2 research outputs found

    Biological fitness of <i>Trichoderma atroviride</i> during long-term storage, after production in different culture conditions

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    <div><p>ABSTRACT</p><p>Identification of the production and storage factors that affect conidium germination and bioactivity (fitness) will assist the success of biological control agents. Effects of culturing conditions on conidium fitness of <i>Trichoderma atroviride</i> LU132 were examined in different storage conditions over time. Abiotic factors (temperature, nutrients, water activity and pH) during production were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against <i>Rhizoctonia solani</i> in dual culture were selected to assess effects of storage conditions on conidium fitness. Fitness of the test conidia was examined after storage at 30°C and at 0% or 50% relative humidity (RH) over 6 months. Fitness declined over time, and the decline was greater for 50% RH than 0% RH, probably through reduced metabolic activity of conidia during long-term storage. Stored conidia were probably affected by dehydration, temperature and other factors such as oxidation, before and during storage, and also by rehydration after storage. The greatest number of conidia and germination percentage resulted from production at 25°C, but greatest bioactivity resulted from those produced at 30°C. No significant effects on bioactivity were detected between the conidium production treatments C : N 5 : 1 and C : N 160 : 1, indicating that C : N ratio in culture medium is not important for conidium survival of <i>T. atroviride</i>.</p></div

    Biochemical characteristics of <i>Trichoderma atroviride</i> associated with conidium fitness for biological control

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    <div><p>ABSTRACT</p><p>Effects of abiotic factors during production (temperature, nutrients, water activity, pH) on conidium fitness (quantity and quality) of <i>Trichoderma atroviride</i> LU132 (a key biocontrol agent) were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against <i>Rhizoctonia solani</i> in dual culture assays were selected to assess effects of storage conditions on conidial fitness over time. Further studies assessed interaction effects of temperatures (20°C or 30°C) and sugars (dextrose or sucrose) on conidium germination and bioactivity as fresh conidia, or after 6 months of storage. Biochemical analyses of sugars and fatty acids were carried out to determine relationships between quality variations and cellular characteristics for conidia produced in different culturing conditions. Low trehalose content in conidia (e.g. at 20°C) was associated with the least conidium fitness, although high trehalose content did not necessarily support conidium fitness. High proportions of total fatty acids in conidia were mostly associated with the least conidium fitness. When <i>Trichoderma</i> was grown at high carbon to nitrogen ratio (e.g. at C:N 160:1), the total conidium fatty acids content increased. This study also indicated that the monosaccharide dextrose is metabolically optimal for <i>T. atroviride</i> LU132 at 20°C while the disaccharide sucrose is optimal at 30°C. These studies indicate that physical growth conditions and nutritional requirements attribute in conidium fitness of <i>T. atroviride</i> LU132, and provide important knowledge supporting optimum production of biocontrol agents based on <i>T. atroviride</i>, and possibly other similar biocontrol agents.</p></div
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