Carvalho Balieiro

doi:10.3389/fmicb.2017.02437

Abstract

Dark septate endophytic (DSE) fungi are facultative biotrophs that associate with hundreds of plant species, contributing to their growth. These fungi may therefore aid in the search for sustainable agricultural practices. However, several ecological functions of DSE fungi need further clarification. The present study investigated the effects of DSE fungi inoculation on nutrient recovery efficiency, nutrient accumulation, and growth of tomato plants fertilized with organic and inorganic N sources. Two experiments were carried out under greenhouse conditions in a randomized blocks design, with five replicates of tomato seedlings grown in pots filled with non-sterile sandy soil. Tomato seedlings (cv. Santa Clara I-5300) inoculated with DSE fungi (isolates A101, A104, and A105) and without DSE fungi (control) were transplanted to pots filled with 12 kg of soil which had previously received finely ground plant material [Canavalia ensiformis (L.)] that was shoot enriched with 0.7 atom % 15N (organic N source experiment) or ammonium sulfate-15N enriched with 1 atom % 15N (mineral N source experiment). Growth indicators, nutrient content, amount of nitrogen (N) in the plant derived from ammonium sulfate-15N or C. ensiformis-15N, and recovery efficiency of 15N, P, and K by plants were quantified 50 days after transplanting. The treatment inoculated with DSE fungi and supplied with an organic N source showed significantly higher recovery efficiency of 15N, P, and K. In addition, the 15N, N, P, K, Ca, Mg, Fe, Mn, and Zn content, plant height, leaf number, leaf area (only for the A104 inoculation), and shoot dry matter increased. In contrast, the only positive effects observed in the presence of an inorganic N source were fertilizer-K recovery efficiency, content of K, and leaf area when inoculated with the fungus A104. Inoculation with A101, A104, and A105 promoted the growth of tomato using organic N source (finely ground C. ensiformis-15N plant material).

Highlights

In agriculture, especially in low-input or organic cultivation, plants can benefit from interactions with microorganisms, such as arbuscular mycorrhizal fungi (AMF) (He and Nara, 2007)
Dark septate endophytic (DSE)-tomato interaction had no effect on aboveground dry biomass, leaf number, and stem diameter of the tomato plants when inorganic N was supplied as ammonium sulfate-15N (Table 2)
The effect of DSE inoculation on 15N recovered was evident only when tomato plants were fertilized by finely ground C. ensiformis-15N (Figures 2A–D)

Summary

Introduction

Especially in low-input or organic cultivation, plants can benefit from interactions with microorganisms, such as arbuscular mycorrhizal fungi (AMF) (He and Nara, 2007). Dark septate endophytic (DSE) fungi are quite diverse facultative biotrophic ascomycetes characterized by dark pigmentation, melanized septate hyphae, and formation of microsclerotia inside the plant roots Such fungi are capable of colonizing root tissues intra and intercellularly of more than 600 plant species [including Solanum lycopersicum (L.) and those non-mycorrhizal ones] without causing pathologies. They can act as plant growth promoters (Jumpponen and Trappe, 1998; Upson et al, 2009; Andrade-Linares et al, 2011a,b; Yuan et al, 2011; Mahmoud and Narisawa, 2013)

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