Thesis (M. A. Agricultural Management (Plant Production)) -- University of Limpopo, 2020 / Although potato seed priming in water is not allowed for quality-related reasons in tubers of the produced crop, it was viewed as necessary to use the technique as a carrier of active ingredients of phytonematicides, with the hope that should the technique work, then other solutions could be used for priming of potato tuber seeds. The objectives of this study were to investigate the feasibility of using potato seed tubers as carriers of cucurbitacin A, cucurbitacin B and momordin from triterpenoid- containing phytonematicides to improve management of nematode population densities in potato plants under greenhouse, microplot and field conditions, respectively. In single treatments (A1B0M0, A0B1M0 and A0M0B1), potato seed tubers were without any phytotoxicity in 3% solutions, in any two permutations (A1B1M0, A1B0M1 and A0M1B1) at 1.5% each and at three permutations (A1B1M1) at 1% each, for 7 h and then dried under shade for 2 h prior to planting. Twenty-cm-diameter plastic pots were filled with 2 700 ml growing medium under greenhouse conditions and placed on benches at 0.3 m × 0.2 m spacing. Under microplot 30-cm-diameter plastic pots were used and pots were then inserted into 20-cm-deep holes at 0. 5 m × 0.5 m spacing and under field conditions potato seed tubers were set at 30-cm-depth with a 0.6 m × 0.6 m spacing. A 2 × 2 × 2 factorial experiment was laid out in a randomised complete block design, with the eight treatments replicated 7 times. Nemarioc-AL (A), Nemafric-BL (B) and Mormodica (M) phytonematicides served as first, second and third factors, respectively. At 56 days after applying treatments, the A1B1M1 interactions were not significant on all plant variables under greenhouse and field conditions however under microplot the interaction was significant (P ≤ 0.05) on fresh tuber mass, fresh root mass and dry root mass, contributing 28, 26 and 26% in Total treatment variation (TTV) of the respective variables. In contrast, the A1B1M1 xxviii interactions were highly significant (P ≤ 0.01) on chlorophyll content, contributing 43 and 40% in TTV. Generally, relative to untreated control, the second and first order interactions, along with individual treatments, significantly increased fresh tuber mass by 31% relative to the untreated control, except for Nemarioc-AL × Mormodica and Nemafric-BL × Mormodica interactions which were not different to the untreated. The A0B1M1 interaction was highly significant on plant height, stem diameter, chlorophyll content, dry shoot mass, dry root mass and fresh tuber mass, contributing 45, 36, 37, 35, 60 and 35% in TTV of the respective variables under greenhouse conditions similar to the microplot experiment, the interaction relative to the untreated control, also did not have any effect on plant variables. However, under field conditions the first order interaction, A0B1M1, was highly significant on dry root mass, contributing 60% in TTV on the variable. Relative to untreated control, the interaction reduced dry root mass by 14%, which was not different to the effect of Mormodica phytonematicide at 13%, but was significantly different to that of Nemafric-BL phytonematicide. A1B0M1 interaction had significant effects on fresh tuber mass, contributing 33% in TTV on the variable. Relative to the untreated control, the interaction increased fresh tuber mass (yield) by 32%, which was not different to that of Nemarioc-AL phytonematicide at 40%, but significantly different to that of Mormodica phytonematicide at 16%. Nemafric-BL and Mormodica phytonematicides under greenhouse conditions, each reduced dry shoot mass by 18 and 22%, respectively, whereas their interaction effects on the variable did not differ significantly from the untreated control. Similarly, under microplot conditions Mormodica phytonematicide alone significantly reduced plant height by 12%, although this was not different from the effects of Nemafric-BL phytonematicide. Also, the effects of Nemafric-BL phytonematicide on plant height was not different to that of the untreated control. However, Mormodica phytonematicide increased FSM, xxix DSM and FTM by 31, 33 and 19%, respectively. Mormodica phytonematicide effect on the variables was significantly different to the untreated control. The phytonematicide also reduced FRM and DRM by 17% and the effect on the two variable which significantly differed from the untreated control. The second order interaction were not significant on nematode variable under greenhouse and field conditions, but the interaction was significant only on total nematodes in roots, reproductive potential (RP) and final population (Pf) of Meloidogyne species on roots of potato plants and in the soil under microplot conditions, contributing 11, 13 and 10% in TTV on the variables, respectively. Relative to untreated control Nemarioc-AL × Nemafric-BL × Mormodica phytonematicide interaction reduced total nematode, RP and PF by 18, 64 and 18%, respectively, whereas their effects on the variables differed significantly from untreated control. Generally, Nemafric-BL × Mormodica interaction consistently in all three experiment reduced all nematodes variables. Nemarioc-AL × Nemafric-BL × Mormodica interactions were only significant on Na, contributing 7% in TTV o the variable. Relative to untreated control the interaction reduced Na by 33% and effects on the variable was significantly different to those of untreated control also Nemarioc-AL, Nemafric-BL and Mormodica alone. However, the second order interactions were not significant in greenhouse and field conditions. The A0B1M1 first order interaction although the interactive effects, contributed highly in TTV on Na and Zn in potato tuber tissues, relative to untreated control, the effects were rather negligent at 2 and 4%, respectively. In all different conditions of the study validating that potato seed tubers could be used as carriers of active ingredients of phytonematicides when used through the priming technology. The Nemafric-BL and Mormodica phytonematicide interactions consistently reduced population densities of the Meloidogyne species and increased yield under microplot and field experiments.

Thesis (M. Agric. (Plant Production)) -- University of Limpopo, 2019 / Phytonematicides have allelochemicals as active ingredients and could be highly phytotoxic on crops being protected against nematode damage. In order to avoid phytotoxicity, the application concentration, technically referred to as mean concentration stimulation point (MCSP), along with the application interval, have to be empirically established. The Curve-fitting Allelochemical Response Data (CARD) computer-based model was adopted at the Green Biotechnologies Research Centre of Excellence (GBRCE) for developing the MCSP. The MCSP is computed from the CARD-generated biological indices and was technically defined as a phytonematicide concentration that could manage the nematode population densities without causing phytotoxicity to the test crop and it is plant-specific. The MCSP and application interval had been empirically established for different crops, but they had not been established for sweet potatoes. Therefore, the objective of the study was to determine the MCSP for Nemarioc-AL phytonematicide on Meloidogyne javanica-infected sweet potato cv. ꞌBopheloꞌ and its application interval. Sweet potato cuttings were planted in 25-cm diameter plastic bags containing steam-pasteurised loam soil and Hygromix at 3:1 (v/v) ratio. Each plant was inoculated with 5 000 eggs and second-stage juveniles (J2) of M. javanica, with seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL phytonematicide, arranged in a randomised complete block design, with five replicates. At 56 days after the initiation of treatment, the MCSP values for plant variables and plant physiology variables were 1.92 and 3.08% Nemarioc-AL phytonematicide, respectively. The overall sensitivity values for plant variables and plant physiology variables were 0 and 1 unit, respectively, showing that the sweet potato cv. ꞌBopheloꞌ was highly sensitive to the product. Nematode variables with increasing concentrations of Nemarioc-AL phytonematicide exhibited positive and quadratic relations. The life cycle of M. javanica and the derived MCSP were used to empirically establish the application interval. Briefly, the location and most materials and methods were as outlined above except that ‘weeks-per-month-of-30 days’, with the MCSP being applied on 0, 7.5, 15, 22.5 and 30 days (0, 1, 2, 3 and 4 weeks) serving as treatments, replicated eight times. At 56 days after the treatments, plant variables and increasing application interval exhibited positive quadratic relations with the average of 2.55 ‘week of-30-day-month’ translating to 19 days (2.55/4 × 30), with nematode variables exhibiting negative quadratic relationships. In conclusion, when the MCSP of Nemarioc AL phytonematicide on sweet potato cv. 'Bophelo' at 1.92% was applied every 19 days, it would not be phytotoxic, but it would be able to suppress nematode population densities of M. javanica. The MCSP for essential nutrient elements could be reduced to that of plant growth variables, since the products are not intended for use as fertilisers.

Thesis ( M.Sc.(Horticulture)) -- University of Limpopo, 2017. / Refer to document / National Research Foundation of South Africa, and the Agricultural Research Council-Universities Collaboration Centre

Thesis(M.Sc.( Agriculture, Horticulture)) -- University of Limpopo, 2019 / Worldwide, tomato (Solanum lycopersicum L.) is one of the most important crops grown for nutritional value and health benefits, and are highly susceptible to root-knot (Meloidogyne species) nematodes. Following the withdrawal of synthetic chemical nematicides, Nemarioc-AL and Nemafric-BL phytonematicides have been researched and developed as alternatives to synthetic chemical nematicides. However, Nemarioc-AL and Nemafric-BL phytonematicides contains allelochemicals namely, cucurbitacin A (C32H46O9) and cucurbitacin B (C32H46O8) as their active ingredients. Therefore, the objective of this study was to determine whether increasing concentration of Nemarioc AL and Nemafric-BL phytonematicides would result in cucurbitacin residues in tomato plant, to generate mean concentration stimulation point (MCSP) values, overall sensitivity (∑k) and selected foliar mineral elements of tomato plant. Two parallel trials of Nemarioc AL and Nemafric-BL phytonematicides were conducted under field conditions, with each validated the next season. Each trial had seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% of Nemarioc-AL or Nemafric-BL phytonematicide concentrations, arranged in a randomised complete block design (RCBD), with five replications. In each trial, the seasonal interaction on variables was not significant and therefore data were pooled across the two seasons (n = 70). In both phytonematicides, the cucurbitacin residues were not detected in soil and tomato fruit. Plant variables and selected foliar nutrient elements were subjected to the Curve-fitting Allelochemical Response Data (CARD) model to generate biological indices which allowed for the calculation of MCSP of phytonematicides on tomato and their ∑k values of tomato to Nemarioc-AL and Nemafric BL phytonematicides. In Nemarioc-AL phytonematicide experiment, MCSP for tomato plant variables was at 1.13%, with the ∑k of 60 units, while the MCSP for selected tomato nutrient elements in leaf tissues was at 2.49%, with the ∑k of 21 units. Plant height, chlorophyll content, stem diameter, number of fruit, dry fruit mass, dry shoot mass and dry root mass each with increasing concentration of Nemarioc-AL phytonematicide exhibited positive quadratic relations with a model explained by 95, 82, 96, 89, 83, 83 and 92%, respectively. Similarly, K, Na and Zn each with increasing Nemarioc-AL phytonematicide concentration exhibited positive quadratic relations with a model explaining a strong relationship by 91, 96 and 89%. In Nemafric-BL phytonematicide experiment, MSCP for tomato plant variables was at 1.75%, with the ∑k of 45 units, whereas MCSP for selected tomato nutrient elements in leaf tissues was at 3.72% with the ∑k of 33 units. Plant height, chlorophyll content, stem diameter, number of fruit, dry fruit mass, dry shoot mass and dry root mass and increasing Nemafric-BL phytonematicide concentration exhibited positive quadratic relations with the model explaining a strong relationship by 92, 83, 97, 96, 87, 94 and 96%. Likewise, Na and Zn each with increasing Nemafric-BL phytonematicide concentration exhibited positive quadratic relations with a model explaining their relationship by 93 and 83%, respectively. In contrast, K with increasing Nemafric-BL phytonematicide concentration exhibited negative quadratic relations with a model explaining the relationship by 96%. In conclusion, tomato plant variables and selected foliar nutrient elements over increasing concentration of phytonematicides exhibited DDG patterns, characterised by three phases, namely, stimulation, neutral and inhibition. The developed non-phytotoxic concentration would be suitable for successful tomato production under field conditions.

Thesis (Ph. D. (Plant Production)) -- University of Limpopo,2016 / Refer to document / University of Limpopo, The Technology Innovation Agency (TIA), The Land Bank Chair of Agriculture ─ University of Limpopo, The Flemish Interuniversity Council (VLIR) and, The Agricultural Research Council - University Collaboration Centre

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. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / Potato (Solanum tuberosum L.) is highly susceptible to root-knot (Meloidogyne species) nematodes, with no known nematode resistant genotypes. In Limpopo Province, two cucurbitacin-containing phytonematicides had been researched and developed. The active ingredients of the cucurbitacin-containing phytonematicides are cucurbitacins, which are allelochemicals that could induce phytotoxicity on crops being protected against nematode damage. The objectives of this study were to determine: (1) mean concentration stimulation point (MCSP) of Nemarioc-AL phytonematicide on potato cultivar ꞌMondial G3ꞌ for managing M. javanica and (2) application interval of Nemarioc AL phytonematicide on potato cultivar ꞌMondial G3ꞌ. Sprouted tubers were planted in 10 cm deep/pot with each pot filled with steam-pasteurised soil and Hygromix at 3:1 (v/v) ratio in the field under microplot conditions. After 100% emergence (2 weeks), each plant was inoculated with 5 000 M. javanica eggs and second-stage juveniles (J2). Seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL phytonematicide were arranged in a randomised complete block design, with 11 replications. In Objective 2, four treatments, namely, 1, 2, 3 and 4 weeks were arranged in randomised complete block design, with 15 replications. Plant variables and nutrient elements were subjected to the Curve-fitting Allelochemical Response Data (CARD) model to generate biological indices used to compute MCSP using the relation MCSP = Dm + Rh/2 and the overall sensitivity value (∑k). The MCSP for plant variables and nutrient elements, were empirically derived as 4.31% and 1.33%, with the ∑k of 18 and 4 units, respectively. Nematode variables and increasing concentrations of Nemarioc-AL phytonematicide exhibited negative quadratic relations where eggs, J2 in soil and roots and total population (Pf) were optimised at xv 14.43, 28.23, 23.30 and 13.55%. To conduct Objective 2 which is application interval, empirically derived MCSP value of 4.31% from Objective 1 was used. Application interval was optimised using the concept of 1, 2, 3, and 4 weeks in weeks-per-month-of-30-days. The application interval of 4.31% was established at 2.43 weeks which translated to 18 days [(2.43 weeks/4 weeks) × 30 days]. All nematode variables in Objective 2 were not significantly different at all intervals. In, conclusion Nemarioc-AL phytonematicide can be used at 4.31% concentration to control nematodes population densities without being phytotoxic to crops at 18 days application interval. / National Research Foundation (NRF) , Agricultural Research Council (ARC) and the Flemish Interuniversity Council of Belgium

Thesis (M.Sc. (Plant Production)) -- University of Limpopo, 2013 / Two phytonematicides were researched and developed from fermented crude extracts of wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus) fruits for use as alternatives to methyl bromide in managing root-knot (Meloidogyne species) nematodes in tomato (Solanum lycopersicum) production. Fruits of C. africanus contain cucurbitacin B (C32H48O8), while those of C. myriocarpus contain cucurbitacin A, which comprises cucumin (C27H40O9) and leptodermin (C27H38O8). Phytonematicides from C. africanus and C. myriocarpus fruits are referred to as nemafric-B and nemarioc-A, respectively. The two phytonematicides, due to their origin from plant species with allelochemicals, have high potential of being phytotoxic to crops. The use of the Curve-fitting Allelochemical Response Dosage (CARD) computer-based model assisted in the establishment of concentrations which were stimulatory to growth of tomato (Solanum lycopersicum) plants, while exhibiting nematoxic properties to Meloidogyne species. The two phytonematicides were developed from crude extracts of fruits dried at 52˚C in air-forced ovens and ground in a Wiley mill through 1-mm-opening sieves. However, equipment for drying and grinding fruits would not be accessible to smallholder farmers who wished to prepare their own products on-farm. The objective of this study therefore, was to determine whether nemafric-BL and nemarioc-AL produced from fresh fruit of the two Cucumis species would be suitable for use (i.e. non phytotoxic) in tomato production for managing population densities of M. incognita race 2. In order to distinguish the products of fresh (F) fruits from those of dried (D) fruits, they were code-named nemafricF-BL or nemariocF-BL and nemafricD-BL or nemariocD AL, respectively, where G and L denoted granular and liquid formulations, respectively. Tomato cv. ‘Floradade’ seedlings were infested with 3 000 eggs and second-stage xv juveniles of M. incognita race 2. An equivalent of 40 g and 80 g dried fruit mass of nemafric-B and nemarioc-A, namely, 284 g and 411 g fresh fruit mass for nemafric-B and nemarioc-A, respectively, were separately fermented using EMROSA effective micro-organisms mixed with 16 L chlorine-free tapwater in 20 L container for 14 days at ± 25˚C, allowing pH to gradually decline to ± 3.7. Separate experiments for each product run concurrently. Treatments, namely, 0, 2, 4, 8, 16, 32 and 64% concentrations, where for instance, 2% = 20 ml/1000 ml x 100, were arranged in a randomised complete block design, with 10 replications. Blocking in the greenhouse was done for wind direction which was regularly erected by fans for cooling down the greenhouse. At 56 days after weekly application of each treatment, flower number, fruit number, dry shoot mass, dry root mass, dry fruit mass, plant height, stem diameter and nematode numbers were each subjected to analysis of variance. Nematode data were, prior to analysis, transformed using log10(x + 1), but untransformed data were reported. Using the sum of squares, nemafric-BL and nemarioc-AL treatments affected dry root mass, dry shoot mass, flowers number, fruit number, plant height and stem diameter. Nemafric-BL contributed 67%, 78%, 58%, 43%, 60% and 26%, while nemarioc-AL contributed 71%, 61%, 19%, 35%, 34% and 24% to total treatment variation of the six respective variables. Plant variables with significant (P ≤ 0.05) treatment effects were further subjected to the CARD model to generate seven biological indices, with three distinct phases, namely, stimulation, neutral and inhibition phases. Using the quantified stimulation phase, the mean concentration stimulation range (MCSR) was computed for each variable using two biological indices, namely, threshold stimulation point (Dm) and saturation point (Rh). The CARD model explained 98%, 99%, 98% and 98% of the quadratic models of dry root mass, dry shoot mass, plant height and stem diameter, xvi respectively, against increasing concentrations of nemarioc-AL. Similarly, the CARD model explained 99%, 96%, 84% and 93% of total treatment variation in the respective plant variables. The integrated MCSR [MSCR = Dm + (Rh/2)] for nemafric-BL on tomato plants was 7%, while that for nemarioc-AL was 4%. In the CARD model, the overall sensitivities (∑k) of tomato plants exposed to nemafric-BL and nemarioc-AL were 3 units and 5 units, respectively. Tomato plants were therefore, less sensitive to nemarioc-AL since it had higher ∑k value than nemafric-BL. At 4% nemarioc-AL and at 7% nemafric-BL, the two phytonematicides were each highly suppressive to population densities of M. incognita race 2. In conclusion, on the basis of non-phytotoxicity of the computed MCSR values and their suppressive effects on population densities of M. incognita race 2, the smallholder farmers could produce nemafric-BL and nemarioc-AL phytonematicides on-farm. However, the production of the two products from fresh fruits would not be sustainable since fruits of the two Cucumis species are highly seasonal due to the high incidence of post-harvest decays. / The Land Bank Chair of Agriculture – University of Limpopo, Limpopo Agro-processing Technology Station,and the Flemish Interuniversity Council of Belgium

Thesis (M. Sc.(Agronomy)) -- University of Limpopo, 2017. / Cleome gynandra is increasingly becoming an important strategy for achieving food and nutrition security among rural households in many developing countries. Root-knot (Meloidogyne species) nematodes, with limited nematode management strategies, limit the successful production of this vegetable crop. Nemafric-BL and Nemarioc-AL phytonematicides are separately being developed in South Africa for sustainable crop production systems. However, the two products have not been simultaneously tested for managing the notorious Meloidogyne species and absorption of phosphorus, with a combination of Vesicular arbuscular mycorrhiza (VAM). The objective of this study therefore was to determine the interactive effects of VAM and each of the two phytonematicides on nutrient content, growth of C. gynandra. A 2 × 2 × 2 factorial experiment, with the first, second and third factors being VAM (V), nematode (N) and Nemafric-BL phytonematicide (P). The eight treatments included (1) untreated control (V0N0P0), (2) nematodes alone (V0N1P0), (3) VAM alone (V1N0P0) (4) Nemarioc-AL phytonematicide alone (V0N0P1), (5) V1N1P0, (6) V0N1P1, (7) V1N0P1 and (8) V1N1P1, were laid out in a randomised complete block design, with ten replications. The same layout experiment was done for the Nemarioc-AL phytonematicide trial which had a similar layout. Seedlings were irrigated with 250 ml chloride-free tapwater every other day for 56 days. Multifeed and NPK (2:3:2(22) fertilisers were applied at transplanting. The second order interaction (V1N1P1), was highly significant (P ≤ 0.01) for plant height contributing 54% in TTV (Total Treatment Variation) of the variable. Among the main factors (N, P and V), only nematode had highly significant effects on stem diameter. All interactions of VAM, nematode and Nemarioc-AL phytonematicide and main factors each had no significant effect on Cleome. The second order (V1N1P1) and the first order interaction (V1N1P1) did not have significant effects on the three nutrient elements except for the first order interaction (V1N0P1) which was significant on foliar Zn contributing 42% in TTV of the variable. Also nematode had highly significant effect on foliar K and significant effect on foliar Zn contributing 49 and 31% in TTV of the respective variables. Using the two-way table, VAM and Nemafric-BL phytonematicide each increased foliar Zn by 27% and 29%, respectively. The second and first order interactions of VAM, N and Nemarioc-AL phytonematicide and the main factors did not have significant effect on foliar K, Fe and Zn. The second order interaction of VAM, nematode and Nemafric-BL phytonematicide had significant effects on gall rating, contributing 2% in TTV of the variable. VAM, nematode and Nemarioc-AL phytonematicide showed that the second and first order interaction except for V1N0P1 interaction on gall rating, were not significant for nematode variables. The V1N0P1 interaction contributed 20% in TTV of gall rating. Using a two-way table, VAM and phytonematicide each increased root galls by 7% and 74%, respectively. Combined, VAM and phytonematicide reduced root galls by 64%. The innovative products interacted together and that Nemafric-BL and Nemarioc-AL phytonematicides and VAM alone could be used in managing nematodes. / National Research Foundation, Agricultural Research Council-Universities Collaboration Centre

Thesis (M.Sc. (Agriculture, Plant Protection)) -- University of Limpopo, 2020 / The unavailability of environment-friendly nematicides for managing root-knot (Meloidogyne species) nematodes in crop husbandry have led to various alternative methods being sort which includes the development of cucurbitacin-containing phytonematicides. The cited phytonematicides consistently suppressed nematode numbers on different crops under greenhouse, microplot and field conditions, although there is lack of information on how the products would affect susceptible Swiss chard infected by root-knot nematodes. Swiss chard is one of most nutritious vegetables, grown throughout the year and is well adapted to different soil types. However, these products have the potential to induce phytotoxicity on various crops, if applied improperly. Phytotoxicity of phytonematicides on different crops, has been resolved by deriving Mean Concentration Stimulation Point (MCSP). The MCSP, developed using the Curve-fitting Allelochemical Response Data (CARD) computer-based model, is crop-specific, hence it should be developed for every crop. The objectives of this study were to investigate (1) whether population densities of Meloidogyne species, growth and accumulation of selected nutrient elements in Swiss chard would respond to increasing concentration of Nemarioc-AL and Nemafric-BL phytonematicides under greenhouse and microplot conditions and (2) whether the nemarioc-group and nemafric-group phytonematicides in liquid and granular formulations would affect population densities of Meloidogyne species and the productivity of Swiss chard with related accumulation of nutrient elements in leaf tissues under field conditions. Parallel experiments for Nemarioc-AL and Nemafric-BL phytonematicides were conducted concurrently under greenhouse and microplot conditions. Greenhouse experiment was prepared by arranging 25-cm-diameter plasticpods on greenhouse benches, whereas microplot experiment was prepared by digging holes and inserting 30-cm-diameter plastic pots in the field. The four-week-old Swiss chard seedlings were transplanted into the pots, filled with steam-pasteurised loam, sand and Hygromix-T at 3:1:1 (v/v) ratio. Treatments comprised 0, 2, 4, 8, 16, 32 and 64% phytonematicides arranged in randomised complete block design (RCBD), with six replications. Treatments were applied seven days after inoculation, with 3000 eggs and J2 of M. incognita race 4 under greenhouse conditions, whereas under microplot conditions were inoculated with 6000 eggs and J2 of M. javanica. Under field conditions, treatments comprised untreated control (0), 2 g Nemarioc-AG and 3% Nemarioc-AL phytonematicides (nemarioc-group) or 0, 2 g Nemafric-BG and 3% Nemafric-BL phytonematicides (nemafric-group), arranged in RCBD, each experiment with 8 replications. At 56 days after initiation of treatments, eggs in roots, J2 in roots and Pf exhibited negative quadratic relations under both greenhouse and microplot conditions. Under greenhouse conditions, dry shoot mass (R2 = 0.81), dry root mass (R2 = 0.87) and leaf number (R2 = 0.91) over Nemarioc-AL phytonematicide exhibited positive quadratic relations. In contrast, dry shoot mass (R2 = 0.78), dry root mass (R2 = 0.93) and leaf number (R2 = 0.70) over Nemafric-BL phytonematicide exhibited positive quadratic relations. Under microplot conditions, dry shoot mass (R2 = 0.95) and gall rating (R2 = 0.96) over Nemarioc-AL phytonematicide, exhibited positive quadratic relations. Dry shoot mass (R2 = 0.84) and gall rating (R2 = 0.97) versus Nemafric-BL phytonematicide exhibited positive quadratic relations. Selected nutrient elements under greenhouse conditions K (R2 = 0.96), Ca (R2 = 0.79), Mg (R2 = 0.64), Fe (R2 = 0.78) and Zn (R2 = 0.77) over Nemarioc-AL phytonematicide exhibited positive quadratic relations. In contrast, only Ca (R2 = 0.90), Mg (R2 = 0.68) and Zn (R2 = 0.84) over Nemafric-BL phytonematicide exhibited positive quadratic relations, whereas K (R2 = 0.72) and Fe (R2 = 0.63) over the product exhibited negative quadratic relations. Under microplot conditions, K (R2 = 0.82), Ca (R2 = 0.90) and Mg (R2 = 0.98) over Nemarioc-AL phytonematicide exhibited positive quadratic relations, whereas Fe (R2 = 0.91) and Zn (R2 = 0.79) over the product exhibited negative quadratic relations. In contrast, K (R2 = 0.60), Ca (R2 = 0.68) and Zn (R2 = 0.95) over Nemafric-BL phytonematicide exhibited positive quadratic relation, whereas Mg and Fe over the product did not have significant relationships. Under greenhouse conditions, MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides on Swiss chard were 3.03 and 2.36%, whereas overall sensitivity (∑k) values of the crop to the product were 3 and 0 units, respectively. In contrast, MCSP values of Nemarioc-AL and Nemafric-BL phytonematicides on Swiss chard under microplot conditions was successfully established at 3.71 and 3.33%, whereas the ∑k values were 2 and 1 units, respectively. Under field conditions, at 64 days after initiating the treatments, the nemarioc-group phytonematicides had highly significant effects on eggs in roots and reproductive potential (RP), contributing 79 and 77% in total treatment variation (TTV) of the respective variables. In contrast, the nemafric-group phytonematicides had highly significant effects on eggs in roots and RP, contributing 67 and 76% in TTV of the respective variables. Under field conditions, all plant growth variables were not significantly affected by the treatments. The nemarioc-group phytonematicides had significant effects on K and Mg in leaf tissues of Swiss chard, contributing nemafric-group phytonematicides had significant effects on Mg, contributing 62% in TTV of the variable. In conclusion, the products could be used on Swiss chard for managing population densities of Meloidogyne species. However, due to the sensitivity of Swiss chard to the products, it would be necessary to use the derived MCSP values to determine the application intervals of the products on the test cultigen / National Research Foundation (NRF) Agricultural Research Council (ARC)