Thesis (Ph. D.)--Open University. BLDSC no. DXN075774.

The $ beta$-tubulin gene family of the parasitic nematode, Brugia pahangi consists of three to five $ beta$-tubulin sequences. Two genomic clones containing $ beta$-tubulin sequences were isolated and characterized. The $ beta$1-tubulin gene spans 3.8 kb, is organized into 9 exons and expresses an mRNA of 1.7 kb which codes for a protein of 448 amino acids. A partial nucleotide sequence of the second clone confirmed the isolation of a distinct $ beta$-tubulin sequence, $ beta$2-tubulin. The $ beta$1-tubulin transcript is found in microfilariae and adult worms, whereas the $ beta$2-tubulin transcript is predominant in male adult worms but absent from microfilariae. Results of this study also indicate that the maturation of the $ beta$1-tubulin message involves the acquisition of the conserved nematode 22-nucleotide splice leader sequence. Antipeptide IgGs raised against the divergent carboxy-terminal region of $ beta$1-tubulin recognize the same $ beta$-tubulin isoform pattern as a phylum cross-reactive monoclonal antibody. This result suggests that the $ beta$1-tubulin is highly represented in B. pahangi adults and microfilariae.

No description available.

No description available.

Nematicides are not only expensive and unaffordable to small-scale farmers but are also harmful to the environment as they kill both the target organisms and non-target micro and macro-organisms, thereby destabilising the ecosystem. Most developed countries have or are in the process of banning use of chemicals for pest management, implying that agricultural products from developing countries using pesticides will not be marketed in the developed countries. In former studies, it was shown that plant parasitic nematodes posed serious problems in sugarcane fields as their attacks on sett roots during germination period decreased sett root weights, delayed bud germination or led to fewer buds germinating as most buds abort. Those that germinate later are then faced with competition for food, space and light from the "older" shoots and often die. The attacks on shoot roots may lead to inefficient uptake of water and nutrients by the plant thereby leading to stunted plants. Fewer and shorter sugarcane stalks due to nematode attacks result in poor yield. In this study, it has been shown that a large number of endoparasites would be needed to reduce sett root weights. Agricultural systems based on monoculture are rarely successful in the long term and because sugarcane fields have been monocultured for a very long time, they are losing their productive capacity and this is termed "Yield Decline". Instead of using nematicides, alternative methods can be used for the management of nematode communities. Research has shown on other plants that nematode communities dominated by Helicotylenchus dihystera are less pathogenic to the plants than other ectoparasitic nematodes, e.g., Xiphinema elongatum and Paratrichodorus spp. A study conducted as a pot experiment showed that sugarcane grown in soil with high H. dihystera grew taller and produced greater root and aerial biomass than one grown in X elongatum infested soil. To induce a nematode community dominated by H. dihystera in the field, two strategies were followed: (i ) abiotic factors that influence the nematode's environment were identified. Certain elements found in soil and sugarcane leaves were found to be correlated to certain species, e.g., H. dihystera was negatively correlated to soil sulphur, medium and coarse sand while X elongatum was positively correlated to these soil types and soil elements. Sugarcane leaves with high levels of Ca, Zn, Cu and Fe were found in areas with high percentages of H. dihystera while the reverse was true for X elongatum. (ii) organic amendments were used to improve the sugarcane growth, modify the environment and decrease competition among species within a community. Application of organic matter to the soil improves soil properties such as water infiltration, water holding capacity, erodibility and nutrient cycling, increases suppressiveness of soils to plant parasitic nematodes and stimulates other anti-nematode micro-organisms, e.g., nematode-trapping fungi. Organic amendments were therefore used in this study not only as screens to protect sugarcane roots from nematode attacks but also to manipulate nematode communities for the less pathogenic species, H. dihystera. In a field study where organic amendments were used, plots treated with filter cake, thume + filter cake, trash + filter cake, filter cake + furfural and Temik (aldicarb) had high percentages of H. dihystera while control plots had high percentages of X elongatum. However, the change in relative proportion of H. dihystera by certain treatments was not followed by an average increase in yield, probability because of the overall variability. The yield results, however, showed that for all treatments, including control, the highest yields corresponded to plots with higher H. dihystera proportions, conflicting the initial hypothesis. As a result, if an organic amendment that can substantially increase the relative proportions of H. dihystera can be found, a substantial increase in yield can be expected. Although the organic amendments did not successfully manipulate the nematode communities for the less pathogenic species, H. dihystera, plots with higher yield were those that had high H. dihystera percentages in their nematode communities. / Thesis (Ph.D.)-University of Natal, Durban, 2004.

This research has focused on the determination of natural populations in the fields, the effect of different inoculum densities on lettuce growth and a study of the association of this fungus with two nematodes (Pratylenchus penetrans Cobb and Meliodogyne hapla Chitwood). Under conditions of artificial infestation of soil the results were satisfactory, but in trials with naturally infested soil the fungus could not be detected. The effect of different inoculum densities was measured at different stages of growth, and only in those plants inoculated 2 weeks after seeding were differences significant and consistent. Some evidence of the detrimental effect of wounding the root system prior to attack by the fungus led to studies of the relationship between this fungus with either P. penetrans or M. hapla. In the first case a negative interaction seemed to exist; no significant increase of the damage caused to the lettuce was observed. In contrast, when the root-knot nematodes and P. tracheiphilum were combined there was a marked reduction of lettuce growth. The interaction was found to be additive.

No description available.

Thesis (M.Sc. (Plant protection)) --University of Limpopo, 2013. / Studies were initiated to investigate (1) the aggressiveness of the citrus nematode (Tylenchulus semipenetrans Cobb) isolates from two provinces in South Africa (2 experiements ) and (2) the biotype of T. semipenetrans in South Africa. In the aggressive study, isolates from Limpopo and Mpumalanga Provinces were used on Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and rough lemon (Citrus jambhiri) seedling rootstocks under greenhouse conditions (18 experiements). Each seedling was inoculated with 0, 10 000, 20 000, 30 000 and 40 000 J2s of T. semipenetrans isolates, which were arranged in a randomised complete block design, with six replications. At 120 days, the reproductive factor of T. semipenetrans isolate from Mpumalanga Province was significantly higher than that from Limpopo Province. Similarly, due to its higher relative impact on the reproductive factor values, the Mpumalanga isolate reduced plant growth variables more than the Limpopo isolate. Consequently, the Mpumalanga isolate was viewed as being more aggressive than the Limpopo isolate, suggesting that there might be genetic variability and/or adaptation in populations from the two locations. A national study, comprising T. semipenetrans isolates from 18 citrus-producing district municipalities in South Africa was then initiated under greenhouse conditions using isolates from each district – for a total of 18 separate experiments. Three differential hosts, viz. rough lemon, P. trifoliata and olive (Olea europaea), served as treatments, arranged in a randomised complete block design, with 15 replications. Initially, an orchard was randomly selected in each of the six citrus-producing provinces, viz. Eastern Cape, KwaZulu Natal, Limpopo, Mpumalanga, North West and Western Cape. Three-month old differential host seedlings were inoculated with approximately 10 000 J2s of T. semipenetrans and allowed to establish and grow under greenhouse conditions. At 120 days, penetration indices and standardised reproductive potentials/g roots demonstrated that T. semipenetrans failed to reproduce and develop on olive, but reproduced and developed on the other two hosts. Using T. semipenetrans biotype classification system, findings suggested that the biotype in citrus-producing district municipalities was Poncirus biotype. This biotype reproduces on P. trifoliata and hybrid rootstocks, which therefore, suggested that trifoliate orange and its hybrid rootstocks were not suitable for use in managing population nematode densities of T. semipenetrans in South Africa. In conclusion, results of this study demonstrated that the South African T. semipenetrans biotype was Poncirus, which suggested different management decisions and strategies for the citrus industry with regard to the management of this nematode. / By National Research Foundation, National Department of Agriculture, Forestry and Fisheries and the Land Bank Chair of Agriculture − University of Limpopo,

Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the distribution, biology and ecology of the Anguina-type nematodes and the bacterium Rathayibacter toxicus which are associated with flood plain staggers, a disease similar to annual ryegrass toxicity. Possible pasture and livestock management options to control the disease are discussed, as is biological control using the fungus Dilophospora alopecuri. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2003?

Thesis (Ph. D.)--University of Wisconsin--Madison, 1919. / Title from added collective thesis title page. Part 1 reprinted from Phytopathology, vol. 4, no. 4 (Aug. 1914), p. [323]-326, plate XXI ; Part 2 reprinted from Phytopathology, vol. IX, no. 2 (Feb. 1919), p. [93]-103, plate IX ; Part 3: Bulletin / United States Department of Agriculture, no. 818 (5 Jan. 1920) (see OCLC #16627505), 14 p., V p. of plates ; Part 4: Bulletin / United States Department of Agriculture, no. 842 (7 Sept. 1920) (see OCLC #16627722), 40 p., VI p. of plates. Includes bibliographical references.