Raman Spectroscopy Can Distinguish Glyphosate-Susceptible and -Resistant Palmer Amaranth (Amaranthus palmeri)

Abstract

The non-judicious use of herbicides has led to a widespread evolution of herbicide resistance in various weed species including Palmer amaranth, one of the most aggressive and troublesome weeds in the United States. Early detection of herbicide resistance in weed populations may help growers devise alternative management strategies before resistance spreads throughout the field. In this study, Raman spectroscopy was utilized as a rapid, non-destructive diagnostic tool to distinguish between three different glyphosate-resistant and four -susceptible Palmer amaranth populations. The glyphosate-resistant populations used in this study were 11-, 32-, and 36-fold more resistant compared to the susceptible standard. The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copy number for these resistant populations ranged from 86 to 116. We found that Raman spectroscopy could be used to differentiate herbicide-treated and non-treated susceptible populations based on changes in the intensity of vibrational bands at 1156, 1186, and 1525 cm–1 that originate from carotenoids. The partial least squares discriminant analysis (PLS-DA) model indicated that within 1 day of glyphosate treatment (D1), the average accuracy of detecting herbicide-treated and non-treated susceptible populations was 90 and 73.3%, respectively. We also found that glyphosate-resistant and -susceptible populations of Palmer amaranth can be easily detected with an accuracy of 84.7 and 71.9%, respectively, as early as D1. There were relative differences in the concentration of carotenoids in plants with different resistance levels, but these changes were not significant. The results of the study illustrate the utility of Raman spectra for evaluation of herbicide resistance and stress response in plants under field conditions.

Combination of spectral index and transfer learning strategy for glyphosate-resistant cultivar identification

“…Planting is an important step to verify the glyphosate tolerance of the new cultivars developed through genetic engineering and other technologies. Visual observation is still the mainstream method for breeders to identify glyphosate resistant cultivars ( Singh et al, 2021 ), which usually takes several weeks and is time-consuming and laborious, severely limiting the breeding process. The difference between resistant and sensitive cultivars is that the response of the latter to glyphosate stress is more easily observed than that of the former ( Shirzadifar et al, 2020b ).…”

“…Generally, many in vitro culture and field screening verifications are often required in the process of new glyphosate resistant cultivars creation. Common screening methods including visual observation and bioassays, take 10–14 days from spraying glyphosate to resistant identification ( Singh et al, 2021 ), which is time-consuming and labor-intensive. Hence, exploring a rapid non-destructive detection of glyphosate-tolerant cultivar method can speed up the breeding process.…”

TRACES OF GLYPHOSATE IN CORN (Zea mays L.) AND AVOCADO (Persea americana Mill.) WEEDS SUPPORTED BY VANT AND RAMAN SPECTROSCOPY

“…Multispectral images determine weed abundance and diversity using NDVI algorithms (Castaldi, 2017), and the resulting map serves as the basis for sample collection for the detection and impact of glyphosate and other herbicides (Esposito et al, 2021). Once the plant sample is obtained, weed identification is carried out, and Raman spectroscopy (RS) is used for the determination of glyphosate traces and residues (Sato-Berrú et al, 2004;Singh et al, 2021, Farber et al, 2019. RS measures the inelastic scattering of light from a monochromatic source, providing information on the chemical composition by recording the molecular vibrations of the constituent components; the "biochemical signature" or "molecular fingerprint" is then obtained (Vallejo-Pérez et al, 2016).…”

“…RS measures the inelastic scattering of light from a monochromatic source, providing information on the chemical composition by recording the molecular vibrations of the constituent components; the "biochemical signature" or "molecular fingerprint" is then obtained (Vallejo-Pérez et al, 2016). Both infrared and Raman spectroscopy provide a characteristic spectrum of the specific vibrations of a molecule and are valuable in identifying a substance, as Raman spectra contain vibrational bands that can be assigned to carbohydrates, carotenoids, proteins, and phenylpropanoids affected by glyphosate (Singh et al, 2021). Based on this knowledge, we propose the hypothesis of using high spectroscopic and radiometric resolution sensors to detect glyphosate traces in weeds and map its distribution in agricultural lands in real time.…”

Time-series monitoring of transgenic maize seedlings phenotyping exhibiting glyphosate tolerance

“…Traditional detection method of herbicide resistance is to observe seedlings’ growing status with the naked eye after spraying the herbicide to them. Generally speaking, it takes 12 days from the application of stress to the determination of herbicide injuries level and final resistance identification (Singh et al , 2021), which is time-consuming, subjective and inefficient. Furthermore, biomass, chlorophyll content, and the activity of antioxidant enzyme were often used to evaluate the level of tolerance to herbicide stress of crops.…”