The role of Phanerochaete australis in enhancing defense activity against Magnaporthe oryzae in upland rice.

The inclusion of biological control in the integrated management of rice blast (Magnaporthe oryzae [Mo]) reduces pesticide application. Phanerochaete australis (Pha) has been shown to be a potential inducer of resistance to rice blast. Pha was isolated saprophytically from the rice phylloplane and studied for its interaction with Mo in the defense process of upland rice plants against the pathogen attack. Investigating the Pha × Mo interaction in a completely randomized design, the suppression of leaf blast and the epidemiological components of disease development were quantified in vivo, whereas the physiological and biochemical aspects, as defense enzymes and oxidative complex components, were evaluated in vitro during the induction of resistance. In the Pha × Mo interaction, it was found that seed treatment can significantly reduce disease severity by up to 93%, increase the photosynthetic apparatus, mobilize photoassimilates to the defense system, intensify defense enzyme and oxidant complex activities (chitinase [CHI], ß-1,3-glucanase [GLU], lipoxygenase [LOX], phenylalanine ammonia-lyase [PAL], poliphenoloxidase [PPO], peroxidase [POX], catalase [CAT], cuperoxide dismutase [SOD]), decrease phenolic compounds (TPCs), and increase photosynthetic pigment levels compared with the negative control (Mo). When treating the seed, we are referring to an induction process where there is no physical contact between the pathogens. The enzymes produced by the interaction between the microorganisms validate this process; thus, Pha acts as an inducer of resistance to upland rice plants challenged with Mo.

Screening bacterial isolates for biocontrol of sheath blight in rice plants.

Sheath blight (Rhizoctonia solani) causes significant yield losses in rice (Oryza sativa L.). Its sustainable management needs an efficient biocontrol agent. The objective was to screen bacterial isolates as an antagonist to R. solani and identify the most efficient ones as sheath blight suppressors under greenhouse conditions. Two assays (E1 and E2) were performed in a completely randomized design with three replications. E1 tested 21 bacterial isolates antagonists to R. solani in vitro. E2 was conducted under greenhouse conditions, with rice cultivar BRS Pampeira sown in plastic pots (7 kg) containing fertilized soil. Sixty old plants were inoculated with a segment of a toothpick containing fragments of R. solani, followed by spray inoculation of a bacterial suspension (108 CFU/mL). The severity of the disease was determined by calculating the relative lesion size formed on the colm. Isolates BRM32112 (Pseudomonas nitroreducens), BRM65929 (Priestia megaterium), and BRM65919 (Bacillus cereus) reduced R. solani colony radial growth by 92.8, 77.56, and 75.56%, respectively while BRM63523 (Serratia marcescens), BRM65923 and BRM65916 (P. megaterium) and BRM65919 (B. cereus) with 23.45, 23.37, 23.62, and 20.17 cm, respectively were effective at suppressing sheath blight in greenhouse, indicating their potential as a biofungicide for sheath blight suppression.

Molecular networking as a tool to annotate the metabolites of Bacillus sp. and Serratia marcescens isolates and evaluate their fungicidal effects against Magnapothe oryzae and Bipolaris oryzae.

Rhizobacteria are valuable sources of compounds that can be used for the integrated management of diseases in rice. Here, we aimed to explore the metabolism and organize and annotate the metabolites of Bacillus sp. and Serratia marcescens isolates using molecular networking and evaluate their fungicidal effects against Magnaporthe oryzae and Bipolaris oryzae. We obtained bacterial extracts after 6 and 16-h incubation via liquid-liquid extraction using ethyl acetate as solvent. We performed UHPLC-MS analysis and data processing using molecular networking and conducted biological assays in rice plants. Using the Global Natural Product Social spectral libraries, we annotated the following compounds: austinoneol, Phe-Pro, N-acetyl-l-leucine, Leu-Gly, Ile-Leu, Phe-Pro, 2,5-piperazinedione, 3-(1H-indol-3-methyl)-6-methyl-cyclo(d-Trp-l-Pro), and cholic acid. Results of the biological assays showed that the bacterial extracts reduced the mycelial growth of both pathogens in all treatments compared to the control. In the greenhouse setup, 8 days after the challenge for leaf gray spot and leaf blast, all treatments affected up to 4.4% of the leaf area, with an area under disease progress curve of 13.24, showing significant difference compared to the control, which affected 23% of the leaf area, with an AUDPC of 44.65. Our study provides potential new sources of natural products to be applied in the integrated management of rice. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03547-6.

Molecular identification of Trichoderma sp. isolates and biochemical characterization of antagonistic interaction against rice blast.

This study aimed to identify four isolates of Trichoderma sp. (Ufra.T06, Ufra.T09, Ufra.T12, and Ufra.T52) and characterize their interaction with Magnaporthe oryzae in vitro and in vivo conditions. The four isolates of Trichoderma sp. were sequenced, investigated as an antagonist against M. oryzae in five Petri plate assays, and as an inhibitor of conidial germination appressoria formation. Finally, were quantified the lytic activity of chitinase (CHI), glucanase (GLU), and protease (PRO) during co-cultivation of Trichoderma sp. and M. oryzae. In vivo, leaf blast suppression was evaluated in two assays: simultaneous and curative application. Both in vitro and in vivo assays were scanned by electron microscopy (SEM). All isolates were identified as Trichoderma asperellum. All in vitro Petri plates assays reduced M. oryzae colony growth (paired-91.18% by Ufra.T09, volatile metabolites-all isolates equally reduced, non-volatile-68.33% by Ufra.T06, thermostability-99.77% by Ufra.T52 and co-cultivate-64.25% by Ufra.T52). The filtrates and conidia suspensions for T. asperellum isolates inhibited the conidia germination and appressoria formation significantly. In co-cultivate (mycelial or cell wall), all enzymes (GLU, CHI, and PRO) and times (24, 48, and 72 h) showed increased activity. In vivo, reduced leaf blast severity until 94.64% (Ufra.T52cs) in a simultaneous and until 85% (Ufra.T09 24 and 48 hasi) in a curative application. T. asperellum isolates showed efficient control of M. oryzae by mycoparasitism, and antibiosis mechanisms were interfered with by the M. oryzae infection process.

Induction of resistance in rice plants using bioproducts produced from Burkholderia pyrrocinia BRM 32113.

Leaf blast is the main rice disease in the world causing significant losses in productivity. Blast integrate management (BIM) requires the use of genetic resistance, cultural practices, and chemical control, although for sustainable BIM, the insertion of biological agents may be the fourth component for. The objective of this work was to test three formulations of Burkholderia pyrrocinia (BRM32113) previously selected and to verify the effectiveness in resistance induction and blast control in rice. Two experiments were carried out, in a completely randomized design with three replications, in the greenhouse (E1 and E2). E1 aimed to select the best treatment for suppressing leaf blast severity and activating plant defense mechanisms. It was composed of 8 treatments: (1) formulated 11+ B. pyrrocina × Magnaporthe oryzae; (2) formulated 17+ B. pyrrocina × M. oryzae; (3) formulated 32+ B. pyrrocina × M. oryzae; (4) formulated 11 × M. oryzae; (5) B. pyrrocinia 17 × M. oryzae; (6) formulated 32 × M. oryzae; (7) B. pyrrocina × M. oryzae; (8) M. oryzae; (9) control (water). E2 aimed to investigate the effect of the best treatments, for the promotion of plant growth and suppression of leaf blast by calculating AUDPC. It was composed of 6 treatments: (1) formulated 11+ B. pyrrocina × M. oryzae; (2) formulated 32+ B. pyrrocina × M. oryzae; (3) formulated 11 × M. oryzae; (4) formulated 32 × M. oryzae; (5) B. pyrrocina × M. oryzae; (6) water. And after, we did two assays aimed to localize this biological agent after application at seed, soil, and rice plant. In E1, formulated 11+ B. pyrrocinia and 32+ formulated and B. pyrrocina were the best, suppressing leaf blast by up to 97% and providing the significant increase of the enzymes ß-1,3-glucanase, chitinase, phenylalanine ammonia lyase, lipoxygenase, and salicylic acid at 24 h and 48 h after inoculation with M. oryzae. In E2, treatments formulated 11+ B. pyrrocinia, formulated 32+ B. pyrrocinia, and B. pyrrocina provided more significant increases in growth promotion and reduced area under disease progress curve. B. pyrrocinia was detected in the rice plant for 18 days, predominantly in the root system (internal and external). The use of B. pyrrocinia formulations based on sugarcane molasses and glycerol can be an essential strategy for sustainable management. Although all the benefits come from these sustainable formulations, the adoption by commercial biological segment depends on an established formulation process. It seems that all the results showed here by this research will be readily assimilated by startups of the organic segment.

Bioagents and silicon promoting fast early upland rice growth.

Upland rice can overcome major challenges through the insertion of silicate fertilization and the presence of plant growth-promoting microorganisms (PGPMs) during its cultivation, as these factors promote an increase in vigor and plant disease resistance. Two consecutive experiments were conducted to evaluate the beneficial effects of silicon fertilization combined with the PGPM, Pseudomonas fluorensces, Burkholderia pyrrocinia, and a pool of Trichoderma asperellum, in upland rice seedlings, cultivar BRS Primavera CL: (a) E1, selecting PGPM type and Si doses for rice growth promotion and leaf blast supression, and (b) E2, evaluating physiological characteristics correlated with mechanisms involved in the higher vegetative growth in highlighted treatments from E1. In E1, 2 Si t ha-1 combined with the application of T. asperellum pool or PGPM mixture increased 54% in root dry matter biomass and 35 and 65% in shoot and root lengths, respectively; it also suppressed 99% of rice blast severity. In E2, shoot and root dry matter biomass and length, photosynthetic rate, water use efficiency, total soluble sugar, and chloroplastidic pigments were superior in BRS Primavera CL seedlings treated with 2 Si t ha-1 and T. asperellum pool or PGPM mixture. Higher salicilic and jasmonic acid levels were found in seedlings treated with Si and T. asperellum pool, individually. These physiological characteristics may explain, in part, the higher vigor of upland rice seedlings promoted by the synergistic effect between silicate fertilization and beneficial microorganisms.

Effects of beneficial microorganisms on lowland rice development.

Microorganisms can promote plant growth by increasing phytomass production, nutrient uptake, photosynthesis rates, and grain yield, which can result in higher profits for farmers. However, there is limited information available about the physiological characteristics of lowland rice after treatment with beneficial microorganisms in the tropical region. This study aimed to determine the effects of different beneficial microorganisms and various application forms on phytomass production, gas exchange, and nutrient contents in the lowland rice cultivar 'BRS Catiana' in a tropical region. The experiment was performed under greenhouse conditions utilizing a completely randomized design and a 7 × 3 + 1 factorial scheme with four replications. The treatments consisted of seven microorganisms, including the rhizobacterial isolates BRM 32113, BRM 32111, BRM 32114, BRM 32112, BRM 32109, and BRM 32110 and Trichoderma asperellum pooled isolates UFRA-06, UFRA-09, UFRA-12, and UFRA-52, which were applied using three different methods (microbiolized seed, microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS), and microbiolized seed + plant spraying with a microorganism suspension at 7 and 15 DAS) with a control (water). The use of microorganisms can provide numerous benefits for rice in terms of crop growth and development. The microorganism types and methods of application positively and differentially affected the physiological characteristics evaluated in the experimental lowland rice plants. Notably, the plants treated with the bioagent BRM 32109 on the seeds and on seeds + soil produced plants with the highest dry matter biomass, gas exchange rate, and N, P, Fe, and Mg uptake. Therefore, our findings indicate strong potential for the use of microorganisms in lowland rice cultivation systems in tropical regions. Currently, an additional field experiment is in its second year to validate the beneficial result reported here and the novel input sustainability.

Biomass, gas exchange, and nutrient contents in upland rice plants affected by application forms of microorganism growth promoters.

Microorganisms are considered a genetic resource with great potential for achieving sustainable development of agricultural areas. The objective of this research was to determine the effect of microorganism application forms on the production of biomass, gas exchange, and nutrient content in upland rice. The experiment was conducted under greenhouse conditions in a completely randomized design in a factorial 7 × 3 + 1, with four replications. The treatments consisted of combining seven microorganisms with three application forms (microbiolized seed; microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS); and microbiolized seed + plant sprayed with a microorganism suspension at 7 and 15 DAS) and a control (water). Treatments with Serratia sp. (BRM32114), Bacillus sp. (BRM32110 and BRM32109), and Trichoderma asperellum pool provided, on average, the highest photosynthetic rate values and dry matter biomass of rice shoots. Plants treated with Burkolderia sp. (BRM32113), Serratia sp. (BRM32114), and Pseudomonas sp. (BRM32111 and BRM32112) led to the greatest nutrient uptake by rice shoots. Serratia sp. (BRM 32114) was the most effective for promoting an increase in the photosynthetic rate, and for the greatest accumulation of nutrients and dry matter at 84 DAS, in rice shoots, which differed from the control treatment. The use of microorganisms can bring numerous benefits of rice, such as improving physiological characteristics, nutrient uptake, biomass production, and grain yield.

Defence responses in rice plants in prior and simultaneous applications of Cladosporium sp. during leaf blast suppression.

An alternative method to control rice blast (Magnaporthe oryzae) is to include biological agent in the disease management strategy. The objective of this study was to assess the leaf blast-suppressing effects of rice phylloplane fungi. One Cladosporium sp. phylloplane fungus was shown to possess biocontrolling traits based on its morphological characteristics and an analysis of its 18S ribosomal DNA. Experiments aimed at determining the optimal time to apply the bioagent and the mechanisms involved in its rice blast-suppressing activities were performed under controlled greenhouse conditions. We used foliar spraying to apply the Cladosporium sp. 48 h prior to applying the pathogen, and we found that this increased the enzymatic activity. Furthermore, in vitro tests performed using isolate C24 showed that it possessed the ability to secrete endoxylanases and endoglucanases. When Cladosporium sp. was applied either prior to or simultaneous with the pathogen, we observed a significant increase in defence enzyme activity, and rice blast was suppressed by 84.0 and 78.6 %, respectively. However, some enzymes showed higher activity at 24 h while others did so at 48 h after the challenge inoculation. Cladosporium sp. is a biological agent that is capable of suppressing rice leaf blast by activating biochemical defence mechanisms in rice plants. It is highly adapted to natural field conditions and should be included in further studies aimed at developing strategies to support ecologically sustainable disease management and reduce environmental pollution by the judicious use of fungicidal sprays.