The rhizobacteria are known to protect plants from different pathogens acting as biocontrol agents and promote growth of plants. This study was conducted to isolate, screen and identify faba bean associating rhizobacteria for their antagonistic properties against Botrytis fabae AAUBF-12 and plant growth-promoting properties under in vitro conditions. In the dual culture assay, the isolates inhibited the mycelia growth of B. fabae AAUBF-12 (6–40 %) upon 3 days of incubation, and the inhibition increased to 9–43 %, 16–50 %, and 24–68 % after five, seven and 9 days of incubation, respectively. The inhibitory activity increased from 6 to 82 % using the culture filtrates of the isolates. Isolate AAUB95 displayed the highest mycelial inhibition (27 %) at 5 % concentration of culture filtrate, followed by AAUB146b that exhibited 21 % inhibition at the same concentration. AAUB146b and AAUB100 effectively inhibited B. fabae AAUBF-12 by 79 % and 80 % at 20 % concentrations of the culture filtrate. The qualitative study demonstrated 75 % of the isolates positive for protease and 60 % for lipase synthesis. Furthermore, the isolates that showed antagonistic activity against B. fabae AAUBF-12, produced IAA and ammonia with 65 % and 60 %, respectively. Moreover, 310–760 μg mL⁻¹ and 200–620 μg mL⁻¹ of tricalcium phosphate (TCP) was released on the 3^rd and 6^th days of incubation, respectively, due to rhizobacterial solubilization. Nevertheless, the Pearson’s correlation analysis between pH and TCP solubilization revealed an inverse relationship (r = -.422∗∗). Based on 16S rRNA sequences analysis, isolate AAUB95, AAUB146b, AAUB100 and AAUB92 were identified as B. subtilis AAUB95, S. nematodiphila AAUB146b, B. tequilensis AAUB100 and B. subtilis AAUB92, respectively. Of the isolates, B. subtilis AAUB95 showed best antagonism of B. fabae AAUBF-12 with multiple plant growth-promoting properties.

Root exudates mediate plant interactions in the environment, and they are affected by physical, chemical and biological factors. Biocontrol agents can modify root exudates and influence plant–pathogen interactions. In this study, we showed that lettuce (Lactuca sativa), a host of the root-knot nematode Meloidogyne incognita, produced root exudates that attracted the second-stage juveniles (J2s) of this nematode and garlic (Allium sativum), an antagonistic plant, produced exudates that repelled them. However, the application of a commercial product containing Bacillus subtilis on lettuce roots made the exudates repellent to J2s of M. incognita, whereas treated garlic exudates were as attractive to the J2s as untreated lettuce. The repulsive behavior of M. incognita to exudates of roots colonized by biocontrol agents is common; however, the attractiveness of treated garlic root exudates was unexpected and not previously reported for non-host plants. Chemotaxis assays also showed that the commercial formulation of B. subtilis was repellent to J2s of M. incognita. The metabolomic analysis conducted on these samples unveiled a combined total of 34 compounds. There was an elevation in the levels of amino acids and peptides in samples that were inoculated with the commercial product. Additionally, certain metabolites appear to be connected to chemotaxis. These metabolic changes induced by the commercial product are interesting for field utilization in a dual control strategy, where lettuce is protected against the nematode due to its repellence and garlic becomes attractive, but is not infected by the nematode.

Ethanol extract of cell mass of Serratia marcescens strain N4-5, when applied as a treatment to cucumber seed, has been shown to provide control of the oomycete soil-borne plant pathogen Pythium ultimum equivalent to that provided by a seed-treatment chemical pesticide in some soils. Two dominant compounds in this extract, prodigiosin and the serratamolide serrawetin W1, were identified based on mass and collision induced dissociation mass fragmentation spectra. An additional four compounds with M+H⁺ masses (487, 541, 543, and 571) consistent with serratamolides reported in the literature were also detected. Several other compounds with M+H⁺ masses of 488, 536, 684, 834, 906, and 908 m/z were detected in this ethanol extract inconsistently over multiple liquid chromatography coupled with tandem mass spectrometry (LC/MS–MS) runs. A purified preparation of prodigiosin provided control of damping-off of cucumber caused by P. ultimum when applied as a seed treatment while ethanol extract of cell mass of strain Tn246, a transposon-mutant-derivative of strain N4-5, did not. Strain Tn246 contained a mini-Tn5 Km insertion in a prodigiosin biosynthetic gene and was deficient in production of prodigiosin. All other compounds detected in N4-5 extract were detected in the Tn246 extract. This is the first report demonstrating that prodigiosin can control a plant disease. Other compounds in ethanol extract of strain N4-5 may contribute to disease control.

Gram-negative, aerobic, rod-shaped, non-spore-forming, motile bacteria, designated CBAS 719 ^T, CBAS 732 and CBAS 720 were isolated from leaf litter samples, collected in Espírito Santo State, Brazil, in 2008. Sequences of the 16S rRNA, gyrB, lepA and recA genes showed that these strains grouped with Burkholderia plantarii LMG 9035 ^T, Burkholderia gladioli LMG 2216 ^T and Burkholderia glumae LMG 2196 ^T in a clade of phytopathogenic Burkholderia species. Digital DNA-DNA hybridization experiments and ANI analyses demonstrated that strain CBAS 719 ^T represents a novel species in this lineage that is very closely related with B. plantarii. The genome sequence of the type strain is 7.57 Mbp and its G + C content is 69.01 mol%. The absence of growth on TSA medium supplemented with 3% (w/v) NaCl, citrate assimilation, β-galactosidase (PNPG) activity, and of lipase C14 activity differentiated strain CBAS 719 ^T from B. plantarii LMG 9035 ^T, its nearest phylogenetic neighbor. Its predominant fatty acid components were C_16:0, C_18:1 ω7c, cyclo-C_17:0 and summed feature 3 (C_16:1 ω7c and/or C_15:0 iso 2-OH). Based on these genotypic and phenotypic characteristics, the strains CBAS 719 ^T, CBAS 732 and CBAS 720 are classified in a novel Burkholderia species, for which the name Burkholderia perseverans sp. nov. is proposed. The type strain is CBAS 719 ^T (= LMG 31557 ^T = INN12^T).

PARTE I – CENÁRIOS: Capítulo 1: Uso atual e perspectivas do Trichoderma no Brasil. Capítulo 2: Produtos comerciais à base de Trichoderma. PARTE II – TAXONOMIA E FISIOLOGIA: Capítulo 3: O gênero Trichoderma. Capítulo 4: Trichoderma e seus mecanismos de ação para o controle de doenças de plantas. Capítulo 5: Trichoderma: metabólitos secundários. Capítulo 6: Trichoderma: interações e estratégias. Capítulo 7: Indução de resistência por Trichoderma. PARTE III – QUALIDADE: Capítulo 8: Produção industrial de Trichoderma. Capítulo 9: Controle de qualidade de produtos biológicos à base de Trichoderma. Capítulo 10: Uso de micro e nanotecnologia com Trichoderma. Capítulo 11: Riscos da produção de microrganismos de forma artesanal. Capítulo 12: Compatibilidade de produtos à base de Trichoderma com fungicidas utilizados no tratamento de sementes. Capítulo 13: Avaliação à campo de Trichoderma em mofo-branco. PARTE IV – APLICAÇÕES: Capítulo 14: Uso do Trichoderma na cultura do arroz. Capítulo 15: Uso do Trichoderma na cultura do algodão. Capítulo 16: Uso do Trichoderma na cultura da batata. Capítulo 17: Uso de Trichoderma na cultura do feijão-comum. Capítulo 18: Uso do Trichoderma em cereais. Capítulo 19: Mofo-branco em soja ? ensaios cooperativos. Capítulo 20: Uso do Trichoderma na cultura da banana. Capítulo 21: Uso do Trichoderma na cultura do cacau. Capítulo 22: Uso do Trichoderma em hortaliças. Capítulo 23: Uso do Trichoderma na cultura da maçã. Capítulo 24: Uso do Trichoderma na cultura do melão. Capítulo 25: Uso do Trichoderma na cultura do morango. Capítulo 26: Uso do Trichoderma na cultura da uva. Capítulo 27: Uso do Trichoderma em culturas florestais.

The rhizosphere is a narrow and dynamic region of plant root-soil interfaces, and it’s considered one of the most intricate and functionally active ecosystems on the Earth, which boosts plant health and alleviates the impact of biotic and abiotic stresses. Improving the key functions of the microbiome via engineering the rhizosphere microbiome is an emerging tool for improving plant growth, resilience, and soil-borne diseases. Recently, the advent of omics tools, gene-editing techniques, and sequencing technology has allowed us to unravel the entangled webs of plant-microbes interactions, enhancing plant fitness and tolerance to biotic and abiotic challenges. Plants secrete signaling compounds with low molecular weight into the rhizosphere, that engage various species to generate a massive deep complex array. The underlying principle governing the multitrophic interactions of the rhizosphere microbiome is yet unknown, however, some efforts have been made for disease management and agricultural sustainability. This review discussed the intra- and inter- microbe-microbe and microbe-animal interactions and their multifunctional roles in rhizosphere microbiome engineering for plant health and soil-borne disease management. Simultaneously, it investigates the significant impact of immunity utilizing PGPR and cover crop strategy in increasing rhizosphere microbiome functions for plant development and protection using omics techniques. The ecological engineering of rhizosphere plant interactions could be used as a potential alternative technology for plant growth improvement, sustainable disease control management, and increased production of economically significant crops

Plant-microbe interactions are critical for the sustainability of agricultural production. In this study, our aims were to characterize the genetic and functional diversity of the culturable bacterial community associated with the cacao rhizosphere and access their potential for growth promotion of cacao seedling. Culture-dependent and molecular methods were used to characterize the population densities and diversity of bacterial communities from soil and cacao plants at two locations and two plant ages. A total of 63 strains were identified through hsp60 sequencing. Pseudomonas and Enterobacter were the most abundant genera in association with the cacao rhizosphere, whereas Bacillus was more numerous in soil. Parameters of seedling growth promotion were evaluated 60 days after inoculation of seeds, with partition of the assessments into root and shoot weight. Each isolate showed beneficial, neutral or deleterious effects on plant growth, depending on the isolate and on the parts of plant assessed. Interestingly, although an apparent overall decrease in total biomass of seedlings (roots + shoots dry matters) was observed for the majority of isolates (89%), 94% of all isolates, in fact, revealed an increase in plant roots/shoots dry biomass ratio. Despite that part of the isolates (35%) appeared to significantly decrease plant height, and that 65% did not influence plant height (neutral effect), 18 had significantly increased root dry biomass; nevertheless, seven of these root growth-increasing isolates simultaneously decreased shoots-related growth parameters. The results of this study evidentiated the functional diversity of culturable cacao rhizobacteria and how the partitioning of roots and shoots in the assessment of plant growth parameters could reveal the biotechnological potential of these isolates for promoting growth of clones for rehabilitation of commercial cacao plantations. KEY POINTS: • The most common culturable bacteria in cacao roots were Pseudomonas and Enterobacter • Most culturable bacteria from cacao roots increased the root/shoot ratio • Roots and shoots should be examined separately to detect cacao beneficial bacteria.

The fungal genus Trichoderma bears species with several beneficial effects to plants, such as the ability to inhibit plant pathogens, induction of plant defense mechanisms, and improvement of plant growth. These fungi are active ingredients of a variety of commercially available biological products. To survey and understand the magnitude of the potential of Trichoderma spp. to reduce negative effects of abiotic stresses in plants, the literature was revised in a systematic way. The characteristics we observed were Trichoderma species and isolates, plants used as experimental models, types of abiotic stresses addressed, response variables of the Trichoderma-plant interaction, and which genes are possibly involved in the interactive mechanisms with Trichoderma that ameliorate abiotic stresses in plants. The complex T. harzianum was the group most commonly represented in studies with abiotic stresses in plants, whereas maize, Arabidopsis, rice, and tomato were the plant species most studied. Salt, drought, and heavy metals were the stress agents most frequently investigated. As a direct consequence of the studied stresses, a recurrent mechanism of action found for Trichoderma spp. was the production and accumulation of proline. The plant genes identified as related to the interaction plant-Trichoderma under abiotic stress were of four main classes: transcription factors, genes involved in metabolic pathways (including the ones related to oxidative stresses), genes required for signaling, and some related to the synthesis of protective compounds. The current knowledge in the interaction plant-Trichoderma as a way to ameliorate abiotic stresses in plants indicates a clear perspective of using such strategy as a promising alternative for development of crop production in sustainable agriculture.

Sisal is an economically and socially significant perennial crop for the semiarid region of the world. Bole rot disease, caused by black aspergilli, mainly by Aspergillus welwitschiae, is responsible for great losses due to the ability of the pathogen to kill the plant. The health status of plants that harbor endophytic biocontrol agents (BCAs) is being investigated in this study. We conducted experiments with endophytic bacteria from different parts of healthy and diseased sisal plants to select potential BCAs to control the disease. Studies on the populational densities showed that leaves have less bacteria when compared to roots and stems, and that diseased plants tended to have higher populations of bacterial endophytes. These results were obtained with both conventional plate counting and qPCR. A total of 497 isolates were screened as potential biocontrol agents on sisal discs and nine were selected as having direct antagonistic activity. Five isolates were from healthy and four from diseased plant parts. All these nine isolates significantly decreased the bole rot disease incidence in two field experiments and were identified by sequencing of the 16S rDNA as species belonging in the genera Bacillus, Brevibacterium, Burkholderia (2 isolates), Paenibacillus, Pseudomonas and Serratia (3 isolates). Isolate 466 of Burkholderia lowered 80% of disease incidence in both field experiments, which was not significantly different from the non-inoculated, negative control. We discussed these findings under an ecological-physiological interaction standpoint, as well as the possibilities of including diseased plants in bioprospection strategies and applying the selected isolates in the development of bioproducts.