Early detection of bacterial wilt in bananas caused by Ralstonia solanacearum using reflectance spectroscopy

Abstract

Bacterial wilt is one of the most important vascular diseases that generate high worldwide losses. The main strategy to control it involves early detection of infected plants that mitigate its spread in the field. This research characterized the spectral response of healthy plants, infected with Ralstonia solanacearum E.F. Smith race 2 and subjected to water stress, in two banana cultivars by spectroscopy reflectance. The spectral data were used to detect vascular wilt during the incubation period of the disease in Gros Michel and Cavendish banana cultivars. The reflectance data were collected from the leaves using a portable spectrometer. Both varieties of healthy plants showed a typical low reflectance in the visible range, with a peak of green of around 12% in Williams and 5% in Gros Michel. In the measured infrared range, the two varieties presented values between 60 and 70% in the latest days post-infection measurements, decreasing to ~ 50% after 12 dpi. The results obtained indicate that plants infected with R. solanacearum have no initial increase in reflectance in the visible (Vis) range, whereas decrease rapidly after 6 dpi in the 700–1000 nm range. This methodology identifies three wavelengths (710, 770, and 965 nm) that allow differentiation between ill and healthy plants after 6 days post-inoculation, with a percentage of correct classification that ranges from 96 to 100%. The spectral response characterization in healthy plants and those subjected to various types of stress is a fundamental input for the development of early disease detection systems based on spectroscopy techniques.