The application of pesticides is unavoidable in conventional agricultural practice. To develop effective biofertilizers, bacterial strains with both pesticide tolerance and plant growth-promoting (PGP) traits were isolated for further testing. Seedlings of rice (Oryza sativa) were planted in soil with 1, 5, or 10 times the recommended rates of the fungicides etridiazole, metalaxyl, and tricyclazole. Endophytic bacteria were isolated from roots of rice seedlings. The bacterial 16S rDNA sequences and related PGP characteristics including potential nitrogen fixation, phosphorus-solubilizing and indole acetic acid (IAA) production ability were further examined. In all, 17 different strains were obtained from rice seedling roots; five strains with both nitrogen fixation potential and IAA production ability included Rhizobium larrymoorei E2, Bacillus aryabhattai E7, Bacillus aryabhattai MN1, Pseudomonas granadensis T6, and Bacillus fortis T9. Except for T9, all strains could tolerate two or more fungicides. We inoculated rice roots with the endophytic bacteria and all conferred rice growth-promoting ability. Bacillus aryabhattai MN1 was further tested and showed high tryptophan dose-dependent IAA production ability, tolerance towards etridiazole and metalaxyl application and should be considered a potential bacterial biofertilizer.

The study aims to develop novel biofungicide formulations against rice blast disease. A total of 300 rhizobacteria strains were isolated from rice field soil and were examined for the inhibition of Magnaporthe oryzae growth in a vitro test. Among them, only six rhizobacteria showed inhibition against M. oryzae. The three strains that showed the highest inhibition were Bacillus subtilis 5, B. cereus 3S5, and Pseudomonas fluorecens 10S2. A rice hull mixture and liquid medium were mixed with the above-mentioned bacterial suspensions into three bacterial formulas and tested separately on the rice cultivar UPLRi-5 after infection by M. oryzae under a controlled condition. The three novel biofungicide formulas significantly inhibited rice blast disease intensity with a mean disease control rate being approximately 31% higher than the control. The formulas proved to be effective and should be considered as promising novel treatments for rice blast disease.

Plant growth-promoting bacteria (PGPB) are beneficial microbes that increase plant growth and yield. However, limited information is currently available on PGPB in onion (Allium cepa Linn.). The aims of the present study were to isolate and identify PGPB in onion and examine the effects of isolated PGPB on germination and growth during the vegetative stage in onion, pak choy (Brassica chinensis), and sweet pepper (Capsicum annuum). Twenty-three strains of PGPB were isolated from the roots, bulbs, and rhizosphere soil of onion. All isolated bacterial strains showed one or more PGP traits, including indole acetic acid production, phosphate solubilization ability, and 1-aminocyclopropane-1-carboxylate deaminase and nitrogenase activities; most of these traits were derived from Bacillus sp., Microbacterium sp., and Pseudomonas sp. Eight bacteria that exhibited strong abilities to produce indole acetic acid were selected for a Petri dish trial, soil pot test, and vermiculate pot test. The Petri dish trial showed that strains ORE8 and ORTB2 simultaneously increased radicle and hypocotyl lengths in onion, but inhibited growth in sweet pepper after 7 d. The soil pot experiment on onion revealed that strains ORE5, ORE8, and ORTB2 strongly promoted growth during the vegetative stage with only a half dose of chemical fertilizer. The present results indicate that ORE8 (Bacillus megaterium) and ORTB2 (Pantoea sp.) are the most promising biofertilizers of onion and may simultaneously inhibit the seedling growth of other plants.

Soils are the largest reservoir of microplastics (MPs) on earth. Since MPs can remain in soils for a very long time, their effects are magnified. In this study, different concentrations of polyethylene (PE) MPs derived from commercial resins (0%, 1%, 7%, and 14%, represented as MP_0, MP_1, MP_7, and MP_14) were added to soils to assess the changes in the soils’ chemical properties, enzyme activities, and bacterial communities during a 70-day incubation period. The results show that PE MP treatments with low concentrations differed from other treatments in terms of exchangeable Ca and Mg, whereas at high concentrations, the pH and availability of phosphate ions differed. Fluorescein diacetate (FDA), acid phosphatase (ACP), and N-acetyl-β-d-glucosaminidase (NAG) enzyme activities exhibited a dose-related trend with the addition of the PE MPs; however, the average FDA and ACP activities were significantly affected only by MP_14. Changes in the microbial communities were observed at both the phylum and family levels with all PE MP treatments. It was revealed that even a low dosage of PE MPs in soils can affect the functional microbes, and a greater impact is observed on those that can survive in polluted environments with limited resources.

In Taiwan, the pesticides dimethomorph and imidacloprid are recommended for pest control in vineyards. Therefore, tank-mixing of these two pesticides is usually a routine practice before application. This study analyzed the influence of vineyard soil microbial flora under the recommended and high dosages (100 times the recommended dosage) of dimethomorph and imidacloprid. Individual and combined applications of pesticides were also tested through batches of soil incubation experiments. Four treatments—control (C), dimethomorph (DT), imidacloprid (IM), and mixed application of dimethomorph and imidacloprid (ID)—were used in the experimental design. From the soil metabolism, no significant reaction was observed after 2 months in the recommended dosage group, regardless of whether the pesticides were being applied individually or combined. For the high dosage, imidacloprid showed a higher effect than the co-exposure treatments, showing a possible prolonged effect after its repetitive application. From PCoA analysis, pesticide treatments altered the soil ecology after 2 months, and the effect of imidacloprid can be explicitly observed at high dosages. At the phylum level,Acidobacteriacan indicate pesticide application around the recommended dosage. It was inhibited by ID on day 7 and was augmented by all pesticides on day 63. The effect of the recommended dosage of pesticide mixtures after 2 months of incubation was revealed in the minor familiesGemmataceaeandPirellulaceae, while the high dosage treatments affected both the core and the minor families. Our findings verified the changes in the composition of microbial communities upon pesticide application, which would affect carbon, nitrogen, sulfur, phosphorous cycles, and contaminant removal ability within the vineyard.

The demand for rice (Oryza sativa L.) as a staple food continues to grow, but rising temperatures due to climate change pose a significant threat to its production. This study addresses the challenge by employing endophytic bacteria and fertilizer to mitigate the adverse effects of high temperatures on rice plants. Seedlings were evaluated for growth parameters, comparing outcomes with non-inoculated counterparts under normal and 40 to 45 °C heat shock conditions. Isolates underwent thorough DNA extraction and 16 S rRNA gene sequencing for identification and were scrutinized for their plant growth-promoting (PGP) traits. The effects of fertilizer and thermotolerant bacteria on rice plants were investigated in controlled chambers at 25 °C for 14 days, succeeded by exposure to 40 °C for 10 days. A consecutive soil pot experiment extended over 150 days, exposing plants to growth chambers set at 35 °C for 60 days, followed by a rapid increase to 40 °C for 30 days and a subsequent reduction to 35 °C for an additional 60 days. Inoculating with the isolates resulted in panicle development and increased plant biomass and length, with fresh grain weights showing a 50% improvement when using bacterial strain W (B. paralicheniformis). Additionally, dry grain weights per panicle rose by 113% with strain W, 83% with strain N (B. pumilus), and 87% with strain D (B. paranthracis) compared to the control. Bacterial strain W exhibited the most pronounced effect on rice yield under heat stress. The results demonstrated a decrease in malondialdehyde (MDA) levels after 150 days of heat stress and half-dose of the recommended fertilizer. Bacterial inoculation increased proline, salicylate, and abscisic acid content, suggesting the alleviation of osmotic stress effects. This highlights the role of endophytic bacteria in stimulating biologically active responses within rice plant cells. Notably, bacterial strains W, N, and D show potential for enhancing plant growth and mitigating heat stress when used in conjunction with NPK50.