Comparison between Four Landraces and a Commercial Variety

Funding Information: Funding: This research was funded by Fundação para a Ciência e a Tecnologia (FCT) and FEDER through ALT20-03-0145-FEDER-029867. Funding Information: This research was funded by Funda??o para a Ci?ncia e a Tecnologia (FCT) and FEDER through ALT20-03-0145-FEDER-029867. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Cowpea (Vigna unguiculata) is a robust legume; nevertheless, yield is always affected by drought, especially when it occurs during reproductive growth and seed filling. Considered a key crop in the effort to attain food security, and a suitable crop for a scenario of climate change, modern disregard for cowpea landraces is particularly detrimental as it causes genetic variability loss, compromising breeding efforts. To contribute to the evaluation of the cowpea germplasm, four Portuguese landraces (L1, L2, L3, L4) were compared with a commercial variety (CV) to evaluate their physiological responses to terminal drought and their inter-variation on productivity, under semi-controlled conditions. Despite no differences in relative water content (RWC) between the CV and the landraces under water deficit (WD), differences in leaf water potential (Ψ) defined the CV as having an isohydric control of stomata in contrast with anisohydric control for landraces. There was an identical decrease in the photosynthetic rate for all plants under stress, caused by both stomatal and non-stomatal limitations, namely, damages at the level of photosystem II as indicated by fluorescence measurements. Instantaneous water use efficiency (iWUE) was improved with stress in L1 and L3. Maintenance of higher relative chlorophyll content for longer periods in the CV revealed a stay-green phenotype. The slim differences observed in terms of stomatal control, iWUE and progression of senescence between the CV and the landraces under WD led to quite important differences in terms of productivity, as inferred from improved yield (number of pods and number of grains per plant). This is a clear result of pragmatic on-farm selection. On one hand it shows that small differences in stomatal responses or water saving strategies under WD may lead to desirable outcomes and should therefore be considered during breeding. On the other hand, it suggests that other traits could be explored in view of drought adaptation. These results highlight the need to preserve and characterize as many genetic pools as possible within a species.publishersversionpublishe

The N-fixing legume Periandra mediterranea constrains the invasion of an exotic grass (Melinis minutiflora P. Beauv) by altering soil N cycling

Melinis minutiflora is an invasive species that threatens the biodiversity of the endemic vegetation of the campo rupestre biome in Brazil, displacing the native vegetation and favouring fire spread. As M. minutiflora invasion has been associated with a high nitrogen (N) demand, we assessed changes in N cycle under four treatments: two treatments with contrasting invasion levels (above and below 50%) and two un-invaded control treatments with native vegetation, in the presence or absence of the leguminous species Periandra mediterranea. This latter species was considered to be the main N source in this site due to its ability to fix N2 in association with Bradyrhizobia species. Soil proteolytic activity was high in treatments with P. mediterranea and in those severely invaded, but not in the first steps of invasion. While ammonium was the N-chemical species dominant in plots with native species, including P.mediterranea, soil nitrate prevailed only in fully invaded plots due to the stimulation of the nitrifying bacterial (AOB) and archaeal (AOA) populations carrying the amoA gene. However, in the presence of P. mediterranea, either in the beginning of the invasion or in uninvaded plots, we observed an inhibition of the nitrifying microbial populations and nitrate formation, suggesting that this is a biotic resistance strategy elicited by P. mediterranea to compete with M. minutiflora. Therefore, the inhibition of proteolytic activity and the nitrification process were the strategies elicited by P.mediterranea to constrain M.munitiflora invasion

O sequestro de carbono em trechos da floresta urbana de Belo Horizonte: por um sistema de espaços livres mais eficiente no provimento de serviços ecossistêmicos urbanos

Este artigo objetiva estudar o papel das florestas urbanas na provisão de serviços ecossistêmicos urbanos por meio da análise do sequestro de carbono em áreas diferenciadas, no sistema de espaços livres da cidade de Belo Horizonte, procurando ofertar indicadores de qualidade de serviços ambientais e subsidiar a proposição de diretrizes paisagísticas direcionadas à sua implantação ou melhoria. Pela interpretação e aplicação de princípios e métodos relacionados ao estudo da paisagem – em especial aqueles das escolas da morfologia urbana e da ecologia da restauração –, foi possível a escolha para estudo de caso dos seguintes trechos de floresta urbana: o Parque Municipal das Mangabeiras, a praça Raul Soares e o Parque Municipal Américo Renê Giannetti. Nessas áreas estimou-se a biomassa vegetal  e do solo, assim como a concentração de substâncias húmicas e de isótopos estáveis de carbono e nitrogênio do solo. Os resultados obtidos foram analisados criticamente em relação aos processos morfológicos e à concepção e tratamento paisagístico de cada área. Com base nisso, delinearam-se diretrizes paisagísticas orientadas para a introdução e melhoria da prestação de serviços ecossistêmicos urbanos em trechos diferenciados de floresta urbana.This article seeks to study the role of urban forests in the provision of urban ecosystems through the analysis of carbon sequestration in differentiated open spaces located in the city of Belo Horizonte. It aims to offer quality indicators regarding environmental services and support the proposal for enhanced landscape guidelines for new or regenerated areas. Through the interpretation and application of landscaping principles and methods, particularly those from the schools of Urban Morphology and Restoration Ecology, the following urban forests were selected as case studies: Parque Municipal das Mangabeiras, Praça Raul Soares and Parque Municipal Américo Renê Giannetti. Their biomasses were estimated and soil samples were collected and sent to a laboratory to be tested for soil fertility, concentration of humic substances and analysis of stable isotopes. The results went through a critical analysis of both their morphological processes and their design and landscaping. Based on that information this article outlines a few landscaping guidelines in order to introduce and improve the provisions of urban ecosystem services in differentiated parts of the urban forest

Germinação de sementes de Senna macranthera, Senna multijuga e Stryphnodendron polyphyllum

With the aim of contributing to the knowledge about the wood legume Senna macranthera and Senna multijuga (Caesalpinaceae), and Stryphnodendron polyphyllum (Mimosaceae) seed germination, the seed imbibition curves were determined to identify the coat-imposed dormancy, and the procedures to overcome it with mechanical or chemical scarification. The coat impermeability was present in these three species and, the mechanical scarification was the most effective treatment to break the dormancy (germination percent up 80%). In S. macranthera, the chemical scarification with sulfuric acid by 12 minutes showed similar efficiency to the mechanical scarification. A variation in coat permeability between non-scarified seeds of S. polyphyllum was observed.Com o objetivo de contribuir para o conhecimento sobre a germinação de Senna macranthera e Senna multijuga (Caesalpinaceae) e Stryphnodendron polyphyllum (Mimosaceae), foram determinadas as curvas de embebição das sementes para identificar o grau de dormência imposta pelo tegumento e os procedimentos para superá-la (escarificação mecânica ou química). Nas três espécies verificou-se a presença de tegumento impermeável e a escarificação mecânica foi o tratamento mais eficiente para quebrar a dormência, com porcentagem de germinação superior à 80%. Em S. macranthera a escarificação química em ácido sulfúrico durante 12 minutos apresentou eficiência similar à escarificação mecânica. Observou-se também uma variação na permeabilidade do tegumento entre as sementes não-escarificadas de S. polyphyllum

Rhizobium strains competitiveness on bean nodulation in Cerrado soils

The objective of this work was to identify the most competitive and effective Rhizobium strains in order to increase common bean yield by nitrogen fixation as alternative or complementation to the nitrogen fertilization. Competitiveness tests were lead in axenic conditions, in Cerrado soil pots and in three field experiments, with native Rhizobium strains that were previously identified, according to their effectiveness and genetic variability. The identification of strains in nodules was performed using serological tests (axenic conditions) - agglutination and enzyme linked immunosorbent (Elisa) assays - and random amplified polymorfic DNA (RAPD) (Cerrado soil). Plant yield was determined using the dry weight (greenhouse conditions), total N and grain yield (field experiments). Among the analyzed Rhizobium strains, native strain SLA 2.2 and commercial strain CIAT 899 were the dominant nodules in plants of the most productive plots, presenting yield productivity similar or higher to those obtained in treatments where 20 kg ha-1 of N were applied.O objetivo deste trabalho foi identificar as estirpes de Rhizobium mais efetivas e competitivas, a fim de maximizar a produtividade do feijoeiro por meio da fixação de nitrogênio, como alternativa à adubação nitrogenada. Foram conduzidos testes de competitividade em condições axênicas, em vasos com solo do Cerrado e em três experimentos de campo, com estirpes de Rhizobium nativas, previamente selecionadas quanto à efetividade e à variabilidade genética. A identificação das estirpes nos nódulos foi efetuada por meio das técnicas de aglutinação e ensaio imunoabsorvente de ligação de enzimas (Elisa), em condições de casa de vegetação, e pela técnica de DNA polimórfico amplificado ao acaso (RAPD), em solo de Cerrado. A produtividade das plantas foi determinada pela produção de matéria seca, teor de N e produção de grãos (condições de campo). A estirpe nativa SLA 2.2 e a estirpe comercial CIAT 899 foram dominantes nos nódulos das plantas das parcelas mais produtivas, com índices de produtividade iguais ou superiores aos obtidos nos tratamentos em que foram aplicados 20 kg ha-1 de N

Spontaneous streptomycin resistance and efficiency of Rhizobium strains native in Brazilian cerrados associated with Stylosanthes

Foram efetuados isolamentos de Rhizobium sp nativos nos Cerrados, associados a Stylosanthes spp, com o objetivo de estudar a natureza dos fatores que interferem no estabelecimento das estirpes de Rhizobium inoculadas, e de avaliar o potencial de fixação de N2 das estirpes nativas. Dentre 122 estirpes isoladas em solo sob Cerrado cultivado, 35% foram resistentes a concentrações iguais ou superiores a 40 μg/ml, enquanto que apenas 10% dentre 92 estirpes isoladas em solo sob Cerrado virgem apresentaram esse nível de resistência. Esses dados sugerem que modificações ecológicas promovidas pelo cultivo dos Cerrados podem induzir a vantagens competitivas para estirpes de Rhizobium sp. resistentes à estreptomicina. Experimentos conduzidos em vasos Leonard com areia e solução nutritiva esterilizada indicaram que cerca de 61% das estirpes isoladas em S. guianensis var. Canescens e S. grandifolia eram pouco ou moderadamente efetivas no hospedeiro homólogo, enquanto que apenas 14% das estirpes apresentaram um nível elevado de fixação do N2. Esse baixo índice de estirpes eficientes sugere a necessidade de se iniciar um trabalho de seleção de Rhizobium sp. adaptado às condições dos Cerrados, visando a produção de inoculantes de alta qualidade para a região.Rhizobium strains were isolated from nodules of Stylosanthes spp. in undisturbed or cultivated Cerrado soils that have never been inoculated, in order to study the nature of the factors that affect stablishment of Rhizobium strains introduced in these soils, as well as to evaluate the N2 fixing capacity of the native strains. Streptomycin resistance level of the Rhizobium strains were tested in yeast-mannitol-agar plates. Among 122 strains isolated in cultivated Cerrado, 35%  were resistant to concentrations equal or above 40 μg/ml, while only 10% within 92 strains isolated in undisturbed Cerrados were resistant to that level. These data suggest that the ecological changes caused by cultivation of virgin savanna land result in competitive advantages for Streptomycin resistent Rhizobium strains. Experiments carried out in Leonard jar assemblies with san and sterilized solution indicated that 61% of the strains isolated in S. guianensis var. Canescens and S. grandifolia were low or moderately effective in the homologous host, while only 14% of the strains had a high level of N2 fixation. This low percentage of efficient strains suggests the necessity of a Rhizobium strain selection program adapted to the Cerrado conditions, aiming to obtain high quality inoculant for the Cerrados region

Intercropping system of tropical leguminous species and Eucalyptus camaldulensis , inoculated with rhizobia and/or mycorrhizal fungi in semiarid Brazil

For the purpose of reforestation and wood supply the leguminous tree Anadenanthera peregrina, a native species, was intercropped with Eucalyptus camaldulensis in a degraded semiarid area of Brazil. Single and mixed stands of these species were inoculated with Rhizobium and/or arbuscular mycorrhizal fungi (AMF). The growth of all species in mixed stands did not differ from those cultivated in monoculture and land equivalent ratio (LER) exceeded unity in intercropped plots. Inoculated plants showed greater height and diameter growth and dry matter and nutrient concentration in plants of A. peregrina was higher in inoculated single plots. The distribution, composition and density of AMF species was related to the rhizosphere effect of plant species. The intercropped model where all the plants were inoculated achieved soil AMF diversity patterns similar to those of the preserved area and showed also higher soil organic matter, nutrient content as well as a reduction in soil macroporosity. This model of intercropping may be considered as an efficient system for reforestation under semiarid conditions.Facultad de Ciencias Naturales y Muse

Decomposição da serrapilheira de Arachis pintoi e Hyparrhenia rufa em sistemas de monocultura e consórcio sob solo de várzea

Tropical grasslands under lowland soils are generally underutilized and the litter of forage legumes may be used to recover these degraded pastures. The objective of this work was to study the dynamics of litter decomposition of Arachis pintoi (pinto peanut), Hyparrhenia rufa (thatching grass) and a mixture of both species in a lowland soil. These treatments were analyzed in three areas: grass monoculture, legume monoculture and legume intercropped with the grass during the dry and wet seasons. Litter bags containing the legume, grass or a mixture of both species were incubated to estimate the decomposition rate and microorganism colonization. Decomposition constants (K) and litter half-lives (T1/2) were estimated by an exponential model whereas number of microorganisms in specific media were determined by plate dilution. The decomposition rate, release of nutrients and microorganisms number, especially bacteria, increased when pinto peanut was added to thatching grass, influenced by favorable lignin/N and C/N ratios in legume litter. When pinto peanut litter was incubated in the grass plots, 50% N and P was released within about 135 days in the dry season and in the wet season, the equivalent release occurred within 20 days. These results indicate that A. pintoi has a great potential for nutrient recycling via litter and can be used to recover degraded areas.Pastagens tropicais sobre solos de várzea são geralmente subutilizadas. A serrapilheira de leguminosas forrageiras pode ser usada para a recuperação destas pastagens. O objetivo deste trabalho foi estudar a dinâmica de decomposição de Arachis pintoi (arachis), Hyparrhenia rufa (capim jaraguá) e da mistura destas espécies, em solo de várzea. Estes tratamentos foram analisados em três áreas: monocultivo da gramínea; monocultivo da leguminosa e no consórcio entre as espécies durante as estações seca e chuvosa. Sacos de decomposição contendo a serrapilheira da leguminosa ou da mistura das espécies foram incubados para estimar a taxa de decomposição e colonização microbiana. A taxa de decomposição e o tempo de meia-vida (T1/2) foram estimados por um modelo exponencial, e o número de microrganismos foi determinado por meio de diluição em placas em meios específicos. A liberação de nutrientes, a taxa de decomposição, e o número de microrganismos, especialmente bactérias, aumentaram quando arachis foi adicionado ao capim jaraguá, com influência da relação favorável de lignina/N e C/N do resto desta cultura. Quando arachis foi incubado em parcelas de monocultivo da gramínea, 50% do total de N e P foi liberado em 135 dias na estação seca e em 20 dias na estação chuvosa. Estes resultados indicam que A. pintoi tem um grande potencial para ciclagem de nutrientes e pode ser uma estratégia na recuperação de áreas degradadas

Changes in protein profiles (SDS-PAGE) of competitive Bradyrhizobium sp. strains during soybean pre-infection stage

Em 1976 a estirpe SEMIA 566 de Bradyrhizobium japonicum (parental) foi introduzida nos Cerrados, onde formou apenas 2% dos nódulos de soja. Atualmente, o sorogrupo SEMIA 566 domina (60%) nos nódulos de soja nos Cerrados, deslocando a 29W e SEMIA 587 que ocupavam 90% dos nódulos. Visando coompreender os mecanismos envolvidos na competitividade, estirpes SEMIA 566 isoladas dos Cerrados foram usadas como inoculante de soja cultivada em duas áreas de Cerrados. Os solos das duas áreas apresentavam populações residentes, respectivamente, dos sorogrupos 29W (Área 1) e SEMIA 587 (Área 2). As estirpes SEMIA 566, mais competitivas ante a 29W, diferem das que venceram a competição com a SEMIA 587. Após seis horas de contato com as raízes de soja, os isolados SEMIA 566 mais competitivos que a 29W apresentaram alterações, em eletroforese(SDS-PAGE), dos polipeptídios do envelope celular com peso molecular (PM) de 46-44kD e 37kD, e as mais competitivas que a SEMIA 587 modificaram as proteínas de 44kD, 42kD, 40kD e 37kD. As estirpes pouco competitivas apresentaram alterações tardias (doze horas) ou não modificaram esses polipeptídios. As estirpes SEMIA 566 isoladas, dos solos de Cerrados diferiram da estirpe SEMIA 566 parental, pela presença de uma proteína de 44kD. Portanto, esses isolados além de mais competitivos constituem nova subpopulação SEMIA 566.When the Bradyrhizobium japonicum SEMIA 566 (parental strain) was introduced into Cerrados soils (Savanna soils) in 1976, this strain was found to be able to occupy only 2% of soybean nodules. In contrast, strains 29W and SEMIA 587 both presented 90% of nodule occupancy. Nowadays, in the same type of soil, the serogroup 566 dominates (60%) in the soybean nodules, dislocating the 29W and SEMIA 587 strains. For comparative analysis of parental and adapted SEMIA 566, some strains SEMIA 566 were re-isolated from Cerrados and used as inoculant to soybean cultivated in two Cerrado areas. The first area showed a resident soil population of serogroup 29W (area 1), and in the second area the established soil population belongs to serogroup SEMIA 587 (area 2). The re-isolates that were more competitive in 29W area were different from those that have shown to be more competitive than SEMIA 587. After six hours of contact with soybean roots, the re-isolates SEMIA 566 that were more competitive than 29W presented alterations of electrophoretic (SDS-PAGE) polypeptidic bands of cellular envelope with molecular weight (MW) of 44-46kD and 37kD. On the other hand, the re-isolates that showed higher nodule occupancy levels in relation to SEMIA 587 registred alterations in proteins of 44kD, 42Kd, 40kD and 37kD. The low competitive strains presented delayed alterations (12 hours) or did not modify these polypeptidic bands. The reisolates SEMIA 566 as well as the parental strain SEMIA 566, are serologically identical, differing from each other in the protein of 44kD which was absent in the parental strain. The strains SEMIA 566, isolated from Cerrados soils differed from the parental SEMIA 566 through the presence of a 44kD protein. Therefore, those isolates, besides being competitive, constitute a new SEMIA 566 subpopulation

Bacterial diversity in the rhizosphere of maize genotypes contrasting for phosphorus use efficiency

O objetivo deste trabalho foi avaliar a diversidade funcional e genética de bactérias associadas à rizosfera de genótipos de milho contrastantes quanto à eficiência de uso de fósforo, por meio do teste de fontes de carbono no sistema EcoPlate e da eletroforese em gel de gradiente desnaturante (DGGE) dos fragmentos amplificados dos genes 16S ribossomais (rDNA) das bactérias. Foram coletadas amostras de solo da rizosfera de linhagens e híbridos contrastantes quanto à eficiência de uso de fósforo, cultivados em Latossolo Vermelho-Escuro fase cerrado, com baixo e alto teor de P. Bactérias da rizosfera de híbridos e linhagens eficientes, sob estresse de P, analisadas pelo sistema EcoPlate, tenderam a se agrupar conforme a análise de componentes principais, o que indica que utilizaram fontes de carbono semelhantes. Não houve diferença na diversidade bacteriana, analisada pela DGGE, entre bactérias associadas a genótipos eficientes e ineficientes no uso de P. Com base no sequenciamento do 16S rDNA, foi verificado que a rizosfera de genótipos de milho sob estresse de P parece selecionar grupos específicos de bactérias. A estrutura populacional genética e metabólica de bactérias da rizosfera foi mais influenciada pelo teor de fósforo no solo do que pela eficiência das plantas em usar o fósforo.The objective of this work was to evaluate the functional and genetic diversity of bacteria associated to the rhizosphere of maize genotypes contrasting for phosphorus use efficiency by means of the EcoPlate carbon source test and denaturing gradient gel electrophoresis (DGGE) of amplified 16S ribosomal DNA (rDNA) fragments of bacteria. Rhizosphere soil samples of maize genotypes (hybrids and lineages) contrasting for phosphorus use efficiency cultivated in an Oxisol with high and low P content were collected. Bacteria from the rhizosphere of P-efficient maize genotypes under P stress conditions analyzed by the EcoPlate system tended to group together according to main components analysis, which indicates that these bacteria used similar carbon sources. Microbial diversity analyzed by DGGE did not differ between P-efficient and inefficient maize genotypes. Based on the 16S rDNA fragment sequencing, the rhizosphere of maize genotypes growing on low-P soils seemed to select specific bacteria species. The genetic and metabolic structure of the rhizosphere bacterial community was more strongly influenced by the level of P in the soil than by the genotypes with contrasting P-use efficiency