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

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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