Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The influence of chemical seed treatments on the germination, seedling
survival and yield of canola (cv. Varola 44) was investigated in a series of
incubation studies, glasshouse experiments, as well as field trials in the
canola producing areas in the Western Cape Province.
Incubation experiments were conducted to compare germination and seedling
growth of untreated (control) seed with that of seed treated at different
application rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® and
SA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 g
a.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The results
indicated that seed treatment (all rates of SA-combination and highest rate of
Cruiser) delayed germination and seedling growth, especially if the seed was
subjected to the Accelerated Ageing Test.
Glasshouse studies with pasteurised soil at different water contents, seed
sources (storage periods) and planting depths confirmed the phytotoxic
effects of the chemical seed treatments in the absence of soil borne
pathogens. From the results it became clear that extreme water conditions
(very wet or dry) increased the suppressing effect on germination and
seedling growth, but that no phytotoxic reactions occurred in moist (favourable
soil water conditions) soil, regardless of application rate of the chemicals
used, planting depth and seed source. In a second glasshouse experiment
conducted in moist soil (kept at 50% of field water capacity to prevent any
toxic effects) from seven different localities that were naturally infested with pathogens, both chemicals proved to be effective where soil borne pathogens
(Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could however
be found due to either chemical or application rates used.
Finally, field trials were conducted to study the effect of chemical seed
treatments on the plant populations and yield of canola planted in different
row widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Results
showed that treated seeds produced more plants.rn" and yielded more than
untreated seeds at Roodebloem Experimental Farm, while the highest
seeding rate produced significantly more plants.rn" (Roodebloem and
Langgewens Experimental Farms), but not significantly higher yields than the
lowest seeding rate at the same locality. Although row width did not have an
effect on plant population, yield (Roodebloem 2003) was significantly less at
the wider (34 cm) rows. As in earlier experiments, no consistent differences
between the two chemicals used were found.
These results clearly illustrated both the negative (in the absence of
pathogens) and positive (where soil borne pathogens do occur) effects that
chemical seed treatments may have on the germination, seedling growth and
even yield of canola under local environmental and soil conditions. Because
no significant differences were found between the chemicals used, both
chemicals should be regarded as efficient. More research, especially under
field conditions and with more cultivars, is needed before the registration of a
chemical for seed treatment could be considered. / AFRIKAANSE OPSOMMING: Die invloed van chemiese saadbehandeling op die ontkieming, saailing
oorlewing en opbrengs van canola (cv. Varola 44) is ondersoek in 'n reeks
inkubasie studies, glashuis eksperimente en veldproewe in die canolaproduserende
gebiede in die Wes Kaap Provinsie.
Inkubasie eksperimente is uitgevoer om die ontkieming en saailing groei van
onbehandelde (kontrole) saad te vergelyk met dié van saad wat behandel is
teen verskillende dosisse (0.5, 1.0 en 2.0 keer die aanbevole) van Cruiser®
en SA-kombinasie (wat bestaan uit Thiulin® teen 0.5g a.i.; Apron® teen
0.0815 g a.i.; Gaucho® teen 0.6125 g a.i. en Rovral® teen 0.9975 g a.i.). Die
resultate het aangedui dat saadbehandeling (vir alle dosisse van SAkombinasie
en die hoogste dosis van Cruiser) ontkieming en saailing groei
vertraag, veral wanneer die saad onderwerp was aan die Versnelde
Verouderings Toets. Glashuis studies met gepasteuriseerde grond by
verskillende waterinhoude, saad bronne (stoor periodes) en plantdieptes, het
die fitotoksiese effekte van die chemiese saadbehandelings bevestig in die
afwesigheid van grondgedraagde patogene. Vanuit die resultate het dit
duidelik geword dat ekstreme water toestande (baie nat of droog) die
onderdrukkende effek op ontkieming en saailinggroei verhoog het, maar dat
geen fitotoksiese reaksies plaasgevind het in klam (gunstige grondwater
toestande) grond nie, ongeag die dosisse of chemikalieë gebruik, plantdiepte
en saad bron. In 'n tweede glashuis eksperiment uitgevoer in klam grond
(gehou by 50% van veldwaterkapasiteit om toksiese effekte te voorkom) van sewe lokaliteite wat natuurlik besmet was met patogene, was beide
chemikalië effektief waar grondgedraagde patogene (Rhizoctonia so/ani en
Pythium spp.) voorgekom het. Geen duidelike tendens is egter waargeneem
vir enige van die chemikalieë of dosisse nie.
Laastens is veldproewe uitgevoer om die effek van chemiese
saadbehandelings op plant populasies en opbrengs te bepaal van canola
geplant in verskillende rywydtes (17 en 34 cm) en saaidigthede (3, 5 en 7
kg.ha-1). Resultate het aangedui dat behandelde saad meer plante.rn"
produseer en 'n groter opbrengs lewer as onbehandelde saad by
Roodebloem Eksperimentele Plaas, terwyl die hoogste saaidigtheid
betekenisvol meer plante.m" (Roodebloem en Langgewens Eksperimentele
Plase), maar nie betekenisvol hoër opbrengste gelewer het as die laagste
saaidigtheid by dieselfde lokaliteit nie. AI het rywydte nie 'n effek op plant
populasie gehad nie, was opbrengs (Roodebloem 2003) betekenisvol minder
by die wyer (34 cm) rye. Soos in vroeëre eksperimente is geen konsekwente
verskille tussen die twee chemikalieë gevind nie.
Hierdie resultate illustreer duidelik beide negatiewe (in die afwesigheid van
grondgedraagde patogene) en positiewe (in die aanwesigheid van
grondgedraagde patogene) effekte wat chemiese saadbehandelings op
ontkieming, saailing groei en selfs opbrengs van canola onder plaaslike
omgewings en grondtoestande kan hê. Omdat geen betekenisvolle verskille
tussen die chemikalieë gevind is nie, moet beide chemikalieë as doeltreffend
aanvaar word. Meer navorsing, veralonder veldtoestande en met meer
kultivars, is egter nodig voordat die registrasie van 'n chemiese middel vir
saadbehandeling oorweeg kan word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50163 |
| Date | 12 1900 |
| Creators | De Villiers, Rykie (Rykie Jacoba) |
| Contributors | Agenbag, G. A., Lamprecht, S. C., Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 79 p. : ill. |
| Rights | Stellenbosch University |
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