[Isolation and identification of dominant microorganisms in rhizosphere of continuous cropping with peanut].

OBJECTIVE: We isolated and identified dominant microorganisms from the rhizosphere of continuous cropping with peanut, to study the relationship between dominant microorganisms and peanut continuous cropping. METHODS: By using dilution-plate method we isolated dominant bacteria, dominant fungi and actinomycetes from the rhizosphere of continuous cropping with peanut. Morphological specificity, culture shape, physiological-biochemical characteristic and partial 16S rDNA sequences were used to identify bacteria and actinomycetes. Morpholog, growth on various media, and Internal Transcribed Spacer (ITS) rDNA sequences homology analysis were performed to identify dominant fungi. RESULTS: We isolated seven dominant bacteria strains, seven dominant fungi and seven dominant actinomycetes. Dominant bacteria were identified as Leifsonia xyli, Arthrobacter chlorophenolicus, Microbacterium flavescens, Sphingomonas sp., Pasteurella sp., Bacillus simplex and Bacillus megaterium. Dominant fungi were identified as Cladosporium cladosporioides, Penicillium purpurogenum , Hypocrea lixii, Exophiala pisciphila, Penicillium janthinellum, Aspergillus sp. and Verticillium dahliae. Dominant actinomycetes were identified as Streptomyces violaceoruber, Streptomyces flaveus, Streptomyces panaciterrae, Streptomyces achromogenes, Streptomyces pseudogriseolus, Streptomyces cellulosae and Streptomyces aureus. CONCLUSION: This study was the first time to isolate and identify dominant microorganisms from the rhizosphere of continuous cropping with peanut. The type of dominant microorganisms changed obviously after planting peanut, although the change was without regularity.