OCCURRENCE OF THE ENDOPHYTIC DIAZOTROPHS HERBASPIRILLUM SPP IN ROOTS,STEMS, AND LEAVES, PREDOMINANTLY OF GRAMINEAE

Since the first description of Herbaspirillum seropedicae in 1986, few data have been published on this diazotroph, possibly due to difficul ties in isolating it from soil. In the present study we found that thi s bacterium seems to be an obligate endophyte which has been isolated from roots, stems, and leaves of a large number of samples of more tha n 10 different species of the Gramineae family, but only exceptionally from other plants. H. rubrisubalbicans, previously misnamed as ''Pseu domonas'' rubrisubalbicans, and known as a mild pathogen of sugarcane causing mottled stripe disease, confirms the endophytic habitat of thi s genus. This species occurs in roots, stems, and leaves of sugarcane and seems to be restricted to this crop. Inoculation of strains from b oth species into soil in high numbers resulted in a rapid decline in t heir numbers. In only 30 days the population of Herbaspirillum spp. in soil decreased below detection limits (<100 cells g(-1)). When sorghu m was planted in this soil, the bacteria reappeared and multiplied wit hin the plant tissues.