Search

Green Chemistry Postgraduate Summer School (online/in-person), 4-9 July 2021, Venice, Italy., Broomrapes (Orobanche and Phelipanche spp.), are holoparasitic weeds that severely infesting a large number of important crops and causing severe yield losses. The main obstacle for long-term management of broomrape infested fields is the durable seedbank with evolved mechanisms of host recognition upon perception of host-derived germination factors. The continuous spread of broomrapes strongly affects the farmers work as heavy infestations lead to a complete crop loss and have a great negative impact over many years. In fact, parasitic seeds can survive in soil for decades until the germination is induced by a chemical signal exuded by the root of the host plant. Current control methods relies on the use of resistant crop varieties and herbicides, albeit success has been marginal. Considering that seed germination is a key phase for parasitic plant development and infestation, a further approach proposed for the management of these weeds has been to use microbial or plant metabolites to stimulate in absence of the host (the so called “suicidal germination) and/or inhibit the broomrape seed germination. Some metabolites induced a rapid cessation of radicle growth with the promotion of a layer of papillae at the radicle tip hampering the contact of the parasite to the host. The development of herbicides based on natural metabolites from wild plant, targeting early stages on parasitic plant development, might contribute to the reduction of broomrape seed bank in soils. This research is innovative as it proposes an alternative method to the massive use of synthetic herbicides for the management of parasitic plants. Natural inspired herbicides could reduce the environmental impact and consequently the risks for humans and animal health. This communication will illustrate the preliminary results on the isolation and chemical characterization of metabolites extracted from root of seventeen weed plants and the results of testing them on the seed germination of different broomrape species.

Xylella fastidiosa is a Gram-negative bacterium causing devastating diseases of many plants, including important crops as grapevine, peach, citrus, almond, coffee and pear. In the last decade, X. fastidiosa has devastated olive heritage in Apulia region (Italy) inducing a severe disease called “Olive Quick Decline Syndrome” The disease also infected millennial olive plants. The bacterium was introduced in this region from abroad and rapidly spread causing heavy economical losses and cultural and social damages. The eradication of infected plants in the restricted area at beginning of infection could be an effective approach to eliminate the bacterium. Unfortunately, this method was too late and partially applied. Studies carried out successively demonstrated that a zinc-copper-citric acid bio-complex allowed a consistent reduction of the infection on olive trees. The use of synthetic bactericides was discouraged as their use could cause resistance in the host plants and because of the long term impact of residues in agricultural products with a risk to human and animal health. Thus, a valid alternative could be the use of natural antibacterial metabolites. Some year ago, radicinin, a pihydropyranopyran-4,5-dione, was proposed as natural pesticide to control the infection of X. fastidiosa causing grapevines (Vitis vinifera L.) Pierce’s disease. Recently, radicinin together with some analogues were isolated from Cochliobolus australiensis, a fungus proposed as mycoherbicide to control buffelgrass (Cenchrus chliaris) an invasive weed in North America. The fungal production of radicinin was very low and this prompted the development of an efficient and ecofriendly total synthesis that afforded in good yield its biosynthetic precursor 3-deoxyradicinin. Further studies showed that 3-deoxyradicin displays phytotoxic activity against buffelgrass and antibacterial activity against X. fastidiosa comparable with those of radicinin. These results allowed us propose both radicinin and 3-deoxyradicinin as potential natural pesticides which, conveniently bioformulated could be used to control of X. fastidiosa., IT; PDF; evidente@unina.it

In the last decades, intensive crop management has involved excessive use of pesticides or fertilizers, compromising environmental integrity and public health. Accordingly, there has been worldwide pressure to find an eco-friendly and safe strategy to ensure agricultural productivity. Recently, Plant Growth-Promoting (PGP) rhizobacteria are receiving increasing attention as suitable biocontrol agents against agricultural pests. In the present study, 22 spore-forming bacteria were selected among a salt-pan rhizobacteria collection for their PGP traits and their antagonistic activity against the plant pathogen fungus Macrophomina phaseolina. Based on the higher antifungal activity, strain RHFS10, identified as Bacillus vallismortis, was furtherly examined and cell-free supernatants assays, column purification, and tandem mass spectrometry employed to purify and preliminarily identify the antifungal metabolites. Interestingly, the minimum inhibitory concentration assessed for the fractions active against M. phaseolina, resulted 10 times lower and more stable than the one estimated for the commercial fungicide pentachloronitrobenzene. These results suggest the use of B. vallismortis strain RHFS10 as a potential Plant Growth Promoting Rhizobacteria to efficiently control phytopathogenic fungus M. phaseolina, in alternative to chemical pesticides.

Botryosphaeria dieback is one of the main trunk diseases of grapevine caused by several species of Botryosphaeriaceae. Twenty-four fungal isolates representing the eight most widespread and most virulent Botryosphaeriaceae were tested for their ability to produce phytotoxic metabolites. The chromatographic profiles of their culture filtrates organic extracts showed the ability of all isolates to produce several and different metabolites. When tested on grapevine leaves and tomato cuttings the organic extracts phytotoxicity varied among isolates and species. To our knowledge, this is the first study on phytotoxic compounds produced by Botryosphaeriaceae species found in Australian vineyards. The phytotoxic metabolites produced by Diplodia seriata, Diplodia mutila, Neofusicoccum australe and, for the first time, by Neofusicoccum luteum were isolated and chemically identified essentially by spectroscopic methods.

Supplemental material, Supplementary data, for A Brief Up-to-Date Overview of Amaryllidaceae Alkaloids: Phytochemical Studies of Narcissus tazetta subsp. tazetta L., Collected in Turkey by Çiğdem Karakoyun, Marco Masi, Alessio Cimmino, Mustafa Ali Önür, Nehir Unver Somer, Alexander Kornienko, and Antonio Evidente in Natural Product Communications

Trabajo presentado en el XXXIX Convegno Nazionale della Divisione di Chimica Organica della Società Chimica Italiana, celebrado en Turín del 8 al 12 de septiembre de 2019., A number of parasitic plants have adapted to agricultural environments becoming weedy and posing a serious threat to important crops. Available control measures rely heavily on use of synthetic herbicides. The side effects on environmental pollution and food health of chemical control prompted studies to find alternative strategies based on the use of natural products. Some sesquiterpene lactones named inuloxins A-D, belonging to different subgroup as germacrane, eudesmane and seco-eudesmane, were isolated from the aerial parts of Dittrichia viscosa (family Asteraceae) and showed to stimulate seed germination leading to suicidal germination, or inhibit germination or disrupting germling growth and haustorium development. The absolute configuration (AC) of inuloxin A was determined by chiroptical and computational methods. The same methods were successively used to assign the AC to inuloxin C, while studies are in progress to assign that of inuloxin D. Recently, considering the potential herbicidal activity of inuloxin A, it was formulated in β-cyclodextrins to overcome its low water solubility and preserving its ability to inhibit Phelipanche ramosa seed germination. In this communication, the purification of other germination stimulants and/or inhibitors of parasitic seed germination, isolated from the same plant, will be illustrated as well as the results of structureactivity relationship studies comparing the biological activity of the natural sesquiterpenoids to that of some their hemisynthetic derivatives.

Botryosphaeria dieback is one of the main trunk diseases of grapevine caused by several species of Botryosphaeriaceae. Twenty-four fungal isolates representing the eight most widespread and most virulent Botryosphaeriaceae were tested for their ability to produce phytotoxic metabolites. The chromatographic profiles of their culture filtrates organic extracts showed the ability of all isolates to produce several and different metabolites. When tested on grapevine leaves and tomato cuttings the organic extracts phytotoxicity varied among isolates and species. To our knowledge, this is the first study on phytotoxic compounds produced by Botryosphaeriaceae species found in Australian vineyards. The phytotoxic metabolites produced by Diplodia seriata, Diplodia mutila, Neofusicoccum australe and, for the first time, by Neofusicoccum luteum were isolated and chemically identified essentially by spectroscopic methods.

Rusts are a noxious group of plant diseases affecting major economically important crops. Crop protection is largely based on chemical control. There is a renewed interest in the discovery of natural products as alternatives to synthetic fungicides for control. In this study we tested two fungal metabolites, namely cyclopaldic acid and epi-epoformin, for their effectiveness in reducing early stages of development of two major rust fungi from the genera Puccinia and Uromyces, P. triticina and U. pisi. Spore germination and appressorium formation were assessed on pretreated detached leaves under controlled conditions. Cyclopaldic acid and epi-epoformin were also tested in infected plants in order to evaluate the level of control achieved by treatments both before and after inoculation.

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017., Pea weevils (Bruchus pisorum) is a pest of the field pea (Pisum sativum) of great economic importance. Recently, pea accessions have been reported to reduce seed infestation, and/or larval development. Pods and seeds from these accessions were collected to check constitutive metabolites able to block the egg lying on pods (seed infestation) while pea seeds to check metabolites hampering larval development. Pea pods and seeds were lyophilized in order to evaluate metabolites that may be involved in pea weevil infestation. Standard method for metabolomics analysis was carried out on lipophilic and hydrophilic metabolites extracted, then compared to find a biomarker of resistance in pea. In this communication the studies aimed to identify metabolites responsible for antixenosis and/or antibiosis in pea resistant accessions to weevils will be discussed.

Trabajo presentado en el 15th Congress of the Mediterranean Phytopathological Union (Plant health sistaining Mediterranean ecosystems), celebrado en Córdoba (España) del 20 al 23 de junio de 2017., Foliar diseases caused by biotrophic pathogens, such as rusts and powdery mildews, are major limiting factors in legume and cereal production worldwide. Crop protection is largely based on chemical control, although there is renewed interest in the discovery of natural products as alternatives to synthetic fungicides., This research was supported by FP7-ARIMNet-MEDILEG and AGL2014-52871 projects and Programme STAR (A.C.) financially supported by UniNa and Compagnia di San Paolo, Italia.

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017., Fusarium oxysporum f. sp. pisi (Fop) is a ubiquitous soil pathogen reducing field pea (Pisum sativum) yield worldwide. Monogenic resistance have been already described and successfully used in breeding. However, monogenic resistance is at risk of breakdown by the constant evolution of the pathogen. To improve the durability of resistance, the genetic base of resistance should be broadened and a better knowledge on the defense mechanisms efficient against Fop should be gathered. To this aim, we identified several Fop-resistant Pisum spp. accessions and characterized the underlying defense mechanisms. A first study on pre-penetration mechanism revealed that the root exudate of three accessions inhibited Fop germination. Further analyses indicated that this pre-penetration mechanism was mainly mediated through the constitutive secretion of pisatin, the main pterocarpan pea phytoalexin. A second study focused on post-penetration defense mechanism at the cellular level, showing that involvement of three main mechanisms, namely papilla formation, cell walls strengthening and accumulation of phenols and carbohydrates. These studies highlight that pea accessions combined several strate gies to delay and efficiently prevent disease development which offer interesting opportunities for breeding.

Trabajo presentado en el 15th Congress of the Mediterranean Phytopathological Union (Plant health sistaining Mediterranean ecosystems), celebrado en Córdoba (España) del 20 al 23 de junio de 2017., Root exudates are important regulators of plant rhizospheres. They can modulate the composition and dynamics of soil micro-organisms and participate in the dialogue between plants and microorganisms. They are known to modulate germination and growth of soil microorganisms. As such, they may contribute to crop resistance to soil-borne pathogens., This research was supported by the European KBBE project LEGATO (FP7-KBBE2013.1.2-02-613551), and the Spanish national project AGL2014-52871-R from the Spanish Ministry of Economy and Competitiveness (MINECO), and was co-financed by the European fund for regional development (FEDER). NR holds a Ramón y Cajal postdoctoral position from MINECO.

Trabajo presentado en la 4th Annual Conference of the COST action SUSTAIN, celebrada en Bled (Slovenia) del 1 al 3 de marzo de 2017., Ascochyta and Botrytis species cause major diseases on legume crops. Fungi from both genera are well known phytotoxins producers. Based on collaboration between CSIC and Univ. Naples necrotrophic effectors produced by Didymella pinodes and Botrytis fabae have been identified and characterized chemically and biologically. Their use in resistance screenings are being tested and will be critically discussed.

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017., Rusts and powdery mildews are major limiting factors worldwide for many crops, including legumes. Despite of continued efforts to develop cultivars with high level of genetic diseases resistance, fungicides are, currently, the mainstay control method and a wide range of synthetic compounds are widely used. However, a renewed interest in the discovery of natural products as alternatives to synthetic fungicides application is recently emerged. Considering that spore germination and fungal penetration are key phases for the initial development of biotrophic plant pathogens, a further approach proposed for their management could be the use of natural metabolites produced by plants and fungi as pathogen inhibitors in these pre-penetration stages. With this aim we studied potential application for disease management of eight fungal and plant metabolites. Their inhibitory effect on early stages infection was studied on 4 rusts and 2 powdery mildew species. Results will be presented and critically discussed., This research was financially supported by AGL2014-52871 projects and Programme STAR financially supported by UniNa and Compagnia di San Paolo, Italy.

Although fungi produce highly structurally diverse metabolites, many of which have served as excellent sources of pharmaceuticals, no fungi-derived agent has been approved as a cancer drug so far. This is despite a tremendous amount of research being aimed at the identification of fungal metabolites with promising anticancer activities. This review discusses the results of clinical testing of fungal metabolites and their synthetic derivatives, with the goal to evaluate how far we are from an approved cancer drug of fungal origin. Also, because in vivo studies in animal models are predictive of the efficacy and toxicity of a given compound in a clinical situation, literature describing animal cancer testing of compounds of fungal origin is reviewed as well. Agents showing the potential to advance to clinical trials are also identified. Finally, the technological challenges involved in the exploitation of fungal biodiversity and procurement of sufficient quantities of clinical candidates are discussed, and potential solutions that could be pursued by researchers are highlighted.

A new 3-substituted-5-diazenylcyclopentendione named kongiidiazadione was isolated from culture filtrates of Diaporthe kongii, associated with stem cankers on sunflower in Australia. Kongiidiazadione was characterized by spectroscopic (essentially nuclear magnetic resonance [NMR] and high-resolution, electrospray ionization, mass spectrometry [HRESIMS]) methods as (-)-5-diazenyl-3-hydroxymethyl-cyclopent-3-en-1,2-dione. The stereochemistry of the diazenyl group was determined by IR spectroscopy, while the (R) absolute configuration at C(5) was assigned by computational analysis of its electronic circular dichroism (ECD) spectrum. When assayed on leaf disks of different plant species at 5 mM, the kongiidiazadione had a differential impact, causing clear necrosis, in particular to Helianthus annuus. Moreover, kongiidiazadione proved to have a weak antibacterial activity against gram-positive Bacillus amyloliquefaciens.

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, low-molecular 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.

Trabajo presentado en el Second International Legume Society Conference "Legumes for a sustainable world" (ILS2), celebrado en Tróia (Portugal) del 11 al 14 de octubre de 2016., Pea weevils (Bruchus pisorum) and pea aphids (Acyrthosiphon pisum) are insect pests of great economic importance for agriculture and represent one major cause of damage and loss in legume crops. Bruchus pisorum is specialist, feeding and developing almost exclusively on pea. Acyrthosiphon pisum feeds on several species of legumes worldwide and ranks among the aphid species in agriculture. Recently, germplasm collections of pea have been screened under field conditions to identify sources of resistance to weevils and aphids in pea. The identification of compounds with phagodeterrent activity, which are able to interfere with aphid host plant selection and host acceptance, is currently becoming of great interest for the design of innovative biotechnical strategies in control of phytophagous insects. In this communication results obtained on the identification of metabolites responsible for antixenosis and/or antibiosis in pea resistant accessions to weevils and aphids will be reported. The effect of natural metabolites against these pests will be discussed, too.

Trabajo presentado en el Second International Legume Society Conference "Legumes for a sustainable world" (ILS2), celebrado en Tróia (Portugal) del 11 al 14 de octubre de 2016., Despite their importance for the agriculture and the environment, the production of food legumes is decreasing in most of the Mediterranean farming systems. A major cause for this is the low and irregular yield as a consequence of biotic and abiotic stresses. Necrotrophic fungi, including essentially Ascochyta and Botrytis species, are among the main biotic constraints. Both fungal genus are well known phytotoxins producers. These toxins, belonging to different classes of natural compounds, are frequently involved in the development of disease symptoms. In this communication the chemical and biological characterization of the necrotrophic effectors produced by Didymella pinodes and Botrytis fabae pathogens of pea and faba bean respectively, will be reported. Furthermore, the studies aimed to identify novel resistance sources in the respective hosts in sensitivity assays will be discussed, too.

Trabajo presentado en la COST action FA1206 meeting (STRigolactons Enhance Agricultural Methodologies), celebrado en Ashdod (Israel) del 14 al 16 de marzo de 2016.

A time-dependent Density Functional Theory (TDDFT) computational simulation of the electronic circular dichroism (ECD) spectrum of the phytotoxin scytalone (1), produced by different plant pathogenic fungi and involved in melanin production, was undertaken with the aim to establish a nonempirical correlation between the spectrum and the absolute configuration of this compound. In fact, very low optical rotation data of 1 do not afford a reliable absolute configuration assignment while, on the contrary, the use of ECD can provide a useful tool for its stereochemical description. This structurally simple molecule displayed a considerable molecular flexibility, which made it mandatory to obtain an accurate conformers distribution to get a good reproduction of the experimental ECD spectrum. Only the application of an implicit integral equation formalism Polarizable Continuum Model (IEF-PCM) solvation model in the calculations allowed us to properly describe the conformer populations and finally obtain a more than satisfactoryspectral simulation.

Pseudomonas tolaasii, P. reactans and Burkholderia gladioli pv. agaricicola, are responsible of diseases on some species of cultivated mushrooms. The main bioactive metabolites produced by both Pseudomonas strains are the lipodepsipeptides (LDPs) tolaasin I and II and the so called White Line Inducing Principle (WLIP), respectively, LDPs which have been extensively studied for their role in the disease process and for their biological properties. In particular, their antimicrobial activity and the alteration of biological and model membranes (red blood cell and liposomes) was established. In the case of tolaasin I interaction with membranes was also related to the tridimensional structure in solution as determined by NMR combined with molecular dynamic calculation techniques. Recently, five news minor tolaasins, tolaasins A-E, were isolated from the culture filtrates of P. tolaasii and their chemical structure was determined by extensive use of NMR and MS spectroscopy. Furthermore, their antimicrobial activity was evaluated on target micro-organisms (fungi-including the cultivated mushrooms Agaricus bisporus, Lentinus edodes, and Pleurotus spp.-chromista, yeast and bacteria). The Gram positive bacteria resulted the most sensible and a significant structure-activity relationships was apparent. The isolation and structure determination of bioactive metabolites produced by B. gladioli pv. agaricicola are still in progress but preliminary results indicate their peptide nature. Furthermore, the exopolysaccharide (EPS) from the culture filtrates of B. gladioli pv. agaricicola, as well as the O-chain and lipid A, from the lipopolysaccharide (LPS) of the three bacteria, were isolated and the structures determined.

Fungi belonging to the Botryosphaeriaceae family are well known as cosmopolitan pathogens, saprophytes and endophytes and occur on a wide range of hosts including grapevine. Grapevine disease symptoms caused by members of this family include leaf spots, fruit rots, shoot dieback, bud necrosis, vascular discoloration of the wood, and perennial cankers (1). The nature and appearance of wood symptoms caused by these pathogens suggest that phytotoxic metabolites could be involved in the host–pathogen interaction. For example phytotoxins such as (3R,4R)-(-) and (3R,4S)-(-)-4-hydroxymelleins, isosclerone and tyrosol has been isolated and identified from a strain of Neofusicoccum parvum isolated from symptomatic grapevines in Catalogna (2). Another species, N. australe involved in the aetiology of grapevine cordon dieback in Italy, showed to produce in vitro structurally different secondary metabolites. The main phytotoxin, named cyclobotryoxide, was characterized as a new cyclohexenone oxide (1). It was produced together with 3-methylcatechol and tyrosol (3).In addition, the species Diplodia seriata showed to produce already known melleins as (3S,4R)-4-hydroxymellein, (3S)-7-hydroxymellein and a new one characterized as (3S,4R)-4,7-dihydroxymellein (4). More recently, a new species of Lasiodiplodia was isolated from declining grapevines in Sardinia (Italy). This still undescribed species showed to produce in liquid culture several phytotoxic secondary metabolites. In this communication the chemical and biological characterization of these bioactive secondary metabolites is discussed together with their role in the pathogenesis process. (1) ÚRBEZ-TORRES, J.R. Phytopathol. Mediterr. 2011, 50, S5-S45. (2) EVIDENTE, A.; PUNZO, B.; ANDOLFI, A.; CIMMINO, A.; MELCK, D.; LUQUE, J. Phytopathol. Mediterr. 2010, 49, 74-79. (3) ANDOLFI, A.; MADDAU, L.; CIMMINO, A.; LINALDEDDU, B.T.; FRANCESCHINI, A.; SERRA, S.; BASSO, S.; MELCK, D.; EVIDENTE, A. J. Nat. Prod. 2012, 75, 1785-1791. (4) ANDOLFI, A.; MUGNAI, L.; LUQUE, J.; SURICO, G.; CIMMINO, A.; EVIDENTE, A. Toxins 2011, 3, 1569-1605.

Phytotoxins are secondary microbial metabolites that play an essential role in the development of disease symptoms induced by fungi on host plants. Although phytotoxins can cause extensive—and in some cases devastating—damage to agricultural crops, they can also represent an important tool to develop natural herbicides when produced by fungi and plants to inhibit the growth and spread of weeds. An alternative strategy to biologically control parasitic plants is based on the use of plant and fungal metabolites, which stimulate seed germination in the absence of the host plant. Nontoxigenic fungi also produce bioactive metabolites with potential fungicide and insecticide activity, and could be applied for crop protection. All these metabolites represent important tools to develop eco-friendly pesticides. This review deals with the relationships between the biological activity of some phytotoxins, seed germination stimulants, fungicides and insecticides, and their stereochemistry

Trabajo presentado en el First International Congress on Strigolactones, celebrado en Wageningen (Holanda) del 1 al 6 de marzo de 2015., Several broomrapes are economically damaging on temperate legume crops, being Orobanche crenata, O. foetida, O. minor and Phelipanche aegyptiaca the most important ones. A better understanding the host/parasite interaction will provide new targets for management and breeding. Here we will concentrate in broomrape seed germination, which might be stimulated or inhibited by chemicals released to the rhizosphere by the plant roots. A number of strigolactones may stimulate germination in a species-specific manner, playing a major role in host specificity. Faba bean and pea accessions that do not induce broomrape seed germination are now available. In pea, there is a range of strigolactone deficient mutants that could be exploited in pea breeding. In faba bean, a number of well adapted breeding lines have been produced now whose resistance is based in low broomrape seed stimulation. This is operative against O. crenata, O. foetida and P. aegyptiaca and is associated with low strigolactone exudation. In addition to these, a number of metabolites different from strigolactones (i.e. peagol, peagoldione, peapolyphenols, soyasapogenol B, trans-22-dehydrocampesterol) have been indentified in pea and common vetch root exudates showing a species-specific stimulation of Orobanche seed germination. These metabolites could be exploited in suicidal germination control strategies by synthesizing and directly applying them to the field. In addition, breeding for high root exudation levels of germination stimulants could identify better candidates for trap crops to be used in a suicidal germination control strategy. For instance, pea is only infected by O. crenata but pea root exudates stimulate germination of P. aegyptiaca, O. foetida and O. minor to which pea is resistant. But communication with broomrape in the rhizosphere does not restrict to the crop plant. Accompanying crops or weeds could also play a relevant role. It has recently been shown that intercrops of temperate grain legumes with a number of crops such as cereals, fenugreek or berseem clover can reduce O. crenata infection being allelopathy a major component for the reduction. Several metabolites with inhibitory effect have been identified in the root exudates of various plants, such as trigoxazonane from fenugreek, ryecyanatines and ryecarbonitrilines from rye that might be responsible for inhibition of O. crenata seed germination. Therefore, breeding for allelopathic potential is another potential target for breeding.

Trabajo presentado en el 13th World Congress on Parasitic Plants (Parasitic plants: the good, the bad, and the mysterious), celebrado en Kunming (China) del 5 al 10 de julio de 2015., Broomrapes (Orobanche and Phelipanche spp.) and dodders (Cuscuta spp.), belonging to Orobanchaceae and Convolvulaceae families, respectively, are parasitic weeds infesting a large number of important crops and causing severe yield losses. The main obstacle for long-term management of broomrape infested fields is the durable seed bank with evolved mechanisms of host recognition upon perception of host-derived germination factors. The continuous spread of broomrapes and dodders strongly affect on the farmers work as heavy infestations lead not only to a complete crop failure, but also have a great negative impact over many years, because seeds can survive in soil for a long period of time. Although a large number of certain agronomic practices have been proposed, effective management of parasitic weeds is very difficult to be reached because of their physiological traits and life cycle. Current control relies on the use of resistant crop varieties and herbicides, albeit success has been marginal. Considering that seed germination is a key phase for parasitic plant development and infestation, a further approach proposed for the management of these weeds has been to use microbial or plant metabolites to stimulate, in absence of the host, and/or inhibit the broomrape seed germination. Some metabolites induced a rapid cessation of radicle growth with the promotion of a layer of papillae at the radicle tip hampering the contact of the parasite to the host. The development of herbicides based on natural metabolites from microbial and plant origin, targeting early stages on parasitic plant development, might contribute to the reduction of broomrape seed bank in agricultural soils. Plant and fungal metabolites were also evaluated for their inhibitory effects on germination and growth of dodder species. This communication will illustrates the results obtained in the isolation and chemical characterization of some plants, plant root exudates and fungal metabolites and their effect on the seed germination of different broomrape and dodder species, to develop alternative and ecofriendly strategies for the management of these dangerous parasitic plants.

Trabajo presentado en el First International Congress on Strigolactones, celebrado en Wageningen (Holanda) del 1 al 6 de marzo de 2015., Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing heavy yield losses on important crops. Current control relies on the use of certain agronomic practices, resistant crop varieties, and herbicides, albeit success has been marginal. Agronomic practices such as the use of allelopathic species in intercropping or cover crops, or the use of direct seedling over residues of allelopathic species incorporate the principle of allelopathy exerted by molecules exuded from roots or released by crop residues to control broomrapes. The isolation of natural substances from root exudates of plants with potential to stimulate or inhibit broomrape development opens the door to the design of new herbicides based on natural and benign sources. In addition, some fungal metabolites exhibited the ability to stimulate and/or inhibit the broomrape seed germination and promotes a rapid cessation of radicle growth with the promotion of a layer of papillae at the radicle tip hampering the contact of the parasite to the host. This communication will illustrates the results obtained in the isolation and chemical characterization of several plants, plant root exudates and fungal metabolites and the results of testing them on the seed germination of different Orobanche and Phelipanche species with the aim to develop alternative and eco friendly strategies to control these very dangerous parasitic plants.

Recently, several Botryosphaeriaceae spp. have been associated with grapevine decline symptoms worldwide including dieback, cankers and characteristic wedgeshaped necrosis in arms and trunks. An increasing number of species including Neofusicoccum parvum have been shown to produce phytotoxic secondary metabolites in vitro, both lipophilic low molecular weight compounds and high molecular weight exopolysaccharides (EPSs), some of which appeared structurally different from previously reported botryosphaerans. Preliminary results on the chemical and biological characterization of these EPSs were previously reported and compared with EPSs produced by Phaeomoniella chlamydospora, a fungus associated with grapevine esca complex along with Phaeoacremonium spp. In this communication, the progress on the chemical and biological characterization of EPSs produced by N. parvum and P. chlamydospora will be reported, as well as the results on the characterization of the EPSs produced by N. australe.

Elytrigia repens L. Desv. ex Nevski (commonly known as quack grass), is a perennial weed widespread through the cold temperate regions all over the world. It is managed only by chemical herbicides1,2 because it easily spreads by seed and rhizomes and produces allelopathic metabolites suppressing the growth of other plants. In surveys carried out with the aim to find pathogens of this species, which could have potential as biological agents for its control, a fungus was isolated from naturally diseased leaves of this species and identified as Ascochyta agropyrina (Fairman) Trotter var. nana Punith. Due to the interest of the authors in studying species belonging to the genus Ascochyta as sources of biologically active metabolites, a previous study led to the isolation of a main phytotoxin from the solid culture of this fungus and to its identification as papyracillic acid.3 On liquid medium A. agropyrina produces different toxins the main one of which, named agropyrenol, was characterized as a new disubstituted benzaldehyde on the basis of its chemical and spectroscopic properties. Other two new 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. When assayed on leaves of some weedy 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 compounds showed antibiotic, fungicidal or zootoxic activity. In this communication the production, isolation, and chemical and biological characterization of the metabolites produced by A. agropyrina var. nana in liquid culture will be illustrated and their potential as safe herbicides will be discussed.

Pinolidoxin, 2-hexadionoyloxy-7-hydroxy-9-propyl-5-nonen-9-olide, is the first phytotoxic nonenolide, isolated from some of us on 1993, together three minor ones as the main toxin produced by Ascochyta pinodes.1 This is the fungal causal agent of pea anthracnose. Successively, phytotoxic nonenolide as putaminoxin, the main one, the close related putaminoxins B-D were also isolated from Phoma putaminum, the fungus proposed as mycoherbicide to biological control Erigeron annuus, a widespread weed in the pasture of northern emisphere.2 Later, stagonolide, a new nonenolide, was also isolated as the main toxin from liquid culture of Stagonospora cirsii proposed for the biological control of Cirsium arvense and Sonchus arvensis, two very noxious perennial weeds of several agrarian crops, essentially cereals. Successively nine related new nonenolides were isolated together to the well known modiolide A, from solid cultures of the same fungus.3 So that some studies were carried out using the toxins some their natural analogues and hemisynthetic derivatives to carry out studies on the structure-activity relationships and on their mode of action.4 Recently, from a strain of Ascochyta pinodes isolated in Spain from infected pea and grown in liquid culture were isolated herbarumin II, and 2-epi-herbarumin II together with a new nonenolide, named pinolide. In this communication an overview on the phytotoxic fungal nonenolides will be illustrated as well as the chemical and biological characterization of pinolide and the potential practical application of some of them as natural eco-friendly herbicides.

Fungal trunk diseases have become a growing threat to viticulture throughout the world. Recent studies revealed that species in the Botryosphaeriaceae family include some of the main pathogens involved in grapevine canker, dieback and decline in most grape-growing regions of Northern and Southern hemispheres. A field survey conducted in a grape-growing area located in northern Sardinia (Italy) detected Neofusicoccum australe as one of the main fungal pathogens associated with grapevine cordon dieback. The nature and appearance of wood symptoms caused by this pathogen suggested that phytotoxic metabolites could be involved in the host-pathogen interaction. To our knowledge, no data are available in the literature on the production of phytotoxic metabolites by N. australe strains involved in grapevine trunk diseases. Thus, a highly virulent isolate of N. australe was examined for its ability to produce in vitro phytotoxic secondary metabolites. For this purpose, the fungus was grown in liquid culture. The culture filtrate and the corresponding organic extract showed to be highly phytotoxic when assayed on host and non-host plants by cutting and leaf puncture assay. This communication reports the chemical and biological characterization of phytotoxic metabolites produced in liquid culture by N. australe isolated in Sardinia from grapevine and other host plants. Their role in the disease will be discussed.

Sphaeropsidins A (1), B (7) and C (10), three fungal phytotoxins, unrearranged pimarane diterpenes produced by Diplodia cupressi and 10 semisynthetic derivatives were evaluated for their in vitro anticancer activities. Among these 13 compounds, sphaeropsidin A and two derivatives (2 and 6) thereof display 50% growth-inhibitory concentration in the low micromolar range for all cell lines analyzed. Structure activity relationship paralleled the phytopathogenic and antimicrobial ones except regarding the vinyl group at C-13 that does not seems to be required as it is for their antipathogenic activity

BACKGROUND: Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing severe yield losses on important crops. Control strategies have largely focused on agronomic practices, resistant crop varieties and herbicides, albeit with marginal success. An alternative control method is the induction of suicidal seed germination with natural substances isolated from root exudates of host and non-host plants. RESULTS: Soyasapogenol B [olean-12-ene-3,22,24-triol(3β,4β,22β)] and trans-22-dehydrocampesterol [(ergosta-5,22-dien-3-ol, (3β,22E,24S)] were isolated from Vicia sativa root exudates. They were identified by comparing their spectroscopic and optical properties with those reported in the literature. Soyasapogenol B was very specific, stimulating the germination of O. minor seeds only, whereas trans-22-dehydrocampesterol stimulated P. aegyptiaca, O. crenata, O. foetida and O. minor. CONCLUSION: Soyasapogenol B and trans-22-deydrocampesterol were isolated for the first time from Vicia sativa root exudates, and their biological activity as stimulants of Orobanche or Phelipanche sp. seed germination was reported.

Perennial weeds, including Cirsium arvense and Sonchus arvensis, are a common problem in crop fields, especially in agricultural systems with reduced herbicide usage. Herbicides recommended for control of these perennials generally are restricted to only a few active ingredients that tend to have low selectivity, especially on dicot crops. Microbial phytotoxins or their synthetic analogues may be candidates for new weed-control options. Many plant pathogens, especially necrotrophic or hemibiotrophic fungi, produce a range of phytotoxins responsible for disease damage and may be a source of such useful metabolites. Several pathogens, including Stagonospora cirsii and Ascochyta sonchi, were found commonly on C. arvense and S. arvensis, and these fungi also produce phytotoxic metabolites. Phyllosticta cirsii and Phomopsis cirsii, belonging to two well-known toxin-producing genera, have also been proposed for biocontrol of C. arvense. Phytotoxins isolated from these fungal pathogens are metabolites belonging to several classes of natural compounds including enol pyruvic acid derivatives, cytochalasins, nonenolides, oxazatricycloalkenones, pentasubstituted bicyclooctatrienyl ester of acetic acid, pentasubstituted hexahydrobenzodioxine carboxylic acid methyl ester, and β-nitropropionic acid. Some of these metabolites may be used as biomarkers, for studies on mode of action and development of structure-activity relationships.

Total ascorbic acid (total-AsA) content and percentage of reduced ascorbic acid (AsA) on total-AsA were investigated and discussed in fruits, leaves, petiole, stem and roots of the Solanum lycopersicum cv M82 and S. pennellii introgression lines IL7-3, IL10-1 and IL12-4. In fruits, total-AsA content showed to be different according to genotype analysed. Higher total-AsA accumulations were observed for IL7-3 and IL12-4 followed by M82 and IL10-1. Total-AsA was generally higher in leaves than in petioles, stems and roots of all genotypes. In roots higher total-AsA concentration and lower AsA percentage was generally observed in introgression lines than M82, in particular for IL7-3.

Trabajo presentado en el 10th Spanish-Italian Symposium of Organic Chemistry (SISOC-X), celebrado en Firenze del 17 al 20 de julio de 2014., Food legumes are annual and multifunctional crops with extraordinary historical importance for the agriculture and the environment of the Mediterranean basin. They are protein-rich and integral part of the Mediterranean diet. Besides, they are used for animal feed and fodder. Grown in rotation with cereals, they improve significantly soil fertility and minimise the use of inorganic nitrogen fetiilizers, contributing to a sustainable and environmentally friendly agriculture in the region. Despite their impotiance, the production of food Iegumes is decreasing in most of the Mediterranean farming systems. A major cause for this is the low and irregular yield as a consequence of biotic and abiotic stresses. The major biotic stress is represented by phytopathogenic fungi belonging to species well known as phytotoxin producers. In this communication we will illustrate the chemical and biological characterization of the phytotoxins produced by Botrytis fabae, the causal agent of chocolate spot of faba bean, and Didymella pinodes, and D. lentis the causal agents of Ascochyta blights of pea and lentil, respectively. For some phytotoxins. the relation between absolute stereochemistry and phytotoxicity will be reported, too.

Trabajo presentado en el 10th Spanish-Italian Symposium of Organic Chemistry (SISOC-X), celebrado en Firenze del 17 al 20 de julio de 2014., Orobanche and Phelipanche species (the broomrapes) are parasitic plants, some of which represent serious weed problems and cause yield reduction of many important crops. The main opstacle for long term management of broomrape infested fields is the durable seedbank. lndeed, seeds of these parasites m ay remain dormant in the soil for many years until the germination is stimulated by a chemical signal exuded by roots of a host plant. Various approaches are possible for seedbank demise including fumigation, solarization, suicidal germination, catch and trap crops and biological control. However, in practice broomrape control relies mainly on chemicals. There is a need for novel, effective and environmentally compatible alternatives as to develop natural product based pesticides to control broomrapes. In this communication we will describe the chemical characterization of metabolites isolated from some host and non-host plant root exudates and their capability to inhibit and/or stimulate germination and radical growth of Orobanche spp. seeds in a differential manner.

Stagonospora cirsii Davis, a fungal pathogen isolated from Cirsium arvense (commonly called Canada thistle) and proposed as a potential mycoherbicide of this perennial noxious weed, produces phytotoxic metabolites in liquid and solid cultures. Stagonolide, the main phytotoxic metabolite, and five new related nonenolides, named stagonolides B-F, were isolated from the fungus. When grown on solid culture, nonenolide yields increased. A further four nonenolides were isolated and characterized by spectroscopy. Three were new compounds and named stagonolides G-I, and the fourth was identified as modiolide A, previously isolated from Paraphaeosphaeria sp., a fungus separated from the horse mussel. Leaf disk-puncture assays at 1 mg/mL of stagonolides H-I and modiolide A were phytotoxic to C. arvense. Only stagonolide H inhibited chicory seedling root growth. The most potent toxin, stagonolide H, indicated selectivity when tested on leaves of eight different plants: Canada thistle was most sensitive to the compound.