Biological control of damping-off of sugar beet by Pseudomonas putida applied to seed pellets |
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| Authors: | D A SHAH-SMITH & R G BURNS |
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| Institution: | Research School of Biosciences, Biological Laboratory, University of Kent, Canterbury, Kent, CT2 7NJ, UK |
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| Abstract: | Pseudomonas putida 40RNF applied to seed pellets reduced the occurrence of Pythium damping-off of sugar beet. A density of 6 × 107 40RNF per pellet reduced Pythium damping-off from 70 to 26% when seeds were sown in artificially infested soil (250 propagules Pythium ultimum per g dry soil). The efficacy of 40RNF was dependent on its density in the seed pellet (in the range 2 × 104–6 × 108 per pellet) and on the number of propagules of Pythium in soil. 40RNF declined to or stabilized at approximately 1 × 106 per pellet 3 days after planting, and this was independent of the inoculum density. This indicated that the crucial steps resulting in damping-off of sugar beet caused by Pythium ultimum must occur within 3–4 days of sowing. 40RNF reduced pericarp colonization by P. ultimum by 43% 48 h after planting and caused a 68% decrease in the number of sporangia of P. ultimum in the surrounding soil (0.0–5.0 mm). P. putida 40RNF also reduced pre and post-emergence damping-off (from 69.5 to 37.5%) caused by indigenous populations of Pythium species in an infested soil and this was as effective as the fungicide hymexazol (69.5 to 40%). |
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