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No. of bitstreams: 2 Dissertação - Camilla Martins de Oliveira - 2015.pdf: 2722272 bytes, checksum: c1b127a024727131109290202bf7f846 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-02-23 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Nematodes cause losses in plants throughout the world that can be translated into many economic losses. The root-knot nematodes (Meloidogyne sp.) are the most common and destructive pathogens within this group. In order to get an efficient method of nematode management, it is need to identify species and quantify accurately and reliably. The aim of this research was to optimize an assay based on real-time PCR to detect and quantify M. incognita. For this purpose the effectiveness of different DNA methods of extraction were compared through the values of Ct intervals. The DNA extraction was made from 100 individual nematodes by the methods: CTAB, Phenol: Chloroform and commercial kit (PureLink® Genomic ADN Kit, Invitrogen). In the comparative analysis using the three methods the CTAB method and commercial kit obtained similar Ct values. The CTAB was the best method of extraction with less variation among the replications and showed higher linearity of the standard curve in comparison with the other methods tested. It was possible to quantify nematodes in the samples based on the intervals of the Ct values established from different numbers of nematodes (1, 10, 25, 100, 250, 500 and 750). This study demonstrated that qPCR technique is a sensitive and reliable alternative for the quantification of M. incognita that may help laboratories of diagnose and field survey. Twenty-six populations of the root-knot nematode (Meloidogyne spp.) from five locations of the state of Bahia, five from the state of Mato Grosso, four from the state of Goiás and one from the state of Minas Gerais, were characterized based on morphology of perineal cut, biochemical analysis through esterase profile and molecular analysis with specific primers. Identification of nematodes in the samples using the analysis of perineal cut, esterase profile and molecular analysis was possible, but with some variations in the perineal patterns and some atypical profiles of esterase. In the analyses of esterase profiles were found 69.23% of M. javanica with esterase profiles J3 and J2, and 30.77% of M. incognita with esterase profile I1. There was a higher occurrence of M. javanica in the areas cultivated with soybeans. Molecular analysis showed to be practical and accurate. / Nematoides causam perdas em plantas em todo o mundo, as quais podem ser traduzidas em muitos prejuízos econômicos. Os nematoides das galhas (Meloidogyne spp.) são os mais comuns e destrutivos dentro deste grupo de patógenos. Para conseguir implantar um método eficiente de manejo de fitonematoides há uma necessidade de identificação das espécies e quantificação precisa e confiável. O objetivo deste trabalho foi a otimização de um ensaio baseado em PCR em tempo real para detectar e quantificar M. incognita. Para isto diferentes métodos de extração de DNA e sua eficiência foram comparados. A extração de DNA foi feita a partir de 100 nematoides pelos métodos do CTAB, Fenol: Clorofórmio e KIT comercial (PureLink® Genomic DNA Kits, Invitrogen). Na análise comparativa destes três métodos de extração de DNA observou-se que o método CTAB e o utilizando o Kit comercial obtiveram igual eficiência, dados pelos valores próximos Ct (cycle threshold). O melhor método de extração foi considerado o CTAB, apresentando menor variação entre as diferentes amostras biológicas utilizadas como repetições e demonstrando maior linearidade na curva-padrão em comparação com os demais métodos testados. Foi possível estabelecer um parâmetro para a quantificação de nematoides nas amostras baseado em faixas de valores de Ct, estabelecidas a partir de diferentes números de indivíduos (1, 10, 25, 100, 250, 500 e 750). Este estudo demonstrou que a técnica de qPCR é uma alternativa sensível e confiável para a quantificação de M. incognita, para auxiliar laboratórios de diagnóstico e o monitoramento no campo desses nematoides. Vinte e seis populações do nematoide das galhas (Meloidogyne spp.), provenientes de cinco municípios do Estado da Bahia, cinco municípios do Estado do Mato Grosso, quatro municípios do Estado de Goiás e um município do Estado de Minas Gerais, foram caracterizados com base em: morfologia do corte perineal, análise bioquímica por meio de perfil de esterase e análise molecular com iniciadores específicos. Baseado nestes parâmetros foi possível a identificação das amostras, porém foram encontradas algumas variações nos padrões perineais e perfis atípicos nos perfis de esterase. Nas análises dos perfis de esterase foram encontradas 69,23% de M. javanica com perfis de esterase J3 e J2, e 30,77% de M. incognita com perfil de esterase I1. Verificou-se a maior ocorrência de M. javanica, nas áreas coletadas cultivadas com soja. A análise molecular se mostrou prática e precisa.

Este projeto objetivou desenvolver um marcador molecular ligado ao gene de resistência a Tobacco mosaic virus (TMV), em vista da necessidade de aprimorar os métodos de melhoramento de plantas para atender crescentes demandas de produtividade. O outro objetivo deste trabalho foi a avaliação de uma população segregante F2 e de retrocruzamento (RC1F1) a Meloidogyne incognita raça 3, oriunda do cruzamento das cultivares comerciais Coker 176 (C176) e Coker 371 Gold (C371G). Para o desenvolvimento do marcador ligado ao gene de resistência a TMV, o gene N, foram desenvolvidos iniciadores específicos para regiões conservadas (TIR, NBS e LRR) deste gene com base em sua seqüência. Estes iniciadores foram utilizados para amplificar um marcador cuja ligação ao referido gene foi confirmada em 200 indivíduos de população segregante F2 oriunda do cruzamento entre uma linhagem resistente (Coker176) e outra suscetível ao vírus (Kentucky326). A proporção entre o número de plantas resistentes e suscetíveis (154:46) não diferiu estatisticamente daquela esperada no caso de segregação de um gene dominante de resistência, que seria de 3:1. Os resultados indicaram que o marcador e o gene estão proximamente ligados segundo taxa de recombinação, que foi de 1%. Na avaliação da hereditariedade a M.incognita utilizou-se 141 indivíduos da população segregante F2 oriunda do cruzamento entre uma linhagem resistente (Coker176) e suscetível (Coker 371G) e 138 indivíduos de RC1F1 ([C176 X C371G] X C371G). Os resultados obtidos entre a proporção entre o número de plantas resistentes e suscetíveis da população F2 (102:39) e da RC1F1 (67:71) não diferiu estatisticamente daquela esperada no caso de segregação de um gene dominante de resistência. / The aim of this study is to develop a molecular marker linked to the resistant gene to Tobacco mosaic virus (TMV) considering the necessity to improve plant breeding to meet growing demands of productivity. The other goal of this study is to evaluate the mode of inheritance of an F2 segregating population and backcross (BCF1) population of Meloidogyne incognita race 3 originated from cross breeding between commercial cultivars Coker 176 and Coker 371 Gold. For the development of the marker linked to the TMV resistant gene, the N gene, specific primers of this gene were developed for conserved regions (TIR, NBS and LRR) based on their sequence. These primers were used to amplify a marker whose connection with the aforementioned gene was confirmed in 200 individuals in a segregating F2 population originated from the cross breeding between a resistant cultivar (Coker176) and another cultivar which is susceptible to the virus (Kentucky326). The proportion between the number of resistant and susceptible plants (154:46) did not statistically differ from the one expected in the segregation of one dominant resistance, which would be a 3:1 segregation ratio. The results indicated that the marker and the gene are narrowly linked according to recombination ratio 1%. In the heredity evaluation of resistance to M.incognita 141 plants of the segregating F2 population originated from the cross breeding of a resistant (Coker176) and susceptible cultivar (Coker 371G) and 138 plants of backcross BC1F1 ([C176 X C371G) X C3371G) were used. The outcome of the proportion between the number of resistant and susceptible plants of segregating F2 (102:39) and BC1F1 population (67:71) were not statistically different from the ones expected for a monogenic dominant resistance.

Le but de cette thèse est de fournir une caractérisation topologique de tresses virtuelles. Les tresses virtuelles sont des classes d’équivalence de diagrammes de type tresses tracés sur le plan. La relation d’équivalence est générée par l’isotopie, les mouvements de Reidemeister et les mouvements de Reidemeister virtuels. L’ensemble des tresses virtuelles est munie d’une opération de groupe. On parlera alors du groupe de tresses virtuelles. Dans le Chapitre 1, nous introduisons les notions de base de la théorie de noeuds virtuels, nous évoquons certains propriétés du groupe tresses virtuelles, et des liens qu’il a avec le groupe de tresses classiques. Dans le Chapitre 2, nous introduisons la notion de diagramme de Gauss tressé (ou diagramme de Gauss horizontal), et on démontre qu’il s’agit là d’une bonne réinterprétation combinatoire pour les tresses virtuelles. On généralise en particulier certains résultats connus en théorie de noeuds virtuels. Un application est de retrouver la présentation classique du groupe de tresses virtuelles pures à l’aide des diagrammes de Gauss tressés. Dans le Chapitre 3, on introduit les tresses abstraites et on montre qu’elles sont en correspondance bijective avec les tresses virtuelles. Les tresses abstraites sont des classes d’équivalence des diagrammes de type tresses tracés sur une surface orientable avec deux composantes de bord. La relation d’équivalence est générée par l’isotopie, la compatibilité, la stabilité et les mouvements de Reidemeister. La compatibilité est la relation d’équivalence générée par les difféomorphismes préservant l’orientation. La stabilité est la relation d’équivalence générée par l’addition ou la suppression d’anses à la surface, dans le complémentaire du diagramme. Dans le Chapitre 4, on démontre que tout tresse abstraite admets une unique représentant de genre minimal, à compatibilité et mouvements de Reidemeister prés. En particulier, les tresses classiques se plongent dans les tresses abstraites. / The purpose of this thesis is to give a topological characterization of virtual braids. Virtual braids are equivalence classes of planar braid-like diagrams identified up to isotopy, Reidemeister and virtual Reidemeister moves. The set of virtual braids admits a group structure and is called the virtual braid group. In Chapter 1 we present a general introduction to the theory of virtual knots, and we discuss some properties of virtual braids and their relations with classical braids. In Chapter 2 we introduce braid-Gauss dia- grams, and we prove that they are a good combinatorial reinterpretation of virtual braids. In particular this generalizes some results known in virtual knot theory. As an application, we use braid-Gauss diagrams to recover a well known presentation of the pure virtual braid group. In Chapter 3 we introduce abstract braids and we prove that they are in a bijective cor- respondence with virtual braids. Abstract braids are equivalence classes of braid-like diagrams on an orientable surface with two boundary components. The equivalence relation is generated by isotopy, compatibility, stability and Reidemeister moves. Compatibility is the equivalence relation generated by orientation preserving diffeomorphisms. Stability is the equivalence relation generated by adding handles to or deleting handles from the surface in the complement of the braid-like diagram. In Chapter 4 we prove that for any abstract braid, there is a unique representative of minimal genus, up to compatibility and Reidemeister equivalence. In particular this implies that classical braids embed in abstract braids.

Dans un article publié en 2003, M.Gromov propose une reformulation de la théorie des petites simplifications en géométrie des groupes. Dans cette version, un graphe fini définit une présentation finie de groupe; les générateurs du groupe sont les étiquettes du graphe; les relateurs sont les mots associés aux cycles; les morceaux, mots "courts " qui permettent les petites simplifications dans un groupe, sont des mots qui étiquettent deux chemins distincts du graphe. Cette thèse prend pour point de départ une brève description de cette théorie publiée par Y. Ollivier en 2006. Le concept de groupe de présentation finie à "petites simplifications", développé par R. Lyndon, M. Greendlinger et autres dans les années 60 et 70, est précurseur des groupes hyperboliques de M.Gromov à la fin des années 80, pour lesquels les propriétés combinatoires de la présentation entraînent des propriétés algébriques du groupe. Dans notre travail, nous fondons de manière rigoureuse la théorie des petites simplifications du point de vue des graphes, et développons le concept de base de "mégatuiles", utilisé implicitement par Y. Ollivier dans son article. Nous étendons ses résultats aux cas non-hyperboliques et non-métriques (par exemple$C(4)-T(4)$). Ce point de vue permet une nouvelle preuve, plus naturelle, de la résolubilité des problèmes du mot et de conjugaison pour les présentations des groupes des entrelacs alternés premiers. Nous prolongeons également les résultats d'un théorème de M. Greendlinger au cas non-métrique, répondant ainsi à une question d'I. Kapovich. / In a paper published in 2003, M.Gromov proposes a rewording of the small cancellation theory in geometric group theory. In this version, a finite graph defines a finitely presented group; generators of the group are the labels of the graph; relators are the words associated with cycles; pieces, "short" words which allow small cancellations in a group, are words which label two distinct paths in the graph.Our thesis relies on a brief description of this theory published in2006 by Y.Ollivier. The concept of finitely presented "small cancellation" group, developed by R.Lyndon, M.Greendlinger and others in the 60's and 70's, is a precursor of Gromovword-hyperbolic groups in the late of the 80's, for which combinatorial properties of the presentation imply algebraic properties of the group. In our work, we build a rigorous small cancellation theory in terms of graphs, and develop the basic concept of "megatiles", implicitly used by Y. Ollivier in his article. We extend his results to non-hyperbolic and non-metric cases (eg. $C(4)-T(4)$). This point of view allows a new proof, more natural, of thesolvability of word and conjugacy problems for presentations of prime alternating link groups. We also extend the results of a M.Greendlinger theorem to thenon-metric case, in response to a question of I. Kapovich.

The outer surface of the human placenta, the syncytiotrophoblast, results from the fusion of many cytotrophoblast cells such that many nuclei are contained in this layer. It is possible for these nuclei to cluster forming syncytial nuclear aggregates (SNAs). SNAs have been linked to pathology with increased numbers and earlier formation of SNAs in preeclampsia and fetal growth restriction (FGR). SNAs can be grouped into subtypes including bridges, knots and sprouts, dependent on morphology and attachment to surrounding placental villi. Little is known about SNA formation, but the pyknotic appearance of nuclei within SNAs has led to development of a hypothesis that SNAs are the terminal point of nuclear turnover in the syncytiotrophoblast. Some cytoskeletal proteins have been associated with SNAs indicating their potential involvement in SNA formation. This project aimed to uncover differences between SNA subtypes, whether the degenerate nuclear morphology represents apoptosis and to understand which mechanisms drive nuclear collection into SNAs. Experimental approaches included a review of an electron micrograph archive and application of immunohistochemical techniques to ex vivo placental tissue. A long-term explant model was developed to examine SNA development in vitro; these experiments were further explored using an isolated primary cytotrophoblast model. Nuclei within SNAs were more frequently pyknotic and less frequently eukaryotic than nuclei dispersed in the syncytiotrophoblast. However, few SNAs were positive for the cytokeratin-M30 neoepitope, a caspase dependent breakdown product of cytokeratin-18 and no subtype of SNA showed greater M30 staining than general areas of syncytiotrophoblast. There were increased syncytial knots and decreased syncytial bridges in placentas from women with preeclampsia compared to controls and FGR. While cytoskeletal proteins are seen surrounding SNAs, inhibition of actin and tubulin had no effect on SNA turnover or stability. Very limited nuclear movement was recorded from in vitro culture indicating that syncytiotrophoblast nuclei move far less than had been expected. These data suggest that cell death was not prominent within SNAs but different prevalence of subtypes were present in preeclampsia indicating that SNAs might represent larger changes in placenta structure. As nuclei moved less and SNAs were more static than expected it is suggests that SNAs are more stable than previously thought. Overall, the hypothesis that SNAs are highly active in preeclampsia is questioned and new hypotheses of the role of SNAs are considered in the light of these experimental findings, including whether they form by chance and represent changes in cell turnover of the syncytiotrophoblast.

Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / The influence of cultural practices can be modified by environmental conditions such as container-type or positioning. The objective of the study was to determine whether container-type and positioning would have an influence on the growth of tomato plants and suppression of Meloidogyne javanica exposed to biomuti (Trial 1) and Afrikelp (Trial 2). Different container-types were filled with approximately 10.4 L growing mixture comprising steam-pasteurised sandy loam soil and Hygromix-T at 3:1 (v/v) ratio. The containers were established in microplots at 0.6 m × 0.6 m spacing, with treatments being brown pot-below; brown pot-above, black pot-below, black pot-above, plastic bag-above and plastic bag-below. Tomato (Solanum lycopersicum L.) cv. 'Floradade' seedlings were each transplanted and irrigated with 500 ml chlorine-free tapwater every other day. Seven days after transplanting, each plant was inoculated with 2000 eggs and second-stage juveniles (J2) of M. javanica. Biomuti and Afrikelp, obtained from the Agricultural Research Council (ARC) Vegetable, Ornamentals and Plants (VOP), were applied in separate trials weekly at 2.5%. At 56 days after inoculation, plant growth including selected nutrient elements and nematode variables were measured. Data were subjected to analysis of variance, with separation of means achieved using Fisher’s Least Significant Difference test at the probability level of 5%. In the biomuti trial, container-type and positioning had a significant effect on plant height, fruit number, dry root mass, dry shoot mass and fruit mass, contributing 82, 48, 44, 85 and 89% in total treatment variation (TTV) of the respective variables. Relative to brown pot-below; black pot above, plastic bag-above and brown pot-above reduced plant variables, whereas treatment effects were not significant on nematode variables. In the Afrikelp trial, trends where similar to those in biomuti, treatments had highly significant effects on xvi plant height, dry root mass, dry shoot mass and gall rating, contributing 91, 88, 66 and 60% in TTV of the respective variables. Relative to brown pot-below; black pot above, plastic bag-above and brown pot-above reduced the plant variables, but had no significant effects on nematode variables. Generally, plastic bags and polyethylene pots below-ground improved most plant growth variables when compared to those in containers positioned above-ground.

Les nématodes à galles (RKN) du genre Meloidogyne spp. sont des parasites obligatoires des plantes qui induisent la formation d’un site nourricier spécialisé au sein des racines. Mon projet de thèse a pour objectif d’identifier des gènes spécifiques de ces nématodes qui sont impliqués dans le parasitisme en se focalisant sur des protéines sécrétées ou effecteurs. La technologie de séquençage Illumina a été utilisée pour comparer les transcriptomes de M. incognita au cours de son cycle de vie. A partir de 307 gènes surexprimés dans -au moins- un stade du cycle de vie, nous avons sélectionné 14 candidats d’effecteurs. Des expériences de RT-qPCR, d’hybridation in situ et d’ARN interférence ont permis de confirmer le profil d’expression, de localiser l’expression des effecteurs et d’étudier leur rôle dans la pathogénicité. Ce travail a permis de démontrer le rôle important d’une petite protéine, MiSCR1, dans les stades précoces du parasitisme. Parallèlement, nous avons réalisé l’assemblage de novo du transcriptome de M. enterolobii, qui représente une nouvelle menace pour l’agriculture mondiale du fait de sa capacité à se reproduire sur la majorité des plantes résistantes aux autres RKN. Les premières comparaisons avec d'autres RKN nous ont permis d'identifier, non seulement des effecteurs en commun, mais aussi ceux qui sont spécifiques à certaines espèces de RKN et qui pourraient expliquer des différences de gamme d'hôtes. En conclusion, les analyses de transcriptomes de RKN ont permis de caractériser des nouveaux effecteurs candidats impliqués dans la pathogénicité, et d’apporter de nouvelles connaissances pour le développement de méthodes de lutte contre ces bioagresseurs / Root-knot nematodes (RKN) are obligate endoparasites that maintain a biotrophic relationship with their hosts inducing specialized feeding cells. My PhD project aims to identify RKN genes specifically involved in plant parasitism with an emphasis on genes encoding new secreted proteins, named effectors. Using Illumina RNA-seq technologies, we compared transcriptomes of Meloidogyne incognita during its life cycle. From 307 genes over-expressed at -at least- one stage of the life cycle, we selected 14 effector candidates. RT-qPCR, in situ hybridisation and siRNA soaking experiments were carried out to confirm their expression profile, localize the spatial expression of these candidates in the nematode and to study their role in pathogenicity. The silencing of the dorsal gland specific-Minc18876 gene and its paralogues resulted in a significant, reproducible decrease in the number of egg masses, demonstrating a potentially important role for the small cysteine-rich effector, MiSCR1, it encodes in early stages of giant cell formation. In parallel, we perform a de novo assembly of M. enterolobii transcriptome. This RKN species represents a new threat for the agriculture worldwide because of its ability to reproduce on the majority of known RKN-resistant plants. First comparisons with others RKN allowed us to identify, not only the common set of effectors, but also those specific to some RKN species and possibly involved in host range differences. In conclusion, the transcriptome profiling of RKNs allowed the characterisation of new candidate effectors involved in the plant pathogenicity, and provided a better knowledge for the development of new methods to control these pests

In vivo organogenesis is based on the temporal-spatial developmental processes that depend on cell behaviour, for example on their growth, migration, differentiation and intercellular interactions. Such behaviour is regulated by appropriate transient expression of various signalling molecules. Despite the significant advances in therapeutic strategies, the secret of the development of the biological replacement of a damaged or missing tooth has not yet been revealed. In this context, animal models provide a powerful tool for studying tooth normogenesis and pathogenesis in both basic and applied research. Early development of the tooth shares similar morphological and molecular features with other ectodermal organs. At the same time, these features are largely preserved also between species, which is advantageous for the use of model organisms. The dental formula of both: the human and the mouse are reduced against a common ancestor, but both groups of organisms evince simple as well as multicusped teeth. In both, structures called rudimentary were found. These structures are suppressed during ontogenetic development and generally they are not attributed to essential functions. That is why we aimed to study dental rudiments in detail and reveal their function in odontogenesis. This work presents new...

Thesis (Ph. D. Agriculture (Plant Production)) -- University of Limpopo, 2021 / Plant-parasitic nematodes inflict economic damages on vegetable and field crops due to a lack of suitable crop protection chemicals and integrated crop management practices. Toxic synthetic chemical nematicides were withdrawn from the agro-chemical markets in 2005 due to their damage to the environment and humans. As such, there is continuous need to develop integrated nematode management strategies that are economic, environment friendly yet capable of effectively controlling the pest to alleviate crop loss and food insecurity. Root-knot (Meloidogyne species) nematodes are a major yield- and quality-reducing pest in most potato (Solanum tuberosum L.) producing regions in South Africa. However, little is known about the different plant-parasitic nematode species that are associated with potato in some Provinces. The sustainable production of crops in the absence of nematode resistant genotypes depends on the availability of nematode resistant crops in crop rotation systems. However, the effectiveness of these nematode resistance crops in managing root-knot nematodes in potato-based cropping systems has not been investigated in South Africa. The aim of the study was the development of sustainable cropping sequences for management of population densities of Meloidogyne species in potato production using crops with different mechanisms of nematode resistance. Two main objectives were investigated, but the second objective was sub-divided into three. The objectives of the study were to investigate (1) whether the diversity and abundance of plant-parasitic nematodes associated with potato in Limpopo Province, would be different to those in other potato-producing regions of South Africa, (2) whether (a) monoculturing potato would have any effects on population densities of Meloidogyne species, plant growth and soil health, (b) sequencing potato with a post-infectional nematode resistant crop like Cucumis africanus would have any effects on population densities of Meloidogyne species, plant growth and soil health and (c) sequencing potato with a pre-infectional nematode resistant crop such as sweet stem sorghum would have any effects on population densities of Meloidogyne species, plant growth and soil health. Ten known nematode genera, namely, Scutellonema, Helicotylenchus, Telotylenchus, Rotylenchulus, Paratylenchus, Tylenchorhynchus, Criconema, Nanidorus, Meloidogyne and Pratylenchus species were present in potato production fields in Limpopo Province, South Africa. The study was conducted on 30 farms, located in Mopani, Sekhukhune, Capricorn, and Waterberg districts by randomly collecting 10 core soil samples per hectare in a zigzag-sampling pattern. A total of eight nematode genera except two (Meloidogyne and Pratylenchus species) were recorded for the first time in potato fields in Limpopo Province. Additionally, the sampled districts were predominated by different nematode species. The Meloidogyne species were the most prevalent nematodes associated with potato crops followed by Helicotylenchus and Scutellonema species. In contrast, the Tylenchorhynchus and Nanidorus species were the least prevalent parasitic nematodes in potato production fields in the Limpopo Province. To achieve Objective 2, two field experiments were conducted at the University of Limpopo (UL) and the Agricultural Research Council-Vegetable and Ornamental Plants (ARC-VOP). In Sequence 1, the treatments (sorghum cv. ʹNdendaneʹ, potato cv. ′Mondial G3′, Cucumis africanus and potato (cv. ′Mondial G3′)-(Velum) were laid out in a randomised complete block design. In Sequence 2, potato (cv. ′Mondial G3′) was cultivated on all plots as the successor main crop. In Sequence 3, the treatments were laid out as in Sequence 1, whereas in Sequence 4 sole potato crop was cultivated as in Sequence 2. Therefore, four cropping sequences namely, sorghum-potato, potato monoculture, C. africanus–potato and potato-(Velum)-potato (control) were investigated simultaneously.Generally, post-infectional resistant C. africanus-potato was more effective than pre-infectional nematode resistant sorghum-potato or potato monoculture cropping sequences in reducing the population densities of Meloidogyne species in the soil. This has led to reduced damage to subsequent potato crop providing higher tuber yield, increased shoot mass and nutrients elements accumulation in potato leaf tissues at both sites. The high soil organic carbon content, microbial diversity and enzyme activity observed in C. africanus-potato and sorghum-potato showed that these two cropping sequences enhanced soil health better than the monoculture production system of potato with or without Velum application. The different indices (maturity index, channel index, enrichment index and structure index) collectively demonstrated that the soil was highly disturbed with bacteria dominated decomposition pathways. The nematode faunal profile showed that sorghum-potato was the only cropping sequence that improved soil structure as exhibited by high structure index. Therefore, the inclusion of nematode resistant sweet stem sorghum in potato-based cropping system promoted soil health better than the other cropping sequences. In conclusion, C. africanus-potato sequence could be used to effectively manage root-knot nematode population densities, whereas sorghum-potato sequence could be considered where the aim is to improve soil health. / National Research Foundation(NRF) Green Biotechnologies Research Centre of Excellence(GBRCE) Agricultural Research Council-Vegetable and Ornamental Plants(ARC-VOP)

Tack vare vissa önskade egenskaper gjordes en storsatsning på contortatall (Pinus contorta) i Sverige på 70-talet. Idag finns cirka 600 000 ha i Sverige som det gjorts provsågningar på och är nu dags att hitta användningsområden till. Syftet med denna studie var att undersöka skillnaden i utbyte mellan contortatall och gran (Picea abies) efter hyvling. Målet var att undersöka om sidobrädor av contortatall kan vara ett substitut till sidobrädor av gran vid hyvling ämnat för den amerikanska marknaden.Efter skanning av brädor samt manuell visuell sortering visade det sig att 92 % av granbrädorna var utan defekt medan 24 % av contortatallen var det. 34 % av contortatallen nedklassades för hål och 3 % av granen. Slutsatsen av studien visar att mängden och storleken på kvistarna är ett problem för contortatallvirket. För att få ett högkvalitativt virke behövs en djupare översyn av tillvägagångssättet för torkning och trädens tillväxtförhållanden.