Biochemical characteristics ofTrichoderma atrovirideassociated with conidium fitness for biological control

Abstract

Effects of abiotic factors during production (temperature, nutrients, water activity, pH) on conidium fitness (quantity and quality) of Trichoderma atroviride LU132 (a key biocontrol agent) were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against Rhizoctonia solani 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 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 Trichoderma 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 T. atroviride 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 T. atroviride LU132, and provide important knowledge supporting optimum production of biocontrol agents based on T. atroviride, and possibly other similar biocontrol agents.

Effects of temperature, light and incubation period on production, germination and bioactivity ofTrichoderma atroviride

“…This could be related to the lower physiological activity of T. atroviride LU132 at these low or high temperatures, resulting in fewer conidia being produced (see Daryaei et al . ). Similar results for high temperatures were reported by Abbas et al .…”

“…Elevated germination percentage in T. atroviride LU132 in the present germination assays could be due to optimization of polyol concentration in conidia during conidium production at 30°C (see also Daryaei et al . ).…”

“…This study was part of a programme aimed to develop new knowledge of effects of growth conditions, to increase persistence and efficiency of the key agent T. atroviride LU132, which has been commercialized and to understand the factors which may influence conidium fitness (quantity and quality) for biological control formulations of conidia that are robust (long‐surviving) and active against target plant pathogens (Daryaei ; Daryaei et al . ,b,c,d). Although the effects of culture conditions on the quantity of conidia produced of this strain have been previously studied (Steyaert et al .…”

Culturing conditions affect biological control activity ofTrichoderma atrovirideagainstRhizoctonia solaniin ryegrass

“…Similarly, previous studies have shown that T. atroviride LU132 outcompeted R. solani on dual plate assays (Daryaei et al . ,b,c,d,e). It has been suggested that Trichoderma metabolites contribute fungistatically to supress the growth and development of R. solani in soil or in agar dual cultures, which are proposed to be differentially modulated by NADPH oxidase (Dr Artemio Mendoza‐Mendoza 2014; personal communication).…”

“…Fresh or dry conidia obtained from different culture‐growing conditions were also assessed (during 6 months of storage) for quantities of conidia produced and their quality, as indicated by germination and subsequent bioactivity against R. solani (see Daryaei et al . ,c). Effects of inoculum production conditions on conidium quality, both the ability of Trichoderma conidia to colonize and to maintain populations in host rhizospheres, and the ability to promote plant growth and suppress soil‐borne disease, have not been investigated.…”