ISHS Acta Horticulturae 704: X International Workshop on Fireblight
COLONIZATION OF FLOWERS BY PSEUDOMONAS FLUORESCENS A506 FORMULATED IN A BIOPOLYMER GEL |
| Authors: | V.O. Stockwell, K.B. Johnson, V.W. Johnson |
| Keywords: | apple, pear, BlightBan A506, fire blight, biological control, formulation |
| Abstract:
Economical, stable formulations of gram-negative bacteria are needed for commercial biocontrol products. The fire blight biocontrol product, BlightBan A506 (Pseudomonas fluorescens A506; NuFarm Americas, Sugarland, TX) is distributed as frozen, lyophilized cells (1 X 1010 CFU/g) in a foil pouch. This formulation is relatively expensive, which creates a trade-off between cost and the concentration of cells suspended in the spray tank. For example, when mixed by label directions, BlightBan A506 is sprayed onto trees at ca. 8 X 105 to 8 X 106 CFU/ml. In contrast, most research on fire blight biocontrol has been conducted with suspensions of 1 X 108 CFU/ml. In 2002 and 2003, we tested colonization of flowers by A506 in an alternative formulation. Cells of A506 were collected from broth culture and formulated in a proprietary biopolymer gel to 6 X 1010 CFU/g. The biopolymer formulation of A506 was sealed in plastic containers and stored at 4°C. Pear and apple trees were treated at 80% bloom with either ca. 106 or 107 CFU/ml BlightBan A506 or 106 to 108 CFU/ml biopolymer A506. In five trials, inoculum dose, not formulation, significantly affected the incidence of detection and population size of A506 on flowers. With doses of 106 CFU/ml, only 25 to 75% of sprayed flowers had detectable populations of A506; at 107 and 108 CFU/ml, 55 to 95% of flowers were colonized. Because effective disease control depends on establishment of large populations of A506, a high-titer formulation may reduce variability in efficacy of BlightBan A506. The refrigerated biopolymer formulation has several apparent cost advantages over a lyophilized formulation including lower cell attrition and energy inputs during formulation, storage and transport. The biopolymer formulation may represent an economic method to produce a stable, high-titer product of A506 for fire blight control. | |
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