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Fusarium wilt of bananas caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4) poses the most serious threat to banana production globally. The disease has been managed using chemical fungicides, yet the control levels are still unsatisfactory. This study investigated the antifungal activities of tea tree (Melaleuca alternifolia) essential oil (TTO) and hydrosol (TTH) against Foc TR4 and their bioactive components. The potential of TTO and TTH in inhibiting the growth of Foc TR4 was evaluated in vitro using agar well diffusion and spore germination assays. Compared to the chemical fungicide, TTO effectively suppressed the mycelial growth of Foc TR4 at 69%. Both the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of TTO and TTH were established at 0.2 µg/µL and 50% v/v, respectively, suggesting the fungicidal nature of the plant extracts. The disease control efficacies were also demonstrated by a (p ≤ 0.05) delayed Fusarium wilt symptom development in the susceptible banana plants with reduced LSI dan RDI scores from 70% to around 20–30%. A GC/MS analysis of TTO identified terpinen-4-ol, eucalyptol, and α-terpineol as the major components. In contrast, an LC/MS analysis of TTH identified different compounds, including dihydro-jasmonic acid and methyl ester. Our findings indicate the potential of tea tree extracts as natural alternatives to chemical fungicides to control Foc TR4. [ABSTRACT FROM AUTHOR]

The expression profile of pathogenesis related genes are signatures of an infection response in plant cells. Pathogenic infections can increase or reduce gene expression in a plant system in a relatively specific pattern. These expression patterns can be used as standards in pathogenicity studies and, where phenotypic expression is normally used to gauge a plants response to infection, it could additionally present a more rapid and early screening reference tool. Three genes: catalase (CAT), pathogen related protein (PR10), and phenylalanine ammonia (PAL) all implicitly implicated in the plant disease response pathway were targeted for analysis during the infection of Fusarium oxysporum f. sp. cubense tropical race 4 (FOCR4) in banana Musa acuminata cv. Berangan seedlings after a standard challenge under growth room conditions. Distinct patterns of gene expression were observed at three infection time points by real time expression analysis. There was a sequential 10-fold reduction in expression for the PR gene while, the PAL and CAT genes were both upregulated. These results present a set of reference genes that could be used for screening of a plant's response to Fusarium before the onset of symptoms. [ABSTRACT FROM AUTHOR]