ABSTRACT
Citrus canker is a serious disease caused by Xanthomonas citri subsp. citri bacteria, which infects citrus plants (Citrus spp.) leading to large economic losses in citrus production worldwide. In this work, laser induced fluorescence spectroscopy (LIF) was investigated as a diagnostic technique for citrus canker disease in citrus trees at an orchard using a portable optical fiber based spectrometer. For comparison we have applied LIF to leaves contaminated with citrus canker, citrus scab, citrus variegates chlorosis, and Huanglongbing (HLB, Greening). In order to reduce the noise in the data, we collected spectra from ten leaves with visual symptoms of diseases and from five healthy leaves per plant. This procedure is carried out in order to minimize the environmental effect on the spectrum (water and nutrient supply) of each plant. Our results show that this method presents a high sensitivity (approximately 90%), however it does present a low specificity (approximately 70%) for citrus canker diagnostic. We believe that such poor performance is due to the fact that the optical fiber collects light from only a small part of the leaf. Such results may be improved using the fluorescence imaging technique on the whole leaf.
Subject(s)
Citrus/microbiology , Lasers , Optical Fibers , Plant Diseases/microbiology , Spectrometry, Fluorescence/methods , Xanthomonas/isolation & purification , Brazil , Plant Leaves/microbiologyABSTRACT
We have been studying the antagonistic activity of the Streptoverticillium griseocarneum, strain IA-7527. It produces a strong antifungal substance which we named griseocarnin. Its antimicrobial power to Neurospora crassa, Rhodotorula, rubra, Hansenula suaveolens and Candida albicans deserves to be exceled. The isolated substance was compared with other antifungal antibiotics presenting close similarity with the heptaens Ascosin and PA-150. The production, extraction and purification methods as well as physical, chemical and biological properties are included in this work.