1. Improving fruit set of ‘Kordia’ and ‘Regina’ sweet cherry with AVG
 XII International Symposium on Plant Bioregulators in Fruit Production Orlando, Florida USA  28 July - 1 August 2013
Improving fruit set of ‘Kordia’ and ‘Regina’ sweet cherry with AVG
Sally Bound1, Dugald Close1, Matthew Whiting2
1Perennial Horticulture Centre, Tasmanian Institute of Agriculture, University of Tasmania, Australia
2Washington State University, Prosser, USA
This project has been funded by HAL using the cherry industry levy, voluntary contribution from the Washington Tree Fruit Research Commission and matched funds from the Australian Government

2. Australian Cherry Industry
2012/13
Total production = 15,500 t
Exported = 3,256 t
59% (1,920 T) from Tasmania

3. Background Tasmania largest production state*
2,000 T in 2006/07 to 5,000 T (87% packout) in 2012/13
High quality reflected in price: Tas $13/kg vs other states $8/kg**
Export to > 20 countries - freedom from fruit fly
Vigorous rootstocks: Mazzard F12/1 and Colt
Main varieties: Lapin, Simone, Sweetheart, Sylvia, Regina, Kordia, Sweet Georgia
Regina and Kordia difficult to set fruit
Industry grown from 2,000 T in 2006/07 to 5,000 T (=87% packout) in 2012/13 – largest production state*
High quality reflected in price: Tas $13/kg vs other states $8/kg**
Driven by export markets in Taiwan, Hong Kong (Chinese New Year) , Singapore, China, Malaysia (freedom from fruit fly)
Kym Green Bush (KGB) training system of uprights (better IRR as no trellis and easy to prune) on vigorous rootstocks, Colt and Mazzard F12/1
Main varieties: Lapin, Simone, Sweetheart, Sylvia, Regina, Kordia, Sweet Georgia
Regina and Kordia difficult to set fruit under Tasmanian conditions
Mainland growers have better success with dwarfing Gisela rootstocks, but access to these is limited in Tas
* Fruit Growers Tasmania
**Horticulture Australia Market Intelligence report

4. Objective
to investigate the efficacy of Retain® (S)-trans-2-amino-4-[2-aminoethoxy]-3-butenoic acid hydrochloride (AVG) for improving fruit set on ‘Kordia’ & ‘Regina’

5. Methods – trial design Two trials: Kordia 2011/12 Regina 2012/13
Design: RCB with 5 replicates single tree plots
Treatments: 3x2 factorial + untreated control
3 application times single application at 30% or 80% bloom, or double application at 30 & 80% bloom
2 rates or 750 g Retain/ha (Kordia) or 1,000 g Retain/ha (Regina)

6. Methods – treatment application
Retain applied to whole trees by hydraulic hand lance
1 L spray per tree as a fine mist
Retain application
Kordia
Regina
30% bloom
3 Oct 2011
6 Oct 2012
80% bloom
10 Oct 2011
11 Oct 2012
(Full bloom date)
11-12 Oct 2011
13 Oct 2012
organosilicone surfactant Maxx™ added to spray solution at label rate of 0.5 mL/L in ‘Kordia’
no surfactant used in the ‘Regina’ orchard

7. Methods – assessments two limbs per tree tagged & girthed
flowers and fruit set counted on each tagged limb
tagged limbs harvested individually
fruit number & weight recorded
% cracked fruit
subsample of 25 fruit from each limb for quality analysis
Assessments
Kordia
Regina
(Full bloom date)
11-12 Oct 2011
13 Oct 2012
Bud/flower counts
11 Oct 2011
8 Oct 2012
Fruit set counts
18 Dec 2011
6 Nov 2012
Trial harvest
9 Jan 2012
14 Jan 2013
Flower counts
Fruit set counts

8. Methods – quality assessments
weight
size (diameter and height)
skin colour
flesh firmness (BioWorks Firmtech & Guss FTA)
skin puncture
stem pull force
total soluble solids pH
titratable acidity

9. Results: Fruit set Kordia - 3 weeks before harvest
Regina - 10 weeks before harvest
No significant differences for
- Retain rate, or
- time of application (30% bloom, 80% bloom or 30 & 80% bloom

10. Results: Fruit set / spur
Kordia
Regina
No significant differences for
- Retain rate, or
- time of application (30% bloom, 80% bloom or 30 & 80% bloom

11. Results: % cracked fruit
Kordia
Regina
No treatment effect
- minimal cracking in 2012/13 due to dry season
2011/12 was a very wet season and there were major problems with fruit cracking,
but Retain treated trees showed significantly less cracked fruit than controls, reducing the incidence of rain-cracked fruit from 25% to 14% in the ‘Kordia’ orchard.
The 2012/13 season when the Regina trial was conducted was a dry season and there was very little cracking.
44% reduction in cracking with Retain
No significant differences for
- Retain rate (500 or 750 g/ha), or
- time of application (30% bloom, 80% bloom or 30 & 80% bloom)

12. Results: Fruit weight Kordia Regina
No sig difference between Retain treated and control
In the Regina trial Retain had no effect on fruit weight,
but weight was lower in the Kordia fruit by 1.6 g
Fruit weight lower in Retain treatments

13. Results: Fruit weight Kordia Regina
In both cultivars the higher rate of Retain reduced fruit weight by
approx 0.5 g
Higher rate reduced fruit weight in both varieties

14. Results: Fruit weight Kordia Regina Double application reduced weight
No difference with application time
The double application of Retain reduced fruit weight by
0.8 g compared with the early application and
1.5 g compared with the 80% bloom application.
Application time had no effect on Regina fruit weight.
Double application reduced weight

15. Results: Fruit size Kordia Regina
Kordia Control fruit were 1.3 mm larger in diameter than Retain treated
But in Regina, Retain improved fruit size slightly (0.25 mm)
Untreated Kordia fruit were approx 3.2 mm larger than Regina
Conflicting results between 2 varieties

16. Results: Fruit size Kordia Regina
Fruit diameter was reduced by the higher Retain rate in both varieties
Higher rate reduced fruit size in both varieties

17. Results: Fruit size Kordia Regina
The double application reduced fruit diameter by 0.7 mm cf 30% bloom application and 1.5 mm cf 80% bloom application in the Kordia
But had no effect in Regina. The difference between the double application and 30% bloom was 0.4 mm
Double application reduced size in Kordia but not Regina

18. Results: Fruit flesh firmness
Kordia
Regina
Fruit flesh firmness results differed for the two varieties
In Kordia, Retain treated fruit were firmer
But softer in Regina
Firmness of untreated was similar in both cultivars
Conflicting results across 2 varieties

19. Results: Fruit flesh firmness
Kordia
Regina
The higher Retain rate reduced firmness in both varieties
Higher Retain rate reduced firmness in both varieties

20. Results: Fruit flesh firmness
Kordia
Regina
Double application highest firmness in both varieties

21. Results: Fruit skin puncture
Kordia
Regina
Retain application increased skin strength in Kordia
but had no effect on Regina fruit
Higher application rate reduced skin strength in Regina, but application rate was not significant in the Kordia
Retain increased skin strength in Kordia but not in Regina
Higher application rate reduced skin strength in Regina

22. Results: Stem pull force
Kordia
Kordia
Stem pull force of Kordia fruit was lower in retain treated fruit cf the control fruit
The double application also resulted in reduced stem pull force
but Rate had no effect
Similar trends were observed in the Regina but they were not significant
No significant differences for
- Retain rate (500 or 750 g/ha)
Similar trends in Regina but not significant

23. Results: other quality parameters
Retain had no effect on:
- TSS
- juice pH
- titratable acidity
- skin colour

24. Conclusions
Positive effects were observed on fruit set % fruit set increase in Kordia % fruit set increase in Regina
Reduction in fruit cracking
Inconsistencies in fruit weight, diameter & firmness
Reduction in stem retention
No effect on other quality parameters
Conclude that Retain is beneficial, but need to clarify effect on size and firmness
Retain applications increased fruit set by 57% in ‘Kordia’ and 33% in ‘Regina’, compared to untreated control trees.
We found no significant differences between the two application rates, nor was there any effect of application timing.
In the ‘Kordia’ orchard we recorded a slight (4.4%) reduction in fruit diameter in the Retain-treated trees. The double application also reduced size by 3.7% compared with a single application (p<0.01). However fruit size was increased slightly (2%) by the lower, but not the higher, rate of Retain in the ‘Regina’ trial (p<0.001).
Retain reduced the incidence of rain-cracked fruit from 25% to 14% in the ‘Kordia’ orchard.
Fruit firmness in ‘Kordia’ was significantly higher in the Retain-treated fruit than the control fruit (7%),
but stem retention force was reduced by 16%.
This work has demonstrated that Retain may be useful for improving fruit set (yield) in sweet cherry cultivars that are chronically low-yielding.
Further work is needed to substantiate these results in different production regions and clarify the effect of Retain on fruit firmness.

25. Thanks to…… Steve Paterson and Justin Direen for technical support
Nic Hansen from Cherries Tasmania for use of trees
Horticulture Australia and the Australian cherry industry for funds
Valent BioSciences for provision of Retain