Diagnóstico de doenças de citros utilizando espectroscopia de fluorescência / Diagnosis of citrus diseases using fluorescence spectroscopy

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Currently the largest portion of money applied to citriculture focus on health of the orchard. The phytosanitary costs, along with fertilizers, exceed 60% of the production cost. The control of diseases such as Sudden Death of Citrus (SDC), Decline and Greening, also known as Huanglongbing, is done by visual inspection, which confers to the method a high level of subjectivity and imprecision. This work was intended to develop a quick and safe methodology of diagnosis for the diseases mentioned above using fluorescence spectroscopy and laser-induced fluorescence (LIF). It was used in this study two rootstocks, Cravo and Cleopatra, and four varieties of crown: Pera, Natal, Valencia and Hamlin. The diseases studied were also classified into different levels of severity. The index 1 was used for low severity SDC, and 2 for a more advanced stage of this disease. For Greening has been made a distinction between symptomatic and asymptomatic leaves. The Decline of Citrus disease was also part of this study because its symptoms are very similar to those in the initial phase of SDC, and this is a serious problem for the evaluation of contamination in the field. Initially, studies have been made on the fluorescence of photosynthetic pigments from the extracts of ill and healthy leaves using a non-portable fluorimeter. For the leaf analyses we used a portable system of laser-induced fluorescence spectroscopy developed in LOLEIA. The study of extracts revealed that the largest cariations occur in the concentrations of chlorophyll a and b, and that acessory pigments like ? and ?-carotones do not fluoresce in the wavelength used. In general, it is possible to say that ill plants have a decrease of chlorophylls a e b. The leaf results were analyzed through the statistical method Principal Component Analysis (PCA) in order to facilitate the observation of spectral changes. Through the developed methodology it was possible to identify and distinguish the diseases with efficiency greater than 93%. However, these results contributed for the development of a methodology for diagnosis of citrus diseases in a quick, accurate and economically viable way.

ASSUNTO(S)

fluorescence fluorescência citros citrus diagnosis diagnóstico

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