RESUMO Várias espécies lenhosas tropicais são altamente responsivas a fungos micorrízicos arbusculares (FMA) e dependem da simbiose para nutrição e sucesso no estabelecimento em campo. O objetivo deste estudo foi avaliar a resposta de Schinus terebinthifolius, uma espécie nativa da Mata Atlântica e Caatinga, à inoculação com três espécies de FMA (Dentiscutata heterogama, Gigaspora margarita e Rhizophagus clarus), individualmente ou misturadas, em diferentes níveis de adubação fosfatada (0, 71, 213 e 650 mg kg−1 de P). O experimento foi conduzido em vasos de 1 kg, seguindo um delineamento inteiramente casualizado com seis repetições por tratamento, para avaliar as características morfológicas e nutricionais, após 116 dias, incluindo diâmetro do colo, altura, biomassa e teor de P na parte aérea da planta. Nossos resultados evidenciaram que S. terebinthifolius foi altamente dependente de micorrizas e apresentou respostas diferentes dependendo da espécie de FMA. O maior acúmulo de biomassa total ocorreu quando foi utilizada uma mistura das três espécies de FMA, o que indicou sinergismo entre os fungos. De uma forma geral, a maior resposta positiva à inoculação foi observada em nível intermediário de P (213 mg kg−1), e embora a biomassa da parte aérea tenha sido reduzida nas doses intermediárias de P, foi observada uma compensação com um aumento na biomassa radicular. Esses resultados indicam complementaridade em oposição à redundância funcional das espécies de FMA e destacam a importância do uso de inóculo misto na produção de mudas de S. terebinthifolius para programas de revegetação.

ABSTRACT Several tropical woody species are highly responsive to arbuscular mycorrhizal fungi (AMF) and depend on their symbiosis for nutrition and successful establishment in the field. The objective of this study was to evaluate the response of Schinus terebinthifolius, a native species of the Brazilian Atlantic Forest and Caatinga, to inoculation with three AMF species (Dentiscutata heterogama, Gigaspora margarita, and Rhizophagus clarus), either individually or mixed, at different levels of phosphorus fertilization (0, 71, 213, and 650 mg kg−1 of P). We conducted the experiment in 1 kg pots, following a completely randomized design with six replicates per treatment, to evaluate morphological and nutritional traits after 116 days, including stem diameter, plant height, plant biomass, and shoot P content. Our results showed that S. terebinthifolius was highly dependent on mycorrhizae and presented different responses depending on the AMF species. The greatest total biomass accumulation occurred when a mixture of the three AMF species was used, which indicated synergism between the fungi. The highest overall positive response to inoculation were observed at an intermediate P level (213 mg kg−1), and although shoot biomass was reduced at the intermediate P doses, an increase in root biomass compensated for this. These results indicate complementarity as opposed to functional redundancy of the AMF species and highlight the importance of using a mixed inoculum in seedling production of S. terebinthifolius for revegetation programs.

RESUMO O presente estudo teve como objetivo avaliar o efeito da inoculação com bactérias fixadoras de nitrogênio (BFNs) e fungos micorrízicos arbusculares (FMAs) no desenvolvimento de mudas de Tachigali vulgaris em condições de viveiro. As mudas foram produzidas em sacos de 1 kg em substrato areia e vermiculita (1:1), seguindo delineamento experimental inteiramente casualizado, em esquema fatorial 3 (BFNs) x 2 (com e sem FMAs), com 3 tratamentos testemunhas adicionais consistindo de mudas inoculadas apenas com os FMAs (testemunha micorrizada), mudas não inoculadas fertilizadas com N (testemunha nitrogenada) ou sem N (testemunha absoluta). As seguintes variáveis foram avaliadas: altura, diâmetro a altura do colo (DAC), massa seca de parte aérea (MSPA), raízes (MSR) e nódulos (MSN), acúmulo de P na parte aérea e colonização micorrízica (CM) das raízes. Calculou-se a eficiência e a eficácia para avaliar a resposta das plantas à dupla inoculação. Os tratamentos demonstraram efeito significativo para todas as variáveis, com exceção de colonização micorrízica, número e massa de nódulos secos, sendo o tratamento nitrogenado o que apresentou os maiores valores de crescimento. Plantas submetidas à dupla inoculação apresentaram maior acúmulo de matéria seca, altura e DAC, alcançando MSR 124% maior em relação à testemunha absoluta, 90% mais MSPA e 207% mais MSN em relação às mudas inoculadas somente com rizóbio. O efeito positivo da dupla inoculação ocorreu independente da estirpe utilizada. Os resultados indicam que a inoculação conjunta de BFNs e FMAs foi benéfica para a espécie, promovendo o seu crescimento.

ABSTRACT The present study aimed to evaluate the effect of inoculation with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) on the development of Tachigali vulgaris seedlings under nursery conditions. The seedlings were produced in 1 kg bags on a substrate of sand and vermiculite (1:1), following a completely randomized experimental design in a 3 (NFB) x 2 (with and without AMF) factorial scheme with 3 additional control treatments consisting of: seedlings inoculated only with AMF (mycorrhizal control), non-inoculated seedlings fertilized with N (nitrogenized control) and without N (absolute control). The following variables were evaluated: height, stem diameter (SD), shoot dry mass (SDM), root dry mass (RDM) and nodule dry mass (NDM), P accumulation in the shoot, and root mycorrhizal colonization (RMC). Efficiency and effectiveness were calculated to evaluate the plant response to double inoculation. The treatments showed a significant effect for all variables, except for mycorrhizal colonization, nodule number, and dry mass, with the nitrogen treatment having the highest growth values. Plants submitted to double inoculation showed a higher accumulation of dry matter, height and SD, reaching a 124% higher RDM regarding the absolute control, 90% more SDM, and 207% more NDM regarding the seedlings inoculated only with rhizobia. The positive effect of double inoculation occurred regardless of the strain used. The results indicate that the joint inoculation of NFB and AMF was beneficial for the species, promoting its growth.

RESUMO A exploração de petróleo em terra é uma das principais atividades econômicas da região semiárida (Caatinga) do estado do Rio Grande do Norte. Um dos impactos ambientais desta atividade constitui a exploração mineral da piçarra, tipo de cascalho utilizado no embasamento de instalações, como bases de poços, e na construção de estradas de acesso. Ao final da exploração, as jazidas de piçarra e demais áreas descomissionadas, onde a piçarra foi depositada, devem ser revegetadas com espécies nativas do bioma. O plantio de espécies leguminosas, capazes de realizar associações com rizóbios e fungos micorrízicos arbusculares (FMA), tem se mostrado uma estratégia eficiente para revegetação de áreas degradadas. Entretanto, o impacto das atividades de exploração sobre as populações autóctones desses microrganismos é desconhecido. Esse estudo objetivou caracterizar a densidade de rizóbios e de esporos de FMA em quatro áreas impactadas pela exploração de petróleo no RN em relação ao presente em áreas adjacentes não impactadas. Amostras de piçarra foram coletadas nas estações seca e chuvosa em duas jazidas, uma base de poço e uma central de resíduos. Paralelamente, amostras de solo superficial (topsoil) foram coletadas em áreas adjacentes com vegetação nativa da Caatinga. Ensaios foram conduzidos visando obter o número mais provável (NMP) de rizóbios e a densidade e identificação de fungos micorrízicos arbusculares (FMA). Utilizou-se como plantas-isca de rizóbios Mimosa tenuiflora (Mart.) Benth. e Mimosa caesalpiniifolia Benth. O NMP de rizóbios mostrou-se baixo em todas as áreas, sendo superior no período chuvoso. As maiores quantidade e diversidade de esporos de FMA foram obtidas no período seco. Dos microrganismos simbiontes estudados, os FMA apresentaram-se em baixas densidades nas áreas de exploração mineral em relação às de vegetação nativa, refletindo o impacto dessa atividade.

ABSTRACT On-shore oil exploration is one of the main economic activities in the semiarid region (Caatinga biome) of the state of Rio Grande do Norte (RN), Brazil. Gravel mining is an activity associated with oil exploration that causes environmental impacts. Gravel is a base-material for constructions, such as roads and pumpjack bases. The areas of gravel mining and other decommissioned areas where the gravel has been deposited must be revegetated with species native to the biome at end of the activity in the site. An efficient strategy for revegetation of degraded areas has been the planting of leguminous species that can associate with rhizobia and arbuscular mycorrhizal fungi (AMF). Nevertheless, the impact of mining activities on the autochthonous populations of these microorganisms is unknown. The objective of the present work is to characterize the density of rhizobia and AMF spores in four areas impacted by the oil exploration in RN when compared to non-impacted adjacent areas. Gravel samples were collected in dry and rainy seasons in two mining areas: one in a pumpjack base, and one in a waste disposal area. Surface soil (topsoil) samples were collected in adjacent areas with native Caatinga vegetation. Assays were carried out to evaluate the most probable number (MPN) of rhizobia and to identify the type and density of arbuscular mycorrhizal fungi (AMF), using rhizobia trap plants Mimosa tenuiflora (Mart.) Benth. and Mimosa caesalpiniifolia Benth. The MPN of rhizobia was low in all areas, but higher in the rainy season. The highest amount and diversity of AMF spores were found in the dry season. Among the symbiotic microorganisms studied, the AMF presented lower densities in the evaluated areas when compared to those in the adjcent native vegetation areas, denoting the impact of this activity.

ABSTRACT Studies in the Amazon indicate a wide diversity of rhizobia with the ability for biological nitrogen fixation (BNF), which could expand the number of strains approved for cowpea. Thus, the aim of this field study was to evaluate the agronomic performance in cowpea of the several strains isolated from the soils of the Brazilian states Acre and Rondônia, and to compare them withstrains approved by the Ministry of Agriculture (MAPA) and withnon-inoculated controls (without and with mineral nitrogen fertilizer). The inoculants performed well. Though less effective than the other strains, the UFLA 03-36 strain also was prominent with respect to grain yield. Because of the positive response of the UFLA 03-129 strain, which led to yield increases greater than the obtained from the control without inoculation plus mineral-N, it can be recommended as an inoculum for cowpea. Further investigations should be carried out to obtain MAPA’s approval for their use. Other experiments involving this strain and several cultivars are being carried out on other types of soil and environmental conditions of the state of Minas Gerais.

Abstract The family Leguminosae comprises approximately 20,000 species that mostly form symbioses with arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB). This study is aimed at investigating and confirming the dependence on nodulation and biological nitrogen fixation in the specie Piptadenia gonoacantha (Mart.) Macbr., which belongs to the Piptadenia group. Two consecutive experiments were performed in a greenhouse. The experiments were fully randomized with six replicates and a factorial scheme. For the treatments, the two AMF species and three NFB strains were combined to nodulate P. gonoacantha in addition to the control treatments. The results indicate this species’ capacity for nodulation without the AMF; however, the AMF + NFB combinations yielded a considerable gain in P. gonoacantha shoot weight compared with the treatments that only included inoculating with bacteria or AMF. The results also confirm that the treatment effects among the AMF + NFB combinations produced different shoot dry weight/root dry weight ratios. We conclude that AMF is not necessary for nodulation and that this dependence improves species development because plant growth increases upon co-inoculation.

ABSTRACT Inoculation with arbuscular mycorrhizal fungi (AMF) is a strategy to improve the efficiency of forest plantations, reducing costs and increasing the survival of plant species. The objective of this study was to assess the response and mycorrhizal dependency of seedlings of the forest species Apuleia leiocarpa (Vogel) J.F. Macbr to inoculation with AMF. The experiment was conducted in a completely randomized design using a 5 × 5 factorial arrangement with six replications. The treatments consisted of combinations of five P rates (0, 24, 71, 213, and 650 mg kg-1) with five types of inoculations with AMF (inoculation with the fungi Rhizophagus clarus, Gigaspora margarita, Dentiscutata heterogama, inoculation with an AMF mix of these three species, and a treatment without inoculation). The A. leiocarpa showed the highest biomass accumulations in inoculation with D. hetorogama combined with the P rates of 213 and 650 mg kg-1, and in the AMF mix combined with the P rates of 71, 213, and 650 kg-1. Biomass accumulation showed a linear, positive response to inoculation with D. heterogama combined with the different P rates, and a positive square root fit to inoculation with the AMF mix. The plants inoculated with G. margarita had no significant biomass accumulation. The plant species had a positive response to inoculation with R. clarus combined with the lowest P rates; however, it had a negative response to combination with the highest P rate (650 mg kg-1). The relative benefit of inoculation with these fungi was more than 100 % in most treatments, showing the high mycorrhizal dependency of A. leiocarpa and the nutritional benefit of AMF inoculation for this species. However, this response is dependent on the fungus species that colonize the plant roots. The best combination between fungus and P rate was inoculation with the AMF mix combined with the P rate of 71 mg kg-1.

O objetivo deste trabalho foi verificar o efeito de três sistemas de uso da terra da Amazônia Ocidental sobre a diversidade fenotípica de bactérias que nodulam siratro. Os sistemas estudados foram cultivo de mandioca, cultivo de pupunheira e floresta de terra firme. As densidades de bactérias foram avaliadas pela técnica do número mais provável, pela inoculação de suspensões de solo diluídas em siratro (Macroptilium atropurpureum), e foram semelhantes nas áreas estudadas. Foram caracterizados 257 isolados, provenientes dos nódulos de siratro, os quais formaram 63 grupos culturais a 80% de similaridade. Poucos isolados foram obtidos a partir de solo sob floresta, enquanto um maior número de isolados foi obtido nas áreas cultivadas. A diversidade pelo índice de Shannon e a riqueza foram maiores na área com mandioca e menores na floresta. Porém, a riqueza foi similar nos três sistemas quando determinada pela análise de rarefação. Houve diferença na proporção de tipos de culturais, a qual pôde ser explicada pela diferença na utilização da terra. Houve influência dos sistemas de uso da terra sobre a diversidade de bactérias que nodulam leguminosas.

The aim of this work was to evaluate the effect of three different land use systems from the Brazilian Western Amazon on Leguminosae nodulating bacteria diversity. The land use systems studied were cassava crop, peach palm crop and upland forest. Rhizobial densities were evaluated by the most probable number technique, after inoculation of Macroptilium atropurpureum with diluted soil samples, and they were similar for the three systems studied. Two hundred and fifty-seven bacteria isolated from the nodules were characterized and clustered into 63 groups of isolates with 80% similarity. Few isolates were obtained from forest, whereas a large number of isolates was obtained in the crop systems. The highest richness and Shannon diversity were found in the cassava crop and the lowest ones were found in the forest. However, the richness was similar for the three systems when it was determined with a rarefaction analysis. Differences in the proportion of types of growth were found and can be explained by differences amongst the systems. The land use systems influenced the Leguminosae nodulating bacterial diversity.

As espécies de leguminosas Piptadenia gonoacantha e Piptadenia paniculata apresentam dificuldade para nodular e crescer em substratos esterilizados, o que dificulta a seleção de estirpes de rizóbio eficientes dessas espécies. As plantas que apresentam nódulos no campo estão micorrizadas. Assim, a boa resposta das plantas no campo pode ser devida à presença de FMAs. O objetivo deste trabalho foi estudar o efeito da micorrização sobre a nodulação e crescimento de plantas de P. gonoacantha e P. paniculata. Os experimentos foram realizados em casa de vegetação, na Embrapa Agrobiologia, Rio de Janeiro. As plantas foram inoculadas com estirpes de rizóbio específicas de cada espécie e com os fungos Gigaspora margarita e Glomus clarum. Ambas as espécies vegetais demonstraram-se altamente responsivas à inoculação com FMAs. Plantas que receberam rizóbios e fungos micorrízicos apresentaram-se noduladas, com maior produção de matéria seca. Já as plantas inoculadas apenas com rizóbio não exibiram nódulos e tiveram menor acúmulo de matéria seca. As plantas de P. gonoacantha apresentaram maior conteúdo de P na parte aérea quando inoculadas com FMAs. Esses resultados indicam que a micorrização é necessária para a nodulação e crescimento satisfatórios das espécies estudadas, e sugere-se a inoculação com FMAs para a seleção de estirpes eficientes de rizóbio em leguminosas com dificuldade de crescimento no sistema convencional de seleção de estirpes.

The leguminous species Piptadenia gonoacantha and Piptadenia paniculata do not nodulate and grow well on sterilized substrates. For this reason selection of efficient rhizobial strains for these species becomes hard to perform. Plants growing in the field are well nodulated and colonized with mycorrhizal fungi. Mycorrhizal colonization may be an explanation for the good plant responses in the field. The effect of mycorrhizal inoculation on nodulation and growth of the woody legume species P. gonoacantha and P. paniculata was studied. The experiments were carried out under greenhouse conditions, at Embrapa Agrobiologia, Rio de Janeiro. The species were inoculated with specific rhizobia and with the mycorrhizal fungi Gigaspora margarita and Glomus clarum. Both tree species were highly responsive to mycorrhizal inoculation. Only the plants inoculated with both rhizobium and mycorrhizal fungi were nodulated. Plants inoculated with both rhizobia and mycorrhizal fungi presented higher dry matter than those inoculated only with rhizobia. P. gonoacantha plants presented higher shoot phosphorus content when inoculated with mycorrhizal fungi. These results show that mycorrhizal inoculation is needed for nodulation and growth of the tree species studied. We suggest the use of mycorrhizal fungi to select rhizobial strains for legumes which have difficulty to grow in Leonard jars.