RESUMO

Maize (Zea mays L.) is an essential commodity for global food security and the agricultural economy, particularly in regions such as San Martin, Peru. This study investigated the plant growth-promoting characteristics of native rhizobacteria isolated from maize crops in the San Martin region of Peru with the aim of identifying microorganisms with biotechnological potential. Soil and root samples were collected from maize plants in four productive zones in the region: Lamas, El Dorado, Picota, and Bellavista. The potential of twelve bacterial isolates was evaluated through traits, such as biological nitrogen fixation, indole acetic acid (IAA) production, phosphate solubilization, and siderophore production, and a completely randomized design was used for these assays. A completely randomized block design was employed to assess the effects of bacterial strains and nitrogen doses on maize seedlings. The B3, B5, and NSM3 strains, as well as maize seeds of the yellow hard 'Advanta 9139' variety, were used in this experiment. Two of these isolates, B5 and NSM3, exhibited outstanding characteristics as plant growth promoters; these strains were capable of nitrogen fixation, IAA production (35.65 and 26.94 µg mL-1, respectively), phosphate solubilization (233.91 and 193.31 µg mL-1, respectively), and siderophore production (34.05 and 89.19%, respectively). Furthermore, molecular sequencing identified the NSM3 isolate as belonging to Sporosarcina sp. NSM3 OP861656, while the B5 isolate was identified as Peribacillus sp. B5 OP861655. These strains show promising potential for future use as biofertilizers, which could promote more sustainable agricultural practices in the region.

RESUMO

The use of arbuscular mycorrhizal fungi (AMF) offers promising benefits to agriculture in the Amazon regions, where soils are characteristically acidic and nutrient-poor. The purpose of this research was to investigate the potential effects of two recently described species of AMF (Nanoglomus plukenetiae and Rhizoglomus variabile) native to the Peruvian Amazon for improving the plant growth of Plukenetia volubilis (inka nut or sacha inchi) and protecting the roots against soil pathogens. Two assays were simultaneously conducted under greenhouse conditions in Peru. The first focused on evaluating the biofertilizer effect of AMF inoculation, while the second examined the bioprotective effect against the root knot nematode, Meloidogyne incognita. Overall, the results showed that AMF inoculation of P. volubilis seedlings positively improved their development, particularly their biomass, height, and the leaf nutrient contents. When seedlings were exposed to M. incognita, plant growth was also noticeably higher for AMF-inoculated plants than those without AMF inoculation. Nematode reproduction was significantly suppressed by the presence of AMF, in particular R. variabile, and especially when inoculated prior to nematode exposure. The dual AMF inoculation did not necessarily lead to improved crop growth but notably improved P and K leaf contents. The findings provide strong justification for the development of products based on AMF as agro-inputs to catalyze nutrient use and uptake and protect crops against pests and diseases, especially those that are locally adapted to local crops and cropping conditions.

RESUMO

Strain CMT1 was isolated from nodules of non-inoculated Roundup Ready (RR) soybean plants (Glycine max L. Merrill), which were collected in fields in Itauguá, Paraguay. The genome of this strain had 338,984,909 bp; 59.2 % G + C content; 377648 bp N50; 5 L50; 55 contigs; 51 RNAs and 5,272 predicted coding DNA sequences (CDS) distributed in 327 subsystems. Based on overall genome-relatedness indices (OGRIs), this strain was taxonomically affiliated with Agrobacterium pusense. Based on genome mining, strain CMT1 is a promising plant growth-promoting bacterium that could be validated in agricultural fields for increasing soybean yield and quality, diminishing the economic, environmental, and health costs of non-sustainable food production.

RESUMO

The utilization of a novel (systemic) biofertilizer containing Pseudomonas fluorescens, Azospirillum brasilense, and Bacillus subtilis and possessing the technology to facilitate the entry of bacteria through the stomata, was evaluated at three localities in Mexico (Potrero Nuevo, Veracruz; Ameca, Jalisco; and Champotón, Campeche) in two sugarcane varieties (NCO-310 and Mex 57-473) at different time scales. Inoculation of the systemic biofertilizer was imposed over the local agricultural management of the sugarcane; chemical fertilization of the experimental parcels at Potrero Nuevo was done using 70-20-20 and 120-80-80 at Ameca and Champotón. Three doses of the biofertilizer per hectare were applied during the annual productive cycle of sugarcane at each site; one year at Potrero Nuevo and Champotón; and six years at Ameca. The annual sugarcane yield was evaluated at each site. Additionally, sugar quality (°Brix or sucrose content) was evaluated at the three localities, while different variables of stalk performance were also measured at Ameca and Champotón. Our data provide evidence that this systemic biofertilizer consistently and reliably increased the sugarcane yield at all localities during the time of evaluation, ranging from 73.7 tons ha-1 at Potrero Nuevo (2.5 times increase; P < 0.05) and 77.7 tons ha-1 at Ameca (1.9 times increase; P < 0.05) to 23.8 tons ha-1 at Champotón (1.4 times increase; P < 0.05). This increase in sugarcane biomass was related to increased tillering rather than increased stalk height or diameter. This novel biological product improved the sugarcane quality in terms of °Brix (P < 0.05, 2.6° difference) and sucrose content (P < 0.5, 0.7% difference).

RESUMO

Coffee (Coffea arabica) is among the world's most economically important crops. Coffee was shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) in traditionally managed coffee plantations in the tropics. The objective of this study was to assess AMF species richness in coffee plantations of four provinces in Perú, to isolate AMF isolates native to these provinces, and to test the effects of selected indigenous AMF strains on coffee growth. AMF species were identified by morphological tools on the genus level, and if possible further to the species level. Two native species, Rhizoglomus variabile and Nanoglomus plukenetiae, recently described from the Peruvian mountain ranges, were successfully cultured in the greenhouse on host plants. In two independent experiments, both species were assessed for their ability to colonize coffee seedlings and improve coffee growth over 135 days. A total of 35 AMF morphospecies were identified from 12 plantations. The two inoculated species effectively colonized coffee roots, which resulted in 3.0-8.6 times higher shoot, root and total biomass, when compared to the non-mycorrhizal controls. R. variabile was superior to N. plukenetiae in all measured parameters, increasing shoot, root, and total biomass dry weight by 4.7, 8.6 and 5.5 times, respectively. The dual inoculation of both species, however, did not further improve plant growth, when compared to single-species inoculations. The colonization of coffee by either R. variabile or N. plukenetiae strongly enhances coffee plant growth. R. variabile, in particular, offers enormous potential for improving coffee establishment and productivity. Assessment of further AMF species, including species from other AMF families should be considered for optimization of coffee growth promotion, both alone and in combination with R. variabile.

RESUMO

Biological treatments have become insufficient to treat municipal wastewater with greater toxicity and excess nitrogen and phosphate species, thus affecting the organisms that consume the water. In this work, a process was implemented for the removal of nutrients through three stages: stage A, complete aeration (24 h, 43 months); stage B, decreased aeration (12 h, 17 months); and stage C, decreased aeration with biocalcium (12 h, 19 months). The addition of biocalcium from eggshell promoted the formation of flocks, which resulted in the removal of nitrites (61 %), nitrates (84 %), total nitrogen (57 %), total phosphorus (8.3 %), sedimentable solids (50 %), total suspended solids (69 %), BOD5 (76 %), helminth eggs (50 %) and fecal coliforms (54 %). The statistical analyses in the three stages indicated that there is a strong correlation between the concentration of fats and oils and the removal of sedimentable solids and total suspended solids, since these parameters were correlated by 97 and 89 %, respectively. Sedimentable solids were correlated with total suspended solids by 94 %, while nitrates and total nitrogen were correlated 92 %, which favors the removal of nutrients in wastewater. The increase in the concentration of nitrogen in the sludge in stage C generated a C:N ratio of 7.98. This ratio shows that the sludge is feasible for use as a mediator of soils and a biofertilizer because of the high contents of calcium, phosphorus and nitrogen. In addition, biocalcium promoted the precipitation of hydroxyapatite, struvite, calcite and quartz. In general, the three stages of the treatment contributed to the stabilization of the wastewater treatment plant (WWTP) in an efficient, economical, and safe way.

RESUMO

Hydrogen sulfide is a highly toxic gas that causes many economic losses in aquaculture ponds. The application of sulfur-oxidizing bacteria (SOB) to remove hydrogen sulfide is an eco-friendly approach. This study aimed to isolate and identify the most efficient SOBs from the sediment of warm-water fish farms. Enrichment and isolation were performed in three different culture media (Starkey, Postgate, and H-3) based on both mineral and organic carbon. Overall, 27 isolates (14 autotrophic and 13 heterotrophic isolates) were purified based on colony and cell morphology differences. Initial screening was performed based on pH decrease. For final screening, the isolates were assessed based on their efficacy in thiosulfate oxidation and the sulfate production on Starkey liquid medium. Among isolated strains, 3 strains of Iran 2 (FH-13), Iran 3 (FH-21), and Iran 1 (FH-14) that belonged to Thiobacillus thioparus species (identified by 16s rRNA) showed the highest ability in thiosulfate oxidation (413.21, 1362.50, and 4188.03 mg/L for 14 days) and the highest sulfate production (3350, 2075, and 1600 mg/L). In the final phase, the performance of these strains under aquarium conditions showed that Iran 1 and Iran 2 had the highest ability in sulfur oxidation. In conclusion, Iran 1 and 2 strains can be used as effective SOB to remove hydrogen sulfide in fish farms. It is very important to evaluate strains in an appropriate strategy using a combination of different criteria to ensure optimal performance of SOB in farm conditions.

Assuntos

RESUMO

The implementation of bioreactor systems for the production of bacterial inoculants as biofertilizers has become very important in recent decades. However, it is essential to know the bacterial growth optimal conditions to optimize the production and efficiency of bioinoculants. The aim of this work was to identify the best nutriment and mixing conditions to improve the specific cell growth rates (µ) of two PGPB (plant growth-promoting bacteria) rhizobial strains at the bioreactor level. For this purpose, the strains Sinorhizobium mexicanum ITTG-R7T and Sinorhizobium chiapanecum ITTG-S70T were previously reactivated in a PY-Ca2+ (peptone casein, yeast extract, and calcium) culture medium. Afterward, a master cell bank (MCB) was made in order to maintain the viability and quality of the strains. The kinetic characterization of each bacterial strain was carried out in s shaken flask. Then, the effect of the carbon and nitrogen sources and mechanical agitation was evaluated through a factorial design and response surface methodology (RSM) for cell growth optimization, where µ was considered a response variable. The efficiency of biomass production was determined in a homemade bioreactor, taking into account the optimal conditions obtained during the experiment conducted at the shaken flask stage. In order to evaluate the biological quality of the product obtained in the bioreactor, the bacterial strains were inoculated in common bean (Phaseolus vulgaris var. Jamapa) plants under bioclimatic chamber conditions. The maximum cell growth rate in both PGPB strains was obtained using a Y-Ca2+ (yeast extract and calcium) medium and stirred at 200 and 300 rpm. Under these growth conditions, the Sinorhizobium strains exhibited a high nitrogen-fixing capacity, which had a significant (p < 0.05) impact on the growth of the test plants. The bioreactor system was found to be an efficient alternative for the large-scale production of PGPB rhizobial bacteria, which are intended for use as biofertilizers in agriculture.

RESUMO

The current research as aimed (i) to isolate and select the purple nonsulfur bacteria (PNSB) possessing the potassium-solubilizing ability from acid paddy fields and (ii) to evaluate the ability to release the plant growth-promoting substances (PGPS) of selected PNSB. A total of 35 acid sulfate (AS) soil samples were collected in An Giang province, Vietnam. Then, 70 PNSB strains were isolated from the AS soil samples. In the current study, the isolated strains were screened and selected according to their tolerability to acidic conditions, ability to solubilize potassium, and characteristics of a plant growth promoter on basic isolation media with various incubation conditions. Therein, three strains, TT07.4, AN05.1, and AC04.1, presented the highest potassium solubilization under the microaerobic light (11.8-17.7 mg L-1) and aerobic dark (16.4-24.7 mg L-1) conditions and stresses from Al3+, Fe2+, and Mn2+ toxicity. The selected strains were identified as Rhodopseudomonas pentothenatexigens by the 16S rDNA sequence, with 99% similarity. The selected acidic-resistant strains possessed the traits of biofertilizers under both microaerobic light and aerobic dark conditions, with abilities to fix nitrogen (0.17-6.24; 7.93-11.2 mg L-1); solubilize phosphorus from insoluble compounds with 3.22-49.9 and 9.49-11.2 mg L-1 for Al-P, 21.9-25.8 and 20.2-25.1 mg L-1 for Ca-P, and 10.1-29.8 and 18.9-23.2 mg L-1 for Fe-P; produce 5-aminolevulinic acid (0.63-3.01; 1.19-6.39 mg L-1), exopolymeric substances (0.14-0.76; 0.21-0.86 mg L-1), indole-3-acetic acid (12.9-32.6; 13.6-17.8 mg L-1), and siderophores (28.4-30.3; 6.15-10.3%). The selected potassium-solubilizing strains have a great potential to apply in liquid form into rice seed and solid form in AS soils to supply nutrients and PGPS for enhancing rice growth and grain yield.

Assuntos

RESUMO

Plant growth promoting bacteria (PGPB) have been used as integrative inputs to minimize the use of chemical fertilizers. However, a holistic comprehension about PGPB-plant-microbiome interactions is still incipient. Furthermore, the interaction among PGPB and the holobiont (host-microbiome association) represent a new frontier to plant breeding programs. We aimed to characterize maize bulk soil and rhizosphere microbiomes in irradiated soil (IS) and a native soil (NS) microbial community gradient (dilution-to-extinction) with Azospirillum brasilense Ab-V5, a PGPB commercial inoculant. Our hypothesis was that plant growth promotion efficiency is a result of PGPB niche occupation and persistence according to the holobiont conditions. The effects of Ab-V5 and NS microbial communities were evaluated in microcosms by a combined approach of microbiomics (species-specific qPCR, 16S rRNA metataxonomics and metagenomics) and plant phenomics (conventional and high-throughput methods). Our results revealed a weak maize growth promoting effect of Ab-V5 inoculation in undiluted NS, contrasting the positive effects of NS dilutions 10-3, 10-6, 10-9 and IS with Ab-V5. Alpha diversity in NS + Ab-V5 soil samples was higher than in all other treatments in a time course of 25 days after sowing (DAS). At 15 DAS, alpha diversity indexes were different between NS and IS, but similar in all NS dilutions in rhizospheric samples. These differences were not persistent at 25 DAS, demonstrating a stabilization process in the rhizobiomes. In NS 10-3 +Ab-V5 and NS 10-6 Ab-V5, Ab-V5 persisted in the maize rhizosphere until 15 DAS in higher abundances compared to NS. In NS + Ab-V5, abundance of six taxa were positively correlated with response to (a)biotic stresses in plant-soil interface. Genes involved in bacterial metabolism of riboses and amino acids, and cresol degradation were abundant on NS 10-3 + Ab-V5, indicating that these pathways can contribute to plant growth promotion and might be a result of Ab-V5 performance as a microbial recruiter of beneficial functions to the plant. Our results demonstrated the effects of holobiont on Ab-V5 performance. The meta-omics integration supported by plant phenomics opens new perspectives to better understanding of inoculants-holobiont interaction and for developing better strategies for optimization in the use of microbial products.