Thesis (MSc. (Horticulture)) -- University of Limpopo, 2016. / Pelargonium sidoides has numerous medicinal applications, with economic potential to
serve as a future cultigen in smallholder farming systems. However, it is highly
susceptible to the root-knot (Meloidogyne species) nematodes, without any identifiable
nematode resistant genotypes. Nemarioc-AL and Nemafric-BL phytonematicides, with
cucurbitacin A and cucurbitacin B active ingredients, respectively, are being researched
and developed as an alternative to synthetic nematicides at the University of Limpopo.
However, since active ingredients in phytonematicides are allelochemicals, the two
phytonematicides have the potential of inducing phytotoxicity on crops protected against
nematode damage. The objectives of the study, therefore, were (1) to determine the
non-phytotoxic concentration of Nemarioc-AL phytonematicide on plant growth of P.
sidoides, and (2) to determine the non-phytotoxic concentration of Nemafric-BL
phytonematicide in plant growth of P. sidoides. Cuttings were raised in 30-cm-diameter
plastic pots containing 10 000 ml steam-pasteurised river sand and Hygromix-T at 3:1
(v/v) under microplot conditions in autumn (March-May) and repeated in spring (August
October) 2015. After establishment each plant was inoculated with 5 000 eggs and
second-stage juveniles (J2s) of M. javanica. Six treatments, namely, 0, 2, 4, 6, 8 and
10% concentrations of each phytonematicide on separate trials were arranged in a
randomised complete block design, with seven replicates. At 56 days after inoculation,
in Experiment 1, Nemarioc-AL phytonematicide, treatment significantly (P ≤ 0.05)
affected plant height, dry root mass and root galls, contributing 62, 69 and 70% to total
treatment variation of the three variables, respectively. Relative to untreated control
Nemarioc-AL phytonematicide increased plant height and dry root mass by 34 to 61%
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and 20 to 76%, respectively, with a slight decrease by 5% in plant height at the highest
concentration. However, the material decreased root galls by 5 to 50%. Significant (P ≤
0.05) plant variables were subjected to Curve fitting-allelochemical respond dosage
model, to generate biological indices which were used to compute the mean
concentration stimulation point (MCSP) using the relation: MCSP = Dm + Rh/2 and the
overall sensitivity value (∑k). In Experiment 1, MCSP = 6.18% and ∑k = 3. Plant
variables and increasing concentration of phytonematicide exhibited quadratic relations.
Treatments reduced nematode variables, at all levels including at the lowest, but the
effect were not different. In Experiment 2, Nemarioc-AL phytonematicide treatment
effects were not significant on plant variables except for root galls, but were significant
for root nematodes except for eggs. Data for plant variables in Experiment 2 were not
subjected to Curve fitting-allelochemical respond dosage model because they were not
significant (P ≤ 0.05). In Experiment 1, Nemafric-BL phytonematicide treatment
significantly (P ≤ 0.05) affected plant height and root galls, contributing 63 and 67% to
total treatment variation of the two variables, respectively. Relatively to untreated
control, plant height was increased by 10 to 36%, while root galls was reduced by 2.43
to 60%. In Experiment 1, MCSP = 2.87% and ∑k = 3. Concentrations of Nemafric-BL
phytonematicide significantly (P ≤ 0.05) reduced eggs, juveniles and Pf at all levels
including at the lowest, but the effect were not significant different, with treatments
contributing 78, 72 and 90% to the total treatment variation. In Experiment 2, Nemafric
BL phytonematicide treatment effects were not significant on plant variables except for
root galls, but were significant for root. In conclusion, Nemarioc-AL and Nemafric-BL
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phytonematicides could be applied at the lowest concentration of 2% where it was
shown to be effective in suppressing population densities of M. javanica. / Agricultural Research Council (ARC),
National Research Fund (NRF) ,
Flemish Inter university Council of Belgium and
Land
Bank Chair of Agriculture ─ University of Limpopo
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/1789 |
| Date | January 2016 |
| Creators | Sithole, Nokuthula Thulisile |
| Contributors | Pofu, K. M., Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xxiii, 66 leaves |
| Relation | Adobe Acrobat Reader |
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