Spectral behavior of banana with Foc R1 infection: Analysis of Williams and Gros Michel clones

Fusarium wilt is the greatest threat to Musaceae production worldwide; remote sensing techniques based on reflectance spectroscopy are proposed for its detection. The spectral response of leaves of healthy plants and plants infected with Fusarium oxysporum f. sp. cubense Race1 (Foc R1) from two banana cultivars during the incubation period of the disease were characterized. Spectra of 400-1000 nm were measured in healthy and Foc R1-infected plants on Gros Michel (GM: susceptible) and Williams (W: resistant) bananas with an Ocean Optics HR2000+ portable spectrometer. Similar general patterns were obtained in the spectra for both cultivars for the Vis, around 25% in the green region, but, as the foliar development progressed, reflectance decreased throughout the entire spectral range, close to 12.5% (green region of Vis range) on leaf 4 of both. Four wavelengths were discriminant for the healthy plants in the cultivars. Additionally, reflectance increased in the infected plants in the incubation period throughout the range, decreasing rapidly once the first visible symptoms appeared. The results suggested that an increase in reflectance at discriminating wavelengths can be used to diagnose diseased plants in the asymptomatic period, and a rapid decrease in this suggests the onset of the symptomatic phase.