Influence of soil type and pH on the colonisation of sugar beet seedlings by antagonistic Pseudomonas and Bacillus strains,and on their control of Pythium damping-off |
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Authors: | Schmidt Christoph Stephan Agostini Francesco Simon Ana-maria Whyte Jennifer Townend John Leifert Carlo Killham Ken Mullins Chris |
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Institution: | (1) Nafferton Ecological Farming Group, Nafferton Farm Stocksfield, Newcastle University, Northumberland, NE43 7XD, UK;(2) ADAS Wolverhampton, Wergs Rd, Wolverhampton, WV6 8QT, UK;(3) School of Biological Sciences, University of Aberdeen, St. Machar Drive, Cruickshank Building, Aberdeen, AB24 3UU, UK |
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Abstract: | In five different soils originating from Scotland (Craibstone and Cruden Bay), Germany (Magdeburg and Uelzen) and Greece (Tymbaki), Pseudomonas fluorescens B5 reached higher population sizes (4.7–5.7logCFU/plant) on 12-day-old sugar beet seedlings than Bacillus subtilis MBI 600 (4.1–4.8logCFU/plant). Total population size per plant was not affected by soil type. In all five soils, the antagonists reached highest population densities in the hypocotyl and the upper 2cm root section (P. fluorescensB5: 5.2–6.8log10CFU/g plant fresh weight, Bacillus subtilisMBI 600: 5.2–6.1log10CFU/g plant fresh weight) and declined to 0–3log10CFU below 4cm root depth. Colonisation by P.
fluorescens B5 down the root was slightly increased in the soils from Craibstone, Magdeburg, and Uelzen compared to the sandy clay loam from Tymbaki. In lux-marked P.
fluorescens B5, population density was positively correlated with light emission in all soils; the light emission indicated physiological activity of the strains. However, P.
fluorescens B5 reduced Pythium damping-off (measurement after 14 days plant growth) only in three of the five soils (Craibstone, Cruden Bay and Magdeburg). Co-inoculation of B.
subtilis MBI 600 increased downward colonisation of the root by P.
fluorescens B5, but not the total population ofP.
fluorescens B5 per plant. Bacillus
subtilisMBI 600 did not reduce Pythium damping-off in any of the soils nor did it influence the efficiency of co-inoculated P.
fluorescens B5; its population consisted mainly of physiologically inactive spores. In Craibstone soil, pH did not affect population density, distribution along the root or biocontrol activity against P. ultimum of P.
fluorescens B5 or B.
subtilis MBI 600. |
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Keywords: | biological control bioluminescence lux-marking rhizosphere root colonisation soil-borne diseases |
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