Tree legumes are a viable option to increase ecosystem services provided by warm‐climate grasslands. Benefits of using tree legumes in silvopasture systems (SPS) include the provision of shade for livestock, biological N2 fixation, and C sequestration. This study assessed cattle performance and pasture characteristics in signalgrass (Brachiaria decumbens Stapf.) pastures in monoculture or in SPS. The following treatments were assessed: (i) signalgrass/sabiá (Mimosa caesalpiniifolia Benth.), (ii) signalgrass/gliricidia [Gliricidia sepium (Jacq.) Kunth ex Walp.], and (iii) signalgrass monoculture. Crossbred steers were managed under continuous stocking and variable stocking rates. Response variables included herbage mass, herbage allowance, stocking rate, average daily gain (ADG), gain per area (GPA), in vitro dry matter digestibility (IVDMD), and crude protein (CP). Total signalgrass herbage mass in monoculture (5091 kg DM ha−1) was greater (P ≤ 0.05) compared with SPS (3964 kg DM ha−1). Green signalgrass herbage mass, however, was greater (P ≤ 0.05) for SPS (2237 kg DM ha−1) compared with monoculture (1934 kg DM ha−1). Herbage allowance, IVDMD, CP, stocking rate, ADG, and GPA did not differ among treatments, with average values of 2.9 kg−1 green herbage mass (DM) kg−1 live weight; 633 g kg−1, 55 g kg−1, 1.9 animal units (AU) ha−1 (1 AU = 450 kg live weight); 0.57 kg−1 AU−1 d−1; and 30 kg ha−1 28 d−1, respectively. During the establishment phase (3 yr), SPS with tree legumes can produce as much livestock gain as signalgrass in monoculture, providing other ecosystem services and marketable products, increasing land use efficiency.Core Ideas Livestock production was similar in silvopasture systems and signalgrass monoculture. Silvopasture systems provided additional ecosystem services compared with grass monoculture. The use of tree legumes adds biologically fixed N2 and provide other ecosystem services. Trees compete with herbaceous vegetation and might reduce livestock production in the long term.

Pasture degradation can cause changes in diazotrophic bacterial communities. Thus, this study aimed to evaluate the culturable and total diazotrophic bacterial community, associated with regions of the rhizosphere and roots of Brachiaria decumbens Stapf. pastures in different stages of degradation. Samples of roots and rhizospheric soil were collected from slightly, partially, and highly degraded pastures. McCrady's table was used to obtain the Most Probable Number (MPN) of bacteria per gram of sample, in order to determine population density and calculate the Shannon-Weaver diversity index. The diversity of total diazotrophic bacterial community was determined by the technique of Denaturing Gradient Gel Electrophoresis (DGGE) of the nif H gene, while the diversity of the culturable diazotrophic bacteria was determined by the Polymerase Chain Reaction (BOX-PCR) technique. The increase in the degradation stage of the B. decumbens Stapf. pasture did not reduce the population density of the cultivated diazotrophic bacterial community, suggesting that the degradation at any degree of severity was highly harmful to the bacteria. The structure of the total diazotrophic bacterial community associated with B. decumbens Stapf. was altered by the pasture degradation stage, suggesting a high adaptive capacity of the bacteria to altered environments.

The Caatinga is an exclusively Brazilian biome that has been under high anthropogenic action, which directly interferes in the quality of its soil. In order to evaluate and monitor the quality of the soil, chemical and biological indicators are used, with the determination of the enzymatic activity gaining prominence. The objective of this study was to evaluate the enzymatic activity of soils of the Caatinga biome in preserved and anthropized areas belonging to the Catimbau National Park, located in Pernambuco, Brazil, during the two periods of the year (rainy and dry), for three consecutive years, 2014, 2015 and 2016. Enzymatic activities of β-glucosidase, urease, arylsulfatase, and acid and alkaline phosphatase in the soil were evaluated. Anthropic action caused reduction in the enzymatic activities of β-glucosidase, arylsulfatase and urease. Regarding the periods of the year, the dry one showed smaller values of enzymatic activity of β-glucosidase, arylsulfatase and urease. Among the evaluation years, when correlating accumulated precipitation and enzymatic activity, the highest correlations were observed in the preserved area in both periods of the year. The fragility of Caatinga soils under anthropic action was observed in both periods of the year, over time. The increasing anthropization of areas of the Catimbau National Park has a direct effect on soil quality, affects its ecological balance, causing degradation and reduction of its quality. Appropriate enforcement measures are urgently needed to ensure their environmental preservation.

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Burkholderia sp. is a bacterial genus extremely versatile in the environment and has been reported for a great potential to promote plant growth via different mechanisms. Here we evaluate the plant growth-promoting mechanisms in twenty-six Burkholderia strains. Strains were evaluated for their ability to promote plant growth by means of: indole-3-acetic acid (IAA) production under different conditions of pH, salt stress and the presence or absence of L-tryptophan; exopolysaccharides (EPS) production and quorum sensing (ALH). The strains were also characterized in terms of their genetic variability and species identification through Sanger sequencing. Then, the bacteria most responsive in the greatest number of plant-growth promotion mechanisms were selected for a corn seed germination test. All bacteria synthesized IAA in medium with 0.0 or 5.0 mM of L-tryptophan in combination with either 1 or 5% of NaCl, and pH values of either 4.5 or 7.2. The EPS production was confirmed for 61.54% of the bacterial strains. Quorum sensing also occurred in 92.3% of the selected bacteria. The Jaccard similarity coefficient revealed 16 clusters with high genetic variability between bacterial strains. Bacterial strains were assigned to seven species: B. anthina, B. cepacia, B. gladioli, B. ambifaria, B. graminis, B. heleia, and Burkholderia spp. The corn seed bacterization did not affect the germination velocity index (GSI), as well as the first count of germinated seeds (FC). However, inoculations formulated with B. heleia strain G28, B. gladioli strain UAGC723, and B. graminis strain UAGC348 promoted significant increases in root length, seedling height and fresh and dry seedling phytomass, respectively. These results indicate the high biotechnological potential of several strains in the genus Burkholderia sp. as seed inoculants, favoring germination and seedling initial development.

Plant growth-promoting bacteria (PGPB) have received great interest in recent decades. However, PGPB mechanisms remain poorly understood in forage species. We aimed to evaluate roots endophytic and rhizospheric bacteria strains from Brachiaria humidicola and Brachiaria decumbens. The strains were evaluated for biological nitrogen-fi xing in saline stress (0 to 10.0 g L -1 of NaCl), N-acyl homoserine lactones and indole-like compounds (ILC) production, the activity of hydrolytic enzymes, and inorganic phosphate solubilization (IPS) under different C sources. The diversity of strains was assessed by BOX-PCR. About 58% of strains were positive for BNF. High salinity levels reduced the growth and BNF. About 58% produced N-acyl homoserine lactones. The ILC was present in 39% of strains. Cellulase, polygalacturonase, pectate lyase, and amylase production were observed in 77, 14, 22, and 25% of strains, respectively. The IPS was observed in 44, 81, and 87% of isolates when glucose, mannitol and sucrose were used, respectively. Comparing two plant species and niches, the strains associated with B. humidicola and root endophytic presented more PGPB mechanisms than others. We found high strain diversity, of which 64% showed similarity lower than 70%. These results can be supporting the bioproducts development to increase forage grasses production in tropical soils.

The resistance induction becomes an alternative to control microorganisms that attacks like plants. Little is known about the dose and its effect on the enzymatic activities associated with the induction of resistance of pepper plants under anthracnose attack. The objective of this study was to evaluate the severity and to estimate the enzymatic activity of Arcade F1 hybrid peppers infected with Colletotrichum gloeosporioides and submitted to different doses of the abiotic acibenzolar-S-methyl inducer. The experimental design was completely randomized blocks with five treatments, four doses of acibenzolar-S-methyl (0.15, 0.30, 0.45 and 0.60 g.L-1), and the control with distilled water only. The evaluation of leaf severity and collection for enzymatic activity of β-1,3-glucanase, catalase, peroxidase, polyphenoloxidase and ascorbate peroxidase were performed on the 4th, 8th and 12th day after inoculation of the phytopathogen. The application of acibenzolar-S-methyl provided a reduction in anthracnose severity, with an increase in all the enzymatic activities evaluated, but there was no prevalence of a specific dose. However, all doses of the evaluated inducers were able to delay the development of the phytopathogen with elevated activity of one or more antioxidant enzyme. KEYWORDS: Antioxidant enzymes, phytopathogenic fungus, Colletotrichum gloeosporioides.

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