Spectral analysis, biocompounds, and physiological assessment of Cork Oak leaves: unveiling the interaction with Phytophthora cinnamomi and beyond

• Autor(a) principal: Guerra, Rui
• Data de Publicação: 2023
• Outros Autores: Pires, Rosa, Brazio, António, Cavaco, Ana Margarida, Schütz, Gabriela, Coelho, Ana Cristina
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/19966
• topic: Cork oak decline; Quercus suber-Phytophthora cinnamomi interaction; Reflectance spectra; Disease spectral monitoring

The cork oak tree (<i>Quercus suber</i> L.) symbolizes <i>the Montado</i> landscape in Portugal and is a central element in the country’s social and economic history. In recent decades, the loss of thousands of cork oaks has been reported, revealing the ongoing decline of these agroforestry ecosystems. This emblematic tree of the Mediterranean Basin is host to the soil-born root pathogen <i>Phytophthora cinnamomi</i>, an active cork oak decline driver. In this framework, the early diagnosis of trees infected by the oomycete by non-invasive methods should contribute to the sustainable management of cork oak ecosystems, which motivated this work. Gas exchange and visible/near-infrared (400–1100 nm) reflectance spectroscopy measurements were conducted on leaves of both control and <i>P. cinnamomi</i> inoculated plants. These measurements were taken at 63, 78, 91, 126, and 248 days after inoculation. Additionally, at the end of the experiment, biochemical assays of pigments, sugars, and starch were performed. The spectroscopic measurements proved effective in distinguishing between control and inoculated plants, while the standard gas exchange and biochemistry data did not exhibit clear differences between the groups. The spectral data were examined both daily and globally, utilizing the PARAFAC method applied to a three-way array of samples × wavelengths × days. The separation of the two plant groups was attributed to variations in water content (4<i>v</i> (<i>O</i>−<i>H</i>)); shifts in the spectra red edge; and structural modifications in the epidermal layer and leaves’ mesophyll. These spectral signatures can assist in the field identification of cork oaks that are interacting with <i>P. cinnamomi</i>.