In an experiment investigating the influence of M. graminicola on rice yield, M. graminicola caused as significant yield reduction in Azucena but not in Bala indicating that this variety is tolerant. The influence of abiotic (nitrogen and water) and biotic (vesicular arbuscular mycorrhiza - VAM) factors on the nematode/rice interaction were also studied. Nitrogen stress affected Azucena plants but not Bala. Drought did not influence susceptibility of either variety but caused a significant reduction in root weight which was greater when nematodes were present in both rice varieties.

Thesis (Ph. D.)--University of California, Riverside, 2008. / Title from first page of PDF file (viewed Febrary 3, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references. Also issued in print.

No description available.

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 54-59).

Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / Available potato (Solanum tuberosum L.) cultivars do not have any genotype that is resistant to the root-knot (Meloidogyne species) nematodes. Due to the susceptibility of potato cultivars to Meloidogyne species, alternative management strategies had to be researched and developed after the withdrawal of methyl bromide from the agro-chemical markets, amongst which were the cucurbitacin-containing phytonematicides. However, of the available application methods of phytonematicides, the ground leaching technology (GLT) and botinemagation technology were not suitable for use in most high-rainfall potato-producing regions, where production is under rain-fed conditions. The objective of the study, therefore, was to determine whether pre- and post-emergent application of Nemafric-BG phytonematicide would have effects on growth of potato and suppression of M. javanica population densities. Parallel pot trials of pre- and post-emergent application of Nemafric-BL phytonematicide were conducted under greenhouse conditions in autumn (February-April: Experiment 1) 2017 and validated (Experiment 2) in 2018. Each plant was inoculated with 3000 M. javanica eggs and second-stage juveniles (J2). Five treatments, namely, 0, 2, 4, 8 and 16 g concentration of Nemafric-BG phytonematicide, arranged in randomised complete block design, were either applied mixed with seed tubers for pre-emergent or spread on the soil surface after emergence for post-emergent trials. In all cases, plant growth variables were assessed using the Curve-fitting Allelochemical Response Data (CARD) model, whereas nutrient elements (Fe, K, Na and Zn) and nematode variables were assessed using analysis of variance, with data subjected to lines of the best fit. In pre-emergent application trial, plant height (R2 = 0.98) and fresh root mass (R2 = 0.99) exhibited quadratic relations, characterised by density dependent growth patterns with increasing concentrations of Nemafric-BG xv phytonematicide in Experiment 1, similar trends were also observed on plant height (R2 = 0.99) and root mass (R2 = 0.99) in Experiment 2. In contrast, in post-emergent application trial, plant height (R2 = 0.97), fresh root mass (R2 = 0.99) and dry shoot (R2 = 0.98) exhibited quadratic relations in Experiment 1, which ascribed to DDG patterns, similar trends were also observed in Experiment 2 on plant height (R2 = 0.99), fresh root mass (R2 = 0.96) and dry shoot (R2 = 0.99) of potato cv. ꞌMondial G3ꞌ. In pre-emergent application trials, Mean Concentration Stimulation Point (MCSP) = 24.18 and 7.82 g, respectively, in Experiment 1 and Experiment 2, with ∑k being equivalent to 20 and 6 units for potato to the product, respectively, in Experiment 1 and Experiment 2. In contrast, post-emergent application trials, MCSP = 9.87 and 12.10 g, respectively, in Experiment 1 and Experiment 2, whereas the ∑k value for potato to the product was 11 and 6 units, respectively in Experiment 1 and Experiment 2. Increasing concentrations of the phytonematicide significantly (P ≤ 0.05) affected the selected nutrient elements. In pre emergent application trials, K (R2  =  0.96) Na (R2  =  0.90) and Zn (R2  =  0.83) each with increasing Nemafric-BG phytonematicide concentrations exhibited positive quadratic fashion, while Fe (R2  =  0.87) exhibited negative quadratic relations in Experiment 1. In Experiment 2, K (R2  = 0.99), Na (R2  = 0.90) and Zn (R2 =  0.97) contents each in leaf tissues against the increasing concentrations of the phytonematicide exhibited negative quadratic relations, while Fe (R2  = 0.88) exhibited positive quadratic relations. In post emergent trials, Fe (R2 = 0.91, Na (R2 = 0.90) and Zn (R2 = 0.99) contents in leaf tissues against increasing Nemafric-BG phytonematicide concentration exhibited negative quadratic relations, whereas K (R2 = 0.86) exhibited positive quadratic relation in Experiment 1. In Experiment 2, Fe (R2 = 0.93), K (R2 = 0.92), Na ( R2  = 0.79) and Zn (R2 xvi = 0.89) contents in leaf tissues of potato exhibited positive quadratic, respectively. In pre emergent trial for Experiment 1, eggs in roots (R2 = 0.78), J2 in roots (R2 = 0.85), J2 in soil (R2 = 0.97) and Pf (R2 = 0.78) of M. javanica against increasing pre-emergent application concentrations of Nemafric-BG phytonematicide exhibited negative quadratic relations, characterised by DDG patterns. Similar trends were observed on eggs in roots (R2 = 0.82), J2 in roots (R2 = 0.99), J2 in soil (R2 = 0.84) and Pf (R2 = 0.85) in Experiment 2. In contrast, in post-emergent application trial, eggs in roots (R2 = 0.87), J2 in roots (R2 = 0.99), J2 in soil (R2 = 0.91) and Pf (R2 = 0.99) of M. javanica against increasing post emergent application concentrations of Nemafric-BG phytonematicide also exhibited negative quadratic relations in Experiment 1, which ascribed to DDG patterns. Similar trends were also observed on eggs in roots (R2 = 0.72), J2 in roots (R2 = 0.68), J2 in soil (R2 = 0.85) and Pf (R2 = 0.83) in Experiment 2. Results from the study demonstrated that Nemafric-BG phytonematicide stimulated plant growth at lower concentration and the product does not have any detrimental effects in accumulation of nutrient elements in leaf tissues. Therefore, it is concluded, that the product could be applied at the recommended rates of 7.82 and 9.87 g/plant in pre and post-emergent application, respectively, for the management of root-knot nematodes, provided the active ingredient does not accumulate in potato tubers or have any detrimental effects in accumulation of nutrient elements in tubers and temper with nutritional value of potatoes.

Submitted by Michele Mologni (mologni@unoeste.br) on 2019-01-24T16:37:31Z No. of bitstreams: 1 Lorrayne Guimarães Bavaresco.pdf: 1579894 bytes, checksum: be828e9da52619462a559db48496ff9a (MD5) / Made available in DSpace on 2019-01-24T16:37:31Z (GMT). No. of bitstreams: 1 Lorrayne Guimarães Bavaresco.pdf: 1579894 bytes, checksum: be828e9da52619462a559db48496ff9a (MD5) Previous issue date: 2018-08-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Among the forms of biological control, the use of rhizobacteria has shown to be promising in the suppression and protection of plants against the attack of phytonematoids. The objective of this work was to evaluate the effect of Bacillus subtilis on the reproduction of Meloidogyne spp., associated to changes in rhizosphere colonization and growth, nutrition and enzymatic activity of tomato cultivars tolerant and susceptible to root-knot nematodes. The methods of application consisted of the inoculation of Bacillus subtilis (AP-3) in pre-planting and post-planting of the tomato. Two experiments were conducted in a plant growth chamber. In the first experiment the tomato plants were cultivated on a sterile substrate, inoculating 5000 eggs of Meloidogyne incognita. In the second, tomato cultivation was carried out in sandy soil naturally infested with root-knot nematodes. The plant growth, nematode reproduction, soil and rhizosphere colonization by bacteria of the genus Bacillus spp., and biochemical changes were evaluated at 40 days after transplanting of the tomato. In both modes of application, the Bacillus subtilis was efficient in increasing root mass and in reducing the reproduction of the root-knot nematode in susceptible tomato cultivated in naturally infested soil. In sterile substrate, inoculation of B. subtilis in post-planting promoted reduction of the number of active forms of the nematode and both applications promoted the decrease of eggs of Meloidogyne incognita in the roots of the tomato. The application of B. subtilis, as a sterile substrate, induced changes in the nutritional uptake of tomato plants, increasing calcium levels and reducing leaf potassium. The application of B. subtilis contributed to the reduction of the peroxidase activity in leaves of the tomato susceptible to root-knot nematodes, in sterile condition. The rhizobacteria, after planting, allowed the increase in the proline content in the leaves of the tomato, cultivated in soil naturally infested with root-knot nematodes. Inoculations with B. subtilis promoted an increase in the number of Bacillus spp. in the sterile substratum and in the rhizosphere of the tomato, being confirmed the persistence of these bacteria at 40 DAP. / Dentre as formas de controle biológico, a utilização de rizobactérias tem se mostrado promissora na supressão e proteção de plantas ao ataque de fitonematoides. O presente trabalho teve como objetivo avaliar o efeito da aplicação de Bacillus subtilis na reprodução de Meloidogyne spp., associado as alterações na colonização da rizosfera e no crescimento, nutrição e atividade enzimática de cultivares de tomateiro tolerante e suscetível aos nematoides-das-galhas. Os modos de aplicação estudados consistiram na inoculação do Bacillus subtilis (AP-3) em pré-plantio e pós-plantio do tomateiro. Foram conduzidos dois experimentos em câmara de crescimento de plantas. No primeiro experimento as plantas de tomateiro foram cultivadas em substrato esterilizado, com inoculação de 5000 ovos de Meloidogyne incognita. No segundo, o cultivo do tomateiro foi realizado em solo arenoso naturalmente infestado por nematoides-das-galhas. Aos 40 dias após o transplantio das mudas, foram avaliados o crescimento das plantas, a reprodução do nematoide, a colonização do solo e da rizosfera por bactérias do gênero Bacillus spp. e as alterações bioquímicas do tomateiro. Em ambos os modos de aplicação, o Bacillus subtilis foi eficiente em aumentar a massa radicular e em reduzir a reprodução do nematoide-das-galhas em tomateiro suscetível, cultivado em solo naturalmente infestado. Em substrato estéril, a inoculação de B. subtilis em pós-plantio promoveu redução do número de formas ativas do nematoide e ambas as aplicações promoveram a diminuição de ovos de Meloidogyne incognita nas raízes do tomateiro. A aplicação de B. subtilis, na condição de substrato estéril, induziu mudanças na absorção nutricional do tomateiro, aumentando os teores de cálcio e reduzindo o potássio foliar. A aplicação de B. subtilis contribuiu para redução da atividade peroxidase nas folhas do tomateiro suscetível a nematoides-das-galhas, em condição estéril. A rizobactéria, em pós-plantio, possibilitou o aumento no teor de prolina nas folhas do tomateiro, cultivado em solo naturalmente infestado com nematoides-das-galhas. As inoculações com B. subtilis promoveram aumento do número de Bacillus spp. no substrato estéril e na rizosfera do tomateiro, sendo comprovada a persistência destas bactérias aos 40 DAP.

Thesis (MSc. Agriculture (Horticulture)) -- University of Limpopo, 2018 / The production of tomato (Solanum lycopersicum L.) plants had been crucial in various parts of the world since tomato fruit contribute widely to human health. However, most tomato cultivars had been shown to be highly susceptible to plant-parasitic nematodes, especially the root-knot (Meloidogyne species) nematodes. Two cucurbitacin-containing phytonematicides, namely, Nemarioc-AL and Nemafric-BL phytonematicides, manufactured from fruits of Cucumis species, are being researched and developed in South Africa as an alternative for management of Meloidogyne species. Most trials on tomato plants and cucurbitacin-containing phytonematicides had been under greenhouse conditions, with limited information on their interactive effects under microplot and field conditions. The objectives of this study were: (1) to determine the interactive effects of Nemarioc-AL and Nemafric-BL phytonematicides on growth and accumulation of nutrient elements in leaf tissues of tomato plants under microplot conditions and (2) to investigate the interactive effects of Nemarioc-AL and Nemafric-BL phytonematicides on growth and accumulation of nutrient elements in leaf tissues of tomato plants under field conditions. In the microplot study, uniform four-week-old tomato cv. 'HTX 14' seedlings were transplanted in 4 L plastic bags containing loam soil and Hygromix-T at the 3:1 ratio (v/v). Plastic bags were inserted into holes at 0.50 m inter-row spacing and 0.60 m intra-row spacing. The 2 x 2 factorial trial, with the first and second factors being Nemarioc-AL and Nemafric-BL phytonematicides, respectively, each at two levels. The four treatments, namely, AL0BL0, AL0AL1, BL0BL1 and AL1BL1, were arranged in a randomised complete block design. Treatments were xxiv applied seven days after transplanting and repeated weekly until harvest. Under field conditions, uniform four-week-old tomato cv. 'HTX 14' seedlings were transplanted into the field at 0.50 m inter-row spacing and 0.60 m intra-row spacing. Treatments, experimental designs and application interval were as those under microplot conditions. At 60 days after the treatments, seedlings AL × BL interaction was not significant on all plant variables in Experiment 1 under microplot conditions, whereas in Experiment 2 the interaction was highly significant (P ≤ 0.01) on dry shoot mass, contributing 72% in total treatment variation (TTV) of the variable. Relative to untreated control, the two-way matrix showed that the interaction reduced dry shoot mass by 8%. Nemarioc-AL phytonematicide had a significant (P ≤ 0.05) effect on stem diameter in Experiment 1 under field conditions, whereas Nemafric-BL phytonematicide had significant effects on plant height in Experiment 2, contributing 39 and 56% in TTV of the respective variables. Relative to untreated control, Nemarioc-AL phytonematicide increased stem diameter by 4%, whereas Nemafric-BL phytonematicide increased plant height by 2%. The interaction was also significant (P ≤ 0.05) on Na and S and highly significant (P ≤ 0.01) on Zn, contributing 76, 26 and 6%, respectively, in TTV of the respective variables in Experiment 1 under field conditions. Using a two-way matrix, the interaction increased Na and S by 12 and 41%, respectively, but reduced Zn by 52%. In Experiment 2, the interaction was highly significant (P ≤ 0.01) on P alone, contributing 16% in TTV of the variable, with the interaction reducing P by 76%. Nemarioc-AL phytonematicide had significant effects (P ≤ 0.05) on Ca and highly significant effects (P ≤ 0.01) on S, contributing 31 and 58% in TTV of the respective variables in Experiment 1. Relative to untreated control, Nemarioc-AL phytonematicide increased P by 39%. In xxv Experiment 2, Nemarioc-AL phytonematicide had significant effects on Ca and highly significant effects (P ≤ 0.01) on S, contributing 66 and 49% in TTV of the respective variables. Relative to untreated control, Nemarioc-AL phytonematicide reduced Ca by 19% and S by 36%, respectively. Nemafric-BL phytonematicide had a significant effect (P ≤ 0.05) on P, contributing 33% in TTV of the variable in Experiment 1. Relative to untreated control, Nemafric-BL phytonematicide increased P by 41%. In Experiment 2, Nemafric-BL phytonematicide had significant effects (P ≤ 0.05) on S, contributing 40% in TTV of the variable. Relative to untreated control, Nemafric-BL phytonematicide reduced S by 33%. At 74 days after initiating the treatments under field conditions, the interaction of Nemarioc-AL and Nemafric-BL phytonematicides were not significant for plant height, stem diameter, fresh fruit and dry shoot mass in both experiments. Nemarioc-AL phytonematicide was also not significant in all plant variables in both experiments. Effects of Nemafric-BL phytonematicide were highly significant on dry shoot mass in Experiment 1 and stem diameter in Experiment 2, contributing 60 and 67% in TTV of the respective variables. Relative to untreated control, Nemafric-BL phytonematicide reduced dry shoot mass by 28% and increased stem diameter by 11% in Experiment 1 and Experiment 2, respectively. The AL × BL interaction had significant effects (P ≤ 0.05) on P, contributing 57% in TTV of the variable in Experiment 1. Relative to untreated control, the interaction increased P by 12%. In Experiment 2, the interaction had significant effects (P ≤ 0.05) on K, Mg, S and Mn, contributing 78, 65, 74 and 68% in TTV of the respective variables. Using a two-way matrix, relative to untreated control, the interaction increased K by 8%, but reduced Mg, Mn and S by 14, 82 and 1%, respectively. Nemarioc-AL phytonematicide was not significant in both the xxvi experiments, whereas Nemafric-BL phytonematicide had significant effects on Mg in Experiment 1, contributing 68% in TTV of the variable. Relative to untreated control, Nemafric-BL phytonematicide increased Mg by 15%. In conclusion, the interaction of Nemarioc-AL and Nemafric-BL phytonematicides were not compatible with each other as they had undesirable effects on growth of tomato plants and accumulation of most essential nutrient elements in leaf tissues of this plant. / National Research Foundation (NRF)

Thesis (M.Agric. (Plant Production)) -- University of Limpopo, 2018 / Meloidogyne incognita race 2 is internationally recognised as one of the most aggressive Meloidogyne species and it is also widely distributed in Limpopo Province, where it occurs alone or as mixed populations with other Meloidogyne species. Traditionally, Meloidogyne species had been managed using synthetic chemical nematicides, most of these products had been withdrawn from agro-chemical markets due to their environment-unfriendliness. Following the withdrawal of synthetic chemical nematicides, nematode resistance had been the most preferred strategy for managing high nematode population densities. The availability of nematode resistant genotypes in sweet potato (Ipomoea batatas) would enhance the use of resistance in managing Meloidogyne species and races in Limpopo Province. Generally, should post-infectional nematode resistance be available in the test sweet potato cultivars, the information would be relayed to plant breeders for use as source of introgression in various commercial cultivars where nematode-resistant genotypes do not exist. The objectives of the study, were to determine: (1) Host-status and host-sensitivity in sweet potato cv. ʹBopheloʹ, ʹBosbokʹ and ʹMvuvheloʹ to M. incognita race 2. (2) the existing nematode resistance mechanism in any of the test cultivars that had resistance to M. incognita race 2. For achieving Objective 1, eight treatments namely, 0, 25, 50, 125, 250, 625, 1250 and 3125 eggs and second stage-juveniles (J2) M. incognita race 2 were used under greenhouse trials for each cultivar. To achieve Objective 2, sweet potato plants were inoculated with 100 J2 with four plants harvested every other day for 30 days counting to 15 harvesting times. At 56 days after inoculation, cv. ʹBopheloʹ had reproductive factor (RF) values above unity for M. incognita race 2 and plant growth variables were reduced. Therefore, the cultivar was a susceptible host to M. incognita race 2 and mechanism trial was not conducted for this cultivar. Meloidogyne incognita race 2 failed to reproduce on cultivars ʹBosbokʹ and ʹMvuvheloʹ whereas nematode infection did not affect plant growth and therefore, the two cultivars were resistant to M. incognita race 2. Mechanisms of resistance to M. incognita race 2 on cultivars ʹBosbokʹ and ʹMvuvheloʹ demonstrated significance existence of (1) necrotic spots, (2) poorly developed giant cells, (3) formation of rootlet interferences (4) absence of root galls and (5) non-detectable J2 in roots. All these features suggested the existence of post-infectional nematode resistance in the two cultivars to M. incognita race 2. In conclusion, cultivar ʹBopheloʹ was susceptible to M. incognita race 2, whereas cultivars ʹBosbokʹ and ʹMvuvheloʹ were resistant to M. incognita race 2, with the evidence of post-infectional nematode resistance to the nematode species

M. Tech. Agriculture / This study was conducted to establish whether genetic resistance to root-knot nematode is present in local available Amaranthus-, Spinacea oleracea-, Beta vulgaris-, Daucus carota-, and Capsicum genotypes. Host suitability trials for the relevant vegetable genotypes were conducted in separate greenhouse studies. Different nematode parameters were used to select for root-knot nematode resistance but reproduction factors values (Rf) were used as main criterion.

Tomato (Solanum lycopersicum L.) produces an array of volatile secondary metabolites that act as constitutive and induced defenses against a variety of insect pests and diseases. We studied the effect of beneficial microorganisms, an arbuscular mycorrhiza fungus (AM), Glomus intraradices, an entomopathogenic fungus (Bb), Beauveria bassiana and a combination of both (AM+Bb), as well as, pests, such as rootknot nematode (RKN) (Meloidogyne incognita) and beet armyworm (BAW) (Spodoptera exiguae H.) on the production of volatile compounds in the leaves and roots of tomato. Benzyl alcohol, 3-hexenoic acid, total other compounds and β-myrcene were significantly increased (P<0.05) in the leaves by AM and Bb colonization. Upon herbivory, control plants showed a trend for high volatile contents among all four treatment groups contrary to the trend observed without herbivory, when control showed low volatile contents. Herbivory significantly decreased all the volatiles in the leaves compared to those without herbivory. Pest bioassay revealed that these two fungi together can significantly induce resistance against BAW. In the experiment with RKN, a trend was observed with low production of most volatile compounds in the leaves from the RKN plants. Varying durations of herbivory exposure had significant effects on many leaf volatile compounds compared to those without herbivory. Effect of RKN was significant (P<0.05) on the production of methyl salicylate, and (Z)-geraniol in the roots. Interaction effect of RKN with 18 hours of herbivory was significant for (Z)-geraniol, and with 42 hours of herbivory, it was significant for (Z)-geraniol, benzyl alcohol, and total volatiles in the roots. Beet armyworm preferred RKN plants and caused greater damage to them compared to the control plants. Semi-quantitative RT-PCR showed higher expression of the SlSAMT gene in the roots colonized with RKN, compared to the control roots and those from a resistant line. The experiments demonstrated that interaction with these organisms can change the volatile compounds in the leaves and roots of tomato plant, can alter herbivore preference, and can upregulate defense genes such as SlSAMT.