Biostimulation of tomato growth and biocontrol of Fusarium wilt disease using certain endophytic fungi

Abstract

Background: Tomato plant (Solanum lycopersicum L.) suffers from numerous fungal pathogens that cause damage to yeild production qualitatively and quantitatively. One of the most destructive disease of tomato is Fusarium wilt that caused by soil borne fungus called F. oxysporum.

Methods: In this study, the anti-Fusarium capabilities of the foliar application of fungal endophytes extracts have been investigated on tomato under Fusarium challenges. Antifungal assay, inhibition of conidial germination, disease severity, photosynthetic pigments, osmolytes, secondary metabolites, oxidative stress, peroxidase (POD) and polyphenol oxidases (PPO) isozymes were tested for potential resistance of tomato growing under Fusarium infection.

Results: Ethyl acetate extracts of A. flavus MZ045563, A. fumigatus MZ045562 and A. nidulans MZ045561 exhibited antifungal activity toward F. oxysporum where inhibition zone diameters were 15, 12 and 20 mm, respectively. Moreover, extracts of all fungal isolates at concentration 7.5 mg/mL reduced conidia germination from 94.4 to 100%. Fusarium infection caused a destructive effects on tomato plant, high severity desiese index 84.37%, reduction in growth parameters, photosynthetic pigments, and soluble protein. However, contents of proline, total phenol, malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and antioxidant enzymes activity were increased in tomato plants grown under Fusarium wilt. Treatment of healthy or infected tomato plants by ethyl acetate fungal extracts showed improvements in morphological traits, photosynthetic pigments, osmolytes, total phenol and antioxidant enzymes activity. Besides, the harmful impacts of Fusarium wilt disease on tomato plants have also been reduced by lowering MDA and H₂O₂ levels. Also, treated tomato plants showed different responses in number and density of POD and PPO isozymes.

Conclusion: It could be suggested that application of ethyl acetate extracts of tested fungal endophytes especially combination of A. flavus, A. nidulans and A. fumigatus could be commercially used as safe biostimulation of tomato plants as well as biofungicide against tomato Fusarium wilt disease.

Keywords: Antioxidant enzymes; Endophytic; Fusarium; Isozymes; Resistance; Tomato.

Fig. 1

Antifungal activity of (1): A. flavus, (2): A. fumigatus, (3): A. nidulans crude extracts and (4): fluconazole against F. oxysporum using agar well diffusion method. (F = front and R = reverse)

Fig. 2

Inhibition of conidial germination of F. oxysporum with different concentrations of the crude extract of A. flavus (T-7), A. fumigatus (T-5), and A. nidulans (T-4) after 24, 48 and 72 h

Fig. 3

Effect of F. oxysporum and endophytic isolates (A. flavus, A. nidulans and A. fumigatus) individual or combination on photosynthetic pigments of tomato plants. Data presented as means ± SD (n = 3). Data followed by different letters (a:f) are significantly different LSD test at P ≤ 0.05. FW: fresh weight. ( T1-Healthy control; T2-Infected control; T3-Healthy treated with A. flavus; T4-Healthy treated with A. nidulance; T5-Healthy treated with A. fumigatus; T6-Healthy treated with combination of A. flavus, A. nidulance and A. fumigatus; T7-Infected treated with A. flavus; T8-Infected treated with A. nidulance; T9-Infected treated with A. fumigatus and T10-Infected treated with combination of A. flavus, A. nidulance and A. fumigatus

Fig. 4

Effect of F. oxysporum and endophytic isolates on osmolytes (mg/g dry weight) of tomato plants. Data presented as means ± SD (n = 3). Data followed by different letters (a:f) are significantly different LSD test at P ≤ 0.05. FW: fresh weight. (T1-Healthy control; T2-Infected control; T3-Healthy treated with A. flavus; T4-Healthy treated with A. nidulance; T5-Healthy treated with A. fumigatus; T6-Healthy treated with combination of A. flavus, A. nidulance and A. fumigatus; T7-Infected treated with A. flavus;T8-Infected treated with A. nidulance; T9-Infected treated with A. fumigatus and T10-Infected treated with combination of A. flavus, A. nidulance and A. fumigatus)

Fig. 5

Effect of F. oxysporum and endophytic isolates on (MDA) (nmol g⁻¹ fresh weight); (H₂O₂) (mg g⁻¹ fresh weight); POD (unit/g) f. wt./h. and PPO(unit/g) f. wt./ h. of tomato plants. Data presented as means ± SD (n = 3). Data followed by different letters are significantly different LSD test at P ≤ 0.05. (T1-Healthy control; T2-Infected control; T3-Healthy treated with A. flavus; T4-Healthy treated with A. nidulance; T5-Healthy treated with A. fumigatus; T6-Healthy treated with combination of A. flavus, A. nidulance and A. fumigatus; T7-Infected treated with A. flavus; T8-Infected treated with A. nidulance; T9-Infected treated with A. fumigatus and T10-Infected treated with combination of A. flavus, A. nidulance and A. fumigatus)

Fig. 6

Effect of F. oxysporum and endophytic isolates on peroxidase isozyme of tomato plants. A POD, B Ideogram analysis of POD isozyme (T1-Healthy control; T2-Infected control; T3-Healthy treated with A. flavus; T4-Healthy treated with A. nidulance; T5-Healthy treated with A. fumigatus; T6-Healthy treated with combination of A. flavus, A. nidulance and A. fumigatus; T7-Infected treated with A. flavus; T8-Infected treated with A. nidulance; T9-Infected treated with A. fumigatus and T10-Infected treated with combination of A. flavus, A. nidulance and A. fumigatus)

Fig. 7

Effect of F. oxysporum and endophytic isolates on PPO isozyme of tomato plants. A PPO, B Ideogram analysis of PPO isozyme (T1-Healthy control; T2-Infected control; T3-Healthy treated with A. flavus; T4-Healthy treated with A. nidulance; T5-Healthy treated with A. fumigatus; T6-Healthy treated with combination of A. flavus, A. nidulance and A. fumigatus; T7-Infected treated with A. flavus; T8-Infected treated with A. nidulance; T9-Infected treated with A. fumigatus and T10-Infected treated with combination of A. flavus, A. nidulance and A. fumigatus)