Orchard practices

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.

Figure 1

Figure 2

Figures 1 and 2

A red blushed pear selection (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

Acknowledgements

Graeme Thomson1, Lexie McClymont2 & Ian Goodwin2

Department of Economic Development, Jobs, Transport & Resources.

1AgriBio Centre, 5 Ring Road, La Trobe University Campus - Bundoora, Victoria 3083, Australia

2Horticulture Centre of Excellence, Private Bag 1, Tatura, Victoria 3616, Australia.

References

Dussi MC, Sugar D, Wrolstad RE (1995) Characterizing and quantifying anthocyanins in red pears and the effect of light quality on fruit color. J Amer Soc Hort Sci. 120(5):785-789.

Dussi M C, Sugar D, Nina Azarenko A, Righetti TL (1997) Effects of cooling by over-tree sprinkler irrigation on fruit color and firmness in ‘Sensation Red Bartlett’ pear. HortTechnology January-March 1997, 7(1): 55-57.

Roberts SC, Steyn WJ, North MS (2008) Effect of rootstock on red colour of bi-coloured ‘Forelle’ pears. Proc. Xth IS on Pear Eds.: A.D. Webster and C.M. Oliveira Acta Hort. 800, ISHS 2008 pages 625-630.

Steyn WJ, Holcroft DM, Wand JE, Jacobs G (2004) Anthocyanin degradation in detached pome fruit with reference to preharvest red color loss and pigmentation patterns of blushed and fully red pears. J Amer Soc Hort Sci. 129(1):13-19.

Steyn WJ, Wand SJE, Holcroft DM, Jacobs G (2005) Red colour development and loss in pears. Proc. IXth IS on Pear Ed.: K.I. Theron, Acta Hort. 671, ISHS 2005, pages 70-85.

Wand SJE, Steyn WJ, Holcroft DM, Mdluli MJ, van den Dool K, Jacobs G (2005) Use of evaporative cooling to improve ‘Rosemarie’ and ‘Forelle’ pear fruit blush colour and quality. Proc. IXth IS on Pear, Ed.: K.I. Theron. Acta Hort. 671, ISHS 2005, pages 103-111.