Biochemical changes in response to canopy position of avocado fruit (cv. 'Carmen' and 'Hass') during growth and development and relationship with maturity

摘要

In the current study, biochemical changes of avocado fruit cv. 'Carmen' and 'Hass' were evaluated during growth, development and maturation. The aim was to determine if exposure of fruit to sunlight could vary the biochemical compounds associated with maturity, and hence be among the causes of uneven maturity, and ripening. The current study also seeks to evaluate if the mesocarp C7 sugars, oil and DM content have a relationship with fruit maturity. The study was conducted in a commercial orchard at Everdon Estates in the KwaZulu-Natal, South Africa. Nine avocado fruit (cv. 'Carmen' and 'Hass' avocado) per canopy were sampled biweekly for assessment of mesocarp dry matter (DM), oil content, D-manno-heptulose, perseitol and total C7 sugars. The significantly (p < 0.001) higher DM and oil content in fruit that were sampled from the outside canopy in both cultivars suggested an early maturity, and vice versa inside canopy. The higher D-manno-heptulose and perseitol in fruit sampled inside canopy as a storage reserve was associated with the rate of respiration, which is slower inside canopy due to cooler temperatures. This results in accumulation of higher overall C7 sugars that are slowly used up as a substrates of respiration for synthesis of overall DM, oils, proteins, C6 sugars and other biochemical constituents associated with ripening. In terms of maturity, higher D-manno-heptulose and perseitol implies that fruit from the inside canopy will take longer to mature and to reach edible ripeness when harvested. This then causes uneven maturity of fruit, only characterized by uneven ripening.