Leaf age is important for assessment of resistance in chrysanthemum against Frankliniella occidentalis

Abstract

Feeding behaviour of pest insects on host plants depends on the plant morphology and chemical composition. So far, leaf position was demonstrated important for estimation of thrips resistance in Capsicum, where resistant associations showed a higher resistance in the youngest leaves compared to old leaves. In the current study, the feeding behaviour of female Frankliniella occidentalis, a major pest of chrysanthemum, and the egg-laying activity was assessed in a non-choice experiment in the climate chamber. We hypothesize that the physiological status, i.e. the age of chrysanthemum leaves, is an important resistance factor influencing thrips silver damage and the number of offspring. In general, the results show significantly higher feeding damage on old (basal) leaves of susceptible cultivars compared to resistant cultivars on the abaxial side of the leaf. In contrast, we detected no significant differences on the adaxial side of the leaves neither for old nor for young leaves. However, feeding damage on different leaf positions is an important factor for resistance level determination. Additionally, we detected significant differences in reproductive activity, i.e. number of hatched larvae on old leaves compared to young leaves for all cultivars. Overall, on old leaves we detected more larvae. The comparison between the old leaves of all cultivars exhibited a significant difference between one resistant and one susceptible cultivar. Contrary to that, the comparison between the young leaves of all cultivars exhibited no significant differences. All findings are important for advancing future resistance screenings in chrysanthemum.