Reducing the variability of GA effect in sweet cherries

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Reducing the variability of GA effect in sweet
cherries
PI E.J. HOGUE Co-PIs Gerry
Neilsen Denise Neilsen Shawn Kuchta
Pacific Agri-Food Research Centre Summerland, BC.
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Objectives for 2008 season
1. Carryout at least two trials on reduced
application water volume, a detailed one at the
Summerland Research Centre site and a cooperative
trial in a grower orchard using grower
application equipment. The former would involve
the use of organosilicone surfactants. 2.
Conduct exploratory trial(s) with RETAIN
(aminoethoxy-vinylglycine) to evaluate its
potential as a complement to gibberellic acid in
increasing cherry fruit firmness and delay of
maturity.
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Rationale for Objectives revision
1.Equipment to apply precise water volumes to
single tree plots was not available. 2.Recently
published research reports indicated that
organosilicone surfactants affected
photosynthesis of fruit trees. 3.Survey of the
literature indicated RETAIN to be ineffective on
non-climacteric fruit species.
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Factors affecting cherry fruit size and firmness.

• There are approximately a dozen factors that
  influence fruit size, of which we considered four
  GA factors
• Application water volume
• Rate of single application
• Single vs. multiple applications
• Timing of single application

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Revised objectives for 2008 season
1. Timing of GA application on Lapins in grower
orchard, with grower application. 2. Timing of
GA application on Staccato in grower orchard,
with grower application. 3. Split applications at
variable rates in Lapins at Summerland Research
Centre site (later cancelled because of crop
failure).
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Timing trials on Lapins cherries, Kelowna.
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Cherry cultivars, treatment and harvest dates at
2 Kelowna trial sites, 2008.
Cultivar
Treatment
Harvest
Applic. date
Lapins Staccato
Check Early Mid Late Check Early Mid Late
July 28 July 28 July 28 July 28 Aug. 14/15 Aug.
14 Aug. 14/15 Aug. 14
--- June 12 June 17 June 20 --- June 26 July
3 July 12
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Timing trials on Lapins cherries, Kelowna.
Early
Late (Early 8 days)
Mid (Early 5 days)
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The effect of a gibberellic acid treatment at
different fruit maturity stages of Lapins sweet
cherries, 2008.
Rate GA (ppm)
Fruit size (g/100 fruit)
Firmnessy (g/mm)
Treatment
Stem pullx (kg)
0.63 a 0.68 a 0.66 a 0.75 a
Check Early Mid Late
--- 30 30 30
1115 az 1224 a 1175 a 1204 a
331 a 389 b 344 b 356 b
zMeans within a column followed by the same
letter are not significantly different at the 5
level yFirmness as measured by the Bioworks Firm
Tech 2 fruit firmness tester xStem pull as
measured by the DART Digital Force Gauge
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Results of GA application to Lapins at different
maturity stages in 2008

• Fruit size
• No fruit size increase at any stage.
• 2. Fruit firmness
• Increased fruit firmness at all 3 stages.
• 3. Stem pull force
• No effect on force required to remove stems at
  any treatment stage.

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Timing trials on Staccato cherries, Kelowna.
Early

• Mid
• (Early 7 days)

Late (Early 16 days)
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The effect of a gibberellic acid treatment at
different fruit maturity stages of Staccato sweet
cherries, 2008.
Rate GA (ppm)
Fruit size (g/100 fruit)
Firmnessy (g/mm)
Treatment
Stem pullx (kg)
0.76 a 0.76 a 0.73 a 0.68 a
Check Early Mid Late
--- 30 30 30
1046 az 1056 a 1030 a 992 a
414 a 458 b 469 b 476 b
zMeans within a column followed by the same
letter are not significantly different at the 5
level yFirmness as measured by the Bioworks Firm
Tech 2 fruit firmness tester xStem pull as
measured by the DART Digital Force Gauge
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Results of GA application to Staccato at
different maturity stages in 2008

• Fruit size
• No fruit size increase at any stage.
• 2. Fruit firmness
• Increased fruit firmness at all 3 stages.
• 3. Stem pull force
• No effect on force required to remove stems at
  any treatment stage.

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Second harvest of Staccato Plot area
The effect of a gibberellic acid application at
mid-pit hardening in grower orchard on fruit size
of Staccato sweet cherries, 2008.
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Fruit size variability
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Summary

• Gibberellic acid applied at the rate of 30ppm at
  early, mid or late pit hardening stages of fruit
  ripening did not increase the size of either
  Lapins or Staccato cherries.
• Gibberellic acid applied at 30ppm at early, mid
  and late pit hardening stages of fruit ripening
  increased fruit firmness of both Lapins and
  Staccato cherries.
• Gibberellic acid application at all three pit
  hardening stages of fruit ripening had no
  significant effect on the force required to
  remove stems from Lapins and Staccato.

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Conclusions

• The lack of statistically significant fruit size
  increase and increase of stem retention capacity
  with gibberellic acid treatment appeared to be
  related to an abnormally high degree of fruit
  size variability caused by early season climatic
  conditions (Neilsen report).
• Statistically significant increase in cherry
  fruit firmness was a confirmation of previous
  experience with GA treatments. Sweet cherry
  firmness is the most sensitive response to GA,
  followed by fruit size.

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Conclusions
3. The firmness response of the 2 varieties
indicated a definite economic benefit from the
use of gibberellic acid even in a season with
adverse conditions to fruit size increase. 4.
The range in fruit size in research samples of
treated and non-treated fruit indicated that
adjustments of statistical design of the trial
may have been warranted.
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Acknowledgements

• OKCGA
• Co-operating grower
• Ag-Canadas Matching Investment Initiative