HYPERSPECTRAL SPECTROSCOPY TO DETECT DIFFERENT RESPONSES OF TWO SOYBEAN (GLYCINE MAX) CULTIVARS TO CHARCOAL ROT (MACROPHOMINA PHASEOLINA) TOXIN

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.