Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / The successful cultivation of nightshade (Solanum retroflexum) as a leafy vegetable with
the nutritional potential of contributing to food security in marginalised communities of
Limpopo Province could be limited by high population densities of root-knot (Meloidogyne
species) nematodes. However, the use of Nemarioc-AL/AG and Nemafric-BL/BG
phytonematicides in suppressing nematodes and not being phytotoxic requires the
empirically-developed non-phytotoxic concentration, technically referred to as 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 objective of this study was to investigate the
influence of Nemarioc-AL/AG and Nemafric-BL/BG phytonematicides on growth of
nightshade, accumulation of essential nutrient elements and cucurbitacin residues in
nightshade leaves. Microplots were established by inserting 20-cm-diameter plastic pots
into 10-cm-deep holes at 0.6 m intra-row and 0.6 m inter-row spacing. Each pot was filled
with 10 000 cm3 steam-pasteurised river sand and Hygromix at 3:1. After establishment,
Nemarioc-AL and Nemafric-BL phytonematicides were applied at 7-day interval, whereas,
Nemarioc-AG and Nemafric-BG phytonematicides were only applied at planting. Two
separate experiments for Nemarioc-AL and Nemafric-BL phytonematicides were
conducted in summer (November-January) 2017/2018 under microplot conditions with
each comprising treatments namely; 0, 2, 4, 8, 16, 32 and 64%, similarly, two separate
experiments for the following phytonematicides, Nemarioc-AG and Nemafric-BG
comprised treatments namely; 0, 2, 4, 6, 8, 10 and 12 g arranged in a randomised
complete block design (RCBD), with 12 replications. The nutrient elements in leaf tissues
of nightshade were analysed using the inductively coupled plasma optical emission
spectrometry (ICPE-9000) while, cucurbitacin A and B were
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each quantified using the isocratic elution Shimadzu HPLC Prominence with Shimadzu
CTO-20A diode array detector. Plant growth and nutrient elements variables were
subjected to the CARD computer-based model to generate biological indices to generate
the curves, quadratic equations and the related biological indices (Dm, Rh, k) (Liu et al.,
2003). The MCSP values were calculated using the biological indices of plant or nutrient
element variables which, along with increasing concentration of Nemarioc-AL, Nemafric
BL, Nemarioc-AG and Nemafric-BG phytonematicides, exhibited positive quadratic
relations, with R2 ≥ 25. Using cucurbitacin A and B standards, residues of Nemarioc
AL/AG and Nemafric-BL/BG phytonematicides, were not detected in nightshade leaves,
respectively. Dry root mass and dry shoot mass of nightshade over increasing
concentration of Nemarioc-AL phytonematicide each exhibited a quadratic relationship,
with the models explained by 93 and 61%, respectively. Dry root mass, dry shoot mass,
plant height, chlorophyll content and stem diameter against increasing concentration of
Nemafric-BL phytonematicide each exhibited positive quadratic relationships with the
models explained by 95, 72, 65, 78 and 62%, respectively. Plant height, stem diameter
and dry root mass against increasing concentration of Nemarioc-AG phytonematicide
each exhibited positive quadratic relationships with their models explained by 93, 88 and
91%, respectively. Dry shoot mass and stem diameter against increasing concentration of
Nemafric-BG phytonematicide each exhibited positive quadratic relationships with their
models explained by 94 and 84%, respectively. Na, Fe and K over increasing
concentration of Nemarioc-AL phytonematicide each exhibited positive quadratic
relationships with their associations explained by 96, 91 and 95%, respectively. Zn over
increasing concentration of Nemafric-BL phytonematicide exhibited positive quadratic
relationship with the model explained by 98%. Fe over increasing concentration of
Nemarioc-AG phytonematicide exhibited positive quadratic
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relationship with the association explained by 91%. Fe, Na, K and Zn over increasing
concentration of Nemafric-BG phytonematicide each exhibited positive quadratic
relationships with their associations explained by 81, 90, 80 and 89%, respectively,
whereas, on the contrary, Zn over increasing concentration of Nemarioc-AG
phytonematicide exhibited negative quadratic relationship with the association
explained by 96%. Significant (P ≤ 0.05) plant variables were subjected to CARD, to
generate biological indices which were used to compute the MCSP using the relation:
MCSP = Dm + Rh/2 and the overall sensitivity value (∑k). In Nemarioc-AL
phytonematicide trial, MCSP = 3.02% and ∑k = 1 for plant variables, whereas, MCSP
and ∑k for nutrient elements were 12.09% and 1, respectively. In Nemafric-BL
phytonematicide trial, MCSP = 3.08% and ∑k = 0 for plant variables, while MCSP =
2484.14% and ∑k = 0 for nutrient elements. In Nemarioc-AG phytonematicide trial,
MCSP = 3.47 g and ∑k = 0 for plant variables, whereas, for nutrient elements MCSP =
8.49 g and ∑k = 1. In Nemafric-BG phytonematicide trial, MCSP = 4.70 g and ∑k = 0
for plant variables, whereas, MCSP =723.75 g and ∑k = 1 for nutrient elements. In
conclusion, the application of Nemarioc-AL/AG and Nemafric-BL/BG phytonematicides
had the ability to stimulate the growth of nightshade and enhance the accumulation of
the selected nutrient elements without leaving cucurbitacin chemical residues in leaf
tissues of nightshade. / National Research
Foundation (NRF)
and the Land Bank Chair of Agriculture
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3171 |
| Date | January 2019 |
| Creators | Malebe, Agreement Leago |
| Contributors | Shadung, K. G., Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xiv, 58 leaves |
| Relation | Adobe Acrobat Reader |
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