Stability of microsclerotial inoculum of Colletotrichum truncatum encapsulated in wheat flour-kaolin granules

• Published in: World journal of microbiology & biotechnology 1997-09, Vol.13 (5), p.549-554
• Main Authors: CONNICK, W. J, JACKSON, M. A, WILLIAMS, K. S, BOYETTE, C. D
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biological control; Biological control and other methods; Biological products; Biotechnology; Flour; Fundamental and applied biological sciences. Psychology; Gluten; Microorganisms; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; Studies; Weeds; Wheat
• ISSN: 0959-3993; 1573-0972
• DOI: 10.1023/a:1018517409756

Maintaining adequate viability of microorganisms in products for biocontrol is critically important for commercial reasons. Microsclerotia (MS) of the mycoherbicide agent, Colletotrichum truncatum, are its hardy, over-wintering fungal structures. Microsclerotial inoculum at 2, 7, and 23 MS/granule were matrix-encapsulated in wheat flour-kaolin granules ('Pesta'), in which the flour provided gluten for the matrix and a food base for the fungus. Pesta granules were dried to a water activity of 0.18-0.29. After storage for 52 weeks at 25°C, granules containing 7 and 23 MS were 100% viable and granules with 2 MS were 95% viable. Granules with 7 MS were 50% viable after 36 weeks at 35°C. Pesta granules (440 granules/g) with conidial inoculum at 3.3×105 c.f.u./g were less storage-stable than granules at the 2 MS/granule level. At all MS inoculum levels, granules stored for up to 2years produced 108 c.f.u./g in vitro when incubated on water agar. High water activity was detrimental to long-term viability. In the greenhouse, 7 MS/granule samples controlled 94% of hemp sesbania when incorporated into the soil pre-planting. The strategy of encapsulation of the naturally stable C. truncatum MS and drying to a favourable water activity led to excellent shelf-life for a live biocontrol agent.[PUBLICATION ABSTRACT]