Functional characterization of fungal endophytes with antagonistic and plant growth-promoting activities in maize
TL;DR
The findings highlight that endophytic fungi exhibit multifunctional roles and show promise as microbial inoculants for sustainable crop improvement, with CJR-4 emerging as the promising candidate for further development.
Abstract
Fungal endophytes play a crucial role in plant-microbe interactions by asymptomatically colonizing host tissues, enhancing plant growth, and providing defense. In the present study, three distinct endophytic fungi, namely Fusarium oxysporum CJR-1 (GenBank Accession No. PZ477045), Penicillium sp. CJR-2 (GenBank Accession No. PZ477429) and Aspergillus cf. terreus CJR-4 (GenBank Accession No. PZ477430) were isolated from Crotalaria juncea L. plants and evaluated for antagonistic activity against phytopathogenic fungi and growth promotion in maize. Among the isolates, CJR-4 showed potent antagonistic activity against both tested phytopathogens, inhibiting the mycelial growth of Fusarium oxysporum (ITCC Accession No. 8111) and Alternaria alternata (ITCC Accession No. 1434) by 72.41 ± 5.02% and 68.31 ± 1.53%. On the other hand, isolate CJR-1 showed the highest mycelial inhibition of 74.60 ± 2.06% against A. alternata. Ethyl acetate crude metabolites of CJR-4 exhibited potent antifungal activity, with the highest zone of inhibition observed against A. alternata (21.66 ± 1.52 mm), followed by F. oxysporum (15.33 ± 1.15 mm) at 150 µL of tested concentration. GC-MS analysis of the ethyl acetate extract of CJR-4 revealed numerous bioactive metabolites, including diphenyl sulphone and 2-nonen-1-ol, which may contribute to its antifungal activity. In addition, 1-methylene-1H-indene and ethanone, 2-(formyloxy)-1-phenyl-, may be associated with antioxidant activity, as evidenced by potent DPPH (80.09 ± 0.11%) and ABTS (92.66 ± 0.17%) scavenging activities. Evaluation of PGP traits showed that CJR-1 produced the highest levels of indole-3-acetic acid (IAA) as 305.69 ± 0.41 µg mL⁻1 and ammonia 85.44 ± 0.63 µg mL⁻1, while CJR-2 exhibited the highest phosphate solubilization index (PSI) of 3.09 ± 0.09. Pot experiments conducted under natural light conditions for 28 days demonstrated significantly enhanced plant growth parameters, biomass accumulation, and photosynthetic pigment levels in maize plants inoculated with the CJR-4 isolate. Overall, the findings highlight that endophytic fungi exhibit multifunctional roles and show promise as microbial inoculants for sustainable crop improvement, with CJR-4 emerging as the promising candidate for further development. To the best of our knowledge, this study is among the first to report the isolation and functional characterization of endophytic fungi from Crotalaria juncea L. plant.