Thesis (M.Sc.(Plant Protection)) -- University of Limpopo, 2022 / Runner beans are extremely sensitive to root-knot (Meloidogyne species)
nematodes. Phytonematicides had been consistently used in managing population
densities of Meloidogyne species in various crops, with the application technologies
being restricted to the ground leaching technology (GLT) and botinemagation
technology, each with its own advantages and disadvantages. The use of seeds as
carriers of active ingredients of phytonematicides and then drying prior to sowing, is
being considered as another potential application strategy in seeds with hypogeal
germination. In such seeds, during seedling emergence the seed cover and the
endosperm remain below the soil surface, just above the developing root system. As
a result, in phytonematicide-primed seeds, the seed structures could serve as
carriers for the active ingredients of phytonematicides. In cucurbitacin
phytonematicides, Nemarioc-AL and Nemafric-BL phytonematicides contain
cucurbitacin A and B, respectively as active ingredients. The objectives of the study
were two-fold, namely, to determine whether runner bean (Phaseolus coccineus L.)
seeds would (1) serve as carriers of active ingredients of cucurbitacin-containing
phytonematicides without affecting seed germination under in vitro conditions, (2)
serve as carriers of cucurbitacins intended for suppression of M. incognita population
densities under greenhouse and microplot conditions. Two separate studies were
conducted under laboratory conditions, with seven treatment solutions at 0, 2, 4, 8,
16, 32 and 64% Nemafric-BL or Nemarioc-AL phytonematicide. After exposure to
separate solutions for 2 h, runner bean seeds were dried on laboratory benches for
72 h. Treatments were arranged in a completely randomised design (CRD), with 8
replications. Two layers of filter papers were placed inside each Petri dish seeded
with 10 primed and dried seeds. Petri dishes were incubated inside LABCON growth
chamber at 25ºC and 75% relative humidity. Successful seed germination, viewed as
emergence of radicle from the testa, was recorded daily for a period of 10 days, with
each count being removed from Petri dish to avoid re-counting. Under greenhouse
and microplot conditions, primed-and dried seeds were sown in plastic pots
containing 2 700 ml steam-pasteurised sandy loam soil, arranged in a randomised
complete block design, replicated six times and eight times, respectively. Each
seedling was inoculated by distributing 5 000 eggs and second-stage juveniles (J2)
of M. incognita race 4 using a 50 ml plastic syringe. Originally, pots were irrigated
using 500 ml chlorine-free tapwater, which was reduced to half after seedling
emergence at every other day. Plant variables were collected at 56 days after
inoculation and data were subjected to the Curve-fitting Allelochemical Response
Dose algorithm model. In vitro, germination percentage (R
2
= 0.96), radicle length
(R
2
= 0.89) and plumule diameter (R
2
= 0.96) versus Nemarioc-AL phytonematicide
exhibited positive quadratic relations. Similarly, the variables versus Nemafric-BL
phytonematicide, exhibited positive quadratic relations. In vitro, Mean Concentration
Stimulation Point (MCSP) value of Nemarioc-AL phytonematicide on runner bean
seeds was 1.05%, whereas for Nemafric-BL phytonematicide MCSP value was
0.58%. Under greenhouse conditions, plant height (R
2
= 0.97), chlorophyll content
(R
2
= 0.92), dry shoot mass (R
2
= 0.98), dead nodule number (R
2
= 0.90), total pod
number (R
2
= 0.97) and active nodule number (R
2
= 0.93) versus Nemarioc-AL
phytonematicide exhibited positive quadratic relations., Similarly, chlorophyll content
(R
2
= 0.95), gall rating (R
2
= 0.82), dry shoot weight (R
2
= 0.69), stem diameter (R
2
=
0.85) and total nodule number (R
2
= 0.86) versus Nemafric-BL phytonematicide
exhibited positive quadratic relations. Under greenhouse conditions, MCSP values
for Nemarioc-AL and Nemafric-BL phytonematicides were 4.18 and 3.69%,
respectively. Under microplot conditions, total number of nodules (R
2
= 0.88),
number of nodules dead (R
2
= 0.99), number of nodules active (R
2
= 0.95), fresh root
mass (R
2
= 0.99), and fresh pod mass (R
2
= 0.99) versus Nemarioc-AL
phytonematicide, exhibited positive quadratic relations, whereas plant height (R
2
=
0.85), number of nodules dead (R
2
= 0.87), dry shoot mass (R
2
= 0.97), fresh root
mass (R
2
= 0.97) and total number of nodules (R
2
= 0.63) versus Nemafric-BL
phytonematicide exhibited positive quadratic relations. Under microplot conditions,
MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides were 3.76 and
3.93%, respectively, each with ∑k = 0. All degrees of Nemarioc-AL and Nemafric-BL
phytonematicides profoundly reduced nematode numbers under greenhouse and
microplot trials. Based on the information obtained from this study, it was confirmed
that runner bean (P. coccineus) is sensitive to Nemafric-BL and Nemarioc-AL
phytonematicides supported by the Curve-fitting Allelochemical Response Dose
(CARD) model results due to most plant variables that had sensitivity values of zero.
In conclusion, the priming technology should be developed further since it has the
potential of being successful in nematode management in seeds with hypogeal
germination / National Research Foundation (NRF) and
Potatoes South Africa
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/4303 |
| Date | January 2022 |
| Creators | Ramoetlo, Motsatsi Priscilla |
| Contributors | Pofu, K. M., Mashela, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xviii, 84 leaves |
| Relation |
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