Biocontrol Science and Technology (2011) 21, 917-927

Wei Tang, Yun-Zhi Zhu, Hua-Qi He, Sheng Qiang and Bruce A. Auld (2011)
Effect of environmental factors and precursors on oxalic acid production, mycelial biomass and virulence of a potential bioherbicide isolate of Sclerotium rolfsii SC64 produced in liquid culture
Biocontrol Science and Technology 21 (8), 917-927
Abstract: Effect of environmental factors and precursors on oxalic acid production, mycelial biomass and virulence of a potential bioherbicide isolate of Sclerotium rolfsii SC64 produced in liquid culture
The fungus Sclerotium rolfsii is presently under development as a bioherbicide for broadleaf weed species using fungus-infested substrates as application material in this laboratory. The effect of environmental factors and three precursors (citric acid, ascorbic acid, and sodium succinate) on mycelial growth, oxalic acid production, and virulence by SC64 in liquid culture were investigated. The results showed that for mycelia growth the optimum liquid medium was Modified Richard's solution (MRS) among the five tested media, but potato dextrose broth (PDB) produced the maximum oxalic acid production and virulence on detached Solidago canadensis leaves. When PDB was used as the basic medium, the oxalic acid/mycelial dry weight (mg g^-1) ratio reached the peak 4 days after inoculation. The optimum temperature for oxalic acid production was at 27°C, but increased mycelial dry weight and virulence were observed at 30°C. The optimum range of initial pH value for oxalic acid accumulation was 4.0-6.0, with the optimal pH 5.0; highest mycelial growth was with an initial pH 3.5-6.0 (optimum pH 5.0) and subsequently pH 3.5-5.5 (maximum at pH 3.5). Both mycelial dry weight and oxalic acid production showed a decreasing trend as a result of the precursor of oxalic acid being added to PDB. Among the three precursors, the greatest decrease in mycelial dry weight, and oxalic acid production was caused by sodium succinate. This clarification of optimal conditions for production of mycelial biomass while insuring high concentrations of oxalic acid and high virulence should be useful for further development of this fungus as biocontrol agent.
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Link to article at publishers website
Database assignments for author(s): Bruce A. Auld

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
rearing/culturing/mass production

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Solidago canadensis (weed)
Athelia rolfsii (weed bioagent)	Solidago canadensis (weed)