Dynamics of Foliage and Thatch Populations of Introduced Pseudomonas fluorescens and Streptomyces sp. on a Fairway Turf

Abstract

Populations of bacteria (Pseudomonas fluorescens A506 and Streptomyces sp. strain 93) applied to a creeping bentgrass/annual bluegrass fairway turf were followed over time on leaves and thatch. While introduced populations remained at detectable levels over a period of 11-25 days, they usually declined gradually and did not increase after their application to turf. Streptomyces rapidly disappeared from leaves while P. fluorescens was able to maintain similar population sizes on both thatch and leaves, after an initial decline of about 1-log unit, showing that it was actively colonizing the foliage despite loss of biomass from lawn mowing. Throughout these experiments, populations of indigenous microbes on foliage and thatch remained stable, about 10 6 and 10 8 cfu g )1 for fungi and bacteria, respectively, and were not affected by the application of bacterial antagonists. Niche-clearing with hydrogen peroxide, which temporarily reduced the population size of indigenous microorganisms two-fold, caused population size of P. fluorescens to increase approximately ten-fold within 24 h, while it declined by about one log unit on untreated turf. It is concluded that the indigenous microflora competes with introduced bacterial antagonists and interferes with their establishment and persistence on turf. Additional studies with P. fluorescens revealed that its population size was inoculum dose-dependent and that solid top dressing was slightly more efficient than spraying liquid suspension in establishing the antagonist. It was possible to maintain P. fluorescens populations above 10 5 cfu/g of thatch and leaves for 2 weeks or more with both top-dressing or spraying with about 1 to 3 Â 10 10 cfu m )2 .

Interaction between bacterial biocontrol-agents and strains of Xanthomonas axonopodis pv. phaseoli effects on biocontrol efficacy of common blight in beans

“…lachrymans, Erwinia tracheiphila and Colletotrichum orbiculare (Raupach and Kloepper, 1998) or combining lytic and antibiotic activities with systemic resistance to control bacterial wilt, Fusarium wilt, charcoal rot and angular leaf spot of common beans (Corrêa et al, 2014). The data of this study show that the independent of the virulence of the pathogen´s strain there was strain-BCA interaction, which shows the importance of selecting a BCA or a combination of BCAs with wider spectrum of action, allowing for greater effect under different situations, thus adding to the product stability (Boer et al, 2003;Mercier et al, 2006). It appears that the combination C01 and the isolate DFs831 have the potential for developing into a practical BCA to control bacterial blight of common beans.…”

“…On the other hand, the BCAs which is more efficient in controlling these strains (C01 and DFs831) were obtained from rhizosphere or parts of the bean plant, which confirms the importance of locality or the site from where the BCA was obtained. It is well known that in some pathosystems, the most appropriate site for the finding an effective antagonist is the host itself (Jensen et al, 2016;Mercier, 2006).…”

Taxonomic Diversity of Rhizosphere Bacteria in Golf Course Putting Greens at Representative Sites in the Southeastern United States

“…Altering the microbial community present from the ''wrong'' or ''bad'' microbes to ''good'' microbes is the purpose of adding natural materials. However, recent studies would indicate that turfgrass systems do have extensive microbial populations (e.g., Bigelow et al, 2002;Elliott et al, 2004;Feng et al, 2002;Mercier, 2006) and diverse microbial communities (e.g., Mueller and Kussow, 2005;Sigler et al, 2001;Yao et al, 2006).…”

“…Although culturable bacteria may represent a small proportion of the total bacteria in the soil or rhizosphere (Alexander, 2005), knowledge of the culturable bacterial species and genera associated with turfgrass roots on golf courses would be useful, because this information might influence the selection of bacteria used for biological pest control or microbial inoculants (Cook et al, 1996;Lugtenberg and Dekkers, 1999;Nijhuis et al, 1993;Weller, 1988) and possibly explain successes and failures that have occurred. Although it is unclear whether introduced bacteria can influence bacterial populations currently present in the phyllosphere, thatch, rhizosphere soil, or bulk soil (Bankhead et al, 2004;Hodges et al, 1993;Lynch, 2002;Mercier, 2006;Mueller and Kussow, 2005;Siciliano and Germida, 1998;Sigler et al, 2001), it is still important to know which bacterial species or groups of species are expected to be present in a turfgrass system.…”