Abstract
In the present study, two Epichloë sinensis endophyte strains isolated from different Festuca sinensis ecotypes were inoculated on potato dextrose agar (PDA) and potato dextrose broth (PDB) media with or without (control) exogenous additives. After 4weeks of growth, the growth (colony diameter, hyphal diameter, and mycelial biomass) and other characteristics (pH and antioxidant capacity of culture filtrate, mycelial ion contents, and hormone contents) were measured. The results showed that the culture conditions had significant effects (p<0.05) on the hyphal diameter, mycelial biomass, and hormone content of the two strains. The mycelial biomass of the two strains in PDB was significantly higher (p<0.05) than that on PDA. Except for strain 1 with indole-3-acetic acid (IAA) treatment and strain 84F with control and VB1 treatments, the hyphal diameter of the two strains in PDB under the other treatments was significantly higher (p<0.05) than that on PDA. In most cases, the IAA, cytokinins (CTK), abscisic acid (ABA), and gibberlic acid (GA) contents in the mycelia on PDA of the two strains were significantly higher (p<0.05) than those in PDB. The two E. sinensis strains exhibited significantly different performances (p<0.05) under the five treatments. The indices, including colony diameter, mycelial biomass, scavenging ability of superoxide anion radicals and hydroxyl radicals, pH of culture filtrate, ion contents, hyphal diameter, and IAA, CTK, GA, and ABA contents were significantly different (p<0.05) between the two strains, although the performance was inconsistent. Exogenous additives had significant effects (p<0.05) on the performance of the two E. sinensis strains. Indole-3-acetic acid and VB1 treatments significantly promoted (p<0.05) the growth of the two strains on both PDA and PDB. Indole-3-acetic acid treatment also significantly increased the hyphal diameters of the two strains in PDB (p<0.05). Indole-3-acetic acid and VB1 treatments significantly reduced (p<0.05) the antioxidant ability of these two strains in PDB. NaCl and ZnCl2 treatments had significant inhibitory effects (p<0.05) on fungal growth and promotion effects on the antioxidant ability of the two strains. The treatments also had significant effects (p<0.05) on hyphal diameters and ion and hormone contents, although the effects varied with different indices.
Highlights
The grass endophytes live asymptomatically and internally within host plant tissues without causing visible damage to the plant (Siegel et al, 1987)
Exogenous additives, including Vitamin B1 (VB1), Indole-3-acetic acid (IAA), sodium chloride (NaCl), and zinc chloride (ZnCl2), were dissolved in sterile water to make 30 g/L, 20 g/L, 23376 g/L, and 750 g/L concentrated solutions; 10 μl or 100 μl of each concentrated solution was added to 1 L sterilized PDA or 100 ml sterilized potato dextrose broth (PDB), respectively, to reach final concentrations of 30 mg/L, 20 mg/L, 0.4 mol/L, and 750 mg/L, respectively. potato dextrose agar and PDB without additives were prepared as controls
Culture conditions significantly affected the hyphal diameters of the two E. sinensis strains
Summary
The grass endophytes live asymptomatically and internally within host plant tissues without causing visible damage to the plant (Siegel et al, 1987). The grass provides fungal endophytes with nutrients and space for growth, and in turn, fungal endophytes confer many benefits to grass hosts, including persistence/fitness, resistance/deterrence to insects, drought and salinity tolerance, and resistance to nematodes and fungal pathogens (Gundel et al, 2013; Vázquez-de-Aldana et al, 2013; Xia et al, 2018; Song et al, 2015a). This is attributed to the production of abundant and diverse secondary metabolites, as observed in a host and pure culture (Song et al, 2015b). Some toxic alkaloids produced through the symbiosis impair animal performance, which has significant economic consequences for the pastoral agricultural sectors (Schardl et al, 2012, 2013)
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