• Degradation of reactive oxygen species in arbuscular mycorrhizas (AM) may be an efficient mechanism to attenuate the activation of plant defenses. Here, we evaluated the activities of superoxid...

Multiple biotic and abiotic factors influence rice cultivation. These factors limit productivity and yield, as well as an irrational use of agrochemicals in rice cultivation. A sustainable alternative is using selected growth-promoting microorganisms to increase nutritional efficiency. In the present study, the direct mechanisms of growth promotion in two strains of Bacillus, three strains of Priestia, and two strains of Burkholderia endophytes of rice were characterized. Bacillus siamensis TUR07-02b and Priestia megaterium SMBH14-02 were selected to promote Oryza sativa var’s growth. “Bellavista” was used at different doses (50, 75, and 100%) of mineral nitrogen (N) using a randomized block design by quintuplicate. Both strains, SMBH14-02 and TUR07-02b, presented outstanding promoter characteristics, including auxin production (123.17 and 335.65 μg mL⁻¹, respectively) and biological nitrogen fixation capacity. Similarly, B. siamensis TUR07-02b could solubilize phosphate-Ca (20.94 μg mL⁻¹), cellulases, and pectinases. Under greenhouse conditions, co-inoculated plants receiving 75% of the total dose of mineral nitrogen showed increased agronomic parameters in relation to panicle length, grains per panicle, grain yield, and harvest index by 25.0, 30.7, 39.5, and 12.5%, respectively, compared to the 75% fertilized treatment without inoculation. The strains of B. siamensis TUR07-02b and P. megaterium SMBH14-02 are potential microbial resources in the formulation of new inoculants to reduce the use of nitrogenous fertilizers. Thus, agronomic validation of the inoculant consortium at the field level will be an essential step in providing an alternative for the sustainable management of rice cultivation and increased productivity of rice farmers in the San Martín region.

This article presents a systematic review of the ecophysiological mechanisms underpinning the essential role of plant-growth-promoting microorganisms (PGPMs) in improving rice yield and quality. The scientific literature is thoroughly reviewed, highlighting how PGPMs positively influence the growth, development, and health of rice plants. Key aspects, such as nitrogen fixation, nutrient solubilization, hormone production, and disease resistance induction, are emphasized. Additionally, technological advancements related to PGPM use are analyzed, including the identification of effective strains, the formulation of enhanced biofertilizers, and genetic engineering. The article concludes that PGPMs represent a promising tool with which to boost the sustainability and productivity of rice cultivation, providing a robust foundation for future research and practical applications in a field crucial to global food security.

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 LMG2196T (100%) and 1 with B. gladioli NBRC 13700T (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.

Arbuscular mycorrhizal fungi (AMF) are organisms that form mutualistic associations with most plants, favoring their development, especially those located in degraded areas. In order to identify the different predominant native AMF morphotypes, and determine the percentage of colonization, and spore density in soils of the Cumbaza sub-basin in San Martin, Peru, soil samples were taken from degraded areas of Chirikyacu, Vista Alegre, El Chontal, San Antonio de Cumbaza, Aucaloma and Shapumba, and they were associated with 4 legumes cover crops among them, Cajanus cajan, Canavalia ensiformis, Crotalaria juncea and Vigna unguiculata. A completely random design was used, considering 6 zones and 4 legumes with 3 replications. The results showed that the treatments with legumes had greater influence in the mycorrhizal colonization in comparison with the zones of study, being Vigna unguiculata the one that had greater colonization (75%). However, the number of spores was influenced mainly by the zones, where the Aucaloma treatment had the highest number (252 spores / 10 g of soil). Eleven native AMF morphotypes were identified, being those of the genus Acaulospora the most predominant.

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.