Plant Seedling Growth Stimulation and Antifungal Activities of Volatile Organic Compounds Emitted by Aspergillus flavus Endophyte

Volatile Organic Compounds (VOCs) produced by Plant Growth Promoting fungi (PGPF) have recently been investigated due to their role in plant growth promotion and defense. Whereas many VOCs produced by PGPF promote seed growth. It is known that VOCs, among several other mechanisms, are responsible for the antagonistic activity produced by microorganisms. In this study, we focused on a comparative study between the VOCs emitted by the endophyte A. flavus AFEG-2017 and its host plant (Eleocharis geniculata) and the role of these VOCs in the growth promotion and biological control of some economic plants.   VOCs from AFEG-2017 and E. geniculata were extracted using ethyl acetate.  Then, the analysis of emitted VOCs was accomplished by using gas chromatography mass (GC-MS). Seedling stimulation assay was investigated on seeds of Trigonella foenum-graecum, Solanum lycopersicum, Portulaca oleracea, and Lepidium sativum. In addition, the antifungal activity of VOCs was evaluated against some plant pathogenic fungi.     The GC-MS analysis of the volatile emitted from A. flavus (AFEG-2017) resulted in 25 organic and bioactive compounds; of them 2-(2-hydroxy-3-isobutoxypropyl) pent-4-enoic acid, hydrazide was the most abundant compound. The findings of the present study advocate that linalool, linalyl acetate, geranyl acetate, oleic acid, 1-eicosanol, and 1-chloro-octadecane are suitable as biocontrol agents against phytopathogenic fungi. In addition, the volatiles of Euphorbia geniculata showed 28 bioactive compounds, in which Phytol was the most abundant one. The VOCs produced by AFEG-2017 enhanced the seedling growth of T. foenum-graecum, S. lycopersicum, P. oleracea, and L. sativum. Also, VOCS showed inhibition in the tested pathogenic fungi growth like Fusarium oxysporum which showed the highest inhibition percentage in the growth (40%).  This study proved that there is a harmony between VOCs produced by the medicinal plant E. geniculata and its endophyte A. flavus. These volatiles could successfully accelerate plant seeding and limit the growth of some important phytopathogens.