Projects

Protea cut flowers are popular internationally but suffer from leaf blackening, a postharvest disorder causing consignment rejection. To avoid this, stems are often exported leafless, losing the foliage’s nutritional support. The shift from air to sea freight exposes stems to longer transport, worsening issues like chilling injury and leaf blackening. Solutions require innovative postharvest treatments based on physiological understanding, prioritizing cooling to reduce respiration. Research into leaf blackening genetics could enable future resistant cultivars, helping South Africa maintain and expand its market share.  Objectives included 1)  To evaluate the use of DCA technology and ILOS for the control of blackening in Protea; 2)  To evaluate the use of an ethanol enzymatic assay for the determination of low levels of internal ethanol which can be effective in inactivating enzymes and/or phenolic reaction that may be causal to leaf blackening; and 3) To characterize the phytochemical profiel of Protea species and hybrid cultivars with the aid of liquid chromatography-ion mobility mass spectrometry with the aim to isolate and study specific metabolites that may serve as a marker for leaf blackening.

The aim of this study was to gain better understanding of pre- and post-harvest factors that contribute to maintenance of high product quality in Leucadendron cut flower stems during long-term cold storage conditions, as required for export, and to provide valuable information to the Cape Flora SA industry. The objectives of this study were to simulate long-term storage of a range of Leucadendron cultivars and determine the optimum storage regime; to establish and characterise different harvest maturity categories for Leucadendron and to evaluate the effect of different harvesting maturities on the development of chilling injury of Leucadendron.

The project aimed to obtain a better understanding of the postharvest physiology and carbohydrate metabolism of Protea cut flower stems that are susceptible to the postharvest disorder, leaf blackening – to improve on current pulsing techniques and/or to develop new innovative postharvest treatments to maintain product quality for the extension of vase life. The efficacy of numerous pulsing reagents was tested: water (control), glucose (industry standard), trehalose, lactulose, ascorbic acid, glycine betaine, amino butyric acid (GABA), sodium nitroprusside (SNP), and nectar biosynthesis inhibitors (cycloheximide and chloramphenicol).