Rising fertilizer prices have led a return to the use of grass-legume mixtures to reduce N costs and improve pasture productivity. The objective of this study was to determine optimal species combinations of binary grass-legume mixtures to improve forage production and pasture nutritive value in irrigated pastures of the Intermountain West. The study was conducted at the Utah State University Intermountain Pature Research Facility near Lewiston, UT. Tall Fescue (TF), Orchardgrass (OG), and meadow brome (MB) were grown with alfalfa (ALF), birdsfoot trefoil (BFTF), and cicer milkvetch (CMV) in legume-grass mixes and monocultures at planting ratios of 25:75, 50:50, 75:25. Grass monocultures were fertilized with 0 (0 N), 67 (67 N), or 134 kg N ha-1 (134 N). Forage was harvested four times each season during 2011-2012. Forage of the mixtures and monocultures from the first and third harvests was analyzed for crude protein (CP) and neutral-detergent fiber (NDF). Average forage production of the unfertilized TF, MB, and OG monocultures was 11.03, 9.76, and 8.10 Mg ha-1, respectively. TF-ALF, OG-ALF, and MB-ALF grass-legume mixes averaged 24.0, 35.0, and 41.0% higher forage production than their respective unfertilized grass monocultures. The grass-legume mixtures with the highest CP were MB-ALF 159, TF-ALF 159, and TF-OG-159 g kg-1 and average 59, 43 and 51% higher than their respective unfertilized grass monocultures. Likewise, the mixtures with the lowest NDF were OG-ALF 453 g kg-1, OG-BFTF 469 g kg-1, and MB-ALF 480 g kg-1. These mixtures had 10, 7, and 18% lower NDF than their respective unfertilized grass monocultures. Individual harvests had similarly higher yields and CP, with lower NDF for the mixtures than the unfertilized grass monocultures. The grass-legume mixture with the 50:50 planting ratio were most productive and had high forage quality. The grass-legume mixtures had similar forage production as the grass monocultures at 134 kg N ha-1. The grass-legume mixtures also had higher CP and lower NDF than the grass monocultures. Cicer milkvetch did not perform well in irrigated pastures. Grass-legume mixtures with ALF and BFTF can be used to replace commercial N while increasing forage nutritive value.

Due to increased environmental stewardship and fertilizer prices, there is increased interest in using legume mixes in perennial croplands. The objective of this study was to compare quantitative genetic parameters and quantitative trait loci (QTLs) associated with intermediate wheatgrass (Thinopyrum intermedium) when grown in 1) a non-competitive spaced environment, 2) a polyculture with alfalfa (Medicago sativa), and 3) a monoculture with crested wheatgrass (Agropyron desertorum). Traits evaluated include plant growth characteristics (Zadok’s maturity, height, and tiller count), biomass, and forage nutritive value (CP, NDF, ADF, ADL, IVTD, NDFD, NFC, ME, RFQ). A linkage map comprised of 3568 single nucleotide polymorphisms in 21 linkage groups corresponding to 21 homologous chromosome pairs of both parents was used to identify QTLs and QTL x environment interactions (QxE) based on trait averages for each genotype in each environment. Significant genotype x environment interactions were detected for biomass, NDF etc. A total of 26 QTLs were identified, including 6 MASS, 2 TILE, 2 TICR, 1 ZAMA, 1 CP, 3 NDF, 2 ADF, 3 IVTD, and 5 NDFD. A subset of 7 QTLs showed significant QxE interaction. These results indicate that breeders need to evaluate plants in polyculture or swards if these are the intended crop management systems.

Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2022 / Soil health support crop production and answer to its sustainability and renewability. This study involved the use of under explored legumes in South Africa, Limpopo under maizelegume intercropping systems as a strategy to mitigate soil quality deterioration. The study was conducted at University of Limpopo (Syferkuil) and University of Venda (UNIVEN) Experimental farms during 2020/2021. A split plot experiment, with the main factor comprised of water regimes (irrigation and rainfed) and second main factor included cropping systems (Intercropping and monocropping). Five treatments comprised of 3 monocrops (Maize, Chickpea, and Mungbean) and 2 intercrops (maize-chickpea and maize-mungbean) replicated three times. Data collected from the soil before planting and after maturity were pH, Electrical conductivity (EC), particle size, bulk density, aggregate stability, organic matter (OM), organic carbon (OC), phosphorus (P), ammonium (NH4-N), nitrate (NO3—N), soil active carbon (SAC), and potentially mineralizable nitrogen (PMN). Plant parameters collected during vegetative and flowering stage included plant height, chlorophyll content, plant vigour, and leaf area index. All data was subjected to descriptive statistics and analysis of variance using GenStat software. Significant effect (p<0.05) was observed between treatments on soil pH (KCl), OM, organic carbon (OC), and ammonium (NH4) at Syferkuil Farm. Also, interaction between water regimes and cropping systems affected NH4 and pH (KCl). Cropping systems had significant effect (p<0.01) on pH (H2O), OM, OC, P, NH4, and NO3 at UNIVEN. Interaction between water regimes and cropping systems affected (p<0.01) pH (H2O), P but no significant effect was observed on OC, NH4, and NO3. Cropping systems and interaction at both locations did not affect particle size, bulk density, aggregate stability, EC, SAC, and PMN. Pure stands of maize and legumes had greater plant height, plant vigour, and chlorophyll content whereas intercrops had greater LAI. The results at both locations revealed that legume intercropping systems improved soil health variables without posing negative feedbacks and hence can be used to boost soil functioning. Keywords: Soil health, maize-legume intercropping, soil quality / National Research Foundation (NRF)

No description available.

Crabgrass is a warm-season annual species that has the potential to provide high-quality summer forage for ruminants in the transition zone between subtropical and temperate regions of the United States. Growing annual lespedeza in association with crabgrass may be beneficial due to nitrogen transfer from the legume to the grass. The objectives of the research reported in this thesis were to (1) determine the effects of pH on establishment and growth of crabgrass; and (2) evaluate the effects of lespedeza seeding rate and N fertilization treatment on the yield, botanical composition, and nutritive value of crabgrass-lespedeza mixtures. A greenhouse study was conducted using three soil pH levels of 4.8, 5.5, and 6.3. Crabgrass germination and root and shoot yields were not affected by soil pH values. A field study was conducted to evaluate the influence of six lespedeza seeding rates (0-28 kg ha-1) and two N fertilization treatments (140 kg total N ha-1 or zero N) on crabgrass-annual lespedeza mixtures. In most cases, increasing lespedeza seeding rate increased lespedeza in the sward. However, lespedeza rate had limited effect on yield and nutritive value of the mixture. Nitrogen fertilization increased crabgrass in the sward and total yield by as much as 46%. Responses of nutritive value parameters to N fertilization were variable and appeared linked to weather factors. In vitro true digestibilities ranged from 750 to 875 g kg-1, and were largely unaffected by N fertilization and seeding rate The results of these studies indicate that crabgrass could provide moderate amounts of highly digestible forage while growing on acidic soils commonly found in the southeastern United States. Annual lespedeza may be grown in association with crabgrass, but limited improvement in yield and nutritive value were found for this practice. / Master of Science

Thesis (PhD(Agric) (Plant Biotechnology))--University of Stellenbosch, 2010. / Includes bibliography. / ENGLISH ABSTRACT: Salinity is one of the major limiting abiotic stresses on legume plant yield, leading to early senescence of root nodules. This occurs because of accumulation of reactive oxygen species (ROS) in plant cells under salinity stress. Concurrent with the increase in cellular reactive oxygen species levels is the increase in cellular antioxidants and corresponding antioxidant enzymes. This feature is observed mostly in the shoots and roots of more tolerant genotypes compared to the susceptible genotypes. It is accepted that the mechanism of plant tolerance to stress is dependent upon the response of the antioxidant systems. Most studies carried out on shoot tissues suggest that scavenging of ROS by the plant antioxidant system is modulated by nitric oxide (NO). However, the pathways by which NO mediates such antioxidant responses are not fully understood. For legumes, salinity stress has adverse effects on yield and this is in part due to inhibition of nitrogen fixation in the root nodules of the legumes, which causes severe nitrogen starvation in nitrogen-deficient soils. Nodules are specialized organs comprising of both the rhizobia and the plant tissue, hence the physiological aspects may vary from the findings from the leaves. It was therefore deemed necessary to establish the role of NO on the nodule antioxidant system in the absence and presence of salinity stress. For the purposes of this study, the effect of both exogenously applied NO and endogenous NO on superoxide dismutase, glutathione peroxidase and glutathione content was determined. The studies involved the use of nitric oxide donors like sodium nitroprusside (SNP) and diethylenetriamine/nitric oxide adduct (DETA/NO), their respective fixed controls potassium ferricyanide and diethylenetriamine (DETA), plus a nitric oxide synthase inhibitor (to inhibit nitric oxide production by the enzyme nitric oxide synthase) on nodulated roots. The data obtained in this work points out specifically at roles played by nitric oxide in regulating superoxide dismutases, glutathione peroxidase and glutathione during salinity stress and proposes a link between nitric oxide-mediated changes in these antioxidant systems and salinity stress tolerance. Both the exogenously applied and endogenous nitric oxide increases the enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione reductase (GR). However, there is both time dependency and nitric oxide concentration dependency on the enzyme activities. The total SOD enzyme activity increases upon nitric oxide exposure and with time of exposure. The individual SOD isoforms identified and studied in the root nodules all contribute to this increase in SOD activity upon nitric oxide treatment except for MnSOD I. This increase in activity is regulated at transcriptional level as the RT-PCR results targeting the individual isoforms reveals an increase in transcript levels after 6 hours of nitric oxide treatment. However, the CuZn SOD I isoform transcripts are reduced upon nitric oxide treatment. A similar response was also observed in GPX enzyme activity in which nitric oxide increased the GPX activity above all the controls. The GR enzyme activity exhibits an opposite response because the activity decreases with time of exposure to NO and concentration of NO. In order to determine the effect of NO under saline conditions, an experiment was set up that involved incubation of nodulated roots in solutions containing 150 mM NaCl. The stressed nodules exhibited generally higher levels of enzyme activities than the non-stressed nodules. Furthermore, exposure to nitric oxide donor in combination with NaCl induced even higher activities of SOD and GPX than NaCl or nitric oxide donor alone. There were also higher levels of reduced glutathione and total glutathione recorded under stress compared to optimal conditions. Nitric oxide increased the concentration of these forms of glutathione, suggesting an improved redox status based on the GSH/GSSG ratios under salinity stress in the presence of nitric oxide. Attenuation of nitric oxide synthesis with L-Nω-Nitroarginine methyl ester (L-NAME) reverses all the recorded effects of nitric oxide on antioxidant enzymes and glutathione pool. This was observed in salinity stressed nodules and non-stressed nodules. This work further establishes that NO plays a pivotal role in modulating the enzymatic activities through a pathway that is mediated by guanosine 3,5-cyclic monophosphate (cGMP). The experiment involving the inhibition of soluble guanylyl cyclase (sCG) (an enzyme that catalyzes the biosynthesis of cGMP), cell-permeable cGMP anaologue and L-NAME revealed that GPx activity is modulated through a cGMP-dependent pathway and NO is positioned up-stream of cGMP in the pathway leading to improved GPX activity. Cyclic GMP also modulates the GPX activity in a concentration dependent manner. NO improves the redox status of the cell under both saline conditions and non-saline conditions and this effect is modulated through a cGMP-dependent pathway. It is thus rational to conclude that; in the root nodules of legumes, like in other plant tissues, the increased accumulation of antioxidants and the increased activity of their corresponding enzymes, as modulated through the cGMP-dependent pathway by nitric oxide, confer root nodule tolerance to salinity. This concept directly points out at an attractive strategy for developing legumes that are genetically improved for enhanced root nodule tolerance to salinity; via differential regulation of antioxidants and antioxidant enzyme genes in the root nodules under abiotic stress. Towards attaining the goal for such genetic improvement, experiments involving construction of an abiotic stress-responsive and nodule-specific chimeric promoter were carried out. By fusing the 5-untranslated (5-UTR) region of the LEA gene that contains an abiotic stress-responsive cis-acting element (from theGmPM9 promoter) to the nodulin N23 promoter bearing the highly functional cluster of motifs for nodule specificity, the candidate nodule specific promoter that is abiotic stress responsive (ASREF/NSP) was constructed. The construct harbouring this ASREF/NSP chimeric promoter was fused to the -glucuronidase (GUS) reporter gene so as to study the functionality of the promoter in Medigaco truncatula plants. The construct was delivered into the Medicago plants through Agrobacterium rhyzogenes mediated transformation to produce composite Medicago plants. The transgenic roots have been cultured for futher manipulation and to confirm the functionality of the promoter. Furthermore several strategies can be deployed via the use of this chimeric promoter so as to enhance the nodular antioxidant system. This would involve either gene regulator-chimeric promoter fusion or the use of a single gene approach. As part of this work, the MtNOA gene homologous to AtNOAs, has been cloned from Medicago trancatula and put as ASREF/NSP fusion in a binary vector pBINPLUS and delivered into Medicago trancatula for nodule-specific and abiotic stress-induced nitric oxide synthesis. Since there is no plant NOS identified to date, the possibility of the use of a regulatory gene in this aspect is still limited. There are other options involving the use of the chimeric promoter with the individual genes encoding the antioxidant enzyme genes such as genes encoding SOD, GPX and the glutathione synthatase to enhance the plant antioxidant system during abiotic stress. / AFRIKAANSE OPSOMMMING: Geen opsomming was ingedien met die tesis

As pastagens são a base da alimentação dos ruminantes na pecuária brasileira. Sistemas de produção em condições pastoris utilizam diversos genótipos forrageiros sob diferentes formas de manejo, no intuito de otimizar respostas produtivas desses sistemas. Algumas decisões quanto ao manejo, no entanto, são tomadas de forma não criteriosa e generalista, tornando o sistema de produção frequentemente propenso a erros na gestão. A intensificação da produção animal em pastagem possibilita o aumento da participação de leguminosas forrageiras no sistema. No entanto, ainda há um limitado entendimento das respostas destas plantas quando submetidas a manejos mais intensificados. Este trabalho teve como objetivo caracterizar quatro cultivares comerciais de Arachis pintoi Krapov. & Greg., sob duas intensidades de desfolhação e dois intervalos entre desfolhas ao longo da estação de crescimento de dois anos consecutivos. Para tanto, foi conduzido um experimento analisando-se os cultivares Alqueire-1, Amarillo, Belmonte e BRS Mandobi sob quatro manejos de colheita: dois intervalos (28 e 35 dias) associados a duas intensidades de desfolha (5 e 10 cm). Determinou-se a produtividade total por estação de crescimento, acúmulo total de forragem, taxa de acúmulo diário, composição morfológica, ângulo foliar, interceptação luminosa, índice de área foliar, composição química e digestibilidade da forragem, fotossíntese foliar, fotossíntese de dossel e compostos orgânicas de reserva. O experimento foi conduzido no município de Piracicaba - SP, sendo a área experimental total de 0,11 ha. O delineamento experimental adotado foi o inteiramente casualizado com arranjo em parcelas subdivididas. À parcela foram alocados as combinações entre cultivares de A. pintoi (Alqueire-1, Amarillo, Belmonte e BRS Mandobi) e intervalos entre cortes (28 e 35 dias) em um fatorial 4 x 2. À subparcela foi designado o fator intensidade de desfolhação, na forma de duas alturas de resíduo (5 e 10 cm), tendo o experimento contado com com 3 repetições. A análise estatística dos dados foi realizada utilizando-se o procedimento MIXED do SAS&reg;. As médias dos tratamentos foram estimadas utilizando-se o LSMEANS e comparadas pelo teste Tukey a 5% de probabilidade. O cultivar Belmonte apresentou média de acúmulo total acima de 11,85 Mg MS ha-1 e taxa de acúmulo diário de 41 kg MS ha-1 nos diferentes manejos adotados, sendo o maior desempenho produtivo em relação aos demais cultivares testados. Em geral, o intervalo de 28 dias com intensidade de desfolha de 5 cm, confere maior produtividade total aos cultivares de A. pintoi. Menores produções de folíolos, pecíolos e estolões foram obtidos para o cultivar Amarillo.O perfil nutricional do cultivar Belmonte apresentou maior potencial em função da alta concentração de proteína bruta (277 g kg-1 MS) e digestibilidade in vitro da matéria orgânica (717 g kg-1 MS) em relação a Alqueire-1 e Amarillo e concentrações de fibra em detergente neutro (366 g kg-1 MS) intermediárias comparativamente aos três cultivares. Variações intraespecífica entre os cultivares apresenta pouco efeito sobre os compostos de reservas, sendo estes mais afetados pelas estratégias de manejo adotadas. Carboidratos totais não estruturais estiveram menos concentrados nos órgãos de reserva de Alqueire-1 (196 g kg-1 MO), e a concentração de N total apresentou variação somente entre os cultivares Belmonte (31 g kg-1 MO) e BRS Mandobi (25 g kg-1 MO). Em geral, a concentração de carboidratos totais não estruturais nos órgãos de reserva é maior quando o manejo de intervalos entre desfolha é de 35 dias. Plantas invasoras são mais evidentes em dosséis manejados com intensidade de desfolha de 5 cm. O cultivar Belmonte apresenta características que lhe conferem maior desempenho agronômico, sendo portanto considerado o material mais promissor. / Pastures are the backbone of the brazilian livestock industry. Pasture-based ruminant production systems make use of a diverse base of forage genotypes under various managements, aiming at the optimization of productive responses. Decisions regarding management, however, are often made under an empirical and generalistic standpoint, making these systems prone to failure. The intensification of animal production on pasture makes can be achieved with the increased participation of forage legumes in the system. However, there is still a limited understanding of the responses of these plants when subjected to more intensive management. This work aimed to characterize four commercial cultivars of Arachis pintoi (Krapov. & Greg.), under two harvest intensities and two harvest intervals throughout the summer growing season of two years. An experiment was carried out with the cultivars Alqueire-1, Amarillo, Belmonte and BRS Mandobi under four harvest management: two intervals (28 and 35 days) associated with two harvest intensities (5 and 10 cm). The total forage accumulation, daily accumulation rate, plant-part composition, leaf angle, light interception, leaf area index, chemical composition and forage digestibility, leaf photosynthesis, canopy photosynthesis and organic reserve compounds. The experiment was carried out in Piracicaba - SP. The experimental design was completely randomized with split-plot arrangement. To the plots were allocated the combinations between cultivars of A. pintoi (Alqueire-1, Amarillo, Belmonte and BRS Mandobi) and harvest intervals (28 and 35 days) in a factorial 4 x 2. To the subplot was designated harvest intensities (5 and 10 cm). Data were analyzed using the MIXED procedure of SAS&reg;. Treatment means were estimated using LSMEANS and compared by the Tukey test at 5% of probability. Belmonte had mean of total accumulation above 11.85 Mg DM ha-1 and daily accumulation rate of 41 kg DM ha-1 in the different managements adopted, the greatest production of all four entries. In general, the 28 day interval with harvest intensity of 5 cm resulted in greater total yield of all cultivars. The nutritional profile of Belmonte was the best due to the high concentration of crude protein (277 g kg-1 DM) and in vitro digestible of organic matter (717 g kg-1 DM) relative to Alqueire-1 and Amarillo and neutral detergent fiber concentrations (366 g kg-1 DM) as compared to the three cultivars. Intraspecific variations among cultivars had less effect on the reserve compounds, being more affected by the management strategies. Total non-structural carbohydrate concentratin was less in Alqueire-1 roots and stubble (196 g kg-1 OM), and total N concentration differed only between Belmonte (31 g kg-1 OM) and BRS Mandobi (25 g kg-1 OM). In general, the concentration of total non-structural carbohydrates in the reserve organs is greater when intervals between harvest is 35 days. Weeds are more evident in canopies managed with harvest intensity of 5 cm. Belmonte seems to have greater agronomic performance, being therefore considered the most promising material.

O presente estudo teve como objetivo avaliar o efeito da inoculação com rizóbio no estabelecimento, crescimento inicial e em alguns aspectos da dinâmica de N em folhas de leguminosas (Fabaceae) arbóreas nativas plantadas por semeadura direta no campo, em área de mata ciliar no Estado de São Paulo. Foi avaliada a emergência de plântulas (% em relação ao número de sementes plantadas) até os 3 meses após a semeadura (MAS) e o crescimento em altura aos 13 MAS. O fracionamento isotópico do N foliar também foi avaliado, pelo método da abundância natural do 15N, além da concentração de N e a razão C/N foliar. Acacia polyphylla foi usada como planta-referência não-fixadora de N2. Em relação ao desenvolvimento inicial, houve grande variação entre as espécies estudadas. Acacia polyphylla e Enterolobium contortisiliquum apresentaram taxa de germinação mediana e rápido crescimento. Mimosa bimucronata e Parapiptadenia rigida tiveram crescimento relativamente rápido, porém baixo potencial germinativo. Erythrina speciosa e Poecilanthe parviflora, com crescimento lento, apresentaram germinação elevada no campo. As espécies fixadoras de N2 mostraram &#948;15 N médio de 2,7&#8240;, enquanto que a referência Acacia polyphylla se mostrou cerca de 4,0&#8240; mais enriquecida em 15N . Erythrina speciosa e Ormosia arborea apresentaram os menores valores de &#948;15N, enquanto que Parapiptadenia rigida, enriquecida em 15N, mostrou estar obtendo N exclusivamente do solo. Poecilanthe parviflora, Mimosa bimucronata e Enterolobium contortisiliquum apresentaram valores intermediários de &#948;15N, com grande variação entre os indivíduos amostrados. A concentração de N nos tecidos foliares variou entre 1,5% e 3,6%. De forma geral, esta variável não mostrou relação direta com o &#948;15N das plantas. A menor razão C/N foi observada em Enterolobium contortisiliquum e Erythrina speciosa, seguida por M. bimucronata. Nas condições experimentais locais, as plantas não responderam à inoculação com rizóbio em nenhum dos parâmetros avaliados (estabelecimento, crescimento inicial, &#948;15N, concentração de N e razão C/N). As espécies de crescimento mais lento e com alta incidência de herbivoria observados no campo (E. speciosa e O. arborea) foram também as que apresentaram &#948;15N na faixa considerada como de ocorrência da fixação biológica de nitrogênio. Os resultados indicam, para as outras espécies, maior aquisição de N proveniente do solo. / The aim of this work was to assess the effect of rhizobia inoculation on the establishment, early growth and some aspects of N dynamics in direct-seeded native legume (Fabaceae) trees in a riparian zone of São Paulo State, Southeastern Brazil. Seedling emergency (% of total planted seeds) was evaluated until three months after sowing (MAS), and the height of the trees were measured at 13 MAS. Isotopic N fractionation was also assessed by the 15N natural abundance method, as well as foliar N content and C/N ratio. Acacia polyphylla was used as a non-N2-fixing reference plant. Acacia polyphylla and Enterolobium contortisiliquum grew most rapidly, with moderate germination rate. Mimosa bimucronata and Parapiptadenia rigida were fast-growing but with low establishment rate. Erythrina speciosa and Poecilanthe parviflora showed low growing rate, but high germination potential. The N2-fixers showed an average foliar &#948;15N of 2,7&#8240;, while the reference-plant was 4,0&#8240; more <sup15>N enriched. Erythrina speciosa and Ormosia arborea showed the lowest &#948;15N values. The high &#948;15N of Parapiptadenia rigida probably indicated that it is obtaining N exclusively from the soil. Poecilanthe parviflora, Mimosa bimucronata and Enterolobium contortisiliquum showed intermediate &#948;15N values, with strong variations among the sampled individuals. Foliar N concentrations varied from 1,5% to 3,6%. In general, N concentrations were not correlated with foliar &#948;15N . The lowest C/N ratio was observed on E. contortisiliquum and E. speciosa , followed by M. bimucronata. In this field trial conditions, rhizobia inoculation did not show differences in all surveyed parameters (establishment, early growth, foliar &#948;15N, total N content and C/N ratio of trees). The slow-growing species, E. speciosa and O. arborea , that also had a high herbivore attack observed in the field, showed foliar &#948;15N in the biological N2 fixation range. The results suggested, for the other species, a larger soil N acquisition.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2016-10-04T21:00:20Z No. of bitstreams: 1 2010 - Joventino Fernandes Moreira.pdf: 3401468 bytes, checksum: 9e89bb418c26be61f0e61413f30a9f7f (MD5) / Made available in DSpace on 2016-10-04T21:00:20Z (GMT). No. of bitstreams: 1 2010 - Joventino Fernandes Moreira.pdf: 3401468 bytes, checksum: 9e89bb418c26be61f0e61413f30a9f7f (MD5) Previous issue date: 2010-02-26 / CAPES / Bio-indicators are frequently used for environmental quality studies, monitoring of degraded areas and recovery processes, because they are intimately associated to specific landscape characteristics and respond to environmental changes by alterations in vital functions. In this sense, the study of the behaviour of edaphic organisms can contribute significantly to the evaluation of the environmental quality and to strategies and processes aiming the recovery and rehabilitation of areas affected by some type of degradation. This study aimed monitoring the colonisation by the soil fauna community of areas degraded by bauxite mining activities and revegetated with a mixture of native and leguminous species in the municipality of Porto Trombetas-PA, Brazil. Material was sampled in the years 2000, 2002, 2003, 2004 and 2008, in a chronosequence of regenerated areas of bauxite waste covered or not with topsoil, and in plantings in former bauxite tailing ponds. The individuals were captured in pitfall traps and separated in the Laboratory of Soil Fauna of the Embrapa Agrobiologia Research Centre. The evaluated parameters were abundance, richness, Shannon index, Pielou?s equitability index and the colonization patterns of fauna groups. The soil fauna profiles were obtained by nonmetric multidimensional scaling (NMS) ordination, and the response of soil fauna community was evaluated using principal response curves (PRC). The results showed that the time from planting and the nutrient availability were determining factors during the environmental recovery of the system, especially in the bauxite waste areas revegetated in 1984, 1992 and 1994, and in the tailing pond areas that received higher amounts of fertilizers. In these areas, the vegetation development caused a better colonization and structuring of the soil fauna community, increasing its diversity and reestablishing the ecological processes. / Bioindicadores s?o frequentemente utilizados para estudos de avalia??o da qualidade ambiental, como no monitoramento de ?reas degradadas e de processos de recupera??o, uma vez que est?o intimamente associados a caracter?sticas espec?ficas da paisagem e respondem ?s mudan?as ambientais por meio de altera??es na composi??o e estrutura das comunidades. Neste sentido, o estudo do comportamento de organismos ed?ficos pode contribuir significativamente para a avalia??o da qualidade ambiental assim como de estrat?gias e processos destinados ? recupera??o e reabilita??o de ?reas que sofreram algum tipo de degrada??o. Este trabalho teve por objetivo acompanhar a coloniza??o da comunidade da fauna ed?fica em ?reas degradadas pela minera??o de bauxita e revegetadas com a mistura de esp?cies nativas e leguminosas arb?reas e arbustivas em Porto Trombetas-PA. As amostragens foram feitas nos anos 2000, 2002, 2003, 2004 e 2008 em reflorestamentos de diferentes idades plantados sobre material est?ril com e sem cobertura de solo superficial e em plantios em tanque de rejeito da lavagem da bauxita. Os indiv?duos foram capturados em armadilhas do tipo ?pitfall? e triados no Laborat?rio de Fauna de Solo da Embrapa Agrobiologia. Os par?metros usados para avalia??o foram: a abund?ncia, a riqueza, o ?ndice de diversidade Shannon, o ?ndice de Equabilidade de Pielou e o padr?o de coloniza??o dos indiv?duos da fauna do solo. Os perfis da fauna do solo foram obtidos pelo ordenamento multivariado atrav?s da t?cnica de escalonamento multidimensional n?o m?trico (NMS) e a resposta da comunidade de fauna ed?fica ?s varia??es ambientais foram avaliadas por meio de curvas de respostas principais (PRC). Os resultados mostraram que a idade do plantio e a disponibilidade de nutrientes foram fatores determinantes na recomposi??o da comunidade de fauna de solo, a qual foi maior nos reflorestamentos de 1984, 1992 e 1994 no est?ril e nas ?reas do tanque de rejeito que receberam maiores quantidades de fertilizantes. Nessas ?reas, o desenvolvimento da vegeta??o levou ? maior coloniza??o e a melhor estrutura??o da comunidade de fauna ed?fica, aumentando a sua diversidade e o restabelecimento de processos ecol?gicos.

En raison de leur capacité à former une symbiose avec des bactéries du sol appelées Rhizobium, ces bactéries fixent l’azote atmosphérique et leurs plantes-hôtes n’ont donc pas besoin de fertilisant azoté, les légumineuses jouent un rôle important dans l'agriculture. En outre, certaines souches de Rhizobium ont la capacité de solubiliser le phosphate, fournissant ainsi du phosphore assimilable aux plantes hôtes. Une aptitude à lutter contre certains agents pathogènes a aussi été démontrée dans plusieurs études. La présente étude évalue l’efficacité symbiotique de rhizobiums tunisiens, leur capacité à solubiliser le phosphate, et leur aptitude à lutter contre la verticilliose ainsi que d’autres champignons pathogènes chez Medicago truncatula. Trente-six isolats de rhizobiums prélevés sur des nodules racinaires de M. truncatula provenant de différentes régions de Tunisie ont été obtenus pour ce travail. Environ 60% de ces isolats étaient capables de solubiliser le phosphate in vitro. Dans une seconde étape, trois rhizobiums solubilisant le phosphate et un isolat incapable de solubiliser le phosphate in vitro ont été utilisés pour des essais en phytotron afin de voir l’effet de la présence des rhizobiums sur les paramètres de croissance des plantes en présence de phosphate inorganique sous forme de CaHPO4 et rocheux sous forme brute. Les résultats de l’essai montrent que les plantes de la lignée A17 traitées au CaHPO4, ont tendance à produire plus de nodules et de biomasse aérienne que la lignée F83005.5 et que la forme du phosphate utilisé, soluble ou non soluble, affecte les paramètres étudiés. L'inoculation de quatre lignées de M. truncatula avec 16 isolats de rhizobium sélectionnés auparavant a montré une interaction significative entre les isolats et les lignées pour la symbiose visible par la formation de nodules. Tous les isolats de rhizobium testés ont augmenté la biomasse aérienne des plantes, réduit la biomasse racinaire et entraîné une teneur plus élevée en azote mais l’effet dépendait de l’isolat de rhizobium et de la lignée de M. truncatula utilisés. Enfin, ces isolats ont été testés pour leur capacité à protéger des plantes de M. truncatula contre une maladie racinaire, la verticilliose. Des activités antagonistes in vitro contre divers champignons pathogènes dont Verticillium et Fusarium ont également été recherchées permettant d’identifier un isolat efficace pour la lutte biologique. Les résultats de cette étude suggèrent que des isolats de rhizobium sélectionnés pourraient être utilisés comme biofertilisants dans les sols pauvres pour réduire l'utilisation d'engrais chimiques azotés et phosphorés mais pas pour lutter contre la verticilliose. / Because of their ability to form a symbiosis with soil bacteria called Rhizobium, legumes play an important role in agriculture. These bacteria fix atmospheric nitrogen; hence their host plants do not need nitrogen fertilizers. In addition, some strains of Rhizobium have the ability to solubilize phosphate, thus providing phosphorus to host plants. An ability to control certain pathogens has also been demonstrated in several studies. The present study evaluates the symbiotic efficiency of Tunisian rhizobia, their ability to solubilize phosphate, and their ability to control Verticillium wilt and other pathogenic fungi in Medicago truncatula. Thirty-six rhizobial isolates were obtained from root nodules of M. truncatula from different parts of Tunisia were used in this work. About 60% of these isolates were able to solubilize phosphate in vitro. In a second step, three phosphate solubilizing rhizobia and one isolate unable to solubilize phosphate in vitro were used for phytotron assays to see the effect of the presence of rhizobia on plant growth parameters in the presence of soluble and insoluble forms of phosphate. The results of the experiment show that A17 plants treated with CaHPO4, tend to produce more nodules and shoot biomass than F83005.5 and that the phosphate form used, soluble or non-soluble, affects parameters studied. Inoculation of four M. truncatula lines with 16 previously selected rhizobial isolates showed significant interaction between isolates and lines for symbiotic abilities as visualised by nodule formation. All rhizobial isolates tested increased above-ground biomass, reduced root biomass, and increased nitrogen content with strains effects of plant genotype and bacterial isolate. Finallly, these isolates were tested for their ability to protect M. truncatula plants against Verticillium wilt, and to inhibit the growth of pathogenic fungi such as Verticillium and Fusarium in vitro. However, no isolate could be identified as effective for biological control. The results of this study suggest that selected rhizobial isolates could be used as biofertilizers in poor soils to reduce the use of nitrogen and phosphorus fertilizers but not to control Verticillium wilt.