Dormancy progression, artificial rest breaking and pollination of 'Independence' almonds under South African growing conditions.
| dc.contributor.advisor | Louw, Esme D. | en_ZA |
| dc.contributor.advisor | Theron, K. I. | en_ZA |
| dc.contributor.author | Du Toit, Tharine | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture. | en_ZA |
| dc.date.accessioned | 2021-03-07T19:14:02Z | |
| dc.date.accessioned | 2021-04-21T14:39:35Z | |
| dc.date.available | 2021-03-07T19:14:02Z | |
| dc.date.available | 2021-04-21T14:39:35Z | |
| dc.date.issued | 2021-04 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Almond (Prunus amygdalus Batsch) has grown in popularity with South African growers, as the need for better alternatives to marginal crops arose in the Western Cape. A failure to establish a local almond industry in the past was ascribed to limited local supply that did not justify investments in expensive machinery needed for almond processing, which further prevented the expansion of the South African almond industry. Since then, advances in almond breeding have offered a wider range of cultivars that are more suitable for production under South African conditions, such as ‘Independence’, a self-compatible almond cultivar characterized by a low chill requirement (400 Utah chill units) and late flowering. Dormancy progression and bud break patterns, together with chilling and heat requirements, were investigated in various ‘Independence’ almond orchards grown throughout the Western Cape. A low level of dormancy was depicted for this almond cultivar, showing endodormancy progression, irrespective of chill accumulation. Dormancy induction and chill requirements varied among orchards, while the release from dormancy seemed more comparable. Results suggest that ‘Independence’ is more reliant on sufficient heat accumulation to ensure successful dormancy release, rather than chill. Regarding climatic conditions, ‘Independence’ is suitable for commercial production under South African conditions. Even though dormancy progression models showed a more acceptable representation of endodormancy release, its ability to accurately represent dormancy induction remains questionable under mild winter conditions. Using chemical rest breaking agents (RBAs) have become standard practice in deciduous fruit production in South Africa. The efficacy of various RBAs in improving bud break and increasing possible bearing positions was evaluated on ‘Independence’ almond trees. None of the RBAs affected reproductive bud break, fruit set, yield and post-harvest quality parameters. However, oil containing treatments enhanced the onset of vegetative bud break, resulting in a greater overlap between reproductive and vegetative growth. As no obvious disadvantage was shown in reproductive development, earlier vegetative bud break could hold potential benefits due to an advanced photosynthetic ability. An increase in spur production was also evident in trees treated with RBAs containing oil. As almond predominantly bears on spurs, these treatments increased the bearing surface, possibly increasing yield potential in subsequent seasons. The 0.5% hydrogen cyanamide treatment, in combination with 2% mineral oil, proved to be the most effective RBA tested to enhance vegetative growth and increase the bearing surface of ‘Independence’ almond trees grown under South African conditions. The effect of commercial beehives and presence of a cross-pollinator (‘Nonpareil’) on fruit set and quality was evaluated. The presence of a compatible cross-pollinator did not have an effect on fruit set, yield efficiency and post-harvest quality parameters, demonstrating that single-cultivar orchards would not compromise yield potential due to a lack of cross-pollinators. Even though the epistigmatic flowers of ‘Independence’ almond trees have autogamic capacity, it was not efficient in ensuring maximum yield potential. The presence of pollen vectors is needed to ensure successful self-pollination and fertilization in this self-compatible almond cultivar, to obtain commercially acceptable crop loads. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die gewildheid van amandel (Prunus amygdalus Batsch) onder Suid-Afrikaanse produsente het toegeneem weens die behoefte aan beter alternatiewe gewasse in die Wes-Kaap. Mislukte pogings om ‘n plaaslike amandelindustrie in die verlede te vestig, word toegeskryf aan beperkte plaaslike aanbod wat nie die belegging in peperduur verwerkingsaanlegte regverdig het nie en verdere uitbreidings verhoed het. Sedertdien het vooruitgang in amandelteelprogramme gelei tot ‘n wyer verskeidenheid kultivars wat meer geskik is vir verbouing onder Suid-Afrikaanse toestande, soos Independence, ‘n selfverenigbare amandelkultivar met karaktereienskappe soos lae kouebehoefte (400 Utah koue eenhede) en later blomperiode. Ondersoek is ingestel na die verloop van dormansie en knopbreekpatrone, asook koue- en hittebehoefte van verskeie ‘Independence’ amandelboorde reg oor die Wes-Kaap. Lae dormansievlakke vir hierdie amandelkultivar is uitgebeeld en dui op ‘n onafhanklikheid ten opsigte van koue-akkumulasie vir die verloop van endodormansie. Alhoewel daar groot verskille tussen boorde aangedui is vir dormansie induksie en kouebehoefte, was die uitgangsproses uit dormansie meer eenvormig. Die resultate dui daarop dat ‘Independence’ ‘n groter afhanklikheid van voldoende hitte akkumulering toon om suksesvolle dormansie-uitgang te verseker, in vergelyking met koue. Met betrekking tot klimaatstoestande blyk ‘Independence’ geskik te wees vir verbouing in Suid-Afrika. Daar is ook gevind dat dormansie-modelle meer geskik is vir die beskrywing van die uitgangsproses uit endodormansie, maar dat dit nie ‘n voldoende verteenwoordiging van dormansie-induksie onder gematigde wintertoestande voorstel nie. Die gebruik van chemiese rusbreekmiddels (RBMs) vorm deel van die standaard verbouingspraktyke vir sagtevrugte in Suid-Afrika. Die doeltreffendheid van verskeie RBMs vir die verbetering van knopbreek en vermeerdering van moontlike draposisies by ‘Indepedence’ amandelbome was ondersoek. Geen van die RBMs het ‘n effek op die reproduktiewe knopbreek, vrugset, opbrengs of na-oes kwaliteitsparameters getoon nie. Olie-bevattende behandelings het egter die aanvang van vegetatiewe knopbreek versnel en gelei tot ‘n groter oorvleueling in reproduktiewe- en vegetatiewe ontwikkeling. Siende dat geen voor die hand liggende verskille in reproduktiewe ontwikkeling getoon is nie, kan versnelde vegetatiewe knopbreek moontlike voordele inhou weens die vervroeging in die fotosintetiese vermoë van bome. Olie-bevattende RBMs het ook gelei tot ‘n hoër spoorproduksie in behandelde bome. Siende dat amandel meestal op spore dra, het hierdie behandelings dus die vrugdraende-oppervlakte verhoog en moontlik ook die opbrengspotensiaal vir die daaropvolgende seisoene. Van al die RBMs wat getoets is, was die 5% waterstof-sianamied behandeling, tesame met 2% mineraalolie, die mees effektiefste RBM vir versnelling in vegetatiewe groei en verhoogde vrugdraende-oppervlakte in ‘Independence’ amandelbome verbou onder Suid-Afrikaanse toestande. Die invloed van kommersiële byekorwe en die teenwoordigheid van ‘n kruisbestuiwer (‘Nonpareil’) op vrugset en kwaliteit is ondersoek. Die teenwoordigheid van hierdie verenigbare kruisbestuiwer het nie ‘n invloed op vrugset, opbrengs of na-oes kwaliteitsparameters getoon nie. Dit dui daarop dat opbrengspotensiaal nie benadeel sal word in die afwesigheid van ‘n kruisbestuiwer in enkelkultivar boorde nie. Die epistigmatiese blomme van ‘Independence’ amandelbome het die kapasiteit vir outogamie, maar dit was nie doeltreffend genoeg om maksimum opbrengste te verseker nie. Die teenwoordigheid van bestuiwers is nodig om suksesvolle selfbestuiwing en –bevrugting te verseker in hierdie selfverenigbare amandelkultivar, indien kommersieël aanvaarbare oesladings verlang word. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.format.extent | ix, 174 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110084 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Almond (Prunus amygdalus Batsch) -- South Africa -- Western Cape | en_ZA |
| dc.subject | Almond industry -- Africa, Southern | en_ZA |
| dc.subject | Dormancy in plants | en_ZA |
| dc.subject | Almond -- Effect of global warming on | en_ZA |
| dc.subject | Flowers -- Anatomy | en_ZA |
| dc.subject | Pollination by insects -- Effect of climatic changes on | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Dormancy progression, artificial rest breaking and pollination of 'Independence' almonds under South African growing conditions. | en_ZA |
| dc.type | Thesis | en_ZA |