Crop Load and Time of Thinning Interact to Affect Fruit Quality in Sweet Cherry

Sally A Bound,Penelope F Measham,Dugald C Close,Matthew D Whiting,Audrey G Quentin

doi:10.5539/jas.v5n8p216

Sally A Bound, Penelope F Measham + Show 3 more

Open Access

https://doi.org/10.5539/jas.v5n8p216

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Abstract

Balanced crop load is key to the production of export-quality cherries. We investigated the level and timing of crop load regulation on fruit quality. Additionally we sought to investigate possible correlation between firmness estimated by compression test or flesh penetrability. Fruit diameter was similar between 1 and 2 bud/spur treatments but was significantly lower in the 4 bud/spur treatment at all thinning times in ‘Van’ in the 2010/11 season. In contrast ‘Sweetheart’ fruit diameter was only decreased at 6 and 8 WAFB in the 4 bud/spur treatment in 2010/11. This decrease in ‘Sweetheart’ was associated with significantly higher soluble solids and starch reserves in leaves, stem, trunk and roots 2-weeks post-harvest in trees thinned at dormancy, relative to trees thinned 8 WAFB. Fruit flesh firmness significantly increased with decreased crop load irrespective of time of thinning in ‘Van’ in 2010/11. In contrast flesh firmness was significantly higher in the 1 bud/spur treatment and similar between other treatments in ‘Sweetheart’ in 2010/11. In 2011/12 flesh firmness, soluble solids and colour significantly increased whilst fruit weight and TA significantly decreased 28 days post-harvest relative to at-harvest values. We found strong correlation between values obtained with the FirmTech II and the Guss fruit texture analyser. Sweet cherry fruit quality is optimised through attaining crop load of approximately 10 fruit per cm2 of limb cross-sectional area through thinning at dormancy or full bloom.

Highlights

Sweet cherry is a high value crop where quality can attract significant premiums
Natural fruit set in the second season (Trial 3) was very low; thinning to 2 buds/spur in this trial reduced crop load to approximately 50% of the natural set (Figure 1, Table 1)
The bud thinning technique employed resulted in a wide spread of crop loads, and is superior to the use of ammonium thiosulfate (ATS) sprays

Summary

Introduction

Sweet cherry is a high value crop where quality can attract significant premiums. High grower returns are important for economic sustainability in countries with high production costs. Due to premium returns in export markets, sweet cherry fruit from Australia are shipped overseas. Ensure the retention of fruit quality, in overseas markets, growers must deliver large, firm fruit with high sugar levels. Regulation of crop load can be achieved by several methods: hand-thinning, chemical thinning, mechanical thinning, artificial spur extinction (removal of complete spur from the branch; Ayala & Andrade, 2009) or bud thinning. Whiting and Lang (2004) reported a reduction in yield and increase in fruit size, firmness and sugar content in the ‘Bing’ variety on dwarfing Gisela 5 rootstock trained to a free-standing, multiple leader open-centre system, Ayala and Andrade (2009) saw no response to spur thinning in ‘Lapins’ on the www.ccsenet.org/jas There is conflicting evidence on the impact of spur extinction and bud thinning on fruit quality and yield. Whiting and Lang (2004) reported a reduction in yield and increase in fruit size, firmness and sugar content in the ‘Bing’ variety on dwarfing Gisela 5 rootstock trained to a free-standing, multiple leader open-centre system, Ayala and Andrade (2009) saw no response to spur thinning in ‘Lapins’ on the www.ccsenet.org/jas

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