Plant response to destruxins visualized by imaging of chlorophyll fluorescence

Abstract

Kinetic fluorescence imaging was used to set a new detection limit for plant exposure to low levels of destruxins – phytotoxins of Alternaria brassicae. A general experimental algorithm is presented that can be used to identify the combination of fluorescence parameters providing the highest contrast between the affected and unaffected plants or plant segments. Leaves of canola (Brassica napus) and white mustard (Sinapis alba) were exposed to various concentrations of destruxins and images of key fluorescence signals (F0, FM, FP, and of FS) were captured in a single kinetic experiment. Contrast was quantified within these images between the leaf areas exposed to destruxins and the untreated areas. The highest contrast was found in the image constructed by pixel‐to‐pixel division of images F0 by FP and F0 by FM. Using the F0/FM ratio image, we were able to detect exposure to destruxin concentration as low as approximately 0.05 mg l−1 applied to canola leaf and approximately 10 mg l−1 when applied to mustard. The detection limits were significantly lower than those obtained by optical microscopy indicating that kinetic chlorophyll fluorescence imaging can be used as a diagnostic tool in screening for varieties with an enhanced resistance to destruxins of Alternaria brassicae.