Emilio Hormazabal

Antifungal activity of volatile metabolites emitted by mycelial cultures of saprophytic fungi

The antifungal activity of molecular identified Chilean saprobiontic fungi, Trichoderma viride, Schizophyllum commune and Trametes versicolor, on the fungal plant pathogens Botrytis cinerea and Fusarium oxysporum, and the saprotrophic mould Mucor miehei was investigated using two types of inhibition bioassay: (1) bi-compartmented Petri dishes and (2) two Erlenmeyer flasks connected by their upper parts. The chemical composition of volatile organic compounds (VOCs) released by saprobiontic fungi was also investigated using headspace solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC-MS) analysis. Of the saprobiontic fungi evaluated, one isolate of S. commune showed the highest inhibitory activity against B. cinerea and M. miehei, 86.0±5.4 and 99.5±0.5% respectively. The volatile profiles of fungal isolates were shown to contain a different class of compounds. The major components in the headspace of mycelial cultures were 6-pentyl-α -pyrone (T. viride), ethanol and β -bisabolol (S. commune), and a sesquiterpene alcohol (Tr. versicolor). This is the first study reported on the release of VOCs by Chilean native fungi and their antifungal activity wrt. plant pathogenic fungi.

Olfactory response of Haematobia irritans (Diptera: Muscidae) to cattle-derived volatile compounds.

ABSTRACT In Chile, the horn fly, Hematobia irritans (L., 1758), is a major pest of grazing cattle and affects livestock production during the summer. Previous studies in Europe and the United States have shown that cattle flies, including H. irritans, are differentially attracted to individual cattle within herds and that volatile semiochemicals are responsible for this phenomenon. This study provides evidence that similar differential attractiveness occurs for the interaction between Chilean Holstein-Friesian cattle herds and local H. irritans populations. Thus, Holstein-Friesian dairy cattle, Bos taurus, which were of similar age and physiological condition, were shown to possess an uneven distribution of H. irritans. Heifers h6904 and h8104 were defined as low-carrier heifers and h5804, h2304 and h1404 as high-carrier heifers. Gas chromatography (GC) and coupled GC-mass spectrometric (GC-MS) analysis of samples collected from heifers revealed the presence of compounds previously reported as semiochemicals for cattle flies, including meta- and para-cresol, methylketones (C8–C11), and 6-methyl-5-hepten-2-one. Other compounds identified included carboxylic acids (butanoic, 3-methylbutanoic, pentanoic, and hexanoic acids), 1-hexanol, and 3-octanone. In Y-tube olfactometer studies, both m- and p-cresol attracted H. irritans at the highest doses tested (10-6 g), as did the positive control l-octen-3-ol. Of the other compounds tested, only 2-decanone and 2-undecanone produced a behavioral response, with significantly more flies being recorded in the control arm when the former compound was tested (at 10-6 and 10-8 g), and more flies being recorded in the treated arm for the latter compound (at 10-7 g). This demonstration of behavioral activity with the identified compounds represents a first step for research into the application of semiochemicals in monitoring and control of cattle flies in Chile.

Fungal volatiles: an environmentally friendly tool to control pathogenic microorganisms in plants

Abstract Fungi are an extraordinary and immensely diverse group of microorganisms that colonize many habitats even competing with other microorganisms. Fungi have received recognition for interesting metabolic activities that have an enormous variety of biotechnological applications. Previously, volatile organic compounds produced by fungi (FVOCs) have been demonstrated to have a great capacity for use as antagonist products against plant pathogens. However, in recent years, FVOCs have been received attention as potential alternatives to the use of traditional pesticides and, therefore, as important eco-friendly biotechnological tools to control plant pathogens. Therefore, highlighting the current state of knowledge of these fascinating FVOCs, the actual detection techniques and the bioactivity against plant pathogens is essential to the discovery of new products that can be used as biopesticides.

Volatiles from white-rot fungi for controlling plant pathogenic fungi

Fungal volatile secondary metabolites play important roles in mediating antagonistic and beneficial interactions among organisms. The effects of eight strains of white-rot fungi cultured on potato waste against the mycelial growth of Botrytis cinerea, Fusarium oxysporum and Mucor miehei were investigated using a bi-compartmented Petri dish assay. The chemical composition of volatile organic compounds released from the strain with the highest inhibitory effect was also investigated by headspace solid-phase microextraction and gas chromatography/mass spectrometry analysis. Of the eight white-rot fungi evaluated, Anthracophyllum discolor. Sp4 showed a high inhibitory activity against M. miehei (approximately 76%) and B. cinerea (approximately 20%). F. oxysporum was inhibited to a lesser extent (approximately 10%) by A. discolor and T. versiscolor. The gas chromatography/mass spectrometry analysis showed nine main volatile compounds released from A. discolor Sp4, among them are the sesquiterpenesα-bisabolene and bulnesene, and the chlorinated aromatic compounds 1,5-dichloro-2,3-dimethoxybenzene, 3,5-dichloro-4-methoxybenzaldehyde and 3-chloro-4-methoxybenzaldehyde. Some of which have been reported previously with antimicrobial activity. The antifungal activity and volatile profile of A. discolor have not been previously reported.

Host Selection and Probing Behavior of the Poplar Aphid Chaitophorus leucomelas (Sternorrhyncha: Aphididae) on Two Poplar Hybrids with Contrasting Susceptibility to Aphids

ABSTRACT Poplars are frequently attacked by aphids. The differential susceptibility of poplar hybrids to the aphid Chaitophorus leucomelas Koch (Sternorrhyncha: Aphididae) has been described, but the mechanism underlying this pattern is unknown. This work tested the hypothesis that poplar resistance to this aphid is associated with the presence of volatiles and secondary plant compounds that affect host selection and feeding behavior. This hypothesis was tested by studying the host choice and feeding be havior of C. leucomelas on two poplar hybrids with contrasting susceptibilities to this aphid ([Populus trichocarpa Torrey & Gray × Populus deltoides Bartram ex Marshall] × P. deltoides [TD × D] , and [P. trichocarpa × Populus maximowiczii Henry] × [P. trichocarpa × P. maximowiczii] [TM × TM]). The results showed that C. leucomelas rejected leaves of the TM × TM hybrid and did not prefer odors from either hybrid. Electronic monitoring of the probing behavior of C. leucomelas suggested the involvement of antifeedant factors in the TM × TM hybrid. In addition, the chemical characterization of volatiles, epicuticular waxes, and internal phenols of leaves from both poplar hybrids revealed that TM × TM had a higher abundance of monoterpenes, sesquiterpenes, n-alkanes, and phenols. These results are discussed in terms of their contribution to poplar breeding programs aimed at enhancing insect resistance.

Antifungal activity of wheat root exudate extracts on Gaeumannomyces graminis var. Tritici growth

Wheat (Triticum aestivum L.) is known for its ability to produce and release al- lelopathic compounds, which have potential for controlling weeds and diseases. Previous reports have shown the fungitoxic effects of allelochemicals present in wheat. Thus, these compounds can be exuded by roots to protect the tissues directly affected by Gaeumannomyces graminis var. tritici (Ggt) fungus that causes wheat take-all disease. The aim of this research was to evaluate in vitro the allelopathic ef- fect of root exudate extracts from four Chilean wheat cultivars on Ggt growth. Root exudates were released from wheat seedlings to a sterile culture medium without nutrients. Afterward, the exudates in the culture medium were separated by liquid- liquid extraction using ethyl acetate. Eight different concentrations were tested for each cultivar. The results showed that the degree to which the extracts strongly in- hibit the phytopathogen growth is highly dependent on both the concentration and the cultivar. The root extract of the Domo cultivar was significantly active against Ggt (MIC=0.36 mg mL -1 ). IC 50 and MIC values obtained for Dollinco and Domo root exudate extracts showed toxicity to Ggt. These findings may be considered in future studies related to the use of allelopathic potential as a selection factor in order to reduce the yield losses caused by various take-all diseases, as an alternative to chemical controls.

Antifeedant activity of red clover root isoflavonoids on Hylastinus obscurus

In the last decade, there has been increasing interest in investigating the impact of flavonoids on insects, specifically for pest control. In this study, we investigated the impact of isoflavonoids upon the feeding behavior of the clover root borer, Hylastinus obscurus Marsham (Coleoptera: Curculionidae), which is one of the most serious global pests associated with red clover, Trifolium pratense L. Four aglycones isoflavonoids: genistein (1), formononetin (2), daidzein (3) and biochanin A (4) were isolated and identified by HPLC, from roots of two Chilean red clover cultivars. The first two compounds, formononetin (2) and genistein (1), showed high feeding deterrent activity when they were evaluated in artificial diets. This antifeedant effect of isoflavones on feeding behavior of H. obscurus suggests that they are responsible for a decreasedin insect weight gain as compared with the control. This information could be useful respectively, to farmers and researcher to produce and create plants resistant to curculionid

Production of ligninolytic enzymes and some diffusible antifungal compounds by white-rot fungi using potato solid wastes as the sole nutrient source

The aim of this study was to evaluate the synthesis of ligninolytic enzymes and some diffusible antifungal compounds by white‐rot fungi (WRF) using peels or discarded potato as the sole nutrient source.

FATTY ACID IN ECTOPARASITE COPEPODS FROM SOUTHERN CHILE CALIGUS ROGERCRESSEYI BOXSHALL & BRAVO 2000, LEPEOPHTHEIRUS MUGILOIDIS VILLALBA & DURAN 1985 AND THE FREE-LIVING SPECIES TIGRIOPUS SP

This work presents the fatty acid composition of copepod species in southern Chile: two of them that are ectoparasites on Eleginops maclovinus (Caligus rogercresseyi and Lepeophtheirus mugiloidis) and one free-living species (Tigriopus sp.). C. rogercresseyi females from different hosts (Salmo salar and E. Maclovinus). Fatty acid methyl esters were determined with GC-MS. The studied species presented a wide variety of saturated, monounsaturated, and polyunsaturated fatty acids, with compounds having from 12 to 24 carbons. The studied species had different percentage compositions of the acids identifed. In all three species, palmitic (C16) and oleic (C18:1) fatty acids dominated the percentage concentrations. The highest percentage concentration (46.59 %) was found for palmitic acid in Tigriopus. Only the females of C. rogercresseyi analyzed were found to have myristoleic acid (C14:1). Stearic (C18) and oleic (C18:1) acids were present in both C. rogercresseyi males and females, but with different distributions. Oleic acid in females was 33.97 % and only 7.64 % in males, whereas stearic acid was 9.95 % in females and 21.51 % in males. The C. rogercresseyi on Patagonian blennie (Eleginops maclovinus) revealed 3.89% C20:4 and 9.60 % C20:5. Eicosapentaenoic and docosahexaenoic acids, detected only in the ectoparasitic copepods, had percentage concentrations of up to 10 %. The possible role of this fatty acid in the stimulation of innate fsh immunity is discussed.