Phenolic Compounds in Different Stages of Ontogenesis in Chrysanthemum—A Potential for Thrips-Resistance Characterisation

Abstract

A number of studies have indicated the potential role of secondary metabolites, referred to as ‘resistance factors’, in plant defence against insect pests. Nevertheless, it remains unclear which metabolites serve as predictors of resistance in chrysanthemum cultivars against thrips. In the present study, the phenolic compounds of chrysanthemum leaves at different ontogenetic stages were analysed using high-performance liquid chromatography (HPLC). Furthermore, the relative epidermal flavonol contents in the leaves were quantified using the Dualex® Scientific 4 sensor, and the suitability of this non-destructive method for the rapid discrimination of resistance levels was evaluated. The results demonstrated that the most notable discrepancies in phenolic metabolite profiles were observed in the older leaves and the vegetative state of the chrysanthemum plants. Multiple discriminant analysis was conducted using HPLC-analysed metabolites to predict the importance of metabolites in resistant, susceptible, or highly susceptible plants in the vegetative stage. The results demonstrated that multiple metabolites, rather than a single metabolite, are responsible for thrips resistance in chrysanthemum. However, the relative flavonol content did not reflect the HPLC-analysed flavonoid glycosides or hydroxycinnamic acid derivatives, indicating that the Dualex® sensor is not a suitable device for determining resistance levels in chrysanthemums. Testing is required to extend and analyse the results in greater depth.