Near-infrared spectroscopy for the evaluation and prediction of injuries associated with the attack of Thaumastocoris peregrinus (Carpintero & Dellapé) in Eucalyptus camaldulensis (Dehnh)

Abstract

Injuries caused by stressor agents cause changes in the photosynthetic efficiency of plants, detectable by means of ecophysiological analysis. Near-infrared spectroscopy (NIRS - Near-infrared Reflectance Spectroscopy) is a viable alternative for evaluating the ecophysiological state of plants. This study aimed to investigate the use of the NIRS technique allied to multivariate calibration methods to evaluate the ecophysiology of Eucalyptus camaldulensis attacked by Thaumastocoris peregrinus. To do this, plants were maintained in an acclimatized room and infested by the insect. During 13 days, at every 48 hours, the initial fluorescence (Fo) and the maximum fluorescence (Fm) were measured on the surface of the attacked leaves to determine the potential quantum efficiency of Photosystem II (Fv/Fm) and the electron transport rate (ETR) with the aid of a fluorometer, the relative chlorophyll content, by means of a chlorophyll meter, and the foliar moisture content, its spectra being obtained in a near-infrared spectrophotometer to develop the models. The method used was that of partial least squares and the validation was crossed. After the calibration and validation, model prediction was performed where the results were evaluated through the correlation coefficient and mean square error. In the prediction step, there was good correlation and lower mean square error for the variables Fv/Fm, ETR and moisture content. The results indicate that the NIRS technique may be employed for the characterization and prediction of damages associated with the attack of the bronze bug.