Legumes play an important role in agriculture as major food sources for humans and as feed for animals. Bioavailable nitrogen is a limiting nutrient for crop growth. Legumes are important because they can form a symbiotic relationship with soil bacteria called rhizobia that results in nitrogen-fixing root nodules. In this symbiosis, rhizobia provide nitrogen to the legumes and the legumes provide carbon sources to the rhizobia. The Medicago truncatula NPF1.7/NIP/LATD gene is essential for root nodule development and also for proper development of root architecture. Work in our lab on the MtNPF1.7/MtNIP/LATD gene has established that it encodes a nitrate transporter and strongly suggests it has another function. Mtnip-1/latd mutants have pleiotropic defects, which are only partially explained by defects in nitrate transport. MtNPF1.7/NIP/LATD is a member of the large and diverse NPF/NRT1(PTR) transporter family. NPF/NRT1(PTR) members have been shown to transport other compounds in addition to nitrate: nitrite, amino acids, di- and tri-peptides, dicarboxylates, auxin, abscisic acid and glucosinolates. In Arabidopsis thaliana, the AtNPF6.3/NRT1.1( CHL1) transporter was shown to transport auxin as well as nitrate. Atchl1 mutants have defects in root architecture, which may be explained by defects in auxin transport and/or nitrate sensing. Considering the pleiotropic phenotypes observed in Mtnip-1/latd mutant plants, it is possible that MtNPF1.7/NIP/LATD could have similar activity as AtNPF6.3/NRT1.1(CHL1). Experimental evidence shows that the MtNPF1.7/NIP/LATD gene is able to restore nitrate-absent responsiveness defects of the Atchl1-5 mutant. The constitutive expression of MtNPF1.7/NIP/LATD gene was able to partially, but not fully restore the wild-type phenotype in the Atchl1-5 mutant line in response to auxin and cytokinin. The constitutive expression of MtNPF1.7/NIP/LATD gene affects the lateral root density of wild-type Col-0 plants differently in response to IAA in the presence of high (1mM) or low (0.1 mM) nitrate. MtNPF1.7/NIP/LATD gene expression is not regulated by nitrate at the concentrations tested and MtNPF1.7/NIP/LATD does not regulate the nitrate-responsive MtNRT2.1 gene. Mtnip-1 plants have an abnormal gravitropic root response implicating an auxin defect. Together with these results, MtNPF1.7/NIP/LATD is associated with nitrate and auxin; however, it does not act in a homologous fashion as AtNPF6.3/NRT1.1(CHL1) does in A. thaliana.

<p>Root phenotyping technology is an essential component of modern agriculture and plant science research. Conducting root-related research in a non-destructive manner is crucial for studying plant roots without damaging the plants themselves and allowing for time-series studies. The research aims to validate the efficacy of MISIRoot, an innovative root phenotyping technology, through the implementation of two projects. The first project focuses on the early detection of western corn rootworm, one of the most devastating corn rootworm species in North America, particularly in midwestern corn-growing areas. The second project focuses on the assessment of the soybean nodulation process, which is crucial for nitrogen fixation by Rhizobia living in the nodules on the soybean roots. The current state-of-the-art methods for western corn rootworm and soybean nodulation assessments still require the whole plant to be dug up, which causes irreversible destruction to the plant itself. Although recently developed root phenotyping methods such as minirhizotron, CT, and MRI scanners offer unique advantages in observing plant roots, their potential for field applications is currently limited.</p> <p>Data collection for both projects was carried out using MISIRoot, a minimally invasive plant root phenotyping robot that works in situ within natural soil. The MISIRoot system mainly consists of an industrial-level robotic arm, a mini-size camera with a lighting set, a plant pot holding platform, and image processing software for root recognition and feature extraction. MISIRoot can take high-resolution color images of the roots in soil with minimal disturbance to the root and reconstruct the plant roots' three-dimensional (3D) structure at an accuracy of 0.1 mm.</p> <p>For the first project, the MISIRoot system successfully distinguished the corn plants inoculated with western corn rootworm larvae from the healthy plants before the shoot section of the corn plants revealed significant differences. For the second project, the MISIRoot system successfully demonstrated its ability to differentiate soybean plants with and without nodules.</p>

Thesis (Ph.D. Agriculture (Plant Production)) -- University of Limpopo, 2022 / The unique phytochemical composition of the medicinal plant cancer bush (Sutherlandia frutescens) have made its foliage to gain much attention in South Africa due to its health benefits. In situ harvesting of the plant parts of this important species serve as one potential strategy to avert its extinction through whole plant harvesting, a common practice by rural communities. However, such a strategy is limited by lack of information on the agronomic requirements of the plant species and its susceptibility to root-knot (Meloidogyne species) nematodes. The objectives of the study were four-fold, namely, to: (1) identify nodulation bacteria associated with wild S. frutescens using morphological and biochemical techniques, (2) assess the efficacy of the nodulation isolates from different centres of biodiversity of S. frutescens in Limpopo Province, South Africa (3) test the compatibility of cucurbitacin-containing phytonematicides on S. frutescens for managing population densities of Meloidogyne species and (4) determine the nutritional water productivity (NWP) of S. frutescens in association with water scarcity of the region where the plant species originated. In achieving Objective 1, nodules from S. frutescens roots were washed in distilled water and healthy, undamaged, firm and pink nodules were sterilised. Aseptic nodules from S. frutescens roots and commercial strains were transferred into a smasher biomerieux polythene bag containing 10 ml distilled water and crashed to produce a milky suspension the milky suspension was streaked on Yeast extract mannitol agar (YEMA). After gram reaction, colony characterisation includes the investigation of shape, colour, configuration, elevation and margin of bacterial colony as observed in colonies on nutrient agar plates of overnight grown microorganisms using a microscope. The medium for biochemical test was prepared, inoculated with 5 μl purified xxv bacterial cultures and incubated at 37°C for 48 h. Identification of the bacterial isolates was performed using VITEK 2 Systems (bioMérieux, Inc., North Carolina, USA). Using morphological and biochemical techniques, the bacterial species associated with roots of S. frutescens in the wild were assayed primarily those in the genera Raoutella ornithinolytica and Enterobacter cloacae species dissolvens. The VITEK 2 Systems confirmed the identification of the bacterial species from 80 to 96% of the samples. Three species were confirmed from another sampling area, Sphingomonas paucimobills, Raoutella ornithinolytica and Enterobacter cloacae species dissolvens from by 86 to 96% of the samples. In achieving Objective 2, the five treatments, namely, Bradyrhizobium spp. (Arachis) strain, Rhizobium leguminosarum strain, Tubatse strain, Sebayeng strain and untreated control, were laid-out in a randomised complete block design, with seven replications during the first season (Experiment 1) and with eight replications during the second season (Experiment 2). The seasonal interactions (Experiment 1 × Experiment 2) on plant and nutrient elements were not significant (P ≤ 0.05) and data for the two seasons were pooled (n = 75). Relative to untreated control, commercial (Bradyrhizobium and Rhizobium strain) and native strains (Tubatse and Sebayeng strain) significantly increased plant height by 31, 33, 44 and 40%, respectively, root length by 30, 41, 40 and 42%, respectively and dry shoot mass by 48,195 and 17%, respectively. Similarly, rhizobia strains significantly contributed to the increase in nitrogen assimilation by 7, 25 and 80%, respectively, protein synthesis by 13, 10, 24, 69%, respectively, and symbiotic efficiency by 31, 133, 292 and 82%, respectively. However, rhizobia inoculants had no significant effects on potassium and phosphorus in leaf tissues. In achieving Objective 3, in Mean Concentration Stimulation Point (MCSP) experiments, seven treatments, xxvi namely, 0, 2, 4, 8, 16, 32 and 64% for each phytonematicide, were arranged in a randomised complete block design (RCBD), with 8 replicates. In application interval experiments, treatments, based on “weeks-per-month-of-30 days” for M. javanica, which translated to 1, 2, 3 and 4 weeks, were arranged in a RCBD, with 10 replicates. Nemarioc-AL and Nemafric-BL phytonematicides had MCSP values of 3.43 and 4.03%, respectively, with the plant having high tolerance level to the products. The respective application interval of the two products for managing population densities of Meloidogyne species were 29 and 17 days. The dosage models for Nemarioc-AL and Nemafric-BL phytonematicides were 6.62 and 13.26%, respectively. In achieving Objective 5, the study used nine treatments designated as T1, T2, T3, T4, T5, T6, T7, T8 and T9, respectively, consisting of 1, 2, 3, 4, 5, 6, 7, 8 and 9 seedlings/hole of drip irrigation transplanted using a 3S planter under field conditions, arranged in randomised complete block design (RCBD) with 9 replications (n = 81) in two seasons. The NWP of total flavonoids, total tannin and total phenol exhibited positive quadratic relations in varied planting density suggesting that this cultural practices could be manipulated to improve NWP of cancer bush. In conclusion, the wild bacterial isolates, sampled from S. frutescens plant grown in the field, outperformed the commercial bacterial strains in enhancing the productivity of the test plants. The empirically established dosage model for Nemarioc-AL and Nemafric-BL phytonematicides could be used to control Meloidogyne species in cancer bush production. There is a need to further investigate the responses of the identified strains to the test phytonematicides. Findings of the study openend new frontiers in the development and commercialisation of the observed native bacterial strains for the cultivation of S. frutescens, which has excellent medicinal importance as a cure or management for cancer. / Agricultural Research Council-Universities Collaboration Centre, the National Research Foundation (NRF) and the Flemish Inter-University Council of Belgium

Broomrapes, <i>Orobanche</i> spp., are holoparasites that affect the growth of a variety of broadleaf crops. One of the distinct characteristics of the family Orobanchaceae is the lack of chlorophyll, and hence inability to synthesize their own food. Broomrapes subsist on the roots of the host plant from which they derive the carbon, water, and nutrients needed for further growth. Parasitism as such leads to yield reductions, and in case of heavy infestations, complete crop failure. Among other plants parasitized by broomrapes are several legumes, some of which are also the world's most economically important crops. As part of their unique biology, legumes provide an ecological niche for diazotropic soil bacteria, which belong to the family Rhizobiaceae. In return, the host plant receives fixed nitrogen from the nodules, specialized structures produced on the roots of most legume plants upon inoculation with bacteria. <i>Orobanche</i> spp. germination depends on the presence of chemical stimulant in host root exudates. It has been reported that inoculation of some legumes resulted in greater infestation by parasitic weeds. In addition, bacterial nodules were assumed to provide a place for broomrape invasion of host legume. Furthermore, infestations were observed to be more intense in aerobic conditions when rhizobia are most active. It is possible that production of the stimulant could be correlated with the infection of roots with <i>Rhizobium</i>, and that the nodules formed on the roots could play a role in broomrape parasitism; however, others have not confirmed this. Studies were conducted to investigate the possibility of interaction between <i>Orobanche</i> spp. attack and <i>Rhizobium</i> nodulation in legumes. Seed germination, number of parasitic attachments, as well as the morphology of two broomrape species, small broomrape (<i>Orobanche minor</i> Sm.) and Egyptian broomrape (<i>Orobanche aegyptiaca</i> Pers.), were studied. <i>O. minor</i> showed a greater percent seed germination, and formed a greater number of attachments on red clover (<i>Trifolium pratense</i> L.) inoculated with <i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> in comparison with non-inoculated plants. However, the addition of the inoculum did not appear to enhance <i>O. aegyptiaca</i> seed germination or the number of its attachments on the host roots compared with the controls. Morphological observations of <i>O. minor</i> attachments on red clover suggest that parasitic attachments were not situated over the bacterial nodules, but perhaps involve parasite-induced enzymatic degradation followed by mechanical protrusion of host plant root cortex, possibly utilizing host plant-rhizobacteria interactions as well. / Master of Science

Nous nous sommes intéressés à évaluer l'influence du changement climatique sur les patrons nets de réponse des plantes aux agents pathogènes. Dans ce travail, nous avons étudié les effets de l’augmentation de la température (20°, 25° et 28°C) sur le phénotype précoces (symptômes de maladie) et sur la fitness en fin de cycle de différentes accessions et mutants de nodulation de la plante légumineuse modèle Medicago truncatula, inoculées par des souches d’agent pathogène racinaire Verticillium adaptées à des différentes températures. Le comportement des variétés de Luzerne cultivée (Medicago sativa) dans ces conditions a été également analysé. Le travail a été divisé en 3 parties. La première partie nous a permis d’identifier parmi 12 souches de Verticillium spp., une souche froide (VA1) et une souche tempérée (V31.2), avec une température optimale de 20°C et 25°C respectivement pour la croissance, la sporulation et l'agressivité sur M. truncatula. Par contre, notre collection des souches ne renfermant pas de souches adaptées à des températures plus élevées. Nous avons obtenu par mutagénèse UV de la souche V31.2 une troisième souche (AS38) chaude qui est agressive à 28°C. Dans la deuxième partie nous avons observé les symptômes de maladie pour sept accessions naturelles de M. truncatula, inoculées par ces trois souches d’agent pathogène, à trois températures 20°, 25° et 28°C et en présence de la souche Sinorhizobium meliloti RCR2011. De faibles symptômes ont été relevés pour deux accessions A17 et DZA315.16 inoculées par VA1 à 20°C. Nous avons observé une sensibilité maximale pour trois accessions (F83005.5, DZA315.16 et L321) inoculées par V31.2 à 25°C, et pour quatre accessions (F83005.5, DZA315.16, L321 et L198) inoculées par AS38 à 28°C. Les résultats des symptômes de maladie ont été confirmés par une quantification moléculaire de l’ADN fongique (qPCR) et par ré-isolement à partir des tissus aériens de la plante. L’effet de VA1 et V31.2 sur trois caractères de fitness (nombre et poids de gousse par plante, ainsi que biomasse aérienne) de M. truncatula a été étudié. L’effet de VA1 s’observe uniquement à 20°C sur l'accession A17. Par contre, V31.2 a montré un impact sur les trois caractères de fitness qui diminuent chez les accessions sensibles, ainsi que sur le nombre de gousse pour l’accession résistante L198. Dans la troisième partie nous avons analysé de la même façon pour quatre mutants de nodulation dans le fond génétique A17. Les mutants ont montré un niveau de résistance à la souche VA1 plus élevé qu’A17, quelle que soit la température étudiée. Vis à vis de la souche V31.2, à 20°C les mutants skl et hcl ont montré le même taux de symptômes qu’A17 tandis que les mutants nfp et sunn ont de taux de symptômes supérieur à celui d'A17. Ces mutants ont tous une sensibilité plus élevé à 25°C. Les résultats des symptômes de maladie ont été confirmés par le test de ré-isolement. Pour ces mutants nous montrons pour la première fois, que seul le mutant sunn (hypernodulant) à la même productivité qu’A17, quelle que soit la condition (contrôle ou inoculées) et la souche (VA1 ou V31.2) étudiée ; alors que le mutant skl (hypernodulant également) a une productivité plus faible. Les deux autres mutants déficients dans la nodulation nfp et hcl ont montré une productivité plus faible qu’A17 quelle que soit la souche et la température étudiée. Enfin une bonne similitude a été trouvée entre la réponse phénotypique précoce (symptômes de maladie) de M. truncatula et de M. sativa inoculées par Verticillium spp. Dans cette thèse, on n’est pas trouvé la corrélation positive entre la capacité de la nodulation et la protection contre la maladie, mais la symbiose augmente la fitness pour certaines de ces plantes. Les résultats suggèrent aussi que l'augmentation de la température pourrait contribuer à faire apparaître une souche adaptée à 28°C (AS38) qui est plus agressive et plus virulente que V31.2 sur M. truncatula. / We were interested to evaluate the influence of climate change on net patterns of plants responses to pathogens. In this work, we studied the effects of temperature increase (20 °, 25 ° and 28 ° C) on early phenotype (symptoms of disease) and on fitness at the end of growth cycle on different accessions and nodulation mutants of the legume model plant Medicago truncatula, inoculated by the root pathogen Verticillium adapted to different temperatures. The behavior of cultivated varieties of alfalfa (Medicago sativa) in these conditions was also analyzed. The work is divided into 3 parts. In the first part, we identified among 12 strains of Verticillium spp., a cold strain (VA1) and a temperate strain (V31.2) with an optimum temperature of growth, sporulation and aggressiveness to M. truncatula of 20°C and 25°C respectively. Since our strain collection doesn’t contain strains adapted to higher temperatures, we have obtained by UV mutagenesis of strain V31.2 a third strain (AS38), considered as a ‘hot’ strain, which is aggressive at 28°C. In the second part, we observed the symptoms of disease on seven natural accessions of M. truncatula, inoculated by the three strains of the pathogen at three temperatures 20°C, 25°C and 28°C in the presence of Sinorhizobium meliloti RCR2011. Mild symptoms were observed for two accessions A17 and DZA315.16 inoculated with VA1 at 20°C. We observed a maximal sensitivity for three accessions (F83005.5, DZA315.16 and L321) inoculated with V31.2 at 25 ° C, and for four accessions (F83005.5, DZA315.16, L321 and L198) inoculated with AS38 at 28 ° C. The results of phenotypic disease symptoms were confirmed by molecular quantification of fungal DNA (qPCR), and re-isolation of the fungus from aerial plant tissues. The effect of strains VA1 and V31.2 on three fitness traits (number and weight of pods per plant and aerial biomass) was studied. The effect negative of VA1 was observed only at 20°C on the A17 accession. In contrast, V31.2 showed an impact on the three fitness traits, which decrease in susceptible accessions, as well as on pod number of the resistant accession L198. In the third part, a similar analysis was made for four nodulation mutants in A17 genetic background. Nodulation mutants showed a higher level of resistance to VA1 than A17, at different studied temperatures. Towards strain V31.2 at 20°C the mutants skl and hcl showed the same symptom scores as A17 whereas nfp and sunn mutants had more susceptible. Mutants showed a higher sensitivity at 25°C to V31.2 fungal strain. The results of phenotypic disease symptoms were confirmed by re-isolation experiments. For the nodulation mutants we showed, for the first time, that only the sunn mutant (hypernodulant) has the same productivity as A17, regardless of the condition (inoculated or control) and the studied strain (VA1 or V31.2); while the skl mutant (hypernodulant also) has a lower productivity. The other two mutants defective in nodulation (nfp and hcl) showed lower productivity than A17 regardless of the strain (VA1 or V31.2) and the temperature studied. Finally, a strong similarity was found between the early phenotypic response symptoms disease in M. truncatula and M. sativa inoculated by Verticillium spp. In this thesis, we didn’t find a positive correlation between the ability of nodulation and protection against the disease, however the symbiosis increases the fitness of some of these plants. The results also suggest that increasing temperatures could favour appearance a strain adapted to 28°C (AS38), which is more aggressive and more virulent than V31.2 on M. truncatula.

La déficience en phosphore est l’un des facteurs limitant la production de légumineuses à graines, dont le haricot (Phaseolus vulgaris). La diversité génétique de cette espèce en Amérique latine a permis d'identifier avec le CIAT, des lignées recombinantes du croisement de DOR364 et BAT477 à fort pouvoir fixateur d'azote (FSN) et à forte efficacité d'utilisation de phosphore (EUP). Les résultats obtenus au cours de ce travail nous ont permis de répondre à notre objectif principal de thèse qui consistait à vérifier la pertinence des critères d'adaptation de la fixation symbiotique de l'azote chez le haricot à la disponibilité de P que nous avons déterminé. Nous avons démontré, d'une part, en milieu hydroaéroponique, que les racines nodulées du haricot, excrètent dans leur rhizosphère une quantité de H+ qui est corrélée à la perméabilité nodulaire. Ce qui laisse penser qu'une part d'H+ excrétée par les racines nodulées est liée à la fixation symbiotique de N2. D'autre part, nous avons démontré que sous déficience en P les lignées tolérantes acidifient plus leur rhizosphère que les sensibles. En multisites les facteurs les plus déterminants de la hiérarchisation des sites sont N-total et P-total. Deux groupes de lignées se distinguent, les tolérantes versus les sensibles à la faible fertilité des sols en P. La lignée locale se distingue des groupes précédents. Elle est capable de croître dans différents sols, notamment les contraignants avec une grande capacité à noduler, par conséquent, à compenser la déficience en N. Nous avons également pu démontrer que les biomasses nodulaire et aérienne sont corrélées au P Olsen du sol / Phosphorus deficiency is one of the limiting factor for grain legume production like bean (Phaseolus vulgaris). The results obtained during this work enabled us to confirm our main aim of this work which is checking the relevance of the criteria of adaptation of the symbiotic nitrogen fixation of bean to P availability. We showed, in controlled conditions that the nodulated roots of bean, release in their rhizosphere a quantity of H+ which is correlated with the nodul permeability. What lets think that a share of H+ released is related to the symbiotic N2 fixing. In addition, we showed that under P deficiency the tolerant lines acidify more their rhizosphere that the sensitive ones. Into multisite trial the most determining factors of the hierarchisation of the sites are total-N and total-P. Two groups of lines are distinguished: tolerant versus sensitive to P deficiency. The local farmer line is distinguished from the studied lines. It is able to grow in various soil fertility, in particular the constraining soils. ones with a great capacity with noduler, consequently, to compensate for deficiency in NR. We also could show that shoot and nodule biomass are correlated with the Olsen-P Olsen of the soil

Atualmente, o termo sustentabilidade vem ganhando destaque dentro das atividades agrícolas e para a produção animal em pastagens não é diferente. As leguminosas forrageiras são conhecidas por algumas características peculiares como grande capacidade de fixação do nitrogênio atmosférico e elevado valor nutritivo, surgindo assim como uma alternativa viável nesse novo modelo de produção. Entretanto, muitas vezes práticas de manejo inadequadas acabam não permitindo a exploração do potencial dessas espécies, levando-as ao desuso. Dessa forma, conhecer a resposta de plantas (alterações em forma e função) a intensidades de pastejo é imprescindível para permitir a idealização de estratégias de manejo eficientes que possam contribuir para a otimização do processo produtivo em sistemas pastoris. Este trabalho fez parte de uma série de experimentos delineados com o propósito de avaliar aspectos gerais de crescimento e desenvolvimento do amendoim forrageiro sob pastejo e suas implicações sobre a produção de forragem e potencial de consumo pelos animais. Seu objetivo específico foi avaliar as características produtivas de Arachis pintoi cv. Belmonte submetido a intensidades de pastejo sob lotação contínua. O experimento foi conduzido na Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, de janeiro a dezembro de 2013. Os tratamentos corresponderam a intensidades de pastejo determinadas por alturas de manejo do pasto (5, 10, 15 e 20 cm), e foram alocados às unidades experimentais (piquetes de aproximadamente 200 m²) segundo delineamento de blocos completos casualizados, com quatro repetições. Foram caracterizadas e determinadas as seguintes variáveis-resposta: índice de área foliar, ângulo da folhagem, interceptação luminosa do dossel, massa de forragem e sua composição botânica e morfológica, número e massa de nódulos radiculares, massa de raízes e acúmulo de forragem. As intensidades de pastejo promoveram alterações no crescimento e desenvolvimento do Arachis pintoi cv. Belmonte. Pastos manejados com intensidade de pastejo mais leniente (15 e 20 cm) apresentaram maior índice de área foliar, ângulo da folhagem, massa de forragem, porcentagem de plantas invasoras e taxa de acúmulo de forragem (exceto no inverno). Em contrapartida, pastejos severos (5 e 10 cm) proporcionaram maiores valores de porcentagem de folíolos e pecíolos, relação folíolo/estolão, número e massa de nódulos, massa de raízes e taxa de acúmulo de forragem durante o inverno. A intensidade de pastejo não afetou o peso médio dos nódulos, somente o seu número e massa total. Outros aspectos produtivos apresentaram efeitos isolados de época do ano como porcentagem de estolão e de material morto, com maiores valores registrados no verão e no inverno, respectivamente. Estolões assim como folhas (folíolos e pecíolos) corresponderam às principais estruturas na determinação do crescimento das plantas, tendo sido afetados de forma direta pela intensidade de pastejo e época do ano. A intensidade de pastejo interferiu com a relação parte aérea/raízes, de forma que maior massa de raízes e de nódulos foram registradas nos pastos manejados a 5 e 10 cm e o maior IAF, interceptação de luz e acúmulo de forragem foram registrados nos pastos manejados a 15 e 20 cm. O fato indica uma relação de compensação entre número e massa de nódulos/raízes e IAF controlando o acúmulo de forragem, revelando grande plasticidade fenotípica potencial dessa planta forrageira e potencial de uso em pastagens. / In recent years the term sustainability is becoming increasingly important in agriculture, including animal production from pastoral systems. Forage legumes are known for some particular characteristics like large capacity for capturing atmospheric nitrogen and high nutritive value of the produced herbage, and for that reason is being considered as a viable alternative in this new production model. However, inadequate management practices often result in no realisation and exploitation of their production potential, resulting in low use of these plant species. For that reason, understanding of plant responses (modifications in form and function) to intensities of grazing is essential for allowing planning of efficient management practices aiming at optimising productivity in pastoral systems of animal production. This study was part of a series of experiments conceived with the purpose of evaluating general aspects of growth and development of forage peanut under grazing and their implications to herbage production and potential of herbage intake by grazing animals. The specific objective was to evaluate the agronomic characteristics of Arachis pintoi cv. Belmonte subjected to intensities of grazing under continuous stocking. The experiment was carried out at Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, from January to December 2013. Treatments corresponded to four intensities of grazing characterised by the sward management heights of 5, 10, 15 and 20 cm. These were allocated to the experimental units (200 m2 paddocks) according to a randomised complete block design, with four replications. The following response variables were evaluated: sward leaf area index (LAI), foliage angle, canopy light interception (LI), herbage mass and its morphological and botanical composition, number and mass of root nodules, root mass and herbage accumulation. The grazing intensities interfered with growth and development of Arachis pintoi cv. Belmonte. Swards managed at 15 and 20 cm showed higher LAI, foliage angle, herbage mass, percentage of weeds and herbage accumulation rates (except in winter) than those managed at 5 and 10 cm. On the other hand, swards managed at 5 and 10 cm showed higher percentage of leaf, leaf-to-stolon ratio, number and mass of root nodules, root mass and winter herbage accumulation rates. Grazing intensity did not affect average nodule weight, only nodule number and total mass. Other productive aspects revealed isolated effects of season of the year like percentages of stolon and dead material, with larger values recorded during summer and winter, respectively. Stolons as well as leaves corresponded to the main structures determining plant growth, and were directly affected by grazing intensity and season of the year. Grazing intensity interfered with the shoot-to-root ratio, with larger root and nodule mass being recorded on swards managed at 5 and 10 cm and larger LAI, LI and herbage accumulation recorded on swards managed at 15 and 20 cm. The fact indicates a compensating relationship between number and mass of nodules/roots and LAI controlling herbage accumulation, highlighting the large potential phonotypical plasticity of this forage plant and potential of use in pastures.

Atualmente, o termo sustentabilidade vem ganhando destaque dentro das atividades agrícolas e para a produção animal em pastagens não é diferente. As leguminosas forrageiras são conhecidas por algumas características peculiares como grande capacidade de fixação do nitrogênio atmosférico e elevado valor nutritivo, surgindo assim como uma alternativa viável nesse novo modelo de produção. Entretanto, muitas vezes práticas de manejo inadequadas acabam não permitindo a exploração do potencial dessas espécies, levando-as ao desuso. Dessa forma, conhecer a resposta de plantas (alterações em forma e função) a intensidades de pastejo é imprescindível para permitir a idealização de estratégias de manejo eficientes que possam contribuir para a otimização do processo produtivo em sistemas pastoris. Este trabalho fez parte de uma série de experimentos delineados com o propósito de avaliar aspectos gerais de crescimento e desenvolvimento do amendoim forrageiro sob pastejo e suas implicações sobre a produção de forragem e potencial de consumo pelos animais. Seu objetivo específico foi avaliar as características produtivas de Arachis pintoi cv. Belmonte submetido a intensidades de pastejo sob lotação contínua. O experimento foi conduzido na Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, de janeiro a dezembro de 2013. Os tratamentos corresponderam a intensidades de pastejo determinadas por alturas de manejo do pasto (5, 10, 15 e 20 cm), e foram alocados às unidades experimentais (piquetes de aproximadamente 200 m²) segundo delineamento de blocos completos casualizados, com quatro repetições. Foram caracterizadas e determinadas as seguintes variáveis-resposta: índice de área foliar, ângulo da folhagem, interceptação luminosa do dossel, massa de forragem e sua composição botânica e morfológica, número e massa de nódulos radiculares, massa de raízes e acúmulo de forragem. As intensidades de pastejo promoveram alterações no crescimento e desenvolvimento do Arachis pintoi cv. Belmonte. Pastos manejados com intensidade de pastejo mais leniente (15 e 20 cm) apresentaram maior índice de área foliar, ângulo da folhagem, massa de forragem, porcentagem de plantas invasoras e taxa de acúmulo de forragem (exceto no inverno). Em contrapartida, pastejos severos (5 e 10 cm) proporcionaram maiores valores de porcentagem de folíolos e pecíolos, relação folíolo/estolão, número e massa de nódulos, massa de raízes e taxa de acúmulo de forragem durante o inverno. A intensidade de pastejo não afetou o peso médio dos nódulos, somente o seu número e massa total. Outros aspectos produtivos apresentaram efeitos isolados de época do ano como porcentagem de estolão e de material morto, com maiores valores registrados no verão e no inverno, respectivamente. Estolões assim como folhas (folíolos e pecíolos) corresponderam às principais estruturas na determinação do crescimento das plantas, tendo sido afetados de forma direta pela intensidade de pastejo e época do ano. A intensidade de pastejo interferiu com a relação parte aérea/raízes, de forma que maior massa de raízes e de nódulos foram registradas nos pastos manejados a 5 e 10 cm e o maior IAF, interceptação de luz e acúmulo de forragem foram registrados nos pastos manejados a 15 e 20 cm. O fato indica uma relação de compensação entre número e massa de nódulos/raízes e IAF controlando o acúmulo de forragem, revelando grande plasticidade fenotípica potencial dessa planta forrageira e potencial de uso em pastagens. / In recent years the term sustainability is becoming increasingly important in agriculture, including animal production from pastoral systems. Forage legumes are known for some particular characteristics like large capacity for capturing atmospheric nitrogen and high nutritive value of the produced herbage, and for that reason is being considered as a viable alternative in this new production model. However, inadequate management practices often result in no realisation and exploitation of their production potential, resulting in low use of these plant species. For that reason, understanding of plant responses (modifications in form and function) to intensities of grazing is essential for allowing planning of efficient management practices aiming at optimising productivity in pastoral systems of animal production. This study was part of a series of experiments conceived with the purpose of evaluating general aspects of growth and development of forage peanut under grazing and their implications to herbage production and potential of herbage intake by grazing animals. The specific objective was to evaluate the agronomic characteristics of Arachis pintoi cv. Belmonte subjected to intensities of grazing under continuous stocking. The experiment was carried out at Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, from January to December 2013. Treatments corresponded to four intensities of grazing characterised by the sward management heights of 5, 10, 15 and 20 cm. These were allocated to the experimental units (200 m2 paddocks) according to a randomised complete block design, with four replications. The following response variables were evaluated: sward leaf area index (LAI), foliage angle, canopy light interception (LI), herbage mass and its morphological and botanical composition, number and mass of root nodules, root mass and herbage accumulation. The grazing intensities interfered with growth and development of Arachis pintoi cv. Belmonte. Swards managed at 15 and 20 cm showed higher LAI, foliage angle, herbage mass, percentage of weeds and herbage accumulation rates (except in winter) than those managed at 5 and 10 cm. On the other hand, swards managed at 5 and 10 cm showed higher percentage of leaf, leaf-to-stolon ratio, number and mass of root nodules, root mass and winter herbage accumulation rates. Grazing intensity did not affect average nodule weight, only nodule number and total mass. Other productive aspects revealed isolated effects of season of the year like percentages of stolon and dead material, with larger values recorded during summer and winter, respectively. Stolons as well as leaves corresponded to the main structures determining plant growth, and were directly affected by grazing intensity and season of the year. Grazing intensity interfered with the shoot-to-root ratio, with larger root and nodule mass being recorded on swards managed at 5 and 10 cm and larger LAI, LI and herbage accumulation recorded on swards managed at 15 and 20 cm. The fact indicates a compensating relationship between number and mass of nodules/roots and LAI controlling herbage accumulation, highlighting the large potential phonotypical plasticity of this forage plant and potential of use in pastures.

Nous avons réalisé la synthèse de précurseurs d'analogues sulfures de facteurs NOD, messagers chimiques intervenant lors du phénomène de nodulation rencontré dans l'association symbiotique entre certaines plantes légumineuses et des bactéries de la famille rhizobium. Cette association permet à la plante de fixer l'azote atmosphérique préalablement métabolisé par les bactéries. Ces analogues devraient permettre de mieux comprendre les différents processus intervenant au cours de la symbiose plante/ bactérie ainsi qu'étudier l'hydrolyse des facteurs NOD par des enzymes, les chitinases. Nous avons choisi de préparer des analogues fonctionnalisés pour lersquels seule la liaison O-glycosidique entre deux unités serait remplacée par une liaison thioglycosidique. Grâce à l'utilisation de donneurs de glycosyle sous la forme de trichloroacétimidate, nous avons réalisé la synthèse d'un thiotrisaccharide ainsi que celle d'un thiotétrasaccharide, précurseur d'analogues de facteurs NOD, dont les unités réductrices et non réductrices sont potentiellement différenciées en vue de leur fonctionnalisation. Par ailleurs, le transfert d'une unité de glucosamine sur un thiodisaccharide, à l'aide de la bétâ-1,4-galactosyltranférase, a conduit à la préparation d'un thiotrisaccharide. Cette dernière étape a permis d'envisager la synthèse d'un thiotétrasaccharide par voie chimio-enzymatique. Ces précurseurs devraient conduire à de nouveaux analogues sulfures de facteurs NOD sur lesquels des tests biologiques pourraient être réalisés afin d'évaluer l'activité de nodulation ainsi que la résistance aux chitinases

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-03-07T15:03:10Z No. of bitstreams: 1 PGCS15MA155.pdf: 1637827 bytes, checksum: aa3300b0757a566af05641eb9e2d70e1 (MD5) / Made available in DSpace on 2018-03-07T15:03:10Z (GMT). No. of bitstreams: 1 PGCS15MA155.pdf: 1637827 bytes, checksum: aa3300b0757a566af05641eb9e2d70e1 (MD5) Previous issue date: 2015-10-27 / The objective of this project was to investigate the existence of native rhizobia strains that promote the anticipation of the formation of nodules capable of fixing the available nitrogen from the atmosphere, and thereby reduce the use of nitrogenous fertilizers in bean crops. In order to accomplish the objective of the present study, this one was divided into two experiments, both in the Lages city, Santa Catarina State, under different abiotic conditions. The treatments consisted of the combination of six levels of factor inoculation within seven levels of factor bean genotype (a total of 42 treatments). Six of the seven rhizobia strains tested were previously evaluated as to genetic diversity from Germplasm bank of the Agronomy and Veterinary Science Center, the seventh is a recommended commercial strain. Among the treatments, there is a control without the use of nitrogen, and a control with application of this nutrient. It was performed the evaluation of various aspects, such as number of nodules, nodules dry weight, shoot dry weight and nitrogen content. The results were submitted to analysis of variance. Significant difference was found a few treatments with regard to shoot dry weight (SDW), probably due to the specificity of interaction between the host plant and the rhizobia strain. Some strains with genotypes combinations tend to form nodules earlier, increasing the nitrogen fixing time. The number of nodules had no effect on SDW. The nodulation of bean plants, which were not inoculated or received mineral N application (absolute control) was similar to the other treatments in one of both experiment carried, showing the existence of high native population of bean rhizobia symbionts. Furthermore, it was observed that the bacteria B2 had a greater influence comparing to the others bacteria tested / Esse projeto teve como objetivo pesquisar a existência de estirpes de rizóbios nativos que promovam a antecipação da formação de nódulos capazes de fixar o nitrogênio livre da atmosfera, e, com isso, reduzam a utilização de fertilizantes nitrogenados na cultura de feijão. Para sua efetivação, o presente estudo foi dividido em dois experimentos, ambos conduzidos no município de Lages, no Estado de Santa Catarina, sob condições distintas no que se referem aos fatores abióticos. Os tratamentos testados foram resultantes da combinação de 6 (seis) níveis do fator inoculação e 7 (sete) níveis do fator genótipo de feijoeiro, previamente avaliados quanto à diversidade genética do banco de Germoplasma do Centro de Ciências Agroveterinárias, e uma estirpe comercial recomendada, obtendo-se um controle sem a aplicação de nitrogênio e um controle com aplicação desse nutriente, perfazendo um total de 42 tratamentos. Foi realizada a avaliação de diversos aspectos, tais como número de nódulos, massa seca de nódulos, massa seca da parte aérea e teor de nitrogênio. Os resultados foram submetidos à análise de variância, onde constatou-se diferença significativa de alguns tratamentos com relação à Massa Seca da Parte Aérea (MSPA), provavelmente pela especificidade da planta hospedeira com a estirpe. Algumas estirpes combinadas com genótipos tendem a formar nódulos precocemente, aumentando o tempo de fixação de N. O número de nódulos não influenciou na MSPA. A nodulação das plantas de feijoeiro, que não foram inoculadas nem receberam aplicação de N mineral (testemunha absoluta) foi semelhante à dos demais tratamentos no segundo experimento, evidenciando a existência de elevada população nativa de rizóbios simbiontes na cultura do feijoeiro. Ainda, observou-se que a bactéria B2 teve uma maior influência em relação às outras bactérias testadas