Understanding the mechanisms responsible for postharvest tip breakdown in asparagus: a biochemical approach

The UK asparagus season is relatively short (from April to June), resulting in large quantities of spears being imported to provide year-round supply. Currently, asparagus quality can only be maintained for one week, plus seven days shelf-life, using cold storage alone. A limiting factor, which contributes significantly towards commercial losses, is the development of the postharvest physiological disorder tip breakdown (also known as tip rot). The disorder is characterised by darkening tips followed by the presence of water-soaked bracts at the tip of the spear and a foul odour. However, the underlying causes of tip breakdown have not yet been fully elucidated. We hypothesise that fast growth, slow rate of sugar transport and localised cell death may be key components of the mechanism. To gain more insight into tip breakdown development, two asparagus cultivars with low and high susceptibility to tip breakdown (‘Early California’ and ‘Aspalim’, respectively) were grown under controlled conditions and subjected to warm (28/14 °C) and cold (18/8 °C) day/ night temperatures. Harvested spears were subjected to shelf-life storage, 14 days at 7 °C, to subjectively assess early symptoms and further development of tip breakdown. Spears were snap frozen for subsequent biochemical analysis (viz. non-structural carbohydrates and plant growth regulators [PGRs]). Results showed that ‘Aspalim’ spears grown at warmer temperatures had higher incidence of tip breakdown than ‘Early California’. The relationship between incidence and severity of asparagus tip breakdown and the role of PGRs and sugar content during the season, as affected by genotype and growing conditions, are also discussed. The fundamental mechanistic understanding of asparagus tip breakdown will aid to implement optimum postharvest storage strategies to reduce food loss and the associated carbon footprint.

XV International Asparagus Symposium 2022

ISHS Acta Horticulturae