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<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>Plant growth-promoting microorganisms (PGPMs) stimulate plant growth by a series of mechanisms, including atmospheric nitrogen fixation, phosphorus solubilization and the synthesis of plant hormones. Within the group of PGPMs, several species of bacteria and fungi have been extensively studied. However, little information is available with regard to soil yeasts. The present study was conducted to identify yeast strains isolated from different soils in Chile that present plant growth promotion activity.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Twenty-three strains were evaluated either for their capacity to synthesize indole-3-acetic acid or show aminocyclopropane-1-carboxylate deaminase activity. The effect on tomato seedling growth was evaluated in vitro<jats:italic>,</jats:italic> and two strains were selected for in vivo evaluation of plant growth and root ethylene synthesis.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>All the strains analyzed presented IAA synthesis within the range between 0.8 and 3.3 μg IAA mL<jats:sup>−1</jats:sup>. <jats:italic>Solicoccozyma aeria</jats:italic> (YCPUC75 and YCPUC79 strains) was the only yeast with ACC deaminase activity. In vitro inoculation of tomato seeds with eight of the evaluated strains resulted in an increase in the root volume and the number of lateral roots. In the second experiment, a 40% reduction in root ethylene synthesis was achieved by adding <jats:italic>S. aeria</jats:italic> (YCPUC79) to the root zone, which resulted in a 26% increase in plant growth.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p><jats:italic>Solicoccozyma aeria</jats:italic> YCPUC79 is an effective plant growth promoter stimulating root growth and reducing root ethylene synthesis.</jats:p> </jats:sec>

<jats:title>Abstract </jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>The intake of selenium, an essential element for animals and humans, in ruminants is largely determined by selenium concentration in ingested forages, which take up selenium mainly from soil. Ruminant excreta is a common source of organic fertilizer, which provides both nutrients and organic matter. This study aims to unentangle the unclear effect of applying different types of ruminant excreta in soils of different organic matter contents on selenium uptake by forage.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Perennial ryegrass (<jats:italic>Lolium perenne</jats:italic>) was grown in soils of different organic matter contents. Urine and/or feces collected from sheep fed with organic or inorganic mineral supplements, including selenium, were applied to the soils. The selenium in the collected samples were analyzed using ICP-MS. The associated biogeochemical reactions were scrutinized by wet chemistry.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>The application of urine and/or feces resulted in either the same or lower selenium concentrations in perennial ryegrass. The excreta type did not affect total selenium accumulation in grass grown in low organic matter soil, whereas in high organic matter soil, feces resulted in significantly lower total selenium accumulation than urine, which was attributed to a possible interaction of selenium sorption in soil and microbial reduction of Se.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>This one-time excreta application did not increase, but further decrease in some treatments, selenium concentration and accumulation in the perennial ryegrass. Consequently, to increase ruminant selenium intake, supplementing selenium directly to animals is more recommended than applying animal manure to soil, which might drive selenium reduction and decrease selenium uptake by grass.</jats:p> </jats:sec>