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Stellenbosch University (2021)

Seed viability versus seed vigour of canola (Brassica napus L.) cultivars in South Africa and the impact on establishment

Lötter, Devan DeVilliers

Titre : Seed viability versus seed vigour of canola (Brassica napus L.) cultivars in South Africa and the impact on establishment

Auteur : Lötter, Devan DeVilliers

Université de soutenance : Stellenbosch University

Grade : Master Degree (Agronomy) 2021

Résumé partiel
Laboratory, greenhouse and field trials were conducted in 2020 to compare the effectiveness of general seed quality parameters and certain seed vigour parameters to the actual field establishment success of several common canola (Brassica napus L.) cultivars from South Africa. Fourteen different, commonly cultivated, canola cultivars that were available on the South African retail seed market for the year 2020, were obtained from various seed marketing companies. For the sake of confidentiality in this study, the 14 cultivars were randomly assigned a code number from 1 to 14 and referred to by these code numbers. The general seed quality parameters determined in this study included germination percentage, thousand seed mass (TSM) and seed size fractioning. The germination percentages of the cultivars were determined by germinating seed as described by the International Seed Testing Association (ISTA). The TSM of all cultivars was determined by counting out 5 replications of 1000 seed from each cultivar and weighing each replication to determine the mean TSM. Seed size fractioning was done by dividing 3 replicates of each cultivar into three size classes and determining the mean percentage of each size class per cultivar. The size classes were classified as small (<1.7 mm), medium/normal (1.7-2.0 mm) and large (>2.0 mm). The vigour testing parameters used to test seed vigour of all the cultivars included germination and emergence after accelerated ageing (AA), planting depth emergence and drought stress emergence. Accelerated ageing (AA) was done by ageing seed for 0, 24, 48 and 72 hours in a temperature-controlled growth chamber at 42 °C ± 0.5 °C before germination and emergence testing. The planting depth emergence was determined by planting seeds from each cultivar at four different depths, 10 mm, 20 mm, 40 mm and 60 mm. The drought stress emergence was determined by determining emergence of each cultivar while watering was done by an 0.2% Polyethylene glycol 6000 (PEG-6000) solution with an osmotic potential of about -500 kPa, simulating 50% field water capacity.

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