The efficacy of γ-aminobutyric acid (GABA) as a postharvest treatment in Protea, to enhance vase life and maintain quality

Protea cut flowers are commercially important and are often transported to international markets for extended periods of time (e.g., one to three weeks via shipping). These periods have a significant effect on the postharvest quality and vase life of these products. Low temperature storage is often used as a postharvest treatment to delay the inflorescences from opening and to maintain quality. During the warm, dry season in the Western Cape, the bracts of the inflorescence of some Protea cultivars are prone to curl inward and appear desiccated, affecting quality and vase life. In addition, preharvest conditions such as heat stress contribute to increased levels of leaf blackening, a common postharvest disorder in Protea. γ-Aminobutyric acid (GABA) is believed to accumulate in plants and horticultural crops during abiotic stress such as heat, drought and low oxygen, and enhances resistance to these stresses. GABA has been widely used for other cut flowers to alleviate chilling injury, spate browning and retard electrolyte leakage. As such, we tested the efficacy of GABA in two Protea cultivars, 'Sylvia' and 'Pink Ice'. GABA was applied in a range of concentrations as a 2-3 h pulsing treatment. Glucose was included as a treatment as it is used as a postharvest treatment in the Protea industry and water was used as the control. Stems were evaluated over an 11-day period and scored for flower quality and leaf blackening. Results show that the incidence of leaf blackening decreases with increasing concentrations of GABA in 'Sylvia' although the effect of the glucose is more significant to control blackening. In 'Pink Ice'the level of blackening in glucose and 20 mM GABA-pulsed stems were the same by day 11. A better flower quality was observed for both cultivars, in stems pulsed with GABA. GABA can therefore be considered as a potential technology for enhancing tolerance of high temperatures and hot, dry conditions, and reduce leaf blackening in Protea.