A SUMMARY OF FACTORS INFLUENCING THE SUSCEPTIBILITY OF COLD STORED RED GLOBE TABLE GRAPES TOSO_2 DAMAGE

摘要

Of all the table grape cultivars currently exported from South Africa, Red Globe is by far the most susceptible to SO_2 damage (Figure 1). Compared to other post storage disorders that manifest on Red Globe grapes, SO_2, damage typically has the highest occurrence. The determination of those factors influencing the occurrence of this disorder, will contribute to improving Red Globe's post storage quality. During the 2003 and 2004 seasons, the following factors were investigated to establish the influence on Red Globe's susceptibility to SO_2 damage: (a) harvest maturity, (b) application of gibberellic acid (GA_3), (c) type of outer bag used for storage of GA_3 treated grapes, (d) wetters used with GA_3 applications, (e) berry colour and (f) packingafter rain. In all trials, Red Globe's quality was evaluated after eight weeks storage at -0.5°C and four days at 7.5°C. In both seasons, Red Globe grapes were harvested at three harvest dates, with biweekly intervals between them. In both seasons theoccurrence of post storage berry split decreased significantly with increased maturity. This could possibly be attributed to a more advanced epidermis and cuticle development, which would enhance the resistance of the grapes to splitting. Typically all split berries exhibit SO_2 damage, and therefore SO_2 damage associated with split berries can be reduced with increasing harvest maturity. In 2003, the more mature grapes showed significantly more stem desiccation and SO_2 damage around the pedicel end of berries than less mature grapes. SO_2, damage confined to the pedicel attachment area is most probably related to moisture loss in this area.