Reducing the variability of GA effect in sweet cherries

1. Reducing the variability of GA effect in sweet cherries PI: E.J. HOGUE Co-PI’s: Gerry Neilsen Denise Neilsen Shawn Kuchta Pacific Agri-Food Research Centre Summerland, BC.

2. 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.

3. 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.

4. 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

5. 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).

6. Timing trials on Lapins cherries, Kelowna.

7. Cherry cultivars, treatment and harvest dates at 2 Kelowna trial sites, 2008. Cultivar Treatment Applic. date Harvest Lapins Staccato Check Early Mid Late Check Early Mid Late --- June 12 June 17 June 20 --- June 26 July 3 July 12 July 28 July 28 July 28 July 28 Aug. 14/15 Aug. 14 Aug. 14/15 Aug. 14

8. Timing trials on Lapins cherries, Kelowna. Early Late (Early + 8 days) Mid (Early + 5 days)

9. The effect of a gibberellic acid treatment at different fruit maturity stages of Lapins sweet cherries, 2008. Treatment Rate GA (ppm) Fruit size (g/100 fruit) Firmnessy (g/mm) 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

10. 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.

11. Timing trials on Staccato cherries, Kelowna. Early • Mid • (Early + 7 days) Late (Early + 16 days)

12. The effect of a gibberellic acid treatment at different fruit maturity stages of Staccato sweet cherries, 2008. Treatment Rate GA (ppm) Fruit size (g/100 fruit) Firmnessy (g/mm) 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

13. 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.

14. Row 39 X X X X X X X X X Row 42 X X X X X X X X X Check, no GA Mid-pit, 30 ppm GA Fruit size (g/100 fruit) Treatment Check-No GA Grower-30ppm GA at mid-pit hardening 1015 az 1079 a zMeans within a column followed by the same letter are not significantly different at the 5% level 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.

15. Fruit size variability

16. Summary Gibberellic acid applied at the rate of 30ppm at early, mid or late pit hardening stages of fruit ripeningdid 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.

17. 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.

18. 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.

19. Acknowledgements • OKCGA • Co-operating grower • Ag-Canada’s Matching Investment Initiative