Antonio Evidente

Lysobacter capsici AZ78 produces cyclo(L-Pro-L-Tyr), a 2,5-diketopiperazine with toxic activity against sporangia of Phytophthora infestans and Plasmopara viticola.

To investigate low molecular weight compounds produced in vitro by Lysobacter capsici AZ78 and their toxic activity against sporangia of plant pathogenic oomycetes.

A new flow cytometry technique to identify Phaeomoniella chlamydospora exopolysaccharides and study mechanisms of esca grapevine foliar symptoms.

A flow cytometry technique that unequivocally identifies some of the toxic metabolites produced by Phaeomoniella chlamydospora, one of the main fungal pathogens causing esca disease of grapevine (Vitis vinifera), was developed. Antibodies raised against exopolysaccharides (EPS)-metabolites produced by Pa. chlamydospora that have been reported to be phytotoxic-were used as antigen to immunize rats. The specificity of these antibodies was assayed by flow cytometry against Pa. chlamydospora polysaccharides and against EPS with a different structure isolated from other phytopathogenic fungi, including Phaeoacremonium aleophilum and the Botryosphaeriaceae species Neofusicoccum luteum and N. parvum. Using this method, Pa. chlamydospora polysaccharides were detected in the symptomatic leaves of esca-affected grapevines, while healthy and asymptomatic leaves from both healthy and diseased vines did not produce a binding reaction. This method potentially could be used to develop a simple kit to study the mechanisms underlying the development of esca foliar symptoms and to indirectly assess the presence of Pa. chlamydospora in grapevine material.

Agropyrenol and agropyrenal, phytotoxins from Ascochyta agropyrina var. nana, a fungal pathogen of Elitrigia repens

A strain of Ascochyta agropyrina var. nana, a fungal pathogen of the perennial weed Elytrigia repens, produced several toxins in a liquid medium, and its primary toxin, named agropyrenol, was characterized as a substituted salicylaldehyde on the basis of its chemical and spectroscopic properties. Its absolute stereochemistry was determined by Moshers method. Two other minor metabolites were isolated from the same culture and named agropyrenal and agropyrenone, respectively. They were characterized as a trisubstituted naphthalene carbaldehyde and a pentasubstituted 3H-benzofuranone, respectively, using the same techniques. When assayed on leaves of several weed plants, i.e., Mercurialis annua, Chenopodium album and Setaria viridis, agropyrenol proved to be phytotoxic, causing the appearance of necrotic lesions, agropyrenal was less active, while agropyrenone was inactive. None of the compounds showed antibiotic, fungicidal or zootoxic activity.

PRODUCTION OF PHYTOTOXIC METABOLITES BY PSEUDOMONAS SYRINGAE pv. ACTINIDIAE, THE CAUSAL AGENT OF BACTERIAL CANKER OF KIWIFRUIT

SUMMARY Pseudomonas syringae pv. actinidiae, the causal agent of bacterial canker of Actinidia chinensis and A. deliciosa, is currently causing severe economic losses worldwide. A study was conducted to verify if a highly virulent Psa strain, isolated during the current outbreaks of bacterial canker of kiwifruit in Italy, produces phytotoxic metabolites in vitro. Culture filtrate, obtained from 14-day-old cells grown in Pseudomonas minimal medium, induced an evident hypersensitivity-like reaction to both tobacco and kiwifruit leaves. From culture filtrates, extracts were obtained using different solvents and pH values. The extracts and their corresponding aqueous phases, were further tested for phytotoxicity. Basic, hydrophilic, lowmolecular weight and hydrophilic, high-molecular weight compounds belonging to exopolysaccharides were isolated and analyzed. These compunds proved highly phytotoxic to kiwifruit, tobacco leaves and lemon fruits. Gas-chromatography-mass-spectrometry analysis carried out on crude exopolysaccharides showed glucose as the main monosaccharide constituent. These results suggest that phytotoxic metabolites, other than the antimetabolite phaseolotoxin, could be involved in the virulence of the pathogen to kiwifruit species.

Inhibition of early development stages of rusts and powdery mildew by fungal and plant metabolites

Trabajo presentado en el 15th Congress of the Mediterranean Phytopathological Union, celebrado en cordoba (Espana) del 20 al 23 de junio de 2017.Comunicacion oral presentada en el 15th Congress of the Mediterranean Phytopathological Union, June 20–23, 2017, Cordoba, Spain.Early assessment of late wilt of maize (Harpophora maydis) and the control effect of Lycium europaeum extracts. C. RODRÍGUEZ-MALLOL1, R. TEJ1,2, L. MOLINERO-RUIZ1. 1Department of Crop Protection, Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), Alameda del Obispo s/n, 14004 Córdoba, Spain. 2Physiology and Biochemistry of Plant Response to Abiotic Stresses Unit, Faculty of Sciences of Tunis, University of Tunis El Manar, 1060 Tunis El Manar, Tunisia. E-mail: lmolinero@ias.csic.es

Constitutive secretion of pisatin in root exudates participates in pea defence against Fusarium oxysporum f. sp. pisi

Trabajo presentado en el 15th Congress of the Mediterranean Phytopathological Union, celebrado en cordoba (Espana) del 20 al 23 de junio de 2017.Comunicacion oral presentada en el 15th Congress of the Mediterranean Phytopathological Union, June 20–23, 2017, Cordoba, Spain.Early assessment of late wilt of maize (Harpophora maydis) and the control effect of Lycium europaeum extracts. C. RODRÍGUEZ-MALLOL1, R. TEJ1,2, L. MOLINERO-RUIZ1. 1Department of Crop Protection, Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), Alameda del Obispo s/n, 14004 Córdoba, Spain. 2Physiology and Biochemistry of Plant Response to Abiotic Stresses Unit, Faculty of Sciences of Tunis, University of Tunis El Manar, 1060 Tunis El Manar, Tunisia. E-mail: lmolinero@ias.csic.es