Fluorescence of chlorophyll a in transgenic maize with herbicide application and attacked by Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

Physiological changes in maize plants, submitted to herbicides and pests, should be studied for integrated management in this crop. The objective was to evaluate the chlorophyll a fluorescence in maize genotypes damaged or not by Spodoptera frugiperda, and sprayed with herbicides. The herbicides atrazine and nicosulfuron were applied to the plants at doses of 3 kg ha− 1 and 0.06 kg ha− 1, respectively. A randomized block design in a factorial scheme with an additional treatment 3 (2 × 2 + 1) was used, being the factor A: maize leaves exposed or not to the attack of S. frugiperda; factor B: Herculex® (transgenic maize encoding the Cry1F protein) and Isohybrid (non-transgenic maize) genotypes and an additional treatment represented by the PowerCore® genotype (stacked transgenic maize encoding the Cry1F, Cry1A.105 and Cry2Ab2 proteins). The initial fluorescence of chlorophyll a (F0 - electrons quantum− 1), maximum fluorescence (Fm - electron quantum− 1), ratio between variable fluorescence and maximum fluorescence of chlorophyll a (Fv/Fm) and electron transport rate ETR-µmols electrons m− 2 s− 1) were analyzed. The initial fluorescence of chlorophyll a increased and Fm, Fv/Fm and ETR decreased in plants attacked by the pest. The PowerCore® chlorophyll fluorescence remained in characteristic patterns. Chlorophyll a fluorescence was similar between genotypes with or without herbicides application. Damage by S. frugiperda increased the initial fluorescence of chlorophyll a and reduced the variable fluorescence/maximum fluorescence ratio and electron transport rate, indicating physiological stress in maize plants. The herbicides do not cause physiological stress in plants of maize genotypes with characteristic values of chlorophyll a fluorescence.