Resumo

ABRIL, Adriana et al. Inoculation with Azospirillum spp. in the semiarid-central region of Argentina: factors involved in rhizosphere colonization. Cienc. suelo [online]. 2006, vol.24, n.1, pp.11-19. ISSN 1850-2067.

The effectivity of inoculation with Azospirillum spp. often lacks consistency under field conditions. Microbial colonization of the rhizosphere is considered a prerequisite for successful inoculation. The objective of this study was to determine the degree of rhizosphere colonization in 11 field inoculation assays under different treatments (sites, crops, strains, cultivars, etc.) performed in the semiarid central region of Argentina in the last 15 years, conforming a total of 32 study cases. For comparative purposes, all the assays were performed following the same experimental design and inoculation and analytic methods. Variation results relative to control treatment were clustered according to each assay characteristic. Colonization degree measurements showed high variation among different cases studied (CV 173%, range: -18 to >100%). In 11 situations, measurements differed significantly from results obtained in the control treatment. No defined pattern that could explain the highly heterogenic results was found. However, it could be speculated that water stress and strain of origin would be the principal factors responsible for the variation observed in rhizosphere colonization by Azospirillum spp. Plant carrying capacity may decrease under stress conditions, promoting microbial competition in the rhizosphere, where native strains appear to take advantage due to their higher adaptation capacity.

Palavras-chave : Field conditions; PGPR; N₂ fixation; Water stress; Native strains.

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