Tea Tree Oil Induces Systemic Resistance against Fusarium wilt in Banana and Xanthomonas Infection in Tomato Plants

The essential tea tree oil (TTO) derived from Melaleuca alternifolia plant is widely used as a biopesticide to protect crops from several plant-pathogens. Its activity raised queries regarding its ability to, not only act as a bio-fungicide or bio-bactericide, but also systemically inducing resistance in plants. This was examined by TTO application to banana plants challenged by Fusarium oxysporum f. sp. cubense (Foc, Race 1) causing Fusarium wilt and to tomato plants challenged by Xanthomonas campestris. Parameters to assess resistance induction included: disease development, enzymatic activity, defense genes expression correlated to systemic acquired resistance (SAR) and induced systemic resistance (ISR) and priming effect. Spraying TTO on field-grown banana plants infected with Foc and greenhouse tomato plants infected with Xanthomonas campestris led to resistance induction in both hosts. Several marker genes of salicylic acid, jasmonic acid and ethylene pathways were significantly up-regulated in parallel with symptoms reduction. For tomato plants, we have also recorded a priming effect following TTO treatment. In addition to fungicidal and bactericidal effect, TTO can be applied in more sustainable strategies to control diseases by enhancing the plants ability to defend themselves against pathogens and ultimately diminish chemical pesticides applications

Tea Tree Oil Induces Systemic Resistance against Fusarium wilt in Banana and Xanthomonas Infection in Tomato Plants

The essential tea tree oil (TTO) derived from Melaleuca alternifolia plant is widely used as a biopesticide to protect crops from several plant-pathogens. Its activity raised queries regarding its ability to, not only act as a bio-fungicide or bio-bactericide, but also systemically inducing resistance in plants. This was examined by TTO application to banana plants challenged by Fusarium oxysporum f. sp. cubense (Foc, Race 1) causing Fusarium wilt and to tomato plants challenged by Xanthomonas campestris. Parameters to assess resistance induction included: disease development, enzymatic activity, defense genes expression correlated to systemic acquired resistance (SAR) and induced systemic resistance (ISR) and priming effect. Spraying TTO on field-grown banana plants infected with Foc and greenhouse tomato plants infected with Xanthomonas campestris led to resistance induction in both hosts. Several marker genes of salicylic acid, jasmonic acid and ethylene pathways were significantly up-regulated in parallel with symptoms reduction. For tomato plants, we have also recorded a priming effect following TTO treatment. In addition to fungicidal and bactericidal effect, TTO can be applied in more sustainable strategies to control diseases by enhancing the plants ability to defend themselves against pathogens and ultimately diminish chemical pesticides applications.</jats:p

Biological Control of Postharvest Diseases by Microbial Antagonists

The postharvest phase has been considered a very suitable environment for successful application of biological control agents (BCAs), since the first work on the biological control of brown rot disease of stone fruit was reported by Pusey and Wilson [1]. Sure enough, the conditions of constant temperature and high humidity seem to offer more chances to BCAs, increasing their antifungal activity [2]. BCAs are living organisms and act following different antagonistic strategies depending on pathogens, host and environment. Knowledge of their modes of action is therefore essential to enhance their viability and increase their potentiality in disease control. In general, antagonists used for biocontrol of postharvest diseases are yeasts and bacteria, and to a lesser extent fungi, and they have been widely reviewed [3\u20137]. Antagonists can display a wide range of modes of action, at different stages of their activity, relating to different hosts, pathogens; sometimes-different modes act simultaneously, and it is therefore difficult to establish which individual mechanism has contributed to a specific antifungal action. Considerable information is available with respect to their efficacy, their application under storage conditions, and their mixture with safe substances or according to the formulation. However, the mechanisms by which BCAs exert their activity against pathogens have not yet been fully elucidated [5] and sometimes, in order to achieve maximum effectiveness in postharvest phase, were combined with physical and chemical methods including heat treatments, gamma or UV-C irradiation, and controlled atmosphere (CA). The bottleneck of the biocontrol matter remains the BCAs formulation often done in association with private companies, due to the high costs of production and the regulatory barriers to BCAs registration in different countries that often do not encourage their dissemination. Also, a formulation often could reduce the activity of antagonists with respect to the fresh cells [2]

Biological Control of Postharvest Diseases by Microbial Antagonists

The postharvest phase has been considered a very suitable environment for successful application of biological control agents (BCAs), since the first work on the biological control of brown rot disease of stone fruit was reported by Pusey and Wilson [1]. Sure enough, the conditions of constant temperature and high humidity seem to offer more chances to BCAs, increasing their antifungal activity [2]. BCAs are living organisms and act following different antagonistic strategies depending on pathogens, host and environment. Knowledge of their modes of action is therefore essential to enhance their viability and increase their potentiality in disease control. In general, antagonists used for biocontrol of postharvest diseases are yeasts and bacteria, and to a lesser extent fungi, and they have been widely reviewed [3–7]. Antagonists can display a wide range of modes of action, at different stages of their activity, relating to different hosts, pathogens; sometimes-different modes act simultaneously, and it is therefore difficult to establish which individual mechanism has contributed to a specific antifungal action. Considerable information is available with respect to their efficacy, their application under storage conditions, and their mixture with safe substances or according to the formulation. However, the mechanisms by which BCAs exert their activity against pathogens have not yet been fully elucidated [5] and sometimes, in order to achieve maximum effectiveness in postharvest phase, were combined with physical and chemical methods including heat treatments, gamma or UV-C irradiation, and controlled atmosphere (CA). The bottleneck of the biocontrol matter remains the BCAs formulation often done in association with private companies, due to the high costs of production and the regulatory barriers to BCAs registration in different countries that often do not encourage their dissemination. Also, a formulation often could reduce the activity of antagonists with respect to the fresh cells [2]