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Stellenbosch University (2002)

Establishment of Guayule (Parthenium argentatum Gray)

Bekaardt CR

Titre : Establishment of Guayule (Parthenium argentatum Gray)

Auteur : Bekaardt CR

Université de soutenance : Stellenbosch University

Grade : Master of Science (MS) 2002

Résumé partiel
Guayule (Parthenium argentatum Gray) is a semi-desert plant with the potential to become an established crop on arid land in South Africa. The plant produces latex, which can be processed into rubber that is useful in application where disease transmission needs to be limited, such as for surgical gloves and condoms. The poor germination and natural dormancy characteristics of the embryo and the seed coats of guayule seed, motivated germination experiments. Germination of seed treated with solutions of gibberellic acid, smoke water and smoke water- gibberellic acid was determined. Furthermore, combinations of gibberellic acid, smoke water and sodium hypochlorite treatment solutions were applied to seed to determine the germination responses. Vegetative propagation of guayule by means of cuttings was also investigated to determine the rooting responses of cuttings with treatment solutions of indole butyric acid, naphthalene acetamide and naphthalene acetic acid. Rooting percentage, root length and root weight was determined for each treatment. Dryland field trial plantings were established at different areas in South Africa to determine the growth potential and biomass production of guayule cultivars under different environmental conditions. Stand count, height, canopy diameter and stem diameter was determined for the different cultivars and areas. Lastly, latex production of guayule cultivars established in trial plots at Elsenburg, Oudtshoom and Graaff- Reinet was determined after one year of growth. Treatment solutions of an aqueous smoke extract ( commonly referred to as smoke water) and gibberellic acid were evaluated to determine their effectiveness in stimulating germination of four guayule seed lines (AZ101, AZ-3, N565 and 11591). The split-plot analyses of variance showed no significant interaction between cultivar and treatment factors (P equals 0.71), but when the day factor was included interaction was highly significant (P lower than 0.0001). The applied treatment thus had an effect on the time required for the germination response. Investigations into optimum germination responses indicated that smoke water-gibberellic acid required the shortest number of days (6.3 days) for optimum germination to occur with cultivar AZ-3. Furthermore, gibberellic acid treatment resulted in the greatest germination with the four cultivars 11591, AZ-3, AZ101 and N565, at 93.78 percent, 93.35 percent, 94.41 percent and 99.42 percent respectively. These results show that guayule seed can be stimulated to genninate by treatment with gibberellic acid and smoke water solutions. Specific concentrations of treatment solutions of gibberellic acid, smoke water and sodium hypochlorite, and combinations thereof were used to evaluate the gennination response of guayule seed cultivar AZ-2. Combinations of treatment solutions did not result in significantly increased seed gennination responses. Single treatment solutions of gibberellic acid and smoke water did not significantly enhance gennination, but sodium hypochlorite however, significantly (p less than 0.0001) suppressed gennination at the 1 percent Cl and 2 percent Cl concentrations with about 5 percent and 10 percent respectively when compared to the control. Therefore, the applied seed treatments did not effectively increase the gennination of guayule cultivar AZ-2 seed. Specific concentrations of indole butyric acid, naphthalene acetamide and naphthalene acetic acid treatment solutions were applied to guayule cuttings of cultivar AZ-3 and rooting response was detennined for rooting percentage, root length and root weight. Naphthalene acetic acid treatment rooted the highest percentage of cuttings (52.38 percent) at a concentration of 60 mg/l. Indole butyric acid treatment produced the longest roots (147.83 mm) at a concentration of 120 mg/l. Naphthalene acetamide obtained the heaviest roots (1.8 g) at a concentration of 120 mg/l. Treatment solutions of indole butyric acid, naphthalene acetamide and naphthalene acetic acid indicated specific concentrations for optimum effect to improve root formation (by 30 percent), root length (by 50 mm) and root weight (by 1.5 g) when compared to the controls. Guayule trial plots of 10x10 m, rows 1 m apart and 30 cm between plants, and each cultivar (10 plants per unit) placed at random and replicated 6 times, were established in different areas under different environmental conditions in South Africa. Plantings were evaluated as a dryland practice, though irrigation was supplied only for establishment. Growth (stand count, height, canopy diameter, stem diameter) and biomass (wet and dry weight) were recorded for (1) one-year old plantings established in April 2001 at Elsenburg, Graaff-Reinet and Oudtshoom, and (2) six-month old plantings established in October 2001 at Bethulie, Glen and Upington

Présentation (NRF)

Page publiée le 17 octobre 2017