ASPECTS OF DELAYED HARVEST OF HASS AVOCADO (PERSEA-AMERICANA MILL) FRUIT IN A COOL SUBTROPICAL CLIMATE .1. FRUIT LIPID AND FATTY-ACID ACCUMULATION

In the cool, mesic, subtropical Natal midlands, where delayed harvesti ng of 'Hass' avocado fruit was practised, fruit lipid levels on a dry- mass basis peaked in September 1991 and August 1992 at the cooler site and October 1991 and September 1992 at the warmer site. In subsequent months lipid levels decreased at the warmer site. These observations suggest that under the experimental conditions, late hanging into the following season was not strongly detrimental to the following crop an d may even be beneficial if fruit lipids are a partially mobile energy source, which may be utilized during periods of peak demand such as f lowering, fruit set and shoot flushing. Fatty acid levels, dominated b y the monounsaturated oleic acid, did not vary significantly with late hanging, and were very similar in the two sites in the cool Natal mid lands. However, compared with fruit harvested in late August in the no rth-eastern Transvaal, total monounsaturated fatty acid levels were so me 10% higher. These findings are discussed with respect to the health aspects of the avocado. Attempts at modelling monounsaturated fatty a cid levels were unsuccessful as levels differed significantly in diffe rent months.