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Apple Flowering and Fruit Quality

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A presentation I delivered at the 2017 IFTA Annual Conference in Wenatchee, WA. This covers the basics of floral initiation in apple and causes of variability in fruit quality.

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Apple Flowering and Fruit Quality

  1. 1. Matthew Whiting Washington State University APPLE FLOWERING & FRUIT QUALITY
  2. 2. Flowering & quality: • Broad topic – Genotype – Environment – Management 1. Initiation 2. Pollination 3. Fruit quality
  3. 3. Floral initiation to fruit harvest Initiation Differentiation Dormancy Flowering Fertilization Fruit growth
  4. 4. Floral initiation • First step in processes of flowering and fruit development • Evolutionary mechanism through which plant distributes seed • Manipulated by growers for profit – Sequence of events – When, where, why
  5. 5. Floral initiation • Flower initials formed within buds – Summer and Fall – A 15-month process • Buds either vegetative or mixed
  6. 6. Floral initiation • Floral buds typically borne on spurs – 2-year-old and older wood • Lateral buds on current season shoot – Cultivar-dependent • Terminal buds on shoots
  7. 7. Initiation of flowering • Transformation of vegetative apex to reproductive apex • Can occur on same tree at widely varying times – Not triggered by specific temp or daylength
  8. 8. Initiation of flowering • Key factors interfering: – Hormonal balance – Availability of nutrients (CH2O in particular) – Interaction of these – Others…..
  9. 9. Floralinitiation Scanning Electron Microscopy Foster et al., 2003 Annals of Bot. 92:199-206 V: Narrow, flat V: Broad, flat R: Domed
  10. 10. Foster et al., 2003 Annals of Bot. 92:199-206 FM – floral meristem B – bract tFM – terminal FM S – sepal
  11. 11. Factors affecting flowering • Fruit load – Heavy cropping will inhibit FBI – Creates biennial/alternate bearing – Excessive crop ‘on’ year leads to light crop ‘off’ year – Effect is local • Half trees can be ‘on’ or ‘off’ • Effect may be more localized – spur only – Thought to be GAs produced in seeded fruit + nutritional
  12. 12. Factors affecting flowering • Light
  13. 13. Uniform flowering in UFO system
  14. 14. Factors affecting flowering • Genotype • Both cultivar and rootstock have great effect Growth regulators – GAs inhibit FBI (GA3 and GA7) – Cytokinins promote FBI • Pruning – High vigor = lower FBI – Summer pruning can improve FBI (ca. 12 lvs)
  15. 15. Dormant hedging “Setting the box” to be followed with summer pruning
  16. 16. Dormant cut made first Summer cut summer cut (see next floral bud) Summer cut Mechanical pruning in summer (10-12 lvs)
  17. 17. Dormant cut Summer cut Floral bud
  18. 18. Floral initiation • Critical first step to productivity • Controlled by developmental processes, endogenous and exogenous factors • May be manipulated for profit – Goal: consistent, balanced floral initiation
  19. 19. Fruit set/fertilization • Pollination • Mediated by Apis mellifera • Pollenizers + pollinators • Fertilization – 5 locules – 10 ovules – Seed set
  20. 20. Pollenizer + pollinator model • Apple requires cross-pollination • Gametophytic incompatibility – Know your S-alleles and bloom timing…...
  21. 21. Fruit set • Trees produce 10-15x more flowers than desirable fruit number/tree • Cell division reduced if too many fruit = small fruit • Critical to adjust fruit numbers early – Benefits fruit size, current season – Benefits bloom, subsequent season
  22. 22. • Insufficient density/distribution • Lack of overlapping bloom • Distribution of pollen born viruses • Harboring pests/diseases No bloom overlap Pollenizers Challenges with P+P model:
  23. 23. • Colony collapse disorder • Increasing cost • Variable colony performance • Distribution & density • Variable environmental conditions Pollinators Challenges with P+P model:
  24. 24. Proposed solution: 1. Collect pollen 2. Suspend pollen 3. Apply pollen via sprayer No pollenizers nor pollinators
  25. 25. Precision pollination ‘Tieton’/ ‘Gisela 5’: 8 years old trained to UFO
  26. 26. Future pollination system?
  27. 27. Fruit quality variability
  28. 28. Fruit Value/Consumer Appeal Genetic Potential Ideal management NumberofFruit Conventional management The ultimate goal:
  29. 29. • Three key questions: 1. By how much does fruit quality vary? 2. What are sources of this variability? 3. How can variability be reduced/improved?
  30. 30. 3rd leaf Fuji – 0.8 x 3 m Defoliated trees Mapped fruit position Mapped wood
  31. 31. 15 yr old Fuji 2.5 x 4 m
  32. 32. 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 10 12 14 16 18 20 tree1 tree2 tree3 bigtree 1. By how much does quality vary? Fruit soluble solids (obrix) 2-fold variability - 10 to 20 brix
  33. 33. 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 50 150 250 350 450 big tree tree1 tree2 tree3 Fruit weight (grams) 1. By how much does quality vary? >4-fold variability - 90 to 400 g
  34. 34. 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 0 20 40 60 80 100 tree1 tree2 tree3 BigTree Fruit color (% red) 1. By how much does quality vary? Tremendous variability - 0 to 100%
  35. 35. Relationship with fruit position?
  36. 36. Fruit position vs. quality 3D canopy models • Defoliate • Map fruit position • Analyze each fruit • Create 3D quality maps
  37. 37. Fruit size and color 3rd leaf Fuji 29 fruit No clear positional effects
  38. 38. Fruit size and color 15-yr old Fuji 384 fruit
  39. 39. Defoliation to improve harvest efficiency & fruit quality
  40. 40. Harvest efficiency +25% 100% colour
  41. 41. Causes of variability?
  42. 42. Which flower has the greatest quality potential?
  43. 43. Treatment Fruit weight (g) Firmness (lb) Soluble solids (%) Hand-thinned control 230 a 17.5 a 12.0 a Thinned to KING flower 203 b 17.3 a 10.7 b Thinned to SIDE flower 230 a 17.5 a 10.6 b Table 1. Effect of hand-thinning every cluster throughout entire trees to either the king or a side flower on fruit quality attributes of Buckeye Gala. Thinning treatments are compared to normal commercial practice (hand-thinned control).
  44. 44. Quality potential similar for king & side flowers
  45. 45. Timing of flowering on fruit quality
  46. 46. y= -4.3517x + 232.75 R²= 0.13 0 50 100 150 200 250 300 350 g Bloom Date 'Buckeye Gala' Fruit Weight 2010 y= -0.5374x + 79.038 R²= 0.14 0 10 20 30 40 50 60 70 80 90 100 mm Bloom Date 'Buckeye Gala' Fruit Diameter 2010 y = -8.947x + 266.37 R² = 0.23 0 50 100 150 200 250 300 350 Weight(g) Bloom Date 'Buckeye Gala' Fruit Weight 2009 y = -0.99x + 82.23 R² = 0.26 60 65 70 75 80 85 90 95 100 Diameter(mm) Bloom Date 'Buckeye Gala' Fruit Diameter 2009 Last-opening flowers appear to have lower quality potential
  47. 47. QUESTIONS? mdwhiting@wsu.eduFB: WSUStoneFruitPhysiology

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