TIME OF HARVEST AND METHOD OF STORAGE AFFECT GRANULATION IN GRAPEFRUIT

Temporal studies were conducted from mid- to late-harvest season of 'R uby Red' grapefruit (Citrus paradisi Macf,) to evaluate the effect of on- and off-tree storage, fruit size, and juice vesicle position on th e development of granulation. Juice vesicle fresh and dry masses were highest at the stem and stylar positions of the fruit section and were not affected significantly by time of harvest or by storage. Juice ve sicles isolated from each position were subjectively evaluated for the presence of granulation. Granulation was highest in stylar juice vesi cles obtained from large fruit (approximate to 600 g) that were harves ted late in the season (March and May) and stored in air at 21 degrees C for 60 days. Large fruit harvested in March and May and examined im mediately, and fruit harvested in January and stored for 60 days had l ow granulation scores. Thus, fruit remaining on the tree until May are less susceptible to the disorder than those harvested in March and he ld in storage until May. Levels of alcohol-insoluble solids (AIS), lar gely composed of pectins and other cell wall materials, were significa ntly higher in juice vesicles that were granulated. The results sugges t that storage itself was not responsible for the marked accumulation of AIS in granulated juice vesicles. Rather, some interaction of fruit size with maturation, as well as other factors such as tree age and r ootstock, likely contributed to the development of granulation.