Spear height at harvest influences postharvest quality of asparagus (Asparagus officinalis)

Asparagus (Asparagus officinalis L.) spears harvested at intervals during a 24-h cycle exhibited a clear diurnal pattern in postharvest shelf-life, wi th spears harvested at 0200 h lasting 1.1 days longer at 20 degreesC than s pears harvested at 1400 h. Susceptibility to tip rot did not appear to fluc tuate with harvest time during the day, but was clearly influenced by time of season. Early season harvests were less susceptible to tip rot, and shor t spears (50 mm) were less susceptible than tall spears (250 mm). Tall spea rs had lower levels of soluble carbohydrate, and much greater proportions o f axillary bud tissue than short spears. First signs of tissue damage durin g tip rot development were observed in floral buds with collapse of the gen erative tissue. As damage increased, bracts, then vegetative buds, and the main stem axis were affected. Microbial growth developed on the surface of damaged tissue. Starch grains present in the stem axis or pith tissue disap peared within a day of harvest, but starch localised in a distinct band eig ht cells in from the cuticle remained until Day 5 after harvest. The postha rvest management of longer grades of asparagus spears will be more difficul t than shorter grades, and spears harvested in cool conditions will be high er quality than spears harvested in warm conditions.