Chilling injury and the control thereof in selected Leucadendron cultivars

Sea freight has emerged as a preferred option over airfreight for Cape Flora ornamental stems. This shift has been driven by the rising cost of aviation fuel, alongside a greater awareness of and commitment to reduce carbon emissions. However, this alternative transport comes with a compromise as long-term cold storage can lead to chilling injury in susceptible ornamental Cape Flora species, selections, and cultivars. The development of chilling injury symptoms has a detrimental impact on the commercial value of the Cape Flora stems, rendering them unmarketable. A study was done to establish and provide insight into effective storage protocols for Leucadendron stems and to obtain a better understanding of the development of chilling injury for this niche product with long-term cold storage. Five Leucadendron cultivars were stored for a period 21, 28 and 35 days at 0°C, 2.5°C and 5°C, respectively, and then evaluated for vase life quality using a hedonic index. As an exception, L. ‘Blush’ was stored for 14 days as well. Results were inconclusive and could not support a general recommendation for a single optimum storage temperature and duration across a range of Leucadendron products. L. ‘Blush’ was regarded as unsuitable for long-term cold storage, whereas L. ‘Safari Sunset’ performed well over all temperature ranges and storage periods. L. ’Chameleon’ performed well at 5°C while L. ‘Laurel Yellow’ stem quality displayed a significant decrease in quality when stored at 2.5°C, suggesting this temperature as a possible killing zone. L. ‘Inca Gold’ stems stored well at 0°C, across all storage durations. To further unravel the requirements for long-term cold storage in Leucadendron, the susceptibility of stems with four different harvest maturities (M1-M4) to chilling injury was studied in L. ’Chameleon’. Stems were stored at 0°C, 2°C, 4°C, and 6°C respectively, for 21 days. Data collection included scores for visual quality over a 14-day vase life period, and quantification of selected stem characteristics aimed to characterise stem maturity. These included information on flower head fresh weight, flower head size, and internode length. Cold-induced physiological stress was determined using chlorophyll fluorescence and electrolyte leakage. Results indicate harvest maturity to have a significant impact on the development of chilling injury. Stems harvested at M1 were negatively impacted by all storage temperatures, whereas stems from M4 remained relatively unaffected by the storage temperatures, yielding marketable stems. This study should be extended to a wider range of Leucadendron cultivars across the harvesting season and in different production regions. Characterisation of the various harvest maturities was not achieved. Fluorescence as a rapid and non-destructive indicator for chilling jury showed promise, whereas the use of electrolyte leakage should be further explored for its application in post-harvest detection of chilling injury in Leucadendron. Further research into pre- and post-harvest factors that contribute to maintaining high product quality in Leucadendron cut flower stems for exports, is essential for overcoming the limitations associated with sea freight.

Grantor dc:publisher

Stellenbosch University

Year dc:date.issued

2025

Author dc:creator

• Van Zyl, Helena Maria

Advisors dc:contributor.advisor

• Hoffman, E. W.
• van Rensburg, K. L.

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/132295

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/132295