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Tropical grassland soils, especially those with alkaline properties, often exhibit limited phosphorus availability due to its precipitation in insoluble forms. Phosphate-solubilizing bacteria (PSB) and rhizobia have demonstrated their potential to enhance the availability of this nutrient and promote the growth of forage legumes. This study, conducted under controlled conditions in a mesh house, evaluated the effect of co-inoculation with PSB, including Micrococcus sp. Sfcm-14-01, Agrobacterium sp. Sfl-043-09, and Enterobacter sp. Sfcm-014-02 and Sfcm-054-06, along with rhizobia (Ensifer terangae R1-012-02 and Bradyrhizobium glycinis Rcm-025-01), under different levels of phosphorus fertilization on the legumes Leucaena leucocephala and Centrosema macrocarpum. The results indicate significant increases in various growth parameters, such as chlorophyll levels (SPAD), biomass (dry weight of roots and aerial parts) (mg), the foliar phosphorus concentration (ppm), and the concentration of available phosphorus in the soil, particularly under low-phosphorus fertilization conditions. The highest level of available phosphorus in the soil was achieved with 75% of the recommended fertilization dose, resulting in concentrations of 13.73 ppm for L. leucocephala and 7.69 ppm for C. macrocarpum, representing increases in phosphorus availability of 170.81% and 240.27%, respectively, compared with no fertilization or inoculation. These findings suggest that the co-inoculation of PSB and native rhizobia is a promising strategy to enhance the biomass productivity and mineral content of forage in tropical grazing systems, especially under phosphorus-limited conditions. [ABSTRACT FROM AUTHOR]

The objective of the research was to isolate the secondary mycelium of Auricularia spp and Pleurotus spp from three natural areas of the San Martín region, as well as to evaluate the growth in agar potato dextrose medium and in sterile substrates based on agro industrial residues. Ten isolates of secondary mycelia were obtained through disinfected carpophores of Pleurotus spp and another 10 isolates of disinfected carpophores of Auricularia spp. The highest growth rate in Auricularia spp was 62,5 μm h-1 (A1) and 75 μm h-1 (B10) for Pleurotus spp. In a second part of the experiment, seed of the fastest strains was produced in sterilized maize grains during a 40-day incubation period. The seed was inoculated into sterile substrates based on agro industrial residues. The native strains A1 of Auricularia spp and B10 of Pleurotus spp developed better in substrate based on coffee pulp residues, achieving a biological efficiency of 30.33% and 18.20%, respectively. It is concluded that the native strains A1 and B10 of edible fungi can be used in seed propagation and edible fungus production, providing the farmer with complementary food of high nutritional value. [ABSTRACT FROM AUTHOR]

Burkholderia vietnamiensis is a diazotroph capable of producing siderophores, as well as colonizing the rhizosphere and endosphere of rice. Although its taxonomy is not completely resolved, more isolations are needed to clarify the phylogenetic relationships with other species. The present work sought to implement a collection of phytobeneficial Burkholderia strains associated with different rice cultivars in the Peruvian jungle in order to carry out comparative genomics studies. 211 root endophytic bacteria were isolated and selected according to their ability to fix atmospheric nitrogen and production of siderophores, subsequently, molecular discrimination was carried out by amplifying the recA housekeeping gene. Only 16.1% of the isolates were able to produce siderophores and fix atmospheric nitrogen, using a specific primer for the genus Burkholderia (recA), the presence of at least 4 strains of Burkholderia was determined. The percentages of similarity in the recA gene varied between 98.36 to 99.51(%) with respect to the type strain. It is concluded that B. vietnamiensis would present growthpromoting characteristics due to its ability to fix nitrogen and siderophores and constitutes a potential Inoculant resource. This work has been financed by PROCIENCIA- CONCYTEC, through Contract 062- 2021-FONDECYT. [ABSTRACT FROM AUTHOR]

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Burkholderia glumae causes bacterial leaf blight in rice, and its global spread has been exacerbated by climate change. To understand the genetic diversity and virulence of B. glumae strains isolated from rice cultivars in Perú, 47 isolates were obtained from infected rice fields, all belonging to B. glumae , and confirmed by rec A and tox B sequences. The BOX-PCR typing group has 38 genomic profiles, and these turn into seven variable number tandem repeats (VNTR) haplotypes. There was no correlation between clustering and geographical origin. Nineteen strains were selected for phenotypic characterization and virulence, using both the maceration level of the onion bulb proxy and inoculation of seeds of two rice cultivars. Several strains produced pigments other than toxoflavin, which correlated with onion bulb maceration. In terms of virulence at the seed level, all strains produced inhibition at the root and coleoptile level, but the severity of symptoms varied significantly between strains, revealing significant differences in pathogenicity. There is no correlation between maceration and virulence scores, probably reflecting different virulence mechanisms depending on the host infection stage. This is the first study to evaluate the VNTR diversity and virulence of Peruvian strains of B. glumae in two commercial cultivars., Competing Interests: The author(s) declare no conflict of interest.

The aim of the present study was to isolate, select and characterize endophytic bacteria in rice inhibiting Burkholderia glumae THT as well as to characterize the genetic diversity and virulence factors in strains of B. glumae and Burkholderia gladioli of rice. Rice plants were collected in 4 departments from the northern region of Peru, isolating endophytic bacteria, after tissue sterilization, at 30°C (48h) in Trypticase Soy Agar (TSA), evaluating the antimicrobial activity against B. glumae THT, production of siderophores, resistance of toxoflavine and partial sequencing of the 16S rRNA gene. Furthermore, B. glumae and B. gladioli were isolated in selective medium (pH 4.5) at 41°C/72h. Molecular identification was performed using BOX-PCR and sequencing of the 16S rRNA gene, in addition to the production of extracellular enzymes, motility tests and sensitivity/resistance to bactericides. One hundred and eighty nine (189) endophytic bacteria were isolated, and only 9 strains showed antimicrobial activity against B. glumae THT, highlighting Burkholderia vietnamiensis TUR04-01, B. vietnamiensis TUR04-03 and Bacillus aryabhattai AMH12-02. The strains produced siderophores and at least 55.5% were resistant to toxoflavin. Additionally, 17 strains were grouped into 9 BOX-PCR profiles, where 16 had similarity with B. glumae LMG2196 T (100%) and 1 with B. gladioli NBRC 13700 T (99.86%). High diversity was found according to geographical origin and virulence factors. In conclusion, strains of the genus Bacillus and Burkholderia are potential biocontrol agents against B. glumae., (Copyright © 2020 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.)