Abstract
Previous studies have confirmed the potential of hyperspectral spectroscopy (HS) to detect charcoal rot toxin effect on soybean (Glycine max). However, there is no evidence that it can differentiate among difference responses to that effect. This research tested the potential of HS (900–2400 nm) to differentiate different responses to charcoal rot effect caused by the fungal pathogen Macrophomina phaseolina. Known susceptible ‘Pharaoh’ and resistant ‘Spencer’ cultivars of soybean seedlings at the V1 stage were tested, and HS reflectance was measured in each treatment at 0 h (just before toxin treatment), 24 h, and 36 h after toxin treatment. For both cultivars, reflectance generally decreased up to 10% over time for controls and increased for treated seedlings up to 22%. Pharaoh had significant increases in reflectance 24 and 36 h after treatment, while Spencer did not exhibit significant changes in reflectance over the 24 and 36-h periods. The ratio of Al-Ahmadi et al. (2018) was also evaluated. Spencer showed a higher ratio than Pharaoh. Based on our results, HS can be used to compare the relative resistance of soybean cultivars to charcoal rot and is a potential screening technique to classify soybean cultivars based on their resistance to charcoal rot toxin.
Highlights
Soybean (Glycine max) is one of the most valuable crops, with a wide range of uses due to its protein and oil content (Lee et al, 2019)
The purpose of this study was to apply the measurement method recommended by Al-Ahmadi et al (2018) and evaluate it with known susceptible and resistant soybean cultivars to see if the method can detect differences in the cultivar response to charcoal rot toxin, indicating the potential of this methodology to be used in screening to identify soybean cultivar resistance to M. phaseolina at the early growth stage (V1)
These results indicate relatively consistent reflectance spectra of the seedlings, within each cultivar, prepared for control and toxin treatments
Summary
Soybean (Glycine max) is one of the most valuable crops, with a wide range of uses due to its protein and oil content (Lee et al, 2019). Soybean can be affected by charcoal rot without any clear early symptoms (Meyer, 1974). Charcoal rot threatens many crops and leads to substantial yield losses. It is caused by the fungus Macrophomina phaseolina (Tassi) Goid, a soil-borne and seed-borne pathogen (Coser et al, 2017) that attacks plants via their root systems (Hemmati et al, 2018), causing wilting symptoms. This pathogen tends to be more active under hot and dry conditions (Nagasubramanian et al, 2018)
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