Microbial Diversity Inside Pumpkins: Microhabitat-Specific Communities Display a High Antagonistic Potential Against Phytopathogens
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Recent and substantial yield losses of Styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) are primarily caused by the ascomycetous fungus Didymella bryoniae but bacterial pathogens are frequently involved as well. The diversity of endophytic microbial communities from seeds (spermosphere), roots (endorhiza), flowers (anthosphere), and fruits (carposphere) of three different pumpkin cultivars was studied to develop a biocontrol strategy. A multiphasic approach combining molecular, microscopic, and cultivation techniques was applied to select a consortium of endophytes for biocontrol. Specific community structures for Pseudomonas and Bacillus, two important plant-associated genera, were found for each microenvironment by fingerprinting of 16S ribosomal RNA genes. All microenvironments were dominated by bacteria; fungi were less abundant. Of the 2,320 microbial isolates analyzed in dual culture assays, 165 (7%) were tested positively for in vitro antagonism against D. bryoniae. Out of these, 43 isolates inhibited the growth of bacterial pumpkin pathogens (Pectobacterium carotovorum, Pseudomonas viridiflava, Xanthomonas cucurbitae); here only bacteria were selected. Microenvironment-specific antagonists were found, and the spermosphere and anthosphere were revealed as underexplored reservoirs for antagonists. In the latter, a potential role of pollen grains as bacterial vectors between flowers was recognized. Six broad spectrum antagonists selected according to their activity, genotypic diversity, and occurrence were evaluated under greenhouse conditions. Disease severity on pumpkins of D. bryoniae was significantly reduced by Pseudomonas chlororaphis treatment and by a combined treatment of strains (Lysobacter gummosus, P. chlororaphis, Paenibacillus polymyxa, and Serratia plymuthica). This result provides a promising prospect to biologically control pumpkin diseases.
KeywordsPumpkin Seed Paenibacillus Polymyxa Mycelium Fragment Ascomycetous Fungus Pectobacterium Carotovorum
We thank Massimiliano Cardinale, Martina Köberl, and Christin Zachow (Graz) for valuable support. Furthermore, we want to thank Johanna Winkler (Saatzucht Gleisdorf) for excellent cooperation regarding pumpkin cultivars and field trials. The project was funded by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management and the governments of the Federal State of Styria.
- 3.Huss H, Winkler J, Greimel C (2007) Der Pilz Didymella bryoniae schädigt steirischen Ölkürbisanbau: Fruchtfäule statt Kernöl. (The fungus Didymella bryoniae affect oil pumpkins in Styria: fruit rot instead of oil). Der Pflanzenarzt 60:14–16Google Scholar
- 4.Sitterly WR, Keinath AP (1996) Gummy stem blight. In: Zitter TA, Hopkins DL, Thomas CE (eds) Compendium of cucurbit diseases. American Phytological Society Press, St. Paul, pp 27–28Google Scholar
- 5.Keinath AP (2010) From native plants in central Europe to cultivated crops worldwide: the emergence of Didymella bryoniae as a cucurbit pathogen. Cucurbitaceae Conference, CharlestonGoogle Scholar
- 6.Grube M, Fürnkranz M, Zitzenbacher S, Huss H, Berg G (2011) Emerging multi-pathogen disease caused by Didymella bryoniae and pathogenic bacteria on Styrian oil pumpkin. Europ J Plant Pathol. doi:10.1007/s10658-011-9829-8Google Scholar
- 7.Huss H (2011) Krankheiten und Schädlinge im Ölkürbisbau. (Diseases and pests in oil pumpkin). Der fortschrittliche Landwirt 3:30–33Google Scholar
- 12.Sessitsch A, Coenye T, Sturz AV, Vandamme P, Barka EA, Salles JF, Van Elsas JD, Faure D, Reiter B, Glick BR, Wang-Pruski G, Nowak J (2005) Burkholderia phytofirmans sp. nov., a novel plant-associated bacterium with plant-beneficial properties. Int J Syst Evol Microbiol 55:1187–1192PubMedCrossRefGoogle Scholar
- 17.Schmid F, Grube M, Berg G (2011) Black fungi and associated bacterial communities in the phyllosphere of grapevine. Fungal Biol doi:10.1016/j.funbio.2011.04.004Google Scholar
- 19.White TJ, Bruns TD, Lee S, Taylor J (1990) Analysis of phylogenetic relationship by amplification and direct sequencing of ribosomal RNA genes. In: Innis MA, Gelfand DH, Sninsky JJ, White TJ (eds) PCR protocols: a guide to methods and applications. Academic, San Diego, pp 315–322Google Scholar
- 25.Rademaker JLW, De Bruijn FJ (1997) Characterization and classification of microbes by REP-PCR genomic fingerprinting and computer-assisted pattern analysis. In: Caetano-Anollés G, Gresshoff PM (eds) DNA markers: protocols, applications and overviews. Wiley, New York, pp 151–171Google Scholar
- 27.Junker RR, Loewel C, Gross R, Dötterl S, Keller A, Blüthgen N (2011) Composition of epiphytic bacterial communities differs on petals and leaves. Plant Biol doi: 10.1111/j.1438-8677.2011.00454.xGoogle Scholar
- 30.van Overbeek LS, Franke AC, Nijhuis EH, Groeneveld RM, da Rocha UN, Lotz LA (2011) Bacterial communities associated with Chenopodium album and Stellaria media seeds from arable soils. Microb Ecol. doi: 10.1007/s00248-011-9845-4