Antifungal Activity of Essential Oils of Origanum majorana and Lavender angustifolia against Fusarium Wilt and Root Rot Disease of Melon Plan

The objective of this study was to evaluate the antifungal activity of essential oils of marjoram (Origanum majorana) and lavender (Lavender angustifolia) against eleven isolates of Fusarium oxysporum f. sp. melonis and ten isolates of Fusarium solani, the causal agents of Fusarium wilt and root rot disease of melon. The effect of essential oils on disease development under in vivo conditions was also tested. GC-MS analysis of marjoram essential oils showed that terpinen-4-ol (34.94%) is the major component, followed by γ-terpinene (24.66%), α-terpinene (13.22%), β-terpinene (5.84%), αterpineol (3.98%), and β-phellandrene (3.16%). Chemical analysis of lavender essential oils showed that α-terpinene (48.76%) is the major component, followed by linalool (16.79%), γ-terpinene (7.00%), β-trans-ocimane (6.47%), β-caryophyllene (5.83%), and lavandulol (3.23%). All essential oils tested in vitro using the disk diffusion method revealed a significant antifungal effect against mycelium growth of all F. oxysporum f. sp. melonis and F. solani isolates. The volatile compounds of essential oils have completely inhibited spore germination of both pathogens. In vivo, the essential oils applied as biofumigant significantly reduced disease severity on melon plants 20 days post-incubation. Lavender essential oils significantly reduced disease severity by almost 60% as compared to control melon plants while Marjoram essential oils reduced disease severity by almost 23% under controlled conditions. These results showed that lavender essential oils may contribute to the development of new antifungal compounds to protect melon crops from Fusarium wilt and root rot diseas

Deciphering the Pathobiome: Intra- and Interkingdom Interactions Involving the Pathogen Erysiphe alphitoides

Plant-inhabiting microorganisms interact directly with each other, forming complex microbial interaction networks. These interactions can either prevent or facilitate the establishment of new microbial species, such as a pathogen infecting the plant. Here, our aim was to identify the most likely interactions between Erysiphe alphitoides, the causal agent of oak powdery mildew, and other foliar microorganisms of pedunculate oak (Quercus robur L.). We combined metabarcoding techniques and a Bayesian method of network inference to decipher these interactions. Our results indicate that infection with E. alphitoides is accompanied by significant changes in the composition of the foliar fungal and bacterial communities. They also highlight 13 fungal operational taxonomic units (OTUs) and 13 bacterial OTUs likely to interact directly with E. alphitoides. Half of these OTUs, including the fungal endophytes Mycosphaerella punctiformis and Monochaetia kansensis, could be antagonists of E. alphitoides according to the inferred microbial network. Further studies will be required to validate these potential interactions experimentally. Overall, we showed that a combination of metabarcoding and network inference, by highlighting potential antagonists of pathogen species, could potentially improve the biological control of plant diseases