Fluorescent seed and root exudates from soybean and its antifungal effect against Macrophomina phaseolina

YARYURA PABLO; LEÓN MARIANA; CORDON GABRIELA; LAGORIO MARÍA GABRIELA; KERBER NORMA; PUCHEU NORMA; GARCÍA AUGUSTO

Rosario. Santa Fé

Congreso; V Congreso Argentino de Microbiología General; 2008

Sociedad Argentina de Microbiología General

The capacity of the seed and root exudates to excrete fluorescent compounds have been demonstrated in very few species, in addition the mechanisms that regulate the liberation of these compounds and whether they have some beneficial effect for the plant, for example in the defense against pathogens, are not known. The identification of these fluorescent compounds in soybean has not been reported. Nevertheless, it is known that certain phenolic compounds such as caffeic, ferulic, p-coumaric acids which are present in leaves of some plants emit fluorescence to a wavelength near 440nm. We have found similar fluorescence spectra, from exudates of seed and root of soybean. The aim of this study was to partially isolate fluorescent exudate components and correlate them with root or seed anti-fungal activity.Four methods of phenolic compound extraction were evaluated, having used organic solvent, with three of these methods we separated a fluorescent extracts and a non-fluorescent extracts. Furthermore, the fluorescent extracts were dialyzed using bags with a cut-off of 2000Kd. Dialysis was performed in order to discard antifungal activity due to small peptides and enzyme.Samples of the crude extract and all the subsequent separation phases were tested on agar plates against Macrophomina phaseolina, a pathogen responsible for the charcoal rot of soybean.Microscopic examination of M. phaseolina in the presence of seed and root crude extracts revealed clear signs of stress and deletion, such as increases in numbers of sclerotia, vacuolation, granulation of cytoplasm, hyphal squeezing and lysis of mycelia fragments. After extractions, these signs only accompanied the fluorescent fractions and that one with compounds smaller than 2000Kb. These results indicate that small molecular weigh fluorescent components of seed and root exudates have negative effect towards growth of pathogen fungus; being a competitive advantage for non-pathogenic microorganisms to colonize seeds.The practical impact of this study is the possible use of natural compounds and their derivatives that could potentially being used as effective alternatives to conventional antifungal agents.