GIGANTEA (GI) is a plant-specific nuclear protein that plays a pleiotropic role in the growth and development of plants. GI’s involvement in circadian clock function, flowering time regulation, and various types of abiotic stress tolerance has been well documented in recent years. Here, the role of GI in response to Fusarium oxysporum (F. oxysporum) infection is investigated at the molecular level comparing Col-0 WT with the gi-100 mutant in Arabidopsis thaliana. Disease progression, photosynthetic parameters, and comparative anatomy confirmed that the spread and damage caused by pathogen infection were less severe in gi-100 than in Col-0 WT plants. F. oxysporum infection induces a remarkable accumulation of GI protein. Our report showed that it is not involved in flowering time regulation during F. oxysporum infection. Estimation of defense hormone after infection showed that jasmonic acid (JA) level is higher and salicylic acid (SA) level is lower in gi-100 compared to Col-0 WT. Here, we show that the relative transcript expression of CORONATINE INSENSITIVE1 (COI1) and PLANT DEFENSIN1.2 (PDF1.2) as a marker of the JA pathway is significantly higher while ISOCHORISMATE SYNTHASE1 (ICS1) and NON-EXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1), the markers of the SA pathway, are downregulated in the gi-100 mutants compared to Col-0 plants. The present study convincingly suggests that the GI module promotes susceptibility to F. oxysporum infection by inducing the SA pathway and inhibiting JA signaling in A. thaliana.

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In the present study, eight different essential oils (Basil, Citronella, Neem, Turmeric, Eucalyptus, Pipermint, Palmarosa, Lemongrass) were tested for their antifungal activities against Aspergillus niger and Fusarium oxysporum. Result of the study revealed that all the tested essential oils showed fungicidal properties against these two test pathogens. Among the eight essential oils tested, Citronella oil showed maximum antifungal activities and this was followed by Lemongrass and Pipermint. The MIC value of the oils ranged from 0.97-500μl/ml. The Minimum Killing Time (MKT) of the oils varied from 0 min to 5hrs, at room temperature. Fungicidal activity of the oils retained even after treating at 100ºC for an hour and on autoclaving (121ºC and 15lb pressure for 20 min), which indicated thermostable and barostable nature of the active components in these oils. When the effect of commercially available synthetic fungicides were studied it was observed that both the pathogens were resistant to copper chloride 50% WP and Carbendazim 50% WP (upto 500 ppm) whereas, the essential oils killed the pathogens at a very lower concentrations and observed to be fungicidal in nature.