https://ri.ufs.br/jspui/handle/riufs/7318 2026-05-01T16:47:05Z 2026-05-01T16:47:05Z Barbosa, João Pedro Ferreira https://ri.ufs.br/jspui/handle/riufs/24742 2026-03-11T19:12:49Z 2026-02-09T00:00:00Z

Título: Uso de Bacillus aryabhattai na cultura do milho: tolerância à seca, aspectos fisiológicos e produtividade Autor(es): Barbosa, João Pedro Ferreira Abstract: Climate change has intensified the frequency and severity of drought periods, affecting maize (Zea mays L.) production. In this context, the use of plant growth-promoting rhizobacteria (PGPR) has emerged as a sustainable biotechnological alternative to mitigate water deficit stress. Among PGPR, Bacillus aryabhattai, strain CMAA 1363, originally isolated from the roots of Cereus jamacaru, a cactus native to the Caatinga biome, promoted drought tolerance and growth in several crops. This dissertation, divided into three articles, characterizes the role of B. aryabhattai, strain CMAA 1363 in mitigating water deficit stress and promoting growth in maize plants. In Article 1, the impact of inoculation under well-watered and water-deficient conditions was evaluated in a pot experiment conducted under controlled greenhouse conditions. Inoculation alleviated the effects of water deficit by increasing relative water content (RWC) and the activity of the antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase, reducing electrolyte leakage (EL) and proline content, and protecting the photosynthetic apparatus, as evidenced by the preservation of chlorophylls and improvements in the oxygen-evolving complex (OEC), reaction center/absorption ratio (RC/ABS), performance indices (PIabs and PIcs), and absorption-based driving force (DFabs). Under wellwatered conditions, inoculation also promoted beneficial changes in OEC, RC/ABS, PIabs, PIcs, DFabs, and energy fluxes per cross-section. In both water regimes, improvements in morpho-agronomic parameters were observed, particularly increased root dry mass. In Article 2, the objective of the experiment was to mitigate water deficit stress during the vegetative stage of maize through inoculation with B. aryabhattai strain CMAA 1363, aiming to understand its subsequent effects on crop productivity after stress exposure. In this field experiment, the PGPR also promoted higher RWC and antioxidant activity of CAT and APX, reduced EL and proline content, and protected the photosynthetic apparatus, which was reflected in improved morphoagronomic parameters and increased productivity. Finally, in Article 3, the effect of inoculation on maize plants during the reproductive stage was evaluated. In this experiment, inoculation increased RWC, reduced EL, and protected the photosynthetic apparatus under water deficit stress; however, these beneficial ecophysiological changes were not reflected in increased productivity. In well-watered conditions, the effect was even more pronounced, with higher chlorophyll indices and photochemical efficiency, yet without greater productivity. Therefore, inoculation with B. aryabhattai strain CMAA 1363 represents a promising strategy for promoting growth and drought tolerance in maize plants, particularly during the vegetative stage of the crop.

2026-02-09T00:00:00Z Pinheiro, Heloisa Safira Santos https://ri.ufs.br/jspui/handle/riufs/24116 2026-01-05T17:41:59Z 2025-07-30T00:00:00Z

Título: Bioinseticidas e personalidade de colônias de Atta spp. (Formicidae: Attini): toxicidade e efeitos subletais Autor(es): Pinheiro, Heloisa Safira Santos Abstract: Leaf-cutting ants [Hymenoptera: Formicidae: Myrmicinae: Attini: Attina] are pests of great importance in tropical agriculture and forestry due to their defoliating habits, wide distribution, and abundance. They live in symbiosis with the basidiomycete fungus Leucoagaricus gongylophorus (Basidiomycota: Agaricaceae) for over 50 million years, using fresh plant material for its cultivation. The economic importance of leaf-cutting ants arises from the billions of dollars in losses they cause to various crops, both agricultural and forestry. Currently, the main control method consists of toxic baits containing active ingredients such as sulfluramid and fipronil. However, sulfluramid has been identified as a precursor of PFOS (perfluorooctane sulfonic acid, C8HF17O3S) in the environment. In this context, botanical insecticides are considered promising as an efficient alternative for managing leaf-cutting ants. Thus, the objectives of this work were: (i) to review the main plant species and their major compounds used in alternative control methods of leaf-cutting ants through essential oils; (ii) to evaluate the insecticidal potential of the Croton grewioides (Euphorbiaceae) essential oil on Atta sexdens workers; and (iii) to conduct behavioral studies on colonies of A. sexdens and A. opaciceps. To achieve these goals, a review was carried out through scientific, technological, and molecular mapping, as well as toxicity tests with workers to determine lethal effects through lethal doses and times (LDs and LTs) and sublethal effects through behavioral and locomotion bioassays. Additionally, the tests included behavioral approaches on colonies stimulated with C. grewioides essential oil and its major compounds. In the review, seven plant families were identified as sources for essential oil extraction: Aristolochiaceae, Euphorbiaceae, Lamiaceae, Myrtaceae, Piperaceae, Verbenaceae, and Winteraceae, as well as 28 patents related to the use of essential oils against pest insects, including leaf-cutting ants. Although Brazil has the largest number of scientific publications on this topic, the number of registered patents does not follow this trend. In the toxicity bioassays, all evaluated botanical compounds were toxic and, overall, the essential oil of C. grewioides and its major compounds showed lethal and, most importantly, significant sublethal effects, such as disruption of social behaviors and high repellency to A. sexdens workers. Behavioral bioassays demonstrated that there are variations in the personality of the leaf-cutting ant species A. sexdens and A. opaciceps, as well as between colonies of each species. The results reinforce the potential of essential oils as sustainable alternatives to conventional insecticides in the management of leaf-cutting ants.

2025-07-30T00:00:00Z Santos, Jéssica Silva https://ri.ufs.br/jspui/handle/riufs/24114 2026-01-05T17:10:47Z 2025-07-25T00:00:00Z

Título: Bioprospecção de bactérias halotolerantes de ambientes litorâneos do estado de Sergipe para biocontrole de fitopatógenos e promoção de crescimento vegetal Autor(es): Santos, Jéssica Silva Abstract: Halotolerant microorganisms possess adaptive mechanisms that make them promising sources of bioactive compounds with biotechnological potential. In the agricultural context, these microorganisms stand out due to their role in promoting plant growth and controlling phytopathogens. This thesis aimed to prospect, characterize, and functionally evaluate halotolerant microorganisms from coastal environments in the state of Sergipe, Brazil, with a focus on sustainable agricultural applications. In the first chapter, 89 bacteria were isolated from dunes, restingas, and apicuns, of which eight exhibited significant antifungal activity. The selected isolates demonstrated halotolerant profiles, with viable growth in up to 20% NaCl, as well as tolerance to multiple abiotic stresses such as pH variations, high temperatures (up to 55 °C), polyethylene glycol exposure, and heavy metals. Isolates RT242, RT241, and AP245 stood out for their superior performance under saline stress, maintaining growth, cell viability, and biofilm formation. Functionally, all isolates presented at least one plant growth-promoting (PGP) activity, including indole-3-acetic acid production, phosphate solubilization, nitrogen fixation, and extracellular enzyme synthesis. Under saline conditions, isolates AP245 and RT241 significantly enhanced early growth of lettuce seedlings, particularly root development. Greenhouse experiments demonstrated that isolates RT242, RT241, and AP245 significantly stimulated biomass and photosynthetic pigment production. Multivariate analysis confirmed positive associations between these isolates and plant morphophysiological parameters. Phylogenomic identification revealed high similarity with species of the genus Bacillus, including B. velezensis, B. stercoris, and B. safensis. Integrated Bonitur analysis highlighted isolate RT242 as the most promising. In the second chapter, a new halotolerant Streptomyces strain (DN246), isolated from dunes, was characterized. This strain exhibited multiple traits associated with plant growth promotion and phytopathogen biocontrol, including production of indole-3-acetic acid, phosphate solubilization, nitrogen fixation, and expression of extracellular enzymes such as cellulase, chitinase, and lipase. In vitro assays showed that DN246 significantly inhibited the growth of phytopathogenic fungi, notably Alternaria alternata (74% inhibition), and reduced spore germination and growth of phytopathogenic bacteria, especially Xanthomonas arboricola pv. pruni. The cell-free supernatant maintained antifungal activity for up to 96 hours and showed a dose-dependent effect, with minimum inhibitory concentrations (MIC) of 100 mg/mL for A. alternata and 15 mg/mL for X. arboricola, also significantly reducing biofilm formation and cell viability. Bioassays with Brassica oleracea demonstrated that inoculation with DN246 resulted in significant increases in fresh weight and root growth of seedlings.The results obtained in this thesis demonstrate that coastal environments harbor microorganisms with potential for the development of agricultural bioinputs.

2025-07-25T00:00:00Z Soares, Caroline Alves https://ri.ufs.br/jspui/handle/riufs/23395 2025-10-08T21:26:13Z 2025-07-23T00:00:00Z

Título: Atividade antimicrobiana e antibiofilme de óleos essenciais de Croton grewioides sobre fitopatógenos do gênero Xanthomonas Autor(es): Soares, Caroline Alves Abstract: Bacterial diseases caused by species of the genus Xanthomonas, such as X. campestris pv. campestris (XCC) and X. campestris pv. melonis (Xmel), significantly compromise agricultural productivity in several economically important crops. Given the limitations of traditional control methods, such as the extensive use of synthetic agrochemicals, essential oils (EOs) from medicinal plants are highlighted as sustainable alternatives. This thesis aimed to evaluate the potential use of C. grewioides EOs (CGEOs), as well as their antimicrobial and antibiofilm activity against the phytopathogens XCC and Xmel. The first article of the thesis consisted of a systematic and bibliometric review of the literature on CGEOs, revealing 24 biological activities attributed to these oils. Five possible chemotypes were identified (estragole, methyl eugenol, eugenol, anethole and (E)-anethole), with estragole and (E)-anethole proposed as chemical markers of the species. In subsequent experimental studies, the compounds eugenol (81.67–84.92%), methyl eugenol (70.10%), and methyl chavicol (69.17%) were identified as major. Evaluating the effect of CGEOs on Xmel, it was observed that the accessions CGR – 106, CGR – 107, CGR – 220 and the combination of eugenol + methyl chavicol compounds presented the lowest MIC (1000 μg.mL−1 ). The MBC for all CGEOs and their compounds was higher than 4000 μg.mL−1 . The kinetics of death showed a reduction in cell prediction from 120 min. It was also possible to observe that CGEOs were able to permeabilize the cell membrane and reduce biofilm formation. For XCC, we observed that biofilm formation was significantly reduced, with eugenol being the compound with the highest antibiofilm activity (VIP = 2.54, PLS-DA). The eradication of preformed biofilms reached up to 71.47% (CGR – 220). Bacterial motility was also inhibited, with CGR – 311 presenting a smaller displacement area (0.35 cm²). Cellulase, endoglucanase, and protease activities were significantly reduced, with inhibitions of 75.9% for endoglucanase (CGR – 204), 59.0% for cellulase (CGR – 204), and 64.0% for protease (CGR – 107). These results highlight the potential of CGEOs as antivirulence agents for the sustainable control of phytopathogens, contributing to the reduction of dependence on synthetic agrochemicals in agriculture.

2025-07-23T00:00:00Z