New strategies to increase South African citrus export ...
Transcript of New strategies to increase South African citrus export ...
New strategies to increase South African
citrus export volume and fruit quality
R Rosalie, OPJ Stander
J North & PJR Cronje
CRI and Department of Horticultural Science, SU
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Efficient use of sun light
• The only thing free in Citriculture is sun light
+ Heat & Light are necessary for: • Color development • Carbon assimilate
accumulation - ↗Heat & Light can cause:
• Damages • Fruit growth
restrictions • Fruit drop
Mandarin cv. Nadorcott
Shade Netting in Citrusdal
• Provide 20% shade • Decrease the light damage • Increase the photoactive period • Increase the water usage
efficiency
• Completely randomized experimental design • 4 Open Blocks • 4 Net Blocks
• Growing conditions measured: • Air temperature • Soil Temperature • Soil water potential • Relative humidity
O1
O4
N1
O3
O2
N4
N2
N3
Impacts of shade netting?
• Does is decrease or increase the temperature? • On one hand shade = lower
temperature • On the other hand green-
house effect
• What is the impact on color development? • Light is necessary for
normal color development • Temperature ≥ 35°C inhibit
carotenoid synthesis
• How do the trees allocate carbon under shade netting? • More growth or better fruit
yield and quality
Reproductive Growth Vegetative Growth
Sampling
• Every months from January to June
• 5 fruits per blocks
• Types of samples: • Albedo • Flavedo • Juice
• Analyses: • Detailed sugars (HPLC) • Detailed acids (HPLC) • Total polysaccharides
Growth conditions
0
5
10
15
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25
30
35
40
8 13 18 23 28
Tem
per
atu
re (
°C)
Week
Max. and Min. Temperature Max_Open Max_Net Min_Open
Min_Net Average_Open Average_Net
-5
0
5
10
15
20
25
30
35
40
45
0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00
Tem
per
atu
re (
°C)
Time
Summer vs winter
Open_Warm Net_Warm
Open_Cold Net_Cold
Internal fruit quality
• Carbohydrates
• Seasonal accumulation
• No Net effect
• Acids
• Seasonal decrease
• Open blocks higher until low contents
0
20
40
60
80
100
120
140
160
Jan Feb Mar Apr May Jun
Tota
l Su
gar
(mg.
ml-1
)
Juice Open Net
*
*
0
20
40
60
80
100
120
140
160
180
Jan Feb Mar Apr May Jun
Tota
l Aci
d (
mg.
ml-1
)
Juice
Rind quality - Carbohydrates
*
*
20
40
60
80
100
120
140
0
100
200
300
400
500
600
janv. févr. mars avr. mai juin juil.Suga
r co
nte
nt
(mgG
lcEq
.gD
W-1
)
Free Sugars_Open Free Sugars__Net Polysaccharides_Open Polysacchirides_Net
*
*
20
40
60
80
100
120
140
0
50
100
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200
250
300
350
400
janv. févr. mars avr. mai juin juil.Suga
r co
nte
nt
(mgG
lcEq
.gD
W-1
)
0
20
40
60
80
100
120
140
160
Jan Feb Mar Apr May Jun
Sucr
ose
(m
g.gD
W-1
) Albedo Open Net
*
*
*
0
10
20
30
40
50
60
70
80
90
Jan Feb Mar Apr May Jun
Sucr
ose
(m
g.gD
W-1
)
Flavedo
Rind quality - Pigments
• Chlorophyll and Carotenoid contents higher under Net on young fruits
• Colour break > Net/Open effect
• No pigment differences
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*
*
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
janv. mars avr. juin
Pig
men
t co
nte
nt
(µg.
gDW
-1)
Chl A - Open Chl A - Net
Chl B - Open Chl B - Net
Carotenoids - Open Carotenoid - Net
Conclusion
• Net (20%) provides:
• Lower max soil T°C in summer and higher min soil T°C
• Higher water potential
• No effect on final internal quality
• Higher sugar accumulation in rind
• No effect on pigment contents
Further work
A bigger project including:
• Horticultural aspects : • Vegetative and reproductive growth • Yields • Fruit quality • Carbon allocation
• Soil science: • Water use efficiency • Soil composition
• Anthomology: • Insect distribution
• Plant pathology: • Pathogene distribution
Fruit irradiation and cold storage • Postharvest disinfestation of citrus fruit for False Codling Moth
mostly achieved through cold treatment (Hofmeyr et al. 1998)
• Current protocol of 22/24 days <0°C detrimental to fruit quality
• Chilling injury = Temperature x Exposure time
• Need for alternative disinfestation treatments with ensured fruit quality
• Irradiation of fruit an approved practise world wide e.g.
• USDA-APHIS approved irradiation as a quarantine treatment for fruits and vegetables in Oct. 2002
Citrus fruit response to irradiation range • Establish irradiation dose threshold for adverse fruit quality effects.
• Earlier exploratory trials indicated sensitive to the range of 200 to 500 Gy.
• 7 cultivars - export quality fruit-
• Star Ruby, Nules, Early/Late Navel, Turkey Valencia, Lemons and Nadorcott
• Exposed to 200, 300, 400 or 500 Gy
• Hepro: Cobalt irradiation source
• Cold stored at either 2 or 7°C for 40 60 d
• Evaluation for quality
• Rind disorder incidence
• Internal quality
• Taste test
Materials and methods
Results: Rind quality
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101520253035404550
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Early Navel Pitting % - 40 Days
Pitting % - 60 Days
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Late Navels Pitting % - 40 d
Pitting % - 60 d
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Star Ruby Pitting % - 40 Days
Pitting % - 60 Days
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200Gy 2°C
300Gy 2°C
400Gy 2°C
500Gy 2°C
0 Gy7°C
200Gy 7°C
300Gy 7°C
400Gy 7°C
500Gy 7°C
Pit
tin
g %
Turkey Valencia Pitting % - 40 d
Pitting % - 40 d
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng/
pet
eca
/sca
ldin
g
1st Lemon Pitting % - 40 Days Pitting % - 60 Days
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Pit
tin
g/p
etec
a/sc
ald
ing
2nd Lemons Pitting % - 40 d Pitting % - 40 d
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Pit
tin
g/st
ain
%
Nadorcott Mandarin Pitting % - 40 d
Pitting % - 60 d
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Nules Clementine Pitting % - 40 Days
Pitting % - 60 Days
Internal quality: no drastic changes expect lemons
Rind colour Juice % °Brix Cit. Acid
Star Ruby
Turkey Val
Lemon 1
Lemons 2
Navel Early
Navel Late
Nules Clementine
Nadorcott mandarin
Internal quality
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1,60
1,80
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Cit
ric
Aci
d
Turkey Valencia Citric Acid 40 days Citric Acid 60 days
4,80
5,00
5,20
5,40
5,60
5,80
6,00
6,20
6,40
6,60
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Cit
ric
Aci
d
Lemon 1 Citric Acid Day 40 Citric Acid Day 60
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
0 Gy -0.6°C
0 Gy2°C
200Gy2°C
300Gy2°C
400Gy2°C
500Gy2°C
0 Gy7°C
200Gy7°C
300Gy7°C
400Gy7°C
500Gy7°C
Cit
ric
Aci
d
Lemon 2
• Only parameter effected - Citric acid in highly sensitive cultivars
• Reduction of Citric acid possibly due to increase in respiration
Conclusion and way forward
• Repeat irradiation in 2016 • Include Midknight and Nova mandarin
• Identify damaging level per cultivar group • Percentage and severity
• In general most cultivars OK <300Gy • Except Turkey<200Gy damaged • Of concern: Nadorcott and lemon
• Data will be used to motivate possible new combined protocol
Thank You
Any Questions?