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
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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
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= 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3162 |
| Date | January 2019 |
| Creators | Huma, Tiego Isaac |
| Contributors | Pofu, K. M., Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xvi, 71 leaves |
| Relation | Adobe Acrobat Reader |
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