Detection and identification of canker and blight on orange trees using a hand‐held Raman spectrometer

Abstract

Huanglongbing (HLB), or citrus greening, is a devastating disease of citrus that is debilitating the U.S. citrus industry. The infected trees exhibit yellowing leaves, premature defoliation, and ultimately death of the entire plant. In addition to the devastating impact of HLB alone, infected trees become an easy target for other diseases. This further decreases the fruit yield, shortens the tree life, and complicates management practices. Raman spectroscopy is a noninvasive and nondestructive analytical technique that provides insight on the chemical structure of a specimen. In this study, we demonstrate that utilization of a hand‐held Raman spectrometer in combination with chemometric analyses enables detection and identification of the secondary disease such as blight on HLB‐infected orange trees (HLB + BL). We also showed that using this spectroscopic approach, we could detect and identify canker and distinguish this disease from healthy trees, HLB, and HLB + BL with high accuracy.

Raman Spectroscopy Enables Non-invasive and Confirmatory Diagnostics of Salinity Stresses, Nitrogen, Phosphorus, and Potassium Deficiencies in Rice

“…The following experimental parameters were used for all collected spectra: 1 s acquisition time, 495 mW power, and baseline spectral subtraction by device software. Previously reported experimental results demonstrated absence of photodegradation of plant material at these experimental conditions (Sanchez et al, 2019a). We also observed neither visual signs of laser-induced photodegradation of rice leaves during spectral acquisition nor any noticeable structural changes in plants in the control group of plants (Supplementary Figure S1).…”

“…These spectroscopic changes can facilitate the elucidation of the molecular mechanisms of plant responses to various biotic and abiotic stresses. Considering the high sensitivity of RS for the diagnostics of biotic stresses on plants (Egging et al, 2018;Farber and Kurouski, 2018;Farber et al, 2019a,b;Sanchez et al, 2019aSanchez et al, ,b, 2020a, one can expect that this spectroscopic approach has farreaching implications in various disciplines, from basic plant biology and pathology to agriculture and horticulture.…”

Raman-Based Diagnostics of Biotic and Abiotic Stresses in Plants. A Review

“…ND is associated with an increase in phenylpropanoids Canker (Sanchez et al, 2019b) Orange, leaf -1,601-1,630 cm −1 (phenylpropanoids)…”

“…At the same time, there are several vibrational bands that originate from aliphatic (CH 2 ) vibrations, such as 1,440 and 1,458 cm −1 . Normalization of spectra on these vibrational bands can be used for an unbiased comparison of Raman spectra collected from both leaves and seeds (Farber et al, 2019b(Farber et al, , 2020cKrimmer et al, 2019;Sanchez et al, 2019bSanchez et al, ,c, 2020b). Such normalization allows for avoiding artificial differences in spectra associated with different coloration of analyzed plant material.…”

“…Another question is whether RS can be used to differentiate between HLB and other diseases, such as CA that can appear on citrus trees. Sanchez and co-workers investigated whether RS can be used to differentiate between healthy, HLB, HLB + BL, and orange trees infected by CA (Sanchez et al, 2019b). It has been found that CA and HLB + BL could be detected and identified with 95 and 96% accuracy, respectively.…”