Thesis (M.Sc. Agriculture (Plant Protection)) -- University of Limpopo, 2021 / In use of phytonematicides as an alternative to synthetic chemical nematicides, the
major challenge had been the development of appropriate application technologies,
which are currently limited to the ground leaching technology (GLT) and
botinemagation (BNT) systems. The former is labour-intensive, whereas the latter
requires infrastructure that could be costly for smallholder farmers. The priming of
seeds with hypogenous germination properties in phytonematicide solutions could
serve as an alternative method of the application of phytonematicides, where the
cotyledons would serve as carriers of the active ingredients that are leached into the
rhizosphere for suppression of nematode numbers. However, since germination is a
chemical process, it is not known whether the active ingredients in cucurbitacin containing phytonematicides would interfere with germination and the subsequent
emergence of the seedlings through the incidence of phytotoxicity as observed in the
use of the products in crop production. The objectives of the study, therefore, were (1)
to investigate the sensitivity and overall sensitivity of pea (Pisum sativum L.) plants to
Nemarioc-AL and Nemafric-BL phytonematicides, and (2) to determine the mean
concentration point (MCSP) for pea-inoculated with Meloidogyne incognita under
greenhouse and microplot conditions, where seeds were previously primed in
phytonematicide solutions. Two separate trials were conducted with seven treatments,
namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL or Nemafric-BL phytonematicide,
arranged in completely randomised design (CRD), with 8 replications each. Pea seeds
were primed in Nemarioc-AL and Nemafric-BL phytonematicide solutions for two hours
and shade dried prior to sowing. In vitro trial, 10 seeds were spread uniformly on a
moistened filter paper in sterilised petri-dishes with lids and placed in an incubator at
25oC. In vivo trials were under greenhouse and micro-plot conditions, pea seeds were
sown in 25-cm and 30-cm diameter plastic pots, respectively. Pots were filled with
pasteurised loam soil. Seedlings were inoculated with 5 000 eggs + second-stage
juveniles (J2) of M. incognita. Treatments in each case included priming seeds as
explained earlier, arranged in a randomised complete block design (RCBD), with 6
replications under greenhouse conditions and 8 replications under micro-plot
conditions. In all cases, plant growth variables were assessed using the Curve-fitting
Allelochemical Response Dose (CARD) model to generate biological indices which
were used to calculate MCSP and the overall sensitivity (Σk). Nematode variables in
inoculated trials were assessed using the regression model. In vitro trials, germination
variables had positive quadratic relation versus Nemafric-BL phytonematicide, with
MCSP= 0.62 % and ∑k = 34 units. In contrast, tested germination variables exhibited
negative quadratic relations versus Nemarioc-AL phytonematicide. In greenhouse
trials, MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides were 0.62
and 2.18 %, respectively, with ∑k = 0. Plant height (R2 = 0.86), stem diameter (R2 =
0.93) and chlorophyll content (R2 = 0.85), exhibited positive quadratic relationship
against Nemarioc-AL phytonematicide, whereas, plant height (R2 = 0.95), stem
diameter (R2 = 0.92), chlorophyll content (R2 = 0.89), number of flowers (R2 = 0.93)
and dry shoot mass (R2 = 0.94), exhibited positive quadratic relationship against
Nemafric-BL phytonematicide. In micro-plot trials, MCSP values for Nemarioc-AL and
Nemafric-BL phytonematicides were 0.71 and 2.45 %, respectively, with ∑k = 0. Plant
height (R2 = 0.95), stem diameter (R2 = 0.98), chlorophyll content (R2 = 0.98), and gall
ratings (R2 = 0.98), exhibited positive quadratic relationships against Nemarioc-AL
phytonematicide, while chlorophyll content (R2 = 0.97) and gall ratings (R2 = 0.96)
exhibited positive quadratic relationships against Nemafric-BL phytonematicide. All
degrees of Nemarioc-AL and Nemafric-BL phytonematicides profoundly reduced
nematode numbers under greenhouse and micro-plot trials. In conclusion, both
Nemarioc-AL and Nemafric-BL phytonematicides could be applied through the priming
technology on pea seeds which have hypogenous germination properties in
suppression of nematode population densities. / National Research Foundation (NRF)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/4297 |
| Date | January 2021 |
| Creators | Ntuli, Vafana Attraction |
| Contributors | Mashele, P. W., Pofu, K. M. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xvii, 70 leaves |
| Relation |
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