ISHS Acta Horticulturae 464: International Postharvest Science Conference Postharvest 96
CHANGES IN PROTEIN PROFILES IN RELATION TO MATURITY IN PLUMS |
| Authors: | N. Abdi, W.B. McGlasson, P. Holford, Y. Mizrahi |
| Abstract:
The objective of this study was to develop molecular markers which can be used as indicators of fruit maturity in plums. To achieve this goal the changes in protein synthesis which occur during fruit growth and ripening were investigated in two cultivars of plums: ‘Gulfruby’ (typical climacteric type) and ‘Shiro’ (slow ripening type). Fruit were harvested at weekly intervals from pit hardening and stored at 20°C at high RH. Changes in the rates of respiration and ethylene production, skin colour, firmness, soluble solids and titratable acidity were determined at each harvest. Proteins were purified from these cultivars and separated by 2-dimensional gel electrophoresis to look for correlation between gene expression and the ripening process. ‘Gulfruby’ demonstrated a clear, climacteric pattern of respiration and ethylene production. ‘Shiro’ has a slow ripening behaviour with a weak climacteric type of behaviour. In ‘Gulfruby’, changes in skin colour and firmness were associated with the climacteric. In contrast, ‘Shiro’ ripened slowly, and changes in skin colour and firmness preceded the climacteric. In ‘Gulfruby’ the aroma volatiles increased gradually throughout the ripening period, whilst in ‘Shiro’ their production was associated with increased ethylene production. Therefore, in ‘Gulfruby’ the fruit becamé acceptable to a consumer following the climacteric whilst in ‘Shiro’ this occurred before the climacteric. Differences in protein profiles have been found in both cultivars during the pre- and post-climacteric stage. In ‘Gulfruby’ some new polypeptides were detected during 25, 29 and 32 days after pit hardening (DAPH). Comparison of these protein profiles to those from fruit harvested at preclimacteric stages (14 and 21 DAPH) suggested that polypeptides with molecular weights between 20 to 40 kD may be related to the ripening process. From these observations, ‘Gulfruby’ plums begin to ripen at 25 DAPH. Changes in proteins of 25 to 43 kD were observed in ‘Shiro’, suggesting this cultivar began to ripen at 45 DAPH. Further work will determine if these patterns can be correlated with optimum harvest maturity. It may be possible to develop maturity markers in plums based on these findings. | |
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