More research is required to better understand the underlying genetics and biochemical pathways for red pigment (i.e. anthocyanin) development in the skin of full red (FR) and blush (B) pear cultivars. Until this knowledge builds, there are limited options in the orchard that can be recommended for growers to manipulate blush levels.
Blush development is restricted when fruit are not exposed to light. In the orchard, dappled sunlight should reach the ground at all times as an indicator of good light penetration through the canopy. Canopy training and pruning methods should open the foliage for light exposure.
Maintaining canopies to allow maximum light exposure is not difficult but foliage thinning can have the counter-effect of exposing fruit surfaces to excess radiation, thereby increasing skin temperature, accelerating anthocyanin degradation and raising incidence of fruit sunburn.
Figures 1 and 2
A red blushed pear selection (Ricō®, previously known as Deliza®) from the Australian National Pear Breeding Program (Tatura) that was grown under nets and photographed on 19 January (figure 1) and 23 February (figure 2). Fruit surface temperature was measured using a fine wire thermocouple inserted just below the skin. This particular fruit was well exposed resulting in progressive blush development through the final weeks up to harvest. Reduction of direct solar radiation by netting prevented excessive rises in skin temperature which can cause sunburn.
Where a leaf has heavily shaded the top right of this pear, blush has not developed – emphasising the importance of appropriately balanced light levels.
Part 1 Light and Temperature
Graeme Thomson1, Lexie McClymont2 & Ian Goodwin2
1AgriBio Centre, 5 Ring Road, La Trobe University Campus - Bundoora, Victoria 3083, Australia
2Horticulture Centre of Excellence, Private Bag 1, Tatura, Victoria 3616, Australia.
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