title: Population densities and genetic diversity of actinomycetes associated to the rhizosphere of Theobroma cacao.
abstract: In spite of the acknowledged importance of growth-promoting bacteria, only a reduced number of studies were conducted with these microorganisms on Theobroma cacao. The objectives of this work were to study the population densities and genetic diversity of actinomycetes associated with the rhizosphere of cacao as a first step in their application in plant growth promotion and biological control. The populations densities of actinomycetes in soil and cacao roots were similar, with mean values of 1,0 x 10(6) CFU/g and 9,6 x 10(5) CFU/g, respectively. All isolates selected and used in this study were identified through sequencing analyses of a fragment of the rpoB gene that encodes the β-subunit of the RNA polymerase as species of the genus Streptomyces. In vitro cellulolytic, xilanolytic and chitinolytic activity, indolacetic acid production and phosphate solubilization activities were observed in most of the isolates tested. The data obtained in this study demonstrate that actinomycetes account for a higher percentage of the total population of culturable bacteria in soil than on cacao roots. Additionally, actinomycetes from the cacao rhizosphere are genetically diverse and have potential applications as agents of growth promotion.
authors.affiliation: Universidade Federal do Recôncavo da Bahia, Campus Universitário de Cruz das Almas , Cruz das Almas, BA , Brasil.
authors.forename: Tâmara R
authors.initials: TR
authors.lastname: Barreto
authors.forename: Augusto C M
authors.initials: AC
authors.lastname: da Silva
authors.forename: Ana Cristina F
authors.initials: AC
authors.lastname: Soares
authors.forename: Jorge T
authors.initials: JT
authors.lastname: de Souza
keywords: Streptomyces spp.; cacao; rpoB sequence analyses
references.citation: New Phytol. 1997 Nov;137(3):495-507
references.pmid: 33863077
references.citation: Int J Syst Bacteriol. 1992 Jan;42(1):166-70
references.pmid: 1371061
references.citation: Brief Bioinform. 2004 Jun;5(2):150-63
references.pmid: 15260895
references.citation: Int J Syst Evol Microbiol. 2004 Mar;54(Pt 2):593-598
references.pmid: 15023980
references.citation: Microbiol Rev. 1987 Jun;51(2):221-71
references.pmid: 2439888
references.citation: Appl Environ Microbiol. 1991 Feb;57(2):535-8
references.pmid: 16348419
references.citation: Can J Microbiol. 1959 Feb;5(1):79-85
references.pmid: 13629388
references.citation: Nucleic Acids Res. 1997 Sep 1;25(17):3389-402
references.pmid: 9254694
references.citation: Appl Microbiol. 1960 May;8:174-8
references.pmid: 14434270
references.citation: Appl Environ Microbiol. 2004 Feb;70(2):1051-8
references.pmid: 14766588
references.citation: Nucleic Acids Res. 1994 Nov 11;22(22):4673-80
references.pmid: 7984417
references.citation: Proc Natl Acad Sci U S A. 2003 Dec 23;100(26):15649-54
references.pmid: 14671327
references.citation: Nature. 1964 May 30;202:928-9
references.pmid: 14190108
references.citation: Phytopathology. 2006 Jan;96(1):61-7
references.pmid: 18944205
references.citation: J Bacteriol. 1999 Jan;181(1):78-82
references.pmid: 9864315