Linking physiological parameters with visible/near-infrared leaf reflectance in the incubation period of vascular wilt disease

Abstract

The photosynthetic pigments are mainly responsible for absorbing the light intended to promote photosynthesis on the chloroplast of the leaves. Different studies have related the spectral response in the leaves of plants with the biotic stress generated by pathogens. In general, maximum differences in reflectance have been found in the range of 380–750 nm between plants subjected to biotic stress and healthy plants. In this study, it was possible to characterize and relate the spectral variance in leaves of S. lycopersicum infected with F. oxysporum with this physiological variation and pathogen concentration in tomato plants during the asymptomatic period of vascular wilt. Photosynthetic parameters derived from gaseous exchange analysis in the tomato leaves correlated related with four bands in the visible range (Vis). Additionally, five specific bands also present a high correlation with the increase in the concentration of F. oxysporum conidia measured at the root: 448–523 nm, 624–696 nm, 740–960 nm, 973–976 nm, and 992–995 nm. These wavelengths allowed a 100% correct classification of the plants inoculated with F. oxysporum from the plants subjected to hydric stress and the control plants in the asymptomatic period of the disease. The spectral response to biotic and abiotic stress in the measured Vis/NIR range can be explained by the general tendency to change the concentration of chlorophyll and carotene in tomato leaves. These studies also highlight the importance of the implementation of robust multivariate analysis over the multiple univariate analysis used in the applied biological sciences and specifically in the agricultural sciences. These results demonstrate that specific wavelength responses are due to physiological changes in plants subjected to stress, and can be used in indexes and algorithms applied to the early detection of diseases in plants on different pathosystems.

Precision Agriculture Digital Technologies for Sustainable Fungal Disease Management of Ornamental Plants

“…Nevertheless, many studies have pointed out on the spectral responses of plants to fungal pathogens using hyperspectral non-imaging sensors in the horticultural sector. For example, in tomato, the VIS/NIR spectroscopy showed a great potential for relating the concentration of conidia of F. oxysporum with the spectral response of leaves [103], as well as for discriminating the plants inoculated with F. oxysporum from those subjected to water stress [104]. However, to the best of our knowledge, very few studies using reflectance hyperspectroscopy have been performed on ornamental plants.…”

Hyperspectral response of cape gooseberry (Physalis peruviana L.) plants inoculated with Fusarium oxysporum f. sp. physali for vascular wilt detection

“…For plant diseases, mainly vascular wilts, the spectral responses of infected plants have been generated for only a low number of pathosystems, such as Capsicum annuum and Verticillium dahliae (Sanogo et al, 2008;Bauriegel and Herppich, 2014), Capsicum annuum -Fusarium spp. (Karadağ et al, 2019) and Solanum lycopersicum and F. oxysporum (Marín-Ortiz et al, 2020). Fusarium-diseased pepper (C. annuum) plants were detected with spectral reflections from leaves before symptoms became visible according to Karadağ et al (2019).…”

“…Fusarium-diseased pepper (C. annuum) plants were detected with spectral reflections from leaves before symptoms became visible according to Karadağ et al (2019). The potential to discriminate healthy from diseased plants before visible symptoms was also demonstrated in tomatoes by Marín-Ortiz et al (2020), based on their spectral response at several wavelengths. Calderón et al (2105) outlined an automatic procedure to classify plants infected by Verticillium dahliae in olive crops for large scale early detection.…”

Functional Hyperspectral Imaging by High-Related Vegetation Indices to Track the Wide-Spectrum Trichoderma Biocontrol Activity Against Soil-Borne Diseases of Baby-Leaf Vegetables

“…The four indices of this study, each applying its own peculiar algorithm, work in the spectral range 550–800 nm, just on the border between VIS and NIR regions, suggesting that this part of the spectrum could be sensitive to the reflectance shifts occurring at canopy level during the plant-pathogen-antagonist interaction. Marín-Ortiz et al ( 2020 ) have found in the VIS/NIR range 448–995 nm the distinctive spectral response of tomato to the Fusarium oxysporum infection that has been also associated to changes in the leaf concentration of chlorophyll and carotene. Similarly, the soil-borne pathogens studied in our systems could bring to the decline of chlorophyll and other pigments, as-well-as growth reduction conditioning the reflectance reaction.…”