Preharvest Foliar Salicylic Acid Sprays Reduce Cracking of Fig Fruit at Harvest

Abstract

Peel cracking and ostiole-end splitting (collectively termed cracking) are common disorders in ripe fig fruit, downgrading fruit quality and thus limiting marketability. This two-year field study addressed the possibility of alleviating cracking at harvest by two foliar salicylic acid (SA) sprays prior to harvest (8 and 5 d). Three SA concentrations (0, 1, and 2 mM) were employed in the first year, and based on the obtained results two (0 and 2 mM) in the second year. A local variety (‘Vasilika’) with excellent organoleptic profile, and high sensitivity to cracking was evaluated. Fruit was harvested at commercial maturity. Fruit marketability was mainly based on the incidence and severity of cracking. Fruit weight, peel color, flesh total soluble solids (TSS), titratable acidity (TA), and pH were estimated for fig quality. The contents of total anthocyanins (TAN), cyanidin-3-rutinoside (c-3-rut; the major anthocyanin in fig), and the expression of four genes coding for regulatory enzymes (phenylalanine ammonia lyase, anthocyanidin synthase, UDP-flavonoid glucosyl transferase 1, and UDP-flavonoid glucosyl transferase 2) of the phenylpropanoid biosynthetic pathway were also determined in the peel. Preharvest SA application (2 mM) increased the percentage of fruit without cracking (sound fruit) by 1.4–2.6-fold, and of marketable fruit (sound and slightly cracked) by 2-fold. SA application (2 mM) was associated with increased flesh TSS and TA, as well as with decreased flesh pH and peel red coloration in stripe. The treatment (2 mM SA) decreased both TAN and c-3-rut contents, which were highly associated (r = 0.978). Responses of transcription level of the four genes to SA application varied, and did not correlate with the other variables in the study. In conclusion, SA appears to be a low-cost and environmentally-safe agent for improving fig fruit quality and marketability, and facilitates harvesting and postharvest management of figs.

Keywords

• <i>Ficus carica</i>
• fruit cracking
• peel color
• PAL gene expression
• flesh total soluble solids