|Mercier, Julian - AGRAQUEST, INC DAVIS, CA|
Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2008
Publication Date: February 1, 2009
Citation: Goates, B., Mercier, J. 2009. Effect of biofumigation with volatiles from Muscodor albus on the viability of Tilletia spp. teliospores. Canadian Journal of Microbiology 2009. Can. J. Microbiol. 55:203-206. Interpretive Summary: Muscodor albus is a tropical fungus that was isolated from a cinnamon tree in Honduras. It produces vapors that inhibit or kill numerous fungi making it an excellent candidate for a biocontrol agent. It has been shown to be effective for control of post harvest molds of fruits such as apples, peaches, grapes, and citrus. The effect of these vapors was tested on teliospores of the smut fungi Tilletia horrida, T. indica, and T. tritici which cause the diseases kernel smut of rice, Karnal bunt of wheat, and common bunt of wheat, respectively. A dry M. albus/rye grain formulation was reactivated with water to produce vapors that were used to fumigate: i) fungal spores freshly plated on agar in petri dishes to induce their germination, ii) dry dormant spores, and iii) dormant spores within intact diseased kernels. The spores of all three species on agar were completely killed when fumigated for 5 days. Fumigation of dry dormant spores of T. tritici caused a 69-97% loss in viability, but there was little effect on spores of the other species. There was no significant effect of fumigation on the spores contained within intact diseased kernels of all three species indicating that the vapors are inefficient for post harvest control of these fungi. However, it appears that M. albus has potential as a seed treatment or in furrow treatment for controlling smut diseases such as covered smut of barley, loose smut of oat, and common bunt of wheat where infection is initiated by germinating spores prior to seedling emergence. If effective, this treatment would be valuable to organic growers that currently have few practical options for controlling these diseases.
Technical Abstract: Volatile organic compounds produced by the fungus Muscodor albus inhibit or kill numerous fungi. The effect of these volatiles was tested on dormant and physiologically active teliospores of the smut fungi Tilletia horrida, T. indica, and T. tritici which cause kernel smut of rice, Karnal bunt of wheat, and common bunt of wheat, respectively. Freshly reactivated rye grain culture of M. albus was used to fumigate dormant teliospores (held dry in empty petri dishes) and physiologically active teliospores (plated on water agar) for up to 5 days at 22° C. Teliospores of all three species were killed when fumigated on agar for 5 days. When T. tritici on agar was fumigated only during the initial 48 h of incubation, viability was reduced by 73% to 99%. Dry loose teliospores of T. tritici lost some viability while teliospores within intact sori were not affected. Dormant teliospores of T. horrida and T. indica were not killed by M. albus volatiles. It appears that M. albus has potential as a seed or soil treatment for controlling seedling-infecting smuts where infection is initiated by germinating teliospores prior to seedling emergence. The volatiles appear to be inefficient for post harvest control of teliospores under the conditions used in these experiments.