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Background: Many Trichoderma species are applied as biofungicides and biofertilizers to agricultural soils to enhance crop growth. These filamentous fungi have the ability to reduce plant diseases and promote plant growth and productivity through overlapping modes of action including induced systemic resistance, antibiosis, enhanced nutrient efficiency, and myco-parasitism. Trichoderma species are prolific producers of many small metabolites with antifungal, antibacterial, and anticancer properties. Volatile metabolites of Trichoderma also have the ability to induce resistance to plant pathogens leading to improved plant health. In this study, Arabidopsis plants were exposed to mixtures of volatile organic compounds (VOCs) emitted by growing cultures of Trichoderma from 20 strains, representing 11 different Trichoderma species.Results: We identified nine Trichoderma strains that produced plant growth promoting VOCs. Exposure to mixtures of VOCs emitted by these strains increased plant biomass (37.1-41.6 %) and chlorophyll content (82.5-89.3 %). Trichoderma volatile-mediated changes in plant growth were strain-and species-specific. VOCs emitted by T. pseudokoningii (CBS 130756) were associated with the greatest Arabidopsis growth promotion. One strain, T. atroviride (CBS 01-209), in our screen decreased growth (50.5 %) and chlorophyll production (13.1 %). Similarly, tomatoes exposed to VOCs from T. viride (BBA 70239) showed a significant increase in plant biomass (>99 %), larger plant size, and significant development of lateral roots. We also observed that the tomato plant growths were dependent on the duration of the volatile exposure. A GC-MS analysis of VOCs from Trichoderma strains identified more than 141 unique compounds including several unknown sesquiterpenes, diterpenes, and tetraterpenes. Conclusions:Plants grown in the presence of fungal VOCs emitted by different species and strains of Trichoderma exhibited a range of effects. This study demonstrates that the blend of volatiles produced by actively growing fungi and volatile exposure time in plant development both influence the outcome of volatile-mediated interactions. Only some of our growth promoting strains produced microbial VOCs known to enhance plant growth. Compounds such as 6-pentyl-2H-pyran-2-one were not common to all promoting strains. We found that biostimulatory strains tended to have a larger number of complex terpenes which may explain the variation in growth induced by different Trichoderma strains.

All odorants are volatile organic compounds (VOCs), i.e., low molecular weight compounds that easily evaporate at normal temperatures and pressure. Fungal VOCs are relatively understudied compared to VOCs of bacterial, plant, or synthetic origin. Much of the research to date on fungal VOCs has focused on their food and flavor properties, their use as indirect indicators of fungal growth in agriculture, or their role as semiochemicals for insects. In addition, research into fungal volatiles has also taken place to monitor spoilage, for purposes of chemotaxonomy, for use in biofilters and for biodiesel, to detect plant and animal disease, for "mycofumigation," and with respect to plant health. As methods for the analysis of gas phase molecules have improved, it has become apparent that fungal VOC are more chemically varied and more biologically active than has generally been realized. In particular, there is increasing data that show that fungal VOCs frequently mediate interactions between organisms within and across different ecological niches. The goal of this mini review is to orchestrate data on fungal VOCs obtained from disparate disciplines as well as to draw attention to the ecological importance of fungal VOCs in signaling between different species. Technologies and approaches that are common in one area of research are often unknown in others, and the study of fungal VOCs would benefit from more cross talk between subdisciplines.

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Prospective epidemiological studies of beach water pollution were conducted in Hong Kong in the summers of 1986 and 1987. For the main study in 1987, a total of 18741 usable responses were obtained from beachgoers on nine beaches at weekends. The study indicated the overall perceived symptom rates for gastrointestinal, ear, eye, skin, respiratory, fever and total illness were significantly higher for swimmers than non-swimmers; and the swimming-associated symptom rates for gastrointestinal, skin, respiratory and total illness were higher at 'barely acceptable' beaches than at 'relatively unpolluted' ones. Escherichia coli was found to be the best indicator of the health effects associated with swimming in the beaches of Hong Kong. It showed the highest correlation with combined swimming-associated gastroenteritis and skin symptom rates when compared with other microbial indicators. A linear relationship between E. coli and the combined symptom rates was established. Staphylococci were correlated with ear, respiratory and total illness, but could not be used for predicting swimming-associated health risks. They should be used to complement E. coli. The setting of health-related bathing-water quality standards based on such a study is discussed.