Pears have been declining in popularity in recent years, but new blush varieties offer opportunities for an image makeover and a revival in fortunes. The physical appearance of a piece of fruit provides the all-important first impression on the consumer. When it comes to purchasing pears, one of the most critical physical attributes according to consumers, is colour. Understanding how colour is impacted by changing exposure to light is therefore key to making that all-important first impression – one that spares no blushes.
Red colour in pears
Red colour in pear skin is attractive and a highly-marketable trait, with the pigments responsible for red colour in fruit (anthocyanins) also known to exhibit a wide range of health benefits. New blush pear cultivars developed through the Australian National Pear Breeding Program (ANPBP) provide a chance to reinvigorate the pear market, both domestically and internationally — provided that there is adequate coverage and quality of red blush on the fruit at harvest. In order to maximise the economic viability of blush pears for the grower, Agriculture Victoria Research initiated a project through the Agriculture Infrastructure and Jobs Fund to better understand how and when pears develop red colour. While the underlying mechanisms of red colour development are well understood for apples, there is still a way to go with pears.
The role of light
Different pear cultivars are not uniform in their seasonal patterns of colour development and their colour responses to environmental stimuli. Light is either an absolute requirement for, or enhances the synthesis of, red pigments in fruit peel. However, high levels of solar radiation can induce the degradation of pigments due to high fruit surface temperatures. With 90 per cent of Australia’s pears currently grown in the high-light environment of the Goulburn Valley, Victoria, the response of new pear cultivars to solar radiation is of significant interest.
The quantity of light penetration in the tree canopy (and therefore the amount reaching the fruit) changes throughout the growing season. The growth of vegetative shoots results in shading and subsequent summer pruning leads to higher exposure. A preliminary experiment performed on the cultivar ANP-0534 demonstrated a highly dynamic response to the application of shade followed by sunlight exposure. Shading during the early and middle parts of fruit growth resulted in complete loss of red colour, with red colour restored within three weeks of re-exposure.
