Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Pathology, 1978.

Thesis (M.Sc.(Agric.))--University of Western Australia, 2006.

Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2019 / Nutritional water productivity (NWP) is an assessment tool, which describes the amount of water that has been used to produce selected mineral malnutrition (MMN) elements and micronutrient malnutrition (MNMN) substances. Therefore, it links agricultural production to human nutrition. Deficiencies in MMN elements and/or MNMN substances in human nutrition referred to as malnutrition, had been linked with fatal diseases. Agricultural soils could be affected by soil-borne pathogens such as plant-parasitic nematodes, which could limit the availability of MMN elements and MNMN substances. In some communities, vegetable crops, including chilli are regarded as a major source of MMN elements and MNMN substances. Effects of root-knot (Meloidogyne species) nematodes on NWP of chilli (Capsicum annuum L.) have not been documented. The objective of the study was to determine the effects of increasing population densities of M. incognita race 2 and M. javanica on the NWP of hot chilli plants. A microplot trial was conducted at the Green Biotechnologies Research Centre of Excellence (GBRCE), University of Limpopo, South Africa. Pots were filled with 10-L steam-pasteurised (300oC) sandy clay loam soil sourced from GBRCE and Hygromix-T (Hygrotech, Pretoria North) growth medium in the ratio 3:1 (v/v). Thereafter, three-week-old hot chilli cv. 'Serrano' seedlings were transplanted into each pot, with inoculum prepared by extracting eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica from roots of grown nematode susceptible tomato cv. 'Floradade' (Solanum lycopersicum L.) in a 1% NaOCl solution. Fourteen days after transplanting, treatments 0, 50, 125, 250, 625, 1250 and 2000 eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica were separately inoculated using a 20 ml plastic syringe into 5-cm-deep holes in pots. At 56 days after the initiation of the treatments, Meloidogyne species xiv decreased soil pH and increased organic carbon, contributing 29 and 43% in total treatment variation (TTV) of the respective variables. Treatment effects caused the pH to decrease. NWP variables against increasing nematode numbers exhibited quadratic relations, with coefficients of determination ranging from 59 to 86% for M. incognita race 2 trial and 80 to 98% for M. javanica trial. Meloidogyne species population densities against plant variables did not show any significant relationship, except for root galling and chlorophyll content where treatments contributed 76, 98 and 47% TTV of the respective variables. Generally, root galling increased with increase in Meloidogyne species population densities, whereas chlorophyll content decreased with increasing inoculum levels. Nematode variables against their increasing population exhibited quadratic relationship with the model explained by 44 to 95% for M. incognita race 2 and 28 to 82%, association, respectively for M. javanica. In conclusion, Meloidogyne species interfered with NWP of mineral elements in chilli plant and therefore, nematode management practices should be done to reduce the nematode population densities that would confer quality to agricultural produce for human health benefits.

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.

Thesis (M. Agricultural Management (Animal Production)) -- University of Limpopo, 2016 / Cultivated potato (Solanum tuberosum L.) cultigens do not have resistant genotypes to root-knot (Meloidogyne species) nematodes. Currently, efforts are underway to introgress nematode resistance in potato breeding programmes, whereas other environment-friendly nematode management strategies are being assessed in various cultigens. Nemafric-BL and Nemarioc-AL phytonematicides have being researched and developed for managing the root-knot nematode whereas Biocult Mycorrhizae are intended to enhance crop productivity through improved absorption of P, which is inherently low in most South African soils. The objectives of the study, therefore, were: (1) to determine the interactive effects of Nemacur (N), Biocult Mycorrhizae (B) and Nemarioc-AL or Nemafric-BL phytonematicide (P) on population densities of M. javanica and growth of potato plants, (2) to investigate the effects of Nemacur (N), Velum (V), Biocult Mycorhizae (B) and Nemarioc-AL or Nemafric-BL phytonematicide (P) on population densities of M. javanica and growth of potato plants. For the microplot experiment, potato cv. ‘Mondial G3’ seeds were sown in 25 cm-diameter plastic pots with 5 000 ml steam-pasteurised river sand and Hygromix-T at 3:1 (v/v) growing mixture in autumn (March-May) 2015. Pots were buried 80% deep into the soil in with 0.5 m inter-row and 0.5 m intra-row spacing. Potato cv. ‘Mondial G3’ seeds were dipped in a mixture of Mancozeb with a wettener for disease management prior to sowing. Appropriate treatments were applied soon after emergence of leaves. Each plant was inoculated by dispensing a mixture of 5 000 eggs and M. javanica J2. Eight treatments, control (N0B0P0), Nemacur (N1B0P0), Biocult (N0B1P0), phytonematicide (N0B0P1), Nemacur × Biocult (N1B1P0), Nemacur × phytonematicide (N1B0P1), Biocult × phytonematicide (N0B1P1) and Nemacur × Biocult × phytonematicide (N1B1P1), were arranged in a randomised complete block xxvi design (RCBD) with 8 replications (n= 64). Under field conditions the study was conducted in summer (October 2015 - January 2016), with 30-cm furrows dug and potato seeds placed in the soil with 30 cm inter-row and 40 cm intra-row spacing. The four treatments, namely, (1) untreated control, (2) Nemacur or Velum (3) Biocult Mycorrhizae and (4) Nemarioc-AL or Nemafric-BL phytonematicide, were arranged in RCBD, replicated three times for the Velum experiment and five times for the Nemacur experiment. At 56 days after inoculation, the second order interaction (N1B1P1) was highly significant (P ≤ 0.01) for eggs in root and total nematodes, contributing 13 and 12% to total treatment variation (TTV) of the two variables, respectively, in the Nemarioc-AL phytonematicide study. Relative to untreated control, the second order interaction (N1B1P1) reduced eggs in root and total nematodes by 42 and 36%, respectively. In both Nemarioc-AL and Nemafric-BL phytonematicide experiments, the combination of phytonematicide and Biocult Mycorrhizae reduced gall rating. Nemacur, Biocult and Nemarioc-AL phytonematicide, the treatment effects were highly significant on eggs, J2 in root and total nematodes, contributing 53, 68 and 57% to TTV of the three variables, respectively. Nemacur, Biocult and Nemafric-BL phytonematicide treatments each was not significant (P ≤ 0.05) for nematodes variables. Both treatments for Nemacur, Biocult and Nemarioc-AL or Nemafric-BL phytonematicides were significant for gall rating, contributing 92 and 70% to TTV of the variable, respectively. In Nemarioc-AL phytonematicide, relative to the untreated control, gall rating was reduced by 48 to 56%, whereas in Nemafric-BL phytonematicide the variable was reduced by 33 to 56%. In the Velum study, Biocult and Nemarioc-AL or Nemafric-BL phytonematicide, the treatment effects in both experiments were highly significant (P ≤ 0.01) on eggs in root, contributing 88% to TTV of the variable. Both treatments from Nemarioc-AL xxvii and Nemafric-BL phytonematicides had no significant effects on all plant variables measured. In microplot, the second order interaction (Nemacur × Biocult × Nemarioc-AL phytonematicide) was highly significant for nematode eggs in root and total nematode. In a three-way matrix, the N1B1P1 interaction had the highest effects on eggs, followed by Biocult alone, then Nemacur alone and then the phytonematicide. The same trend was observed in the three-way matrix for total nematodes. However, in two-way matrix for eggs, Biocult outperformed Nemacur, as was the phytonematicide on J2. In another microplot study, the second order interaction (Nemacur × Biocult × Nemafric-BL phytonematicide) was significant for J2 in soil and roots, with the three-way matrix showing, that Biocult alone had higher effects than the N1B1P1 interaction on J2 in root. A three-way matrix also showed that Nemacur was outperformed by the phytonematicide alone, Biocult alone and the interactions on J2 in soil. In conclusion, Nemarioc-AL and Nemafric-BL phytonematicides could each be used with Biocult Mycorrhizae in the management of population densities of M. javanica in potato production since the impact from Nemacur which is a synthetic nematicide does not have that much difference from that of phytonematicides interacted with Biocult Mycorrhizae. / Agricultural Research Council