Acetylene reduction and indoleacetic acid production by Azospirillum isolates from Cactaceous plants

Abstract

Azospirillum isolates were obtained from rhizosphere soil and roots of three cactaceae species growing under arid conditions. All Azospirillum isolates from rhizosphere and roots of Stenocereus pruinosus and Stenocereus stellatus were identified as A. brasilense; isolates of surface-sterilized roots from Opuntia ficus-indica were both A. brasilense and A. lipoferum. Azospirilla per g of fresh root in the three species ranged from 70 x 10 3 to 11 • 10 3. The most active strains in terms of C2H2 reduction (25-49.6nmol/h-ml) and indoleacetic acid (IAA) production (36.5-77/~g/ml) were those identified as A. brasilense and isolated from Stenocereus roots. A. lipoferum isolated from Opuntia roots produced low amounts of IAA (6.5-17.5/tg/ml) and low C2H2-reduction activity (17.8-21.2 nmol/h, ml).

Burkholderia , a Genus Rich in Plant-Associated Nitrogen Fixers with Wide Environmental and Geographic Distribution

“…Vials with a white or yellowish pellicle at a depth of 1 to 4 mm below of surface were streaked onto PCATm and BAc medium plates and incubated at 29°C. After 4 to 5 days, predominant colonies with different morphology were individually inoculated in vials containing N-free BAz medium, incubated at 29°C for 4 days and assayed for ARA as described previously (24). When ARA was not detected in N-free BAz medium, the isolates were inoculated in N-free semisolid BMGM medium, incubated for 3 days before the ARA assays were carried out.…”

Presence of 16S rRNA genes in multiple replicons in Azospirillum brasilense

“…Azospirillum isolates were recovered from rhizosphere soil and from inside sugarcane stems under the conditions described previously [17], but stalk segments were surface sterilized and treated as in [18]. Only one of the many isolates recovered from each plant or rhizosphere sample was designated a strain.…”

Growth-promotingazospirillumspp. isolated from the roots of several non-gramineous crops in Japan

“…IAA, gibberellin and cytokinin-like substances (Tien et al 1979). Azospirillum strains have also been isolated from the roots of various non-gramineous plants, such as Ipomoea batatas (Crossman and Hill 1987), Manihot esculenta and Pteridium aquilinum (D6bereiner 1978), Brassica juncea (Saha et al 1985), Lotus corniculatus and Hedychiurn coronariurn (Kosslak and Bohlool 1983), Lycopersicon esculentum (Mohandas 1988), and Cactaceous plants (Rao and Venkateswarlu 1982;Marcara-Esparza et al 1988). Azospirillum strains have been isolated from tropical soils more frequently than from temperate-climate soils.…”