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Factors leading to poor fruit set and yield of sweet cherries in South Africa
Thesis (MScAgric (Horticulture))--Stellenbosch University, 2008.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2008
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| _version_ | 1867614126460633088 |
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| access_status_str | Open Access |
| author | Sheard, Andrew Grant |
| author2 | Cook, Nigel |
| author_browse | Cook, Nigel Sheard, Andrew Grant |
| author_facet | Cook, Nigel Sheard, Andrew Grant |
| author_sort | Sheard, Andrew Grant |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric (Horticulture))--Stellenbosch University, 2008. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/2080 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:47:05.324Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2008 |
| publishDateRange | 2008 |
| publishDateSort | 2008 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/2080 Factors leading to poor fruit set and yield of sweet cherries in South Africa Sheard, Andrew Grant Cook, Nigel Johnson, Steve Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. Sweet Cherry Cross pollination Rest breaking agent Ovule longevity Sweet cherry -- Yields -- South Africa Sweet cherry -- Dormancy Sweet cherry -- Flowering Sweet cherry -- Pollination Dissertations -- Horticulture Theses -- Horticulture Thesis (MScAgric (Horticulture))--Stellenbosch University, 2008. Sweet cherries (Prunus avium L.) have a high chilling requirement and grow best in areas receiving >1 100 Utah chill units during winter. The main production areas in South Africa, and particularly the eastern Free State, frequently receive insufficient winter chilling and late spring frosts leading to problems of poor budburst, flowering, floral abnormalities and poor fruit set. Research was conducted on the cultivar ‘Bing’ to determine the main factors causing its low fruit set. Various trials were conducted to optimize the timing of rest breaking agents, identify suitable cross pollinizers that flower synchronously with ‘Bing’, and evaluate the influence of temperature and pollen-pistil interactions on fertilization and fruit set. Pollen biology studies using 2- to 3-year-old ‘Bing’ sweet cherry trees were conducted near Clarens, eastern Free State, during the 2005 and 2006 seasons to determine the most suitable cross pollinizer/s for ‘Bing’ and to assess the influence of temperature and pollen-pistil interactions on pollen tube growth and ovule longevity. Significant differences in pollen germination (‘rates’ deleted) occurred between pollinizers, although differences were noted in pollen performance on the stigma and style (in vivo) compared to the artificial media (in vitro), indicating a lack of correlation between in vitro germination and in vivo pollen-pistil interactions. Pollen tube growth, following cross pollination, was influenced by pollinizer genotype, temperature, and the number of pollen grains deposited on the stigma. The highest pollen tube growth rates in ‘Bing’ styles were recorded for the pollinizers ‘Black Tartarian’ (2006), ‘Lapins’ and ‘Rainier’ sweet cherry cultivars at temperatures of approximately 21°C. Temperature had the most significant influence on ovule longevity with the lower orchard temperatures extending ovule viability compared to the higher laboratory temperatures, although pollen tube growth rates were also reduced, thus shortening the effective pollination period. Cross pollination was also shown to extend ovule viability. The results indicate that ‘Black Tartarian’, ‘Lapins’ and ‘Rainier’ were the most suitable pollinizers for ‘Bing’. Hand-pollination with pollen from these donors resulted in a several-fold increase in seed set over naturally-pollinated control flowers. It appears that the principle factors causing poor fruit set in ‘Bing’ sweet cherry are premature abortion of the ovule before fertilization and inadequate transfer of sufficient viable pollen under orchard conditions. Rest breaking trials were conducted on 4-year-old ‘Bing’ sweet cherry trees on ‘Gisela® 5’ rootstock near Clarens (28°28’S; 28°19’E, 1860m) and Reitz (28°0’S; 28°28’E; 1717m) in the eastern Free State, South Africa, during the 2005 and 2006 seasons respectively. In 2005 five treatments were evaluated; viz. 1% and 2% Dormex® (hydrogen cyanamide, HCN); 1% Dormex® + 3% mineral oil; and 3% Lift® (thidiazuron and mineral oil) sprayed at three dates (29 July 2005, 5 August 2005 and 12 August 2005) preceding expected the “green-tip” stage of flower development, plus an unsprayed control. In 2006 four treatments were evaluated; viz. 1% Dormex®; 1% Dormex® + 3% mineral oil; 3% Lift® applied on three dates (26 July 2006, 7 August 2006 and 12 August 2006) and an unsprayed control. No interaction was observed between time of application and type of rest breaking agent (RBA). RBAs were effective at improving budburst and yield during both seasons with the time of application of RBAs having the most significant influence on budburst and production efficiency in ‘Bing’ sweet cherry trees. RBAs were most effective at improving vegetative budburst when applied 9 to 16 days before the (‘actual’ deleted) “green-tip” stage of flower development. Floral budburst and yield were increased by 1% Dormex® + 3% mineral oil and 3% Lift®, but results varied between seasons indicating that time of RBA application should be based on chilling accumulation and bud development stage and not based on calendar date. This current research suggests that ‘Bing’ sweet cherry is poorly suited climatically to the current production areas of the eastern Free State and short-term research needs to identify methods of improving chilling and fruit set by means of evaporative cooling and fruit set-enhancing plant growth regulators. Longer term work requires the identification of new, lower chill cultivars with improved climatic adaptation to South African conditions. Masters 2008-06-23T11:00:53Z 2010-06-01T08:40:07Z 2008-06-23T11:00:53Z 2010-06-01T08:40:07Z 2008-03 Thesis http://hdl.handle.net/10019.1/2080 en Stellenbosch University application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Sweet Cherry Cross pollination Rest breaking agent Ovule longevity Sweet cherry -- Yields -- South Africa Sweet cherry -- Dormancy Sweet cherry -- Flowering Sweet cherry -- Pollination Dissertations -- Horticulture Theses -- Horticulture Sheard, Andrew Grant Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title | Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title_full | Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title_fullStr | Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title_full_unstemmed | Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title_short | Factors leading to poor fruit set and yield of sweet cherries in South Africa |
| title_sort | factors leading to poor fruit set and yield of sweet cherries in south africa |
| topic | Sweet Cherry Cross pollination Rest breaking agent Ovule longevity Sweet cherry -- Yields -- South Africa Sweet cherry -- Dormancy Sweet cherry -- Flowering Sweet cherry -- Pollination Dissertations -- Horticulture Theses -- Horticulture |
| url | http://hdl.handle.net/10019.1/2080 |
| work_keys_str_mv | AT sheardandrewgrant factorsleadingtopoorfruitsetandyieldofsweetcherriesinsouthafrica |