Screening, Diversity, and Characterization of Fungal Endophytes Isolated From the Halophyte Limonium axillare and the Potential of Biocontrol Antagonists Against Fusarium oxysporum

Abstract

Halophytes, plants that thrive in high-salinity environments, host unique microbial communities, including fungal endophytes, which contribute to plant growth and pathogen resistance. This study aimed to isolate, identify, and evaluate the antagonistic potential of fungal endophytes from the halophytic plant Limonium axillare, collected from both inland and coastal habitats. Fungal endophytes were isolated, identified via molecular techniques, and tested for antagonistic activity against phytopathogenic fungi using dual-culture assays. The results showed a diverse range of fungal endophytes, with Aspergillus and Cladosporium being the dominant genera. A total of 152 endophytic fungi were isolated from both locations, with 95 isolates coming from coastal plants and 57 from inland species. The isolates exhibited varying degrees of antagonistic activity against phytopathogens, highlighting their potential role in plant protection. Further research is needed to clarify these interactions' mechanisms and investigate their practical applications in agriculture. An endophytic isolate of Aspergillus terreus strain ((AL10) lim10qu) (ON210104.1) exhibited potent in vitro antifungal activity against Fusarium oxysporum, a pathogenic fungus affecting tomato plants. Greenhouse experiments demonstrated that the fungus significantly increased both the length of tomato seedlings and the overall plant biomass. Both laboratory-based (in vitro) and field-based (in vivo) evaluations of the strain ((AL10) lim10qu) (A. terreus) against F. oxysporum suggest the promising role of endophytes as effective biological control agents. Analysis using Gas Chromatography-Mass Spectrometry of the fungal extract detected around 100 compounds (secondary metabolites). In addition to gradually reducing the need for chemical fungicides, bio-products can also contribute to sustainable agriculture.

Keywords: biocontrol; fungal endophytes; halophyte; promoting growth.

FIGURE 1

Colonization rate for endophytic fungi isolated from Limonium axillare of two different locations: Location A inland and Location B coastal habitat.

FIGURE 2

Phylogenetic analysis conducted by MEGA 11, using the Maximum Likelihood method of 1000 bootstrap comparisons and Kimura two‐parameter model for the 11 (highlighted) taxa of endophytic fungi isolated from Limonium axillare based on ITS region. Tilletia horrida (AY560653.2) is the outgroup.

FIGURE 3

Colonization frequency (CF) percentage of fungal endophytes from the leaves of the halophytic plant L. axillare.

FIGURE 4

Comparison of fungal endophytic species abundance isolated from L. axillare at two distinct locations: Location A (inland habitat) and Location B (coastal habitat). The abundance is presented based on (1) species level and (2) identified taxa.

FIGURE 5

GC‐MS scan mode chromatogram of extract of the endophyte AL10.

FIGURE 6

Impact of fungal endophyte (AL10) and pathogen F. oxysporum treatments on the shoot height of tomato seedlings after 8 weeks (N = 4). Error bars represent standard errors of the means. Values with the same letter(s) are considered statistically not significant at p ≤ 0.05 according to Tukey's test.

FIGURE 7

Impact of endophyte and pathogen treatments on the biomass of tomato seedlings, including both aboveground and belowground biomass, after 8 weeks (N = 4). Graph (A) shows the fresh weight biomass for aboveground and belowground parts, whereas Graph (B) depicts the dry weight biomass for these sections. Error bars indicate standard errors of the means. Values sharing the same letter(s) are deemed not significant at p ≤ 0.05 according to Tukey's test.

FIGURE 8

Graph (A) represents the chlorophyll content in the tomato under different treatments. Graph (B) represents the number of branches of the tomato seedlings under different treatments. Error bars represent the standard errors of the means. Values with the same letter(s) are considered not significantly different at p ≤ 0.05 according to Tukey's test.