Growth Enhancement of Arabidopsis (Arabidopsis thaliana) and Onion (Allium cepa) With Inoculation of Three Newly Identified Mineral-Solubilizing Fungi in the Genus Aspergillus Section Nigri

Abstract

Some soil fungi play an important role in supplying elements to plants by the solubilizing of insoluble minerals in the soil. The present study was conducted to isolate the mineral-solubilizing fungi from rhizosphere soil in some agricultural areas in northern Thailand. Seven fungal strains were obtained and identified using a polyphasic taxonomic approach with multilocus phylogenetic and phenotypic (morphology and extrolite profile) analyses. All obtained fungal strains were newly identified in the genus Aspergillus section Nigri, Aspergillus chiangmaiensis (SDBR-CMUI4 and SDBR-CMU15), Aspergillus pseudopiperis (SDBR-CMUI1 and SDBR-CMUI7), and Aspergillus pseudotubingensis (SDBR-CMUO2, SDBR-CMUO8, and SDBR-CMU20). All fungal strains were able to solubilize the insoluble mineral form of calcium, copper, cobalt, iron, manganese, magnesium, zinc, phosphorus, feldspar, and kaolin in the agar plate assay. Consequently, the highest phosphate solubilization strains (SDBR-CMUI1, SDBR-CMUI4, and SDBR-CMUO2) of each fungal species were selected for evaluation of their plant growth enhancement ability on Arabidopsis and onion in laboratory and greenhouse experiments, respectively. Plant disease symptoms were not found in any treatment of fungal inoculation and control. All selected fungal strains significantly increased the leaf number, leaf length, dried biomass of shoot and root, chlorophyll content, and cellular inorganic phosphate content in both Arabidopsis and onion plants under supplementation with insoluble mineral phosphate. Additionally, the inoculation of selected fungal strains also improved the yield and quercetin content of onion bulb. Thus, the selected strains reveal the potential in plant growth promotion agents that can be applied as a biofertilizer in the future.

Reducing the number of accepted species inAspergillusseriesNigri

“…The Aspegillus tubingensis lineage (ATL) contains ex-types of ten species: A. chiangmaiensis , A. costaricensis , A. eucalypticola , A. luchuensis , A. neoniger , A. piperis , A. pseudopiperis , A. pseudotubingensis , A. tubingensis and A. vadensis . The sequences of the three recently described species, A. chiangmaiensis, A. pseudopiperis and A. pseudotubingensis ( Khuna et al 2021 ), were of poor quality and contained a large number of errors (indels) in the coding regions and probably also in the noncoding regions of all three genes. Due to this fact and the absence of genomic sequences, we excluded these species from most analyses.…”

“…2019 ). This fact also resulted in the recent description of several cryptic species related to A. niger and A. tubingensis ( Silva et al 2020 , Khuna et al 2021 ). The narrow species definition in the series Nigri is also associated with unsatisfactory identification results of MALDI-TOF MS (matrix-assisted laser desorption ionization time-of-flight mass spectrometry), a widely used identification tool in diagnostic laboratories and applied spheres ( Gautier et al 2016 , D’hooge et al 2019 , Ban et al 2021 ).…”

“…Four novel cryptic species have been proposed since. Silva et al (2020) introduced A. vinaceus as a close relative of A. niger and Khuna et al . (2021) introduced A. chiangmaiensis, A. pseudopiperis and A. pseudotubingensis as close relatives of A. tubingensis .…”

Species Diversity, Distribution, and Phylogeny of Exophiala with the Addition of Four New Species from Thailand

“…Currently, only three Exophiala species have been identified in Thailand, namely E. dermatitidis , E. jeanselmei , and E. spinifera [ 43 , 46 , 67 ]. Accordingly, many studies have proposed that Thailand has proven to be a hot spot for novel microfungal species discovery [ 120 , 121 , 122 ]. During investigations of rock-inhabiting fungi in northern Thailand during the period of 2020 to 2021, we obtained fifteen Exophiala strains that are potentially representative of new species.…”

Mutation breeding ofAspergillus nigerby atmospheric room temperature plasma to enhance phosphorus solubilization ability

“…Organic acids of plant or microbial origin can form organometallic complexes with Fe 2+ and Al 3+ , increasing P availability by the dissolution of phosphate precipitates with these ions ( Pavinato & Rosolem, 2008 ). Previous studies have demonstrated that several mineral-solubilizing fungi could solubilize inorganic minerals into available forms through the production of organic acids ( e.g ., citric, fumaric, gluconic, malic, succinic, tartaric, and oxalic acids) ( Acevedo et al, 2014 ; Wang et al, 2018 ; Khuna et al, 2021 ). Specifically, the secretion of oxalic acid by strains under P-deficient soil conditions was one of the most important P-solubilization mechanisms that plants have adapted to cope with P deficiency ( Song et al, 2008 ; Nascimento et al, 2021 ).…”