scholarly journals Diversity of Rhizobia and Importance of Their Interactions with Legume Trees for Feasibility and Sustainability of the Tropical Agrosystems

Diversity ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 206 ◽  
Author(s):  
Emanoel G. Moura ◽  
Cristina S. Carvalho ◽  
Cassia P. C. Bucher ◽  
Juliana L. B. Souza ◽  
Alana C. F. Aguiar ◽  
...  
Keyword(s):  
Acacia Mangium ◽  
Gliricidia Sepium ◽  
Common Species ◽  
Humid Tropics ◽  
Limiting Factor ◽  
Tropical Environments ◽  
Legume Trees ◽  
Sustainable Agricultural Systems ◽  
Biological Nitrogen ◽  
N Use

Symbiotic biological nitrogen fixation (BNF) is a complex process that involves rhizobia, a diverse group of α and β-proteobacteria bacteria, and legume species. Benefits provided by BNF associated with legume trees in tropical environments include improvements to efficiency of nitrogen (N) use, increase of soil carbon sequestration, stabilization of soil organic matter, decrease of soil penetration resistance, and improvement of soil fertility. All these benefits make BNF a crucial ecosystem service to the sustainability of tropical agriculture. Due to the importance of this ecological process and the high diversity of rhizobia, these bacteria have been extensively characterized worldwide. Currently, over 400 species of rhizobia are known, distributed into seven families. In the humid tropics, Leucaena leucocephala, Acacia mangium, Gliricidia sepium, and Clitoria fairchildiana are four of the most common species used by family farmers to create sustainable agricultural systems. These four legumes perform symbiosis with different groups of rhizobia. Exploring BNF could help to enable sustainable intensification of agriculture in the humid tropics, mainly because it can increase N use efficiency in an environment where N is a limiting factor to plant growth.

Sustainable Agricultural Systems in the Humid Tropics of South America

2020 ◽  
pp. 391-437
Author(s):  
Hugo Villachica ◽  
Jose E. Silva ◽  
Jose Roberto Peres ◽  
Carlos Magno C. da Rocha
Keyword(s):  
South America ◽  
Humid Tropics ◽  
Agricultural Systems ◽  
Sustainable Agricultural Systems

scholarly journals Specific mycorrhizal associations involving the same fungal taxa in common and threatened Caladenia (Orchidaceae): implications for conservation

2020 ◽  
Vol 126 (5) ◽  
pp. 943-955 ◽  
Author(s):  
Noushka Reiter ◽  
Ryan D Phillips ◽  
Nigel D Swarts ◽  
Magali Wright ◽  
Gareth Holmes ◽  
...  
Keyword(s):  
Threatened Species ◽  
Mycorrhizal Fungi ◽  
Sequence Divergence ◽  
High Specificity ◽  
Common Species ◽  
Geographic Range ◽  
Limiting Factor ◽  
Mycorrhizal Associations ◽  
Orchid Conservation ◽  
Australian Continent

Abstract Background and Aims In orchid conservation, quantifying the specificity of mycorrhizal associations, and establishing which orchid species use the same fungal taxa, is important for sourcing suitable fungi for symbiotic propagation and selecting sites for conservation translocation. For Caladenia subgenus Calonema (Orchidaceae), which contains 58 threatened species, we ask the following questions. (1) How many taxa of Serendipita mycorrhizal fungi do threatened species of Caladenia associate with? (2) Do threatened Caladenia share orchid mycorrhizal fungi with common Caladenia? (3) How geographically widespread are mycorrhizal fungi associated with Caladenia? Methods Fungi were isolated from 127 Caladenia species followed by DNA sequencing of the internal transcibed spacer (ITS) sequence locus. We used a 4.1–6 % sequence divergence cut-off range to delimit Serendipita operational taxonomic units (OTUs). We conducted trials testing the ability of fungal isolates to support germination and plant growth. A total of 597 Serendipita isolates from Caladenia, collected from across the Australian continent, were used to estimate the geographic range of OTUs. Key Results Across the genus, Caladenia associated with ten OTUs of Serendipita (Serendipitaceae) mycorrhizal fungi. Specificity was high, with 19 of the 23 threatened Caladenia species sampled in detail associating solely with OTU A, which supported plants from germination to adulthood. The majority of populations of Caladenia associated with one OTU per site. Fungal sharing was extensive, with 62 of the 79 Caladenia sampled in subgenus Calonema associating with OTU A. Most Serendipita OTUs were geographically widespread. Conclusions Mycorrhizal fungi can be isolated from related common species to propagate threatened Caladenia. Because of high specificity of most Caladenia species, only small numbers of OTUs typically need to be considered for conservation translocation. When selecting translocation sites, the geographic range of the fungi is not a limiting factor, and using related Caladenia species to infer the presence of suitable fungal OTUs may be feasible.

scholarly journals Decomposition and Nutrient Release of Tree Legumes in an Agroforest System

2018 ◽  
Vol 10 (8) ◽  
pp. 417
Author(s):  
Larissa Brandao Portela ◽  
Anagila Janenis Cardoso Silva ◽  
Gustavo André de Araújo Santos ◽  
Joab Luhan Ferreira Pedrosa ◽  
Conceição De Maria Batista de Oliveira ◽  
...  
Keyword(s):  
Leucaena Leucocephala ◽  
Alley Cropping ◽  
Block Design ◽  
Acacia Mangium ◽  
Cropping System ◽  
Nutrient Release ◽  
Soil Surface ◽  
Gliricidia Sepium ◽  
Plant Residues ◽  
Randomized Block Design

The research compared biomass production and nutrient release in an alley cropping system in two collection methods, the litterbag method and the direct collection method (Morley, Bennett, & Clark, 1964). The system was implemented in 2015 at 2017, at the Maranhão Federal University, Maranhão, Brazil. The experiment was a randomized block design with four treatments, consisting of leucaena+sombreiro (Leucaena leucocephala and Clitoria fairchildiana), leucena+acacia (Leucaena leucocephala and Acacia mangium), gliricidia+sombreiro (Gliricidia sepium and Clitoria fairchildiana) and gliricidia+acacia (Gliricidia sepium and Acacia mangium). In order to determine the remaining dry matter, nutrient release (N, P, K, Ca, Mg and Mn), the decomposition constants and the half-lives times of plant residues, 100 g of fresh material were conditioned in litterbags (50 g of each species), arranged on the soil surface. The second method was done by randomly throwing a collector on each plot in the same dimensions of the litterbags (0.40 x 0.40 m) and collecting the litter. For the two methods samples were collected at 0, 30, 60, 90 and 120 days after the start of the experiment. The litterbags method showed a higher C/N ratio at day 30 up to 120 days, which implies that this method is providing a different environment from the litter, where it would be overestimating the C/N ratio and retarding the decomposition. The G+S and G+A combinations were more rapidly decomposed than the combinations of L+S and L+A. The following order of release was established for the litterbags method: P > N > K > Ca > Mn > Mg, and for the method of collecting the litter: N > P > Ca > Mg > K > Mn.

scholarly journals Environmental and agricultural benefits of a management system designed for sandy loam soils of the humid tropics

2009 ◽  
Vol 33 (5) ◽  
pp. 1473-1480 ◽  
Author(s):  
Alana das Chagas Ferreira Aguiar ◽  
Andreia Pereira Amorim ◽  
Katia Pereira Coêlho ◽  
Emanoel Gomes de Moura
Keyword(s):  
Leucaena Leucocephala ◽  
Cajanus Cajan ◽  
Alley Cropping ◽  
Soil Layer ◽  
Acacia Mangium ◽  
Humid Tropics ◽  
Base Saturation ◽  
Natural Fertility ◽  
Root Penetration ◽  
Corn Yield

A sustainable management of soils with low natural fertility on family farms in the humid tropics is a great challenge and overcoming it would be an enormous benefit for the environment and the farmers. The objective of this study was to assess the environmental and agronomic benefits of alley cropping, based on the evaluation of C sequestration, soil quality indicators, and corn yields. Combinations of four legumes were used in alley cropping systems in the following treatments: Clitoria fairchildiana + Cajanus cajan; Acacia mangium + Cajanus cajan; Leucaena leucocephala + Cajanus cajan; Clitoria fairchildiana + Leucaena leucocephala; Leucaena leucocephala + Acacia mangium and a control. Corn was used as a cash crop. The C content was determined in the different compartments of soil organic matter, CEC, available P, base saturation, percentage of water saturation, the period of the root hospitality factor below the critical level and corn yield. It was concluded that alley cropping could substitute the slash and burn system in the humid tropics. The main environmental benefit of alley cropping is the maintenance of a dynamic equilibrium between C input and output that could sustain up to 10 Mg ha-1 of C in the litter layer, decreasing atmospheric CO2 levels. Alley cropping is also beneficial from the agricultural point of view, because it increases base saturation and decreases physical resistance to root penetration in the soil layer 0 - 10 cm, which ensures the increase and sustainability of corn yield.

scholarly journals Desempenho de doze espécies arbóreas nativas e introduzidas com potencial de uso múltiplo no estado do Acre, Brasil

2000 ◽  
Vol 30 (3) ◽  
pp. 471-471 ◽  
Author(s):  
Elias Melo de MIRANDA ◽  
Judson Ferreira VALENTIM
Keyword(s):  
Leucaena Leucocephala ◽  
Acacia Mangium ◽  
Gliricidia Sepium ◽  
Cedrela Odorata ◽  
Erythrina Poeppigiana

O objetivo deste estudo foi avaliar o desempenho de espécies arbóreas com potencial de uso múltiplo, nas condições ambientais da Amazônia ocidental brasileira, visando recomendá-las como componentes de sistemas agroflorestais e para recuperação de áreas degradadas. O experimento foi estabelecido na Estação Experimental da Embrapa Acre, com 12 espécies nativas e introduzidas, no espaçamento de 1,50 m entre linhas, por 1,50 m entre plantas. O delineamento experimental foi de blocos casualizados, com quatro repetições. Cada espécie foi representada por cinco plantas em cada repetição. As avaliações, realizadas até quatro anos e meio após o plantio mostraram que: a) todas as espécies apresentaram índices de sobrevivência superiores a 80%, com exceção de Cedrela odorata (75%), Aspidosperma vargasii (65%) e Spondias lutea (65%); b) o incremento médio anual em altura total foi maior em Acacia mangium (2,91 m) e Acacia pollyphylla (2,66 m), seguida por Leucaena leucocephala, Calycophyllum spruceanum e Gliricidia sepium com médias de 2,38, 1,56 e 1,40 m, respectivamente; c) o incremento médio anual em diâmetro basal também foi maior em A. mangium (4,98 cm) e A. pollyphylla (3,92 cm), seguidas de Erythrina fusca (3,06 cm), Spondias lutea (2,37 cm), Erythrina poeppigiana (2,17 cm) e E. berteroana (2,12 cm); d) o incremento anual em diâmetro da copa foi maior em A. pollyphylla (2,50 m), G. sepium (1,03 m), Torresea acreana (0,98 m) e Erythrina fusca (0,87 m). Estes resultados sugerem a boa adaptação das espécies introduzidas que apresentaram desenvolvimento superior à maioria das nativas, principalmente em termos de capacidade de estabelecimento e crescimento inicial.

scholarly journals Influence of Azospirillum brasilense associated with silicon and nitrogen fertilization on macronutrient contents in corn

2020 ◽  
Vol 5 (1) ◽  
pp. 126-137 ◽  
Author(s):  
Fernando Shintate Galindo ◽  
Marcelo Carvalho Minhoto Teixeira Filho ◽  
Salatiér Buzetti ◽  
Willian Lima Rodrigues ◽  
Guilherme Carlos Fernandes ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Soil Acidity ◽  
Block Design ◽  
Nutrient Content ◽  
Biotic And Abiotic Stresses ◽  
No Till ◽  
Randomized Block Design ◽  
N Rates ◽  
Biological Nitrogen ◽  
N Use

AbstractInformation regarding the interaction between biological nitrogen fixation (BNF) with Azospirillum brasilense inoculation and the use of silicon (Si) is needed. Silicon exerts numerous benefits on grasses, especially when the plants are subjected to biotic and abiotic stresses, affecting plant nutrition. The aim of this research was to determine if there is a synergistic effect between the inoculation with A. brasilense and Si use, on macro-nutrient content in corn shoot and root. The field trial was performed in Selvíria, Brazil, on a Typic Rhodic Hapludox soil under no-till system. The experimental design was a completely randomized block design with four replicates arranged in a 2 × 5 × 2 triple factorial arrangement, consisting of two soil acidity corrective sources (dolomitic limestone and Ca and Mg silicate as sources of Si); five N doses (0, 50, 100, 150 and 200 kg ha-1 applied in topdressing); with and without seed inoculation with A. brasilense. The inoculation favored N concentration in shoots and increased the N and S concentration even when associated to high N rates in topdressing. The Si as Ca and Mg silicate associated with the increment of N rates does not promote an increase in the macronutrients uptake. Although it did not favor the N use, the Si also did not negatively affect the benefits of the A. brasilense.

scholarly journals Improving access to endogenous DNA in ancient bones and teeth

2015 ◽  
Author(s):  
Peter de Barros Damgaard ◽  
Ashot Margaryan ◽  
Hannes Schroeder ◽  
Ludovic Orlando ◽  
Eske Willerslev ◽  
...  
Keyword(s):  
Standard Procedure ◽  
Genomic Research ◽  
Limiting Factor ◽  
Digestion Time ◽  
Bone Material ◽  
Tropical Environments ◽  
Molecular Complexity ◽  
A Minor ◽  
Methodological Guidelines ◽  
Digestion Step

Poor DNA preservation is the most limiting factor in ancient genomic research. In the vast majority of ancient bones and teeth, endogenous DNA molecules only represent a minor fraction of the whole DNA extract, rendering traditional shot-gun sequencing approaches cost-ineffective for whole-genome characterization. Based on ancient human bone samples from temperate and tropical environments, we show that an initial EDTA-based enzymatic 'pre-digestion' of powdered bone increases the proportion of endogenous DNA several fold. By performing the pre-digestion step between 30 min and 6 hours on five bones, we identify the optimal pre-digestion time and document an average increase of 2.7 times in the endogenous DNA fraction after 1 hour of pre-digestion. With longer pre-digestion times, the increase is asymptotic while molecular complexity decreases. We repeated the experiment with n=21 and t=15-30', and document a significant increase in endogenous DNA content (one-sided paired t-test: p=0.009). We advocate the implementation of a short pre-digestion step as a standard procedure in ancient DNA extractions from bone material. Finally, we demonstrate on 14 ancient teeth that crushed cementum of the roots contains up to 14 times more endogenous DNA than the dentine. Our presented methodological guidelines considerably advance the ability to characterize ancient genomes.

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