grape berry splitting · • berry splitting can be observed in wa • the symptoms of splitting...
TRANSCRIPT
Grape berry splitting
2016 WSGS Annual Meeting
11/11/2016 Ben-Min Chang, Yun Zhang, and
Markus Keller
Do you see berry splitting?
Véra
ison
Split berries • On berry:
• Exposed flesh • Specific pattern and site
• In cluster: • Randomly distributed • Soft berries only
Hidden splits!
• Small splits
Hidden splits!
• Covered in compact cluster
Hidden splits! • Covered by rippled skin
Hidden splits! • Just not on the vine any more
Consequences • Cuticle failure affects: • Yield
• Dehydration • Berry drops
• Quality
• Risks of diseases • Botrytis • Sour rots
• Higher TSS • Deteriorated
appearance
(Martin and Rose, 2014)
0
5
10
15
20
25
30
35
40
0 5 10 15 20 25 30 35 40
Clus
ter T
SS (%
)
Intact berry TSS (%)
• Concentration • Higher variation among
clusters • Intact berry sampling
• Underestimate TSS • Cluster sampling
• Overestimate maturation of survivor
Water balance of berry Phloem: Water with sugar
Berry growth
Transpiration When High RH% Low VPD Low T
Xylem: To other organ
σ
P P
σ Softening
(a) (b) (c) (d)
𝜎 =𝑃𝑃2𝑡
�𝑖𝑖 ≥ 𝜎𝑡𝑡, 𝐹𝐹𝑖𝐹𝑖𝑖 < 𝜎𝑡𝑡, 𝐼𝐼𝑡𝐹𝐼𝑡
(modified from Boudaoud, 2010)
Cuticle
Epidermal cells
Hypodermal cells
0
100
200
300
400
500
600
0 10 20 30
Criti
cal p
ress
ure
(kPa
)
Brix
Concord
Merlot
Syrah
Zinfandel
Con. Simulation
Mer. Simulation
Sy. Simulation
Zin. Simulation
Pressure in your car tire: 35-80 PSI as 241-552 kPa
0
5
10
15
20
25
0 5 10 15 20 25 30 35
Stra
in (%
)
Brix
ConcordMerlotSyrahZinfandel
Strain: the deformation under fixed pressure -> represent the softness of berry
How split developing?
• Cracking • The failure of skin • Access to absorb
water • Weaker strength
• Splitting • The extreme form of cracking
(Peschel and Knoche, 2005)
Sources of excessive stress
• Inner – Growth – Rain water absorption
• Outer – Birds – Neighbor berries
0 Units?
A
D C
B
In pH 3.5 buffer solution
30
60
90
120
150 seconds
Two-phase actions
• Phase 1 – Initiation
• Excessive stress Skin failure • Due to berry volume increase if source is
growth
• Phase 2 – Expansion
• Relaxation of skin Deeper tissue failure • Release the energy stored in skin (spring)
Birds/Mechanical piercing
• Sharp object penetration
• Cuneiform script – From birds
Compact cluster
• Variety: – Zinfandel – Riesling
• Factors: – Flower number – Berry set – Berry size – Rachis length – Pedicel length
Linear berry density
• Simpler tool • Measurements:
– Total berry numbers • Intact • Split
– Length of peduncle • From the end • To the base of 1st
secondary branch
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2
Sp
litt
ing
rate
(1
00
%)
Linear berry density (berries/mm)
Linear berry density = berry numbers/peduncle length
Zinfandel
25.4 berries/inch
Split peduncle • Alleviate berry splitting • Bunch closure • Green hard berry
dehydration • More space for survivors • In compact clusters
Drought induced defects?
Pre-veraison Post-Veraison Intact berries Split berries Splitting rate (%) Probability 100% 100% 569 6 1.04 Reference 50% 50% 679 7 1.02 50% 100% 625 24 3.70 *
100% 50% 548 1 0.18 * 150% 100% 583 2 0.34
Water stress 510 126 19.81 *
• Severe drought – Increase defects? – Decrease critical pressure – May not survive rainfall
• Moderate drought – Impose deficit irrigation – Pre-véraison seems critical
• Berry splitting can be observed in WA
• The symptoms of splitting are not always obvious
• Knowledge about splitting: – The impacts on yield and quality – Mechanism and process – Sources of stress – Possible impacts of irrigation strategy