In vitro PGPR properties and osmotic tolerance of different Azospirillum native strains and their effects on growth of maize under drought stress.

Osmotic variations in the soil can affect bacterial growth diminishing the number of inoculated bacteria. In a scenario of water deficit having tolerant bacteria would be beneficial to achieve a better response of the plant to stress. Thus, selection of more resistant bacteria could be useful to design new inoculants to be used in arid zones. In this sense, a group of Azospirillum isolates deposited in INTA collection was characterized in order to select strains tolerant to osmotic stress. The results obtained demonstrated that Az19 strain has similar in vitro PGPR characteristics to Az39, the most used strain in Argentina for inoculants industries, with the advantage of a better tolerance to osmotic and salt stress. Inoculation of maize plants with this strain resulted in a better response against water deficit compared to Az39 strain, encouraging us to further study the behavior of this strain in greenhouse and field trials in view of developing new inoculants suitable for areas with water deficit.

Azospirillum spp. from native forage grasses in Brazilian Pantanal floodplain: biodiversity and plant growth promotion potential.

A sustainable alternative to improve yield and the nutritive value of forage is the use of plant growth-promoting bacteria (PGPB) that release nutrients, synthesize plant hormones and protect against phytopathogens (among other mechanisms). Azospirillum genus is considered an important PGPB, due to the beneficial effects observed when inoculated in several plants. The aim of this study was to evaluate the diversity of new Azospirillum isolates and select bacteria according to the plant growth promotion ability in three forage species from the Brazilian Pantanal floodplain: Axonopus purpusii, Hymenachne amplexicaulis and Mesosetum chaseae. The identification of bacterial isolates was performed using specific primers for Azospirillum in PCR reactions and partial sequencing of the 16S rRNA and nifH genes. The isolates were evaluated in vitro considering biological nitrogen fixation (BNF) and indole-3-acetic acid (IAA) production. Based on the results of BNF and IAA, selected isolates and two reference strains were tested by inoculation. At 31 days after planting the plant height, shoot dry matter, shoot protein content and root volume were evaluated. All isolates were able to fix nitrogen and produce IAA, with values ranging from 25.86 to 51.26 mg N mL-1 and 107-1038 µmol L-1, respectively. The inoculation of H. amplexicaulis and A. purpusii increased root volume and shoot dry matter. There were positive effects of Azospirillum inoculation on Mesosetum chaseae regarding plant height, shoot dry matter and root volume. Isolates MAY1, MAY3 and MAY12 were considered promising for subsequent inoculation studies in field conditions.

[Search for conjugative plasmids in Azospirillum brasilense and Azospirillum lipoferum associated with plants]. / Poisk kon''iugativnykh plazmid u assotsiirovannykh s rasteniiami bakterii Azospirillum brasilense i Azospirillum lipoferum.

The conjugative plasmids in Azospirillum brasilense strains S17. Sp107, Sp245, SpBr14, JM6B2, JM82Al, UQ1794, UQI796 and in Azospirillum lipoferum strain RG20 were prove to exist for the first time in connection with their potency to mobilize a non-conjugative IncQ-plasmid pVZ361 from IncQ-group (ori RSF1010, KmR, SuR. 11.4 kb) for conjugated transfer to aplasmid strains Agrobacterium tumefaciens and Pseudomonas putida at high frequencies.

Azospirillum amazonense: su presencia en el área cañera de la provincia de Tucumßn / Azospirillum amazonense: its presence in the sugar cane area of the province of Tucumßn

We confirm the presence of Azospirillum amazonense in the sugar cane area of the Province of Tucumßn. Several strains were isolated from sugar-cane roots in different places. Phenotypic and genotypic characteristics coincided with those described for this species. This new one is being added to the other two species, A. brasilense and A. lipoferum, already reported.(AU)

[Azospirillum amazonense: its presence in the sugar cane area of the province of Tucumán]. / Azospirillum amazonense: su presencia en el área cañera de la provincia de Tucumán.

We confirm the presence of Azospirillum amazonense in the sugar cane area of the Province of Tucumán. Several strains were isolated from sugar-cane roots in different places. Phenotypic and genotypic characteristics coincided with those described for this species. This new one is being added to the other two species, A. brasilense and A. lipoferum, already reported.