This presentation provides data comparing various selections of common winegrape cultivars grown in the San Joaquin Valley, California

1. Selecting Wine Grape Clones to
Improve Yield and Quality
Matthew Fidelibus
Department of Viticulture and Enology
University of California, Davis

2. Species, cultivars, and clones
• California’s wine industry based on a
single species of grape, Vitis vinifera L.
• Most wines made from traditional (old)
cultivated varieties of V. vinifera
• Old cultivars have accumulated many
‘clones’ due to mistaken identity, mutation,
or both
• Variation among clones may be exploited
to improve grapevine yield and quality

3. What is a grapevine clone?
• A population of vines propagated
asexually (e.g., by cuttings) from a single
mother vine.
• Virtually all propagated grapevines are
technically ‘clones’
• Of particular interest are clones or
‘selections’ having distinctive, beneficial,
characteristics

4. How to make a mammalian clone

5. How to make a grapevine clone

7. How can clonal selection
research benefit growers?
• Nurseries offer many different clones of a
given cultivar
• These may differ dramatically with respect to
yield, yield components, fruit composition,
and susceptibility to pests and diseases
• The performance of a given clone can
depend on the climatic region where it is
grown

8. Materials and methods
• Chardonnay, Merlot, and
Zinfandel/Primitivo vines planted in 1997
• Bilateral cordons, two-wire trellis, spur
pruned
• Vine x row spacing = 7.5’ x 10’
• Ten single-vine replicates
• Randomized complete block design
• Within a year, all clones harvested on the
same day

9. Chardonnay characteristics
• Most widely cultivated wine grape in CA
• > 70 different registered clones in CA
• Clone 4, industry standard
• High yields, good fruit composition
• 4 has large, heavy clusters—susceptible
to sour rot

10. Chardonnay clones
Clone Source
4 Martini 5V21, Olmo #66
6 Martini 3V4, Olmo #68
15 Prosser, WA, LR2V6
18 Rauscedo 8, Italy
20 Cornegliano 7, Italy
37 France, 95

11. Chardonnay yield components
Clone Clusters / vine Cluster wt.
(kg.)
Yield / vine
4 78 d 0.29 a 21.9 a
6 107 a 0.22 c 22.0 a
15 107 a 0.20 d 19.9 b
18 93 c 0.26 b 22.6 a
20 98 bc 0.25 b 22.1 a
37 105 ab 0.24 bc 23.2 a

12. Chardonnay berries
Clone Berries / cluster Berry wt
(g)
4 192 a 1.5 b
6 147 cd 1.5 b
15 138 d 1.4 c
18 172 b 1.5 b
20 153 c 1.6 a
37 158 c 1.5 b

13. Chardonnay fruit composition
Clone Brix pH TA
(g/100 ml)
4 23.7 a 3.60 c 0.584 a
6 22.9 b 3.70 a 0.555 b
15 22.8 b 3.69 ab 0.581 a
18 22.7 bc 3.67 b 0.534 c
20 22.4 c 3.68 ab 0.555 b
37 23.0 b 3.68 ab 0.534 c

14. Chardonnay, sour rot incidence
Clone Sour rot incidence
(%)
4 16 a
6 10 b
15 4 c
18 14 ab
20 13 ab
37 15 a

15. Chardonnay clones summary
• Clone 4 had good yields, large clusters,
and good fruit composition but was very
susceptible to sour rot
• Clone 15 had 10% lower yields than 4, but
had much less sour rot than 4

16. Merlot characteristics
• Merlot among the most important red wine
grapes in Calif.
• 20%, by area, and 45%, by yield, grown in
Central Valley
• Clone 3 is standard; consistent set, yield,
fruit composition
• Relative performance compared to other
clones in the valley has not been tested

17. Merlot clones
Clone Source
1 Inglenook, Calif.
3 Inglenook, Calif.
9 Rauscedo, Italy #3
10 Cornegliano, Italy ISV-V-F2
11 Cornegliano, Italy ISV-V-F5
14 Chamber d’Agriculture de al
Gironde, France

18. Merlot yield components
Clone Clusters / vine
(no.)
Cluster wt.
(kg)
Yield / vine
(kg)
1 90 b 0.24 19.83 c
3 91 b 0.25 20.75 bc
9 90 b 0.25 21.50 ab
10 103 a 0.24 22.21 a
11 92 b 0.26 21.08 abc
14 85 b 0.23 18.11 d

19. Merlot berries
Clone Berries / cluster
(no.)
Berry wt
(g)
1 150 1.57 c
3 148 1.66 b
9 149 1.65 b
10 145 1.57 c
11 145 1.73 a
14 146 1.54 c

20. Merlot fruit composition
Clone Brix pH TA
(g/100 ml)
1 23.6 c 3.91 b 0.377 cd
3 23.4 c 3.90 bc 0.374 d
9 23.7 c 3.90 bc 0.373 d
10 23.65 bc 3.87 c 0.398 a
11 24.0 b 3.94 a 0.391 ab
14 24.4 a 3.94 a 0.385 bc

21. Merlot clones summary
• Selection 10 performed best; consistently
higher yields of fruit with low pH and high
TA
• Selection 11 was undesirable; the largest
berries, was the most susceptible to rot,
and had high pH
• Selection 3 performed similar to selections
1 and 9 and was not superior to 10

22. ‘Crljenak kastelanski’
• “The red grape of Kastela”
• Zinfandel and Primitivo are probably
selections of the “Red grape”
• Origin of Zinfandel is obscure, 1850s?
• Primitivo means “early” in Italian
• Primitivo has been grown in Italy for about
200 years

23. Zinfandel characteristics
• Big berries, large clusters, high
fruitfulness, high yields
• Very susceptible to “sour rot” in warm
climates
• Uneven ripening
• Yield declines as the season progresses
• Color can be poor, especially in warm
climates

25. Zinfandel & Primitivo Clones
Clone Source
Zinfandel 1A Lodi, CA, Handel
Zinfandel 2 Lodi, CA, Handel
Zinfandel 3 Livermore, CA, Ruetz
Primitivo 3 Bari, Italy
Primitivo 5 Calo, Italy
Primitivo 6 Calo, Italy

26. Zinfandel, cluster characteristics
Clone Clusters / vine
(no.)
Cluster wt.
(kg)
Yield / vine
(kg)
1A 73 b 0.30 20.4 c
2 75 b 0.31 21.3 bc
3 75 b 0.35 23.4 b
P3 91 a 0.32 26.0 a
P5 79 b 0.30 22.2 bc
P6 80 b 0.31 22.1 bc

27. Zinfandel, berry characteristics
Clone Berries /
cluster
Berry wt
(g)
1A 104 2.77 a
2 107 2.75 a
3 126 2.76 a
P3 116 2.64 b
P5 117 2.57 b
P6 110 2.78 a

28. Zinfandel, fruit composition
Clone Brix pH TA
(g/100 ml)
1A 20.05 c 3.47 b 0.60
2 20.16 c 3.45 b 0.60
3 19.56 d 3.45 b 0.59
P3 21.10 b 3.46 b 0.61
P5 20.82 b 3.48 b 0.62
P6 22.00 a 3.52 a 0.60

29. Zinfandel, sour rot susceptibility
Clone Sour rot incidence
(%)
1A 50 ab
2 55 a
3 52 ab
P3 40 cd
P5 44 bc
P6 34 d

30. Zinfandel clones summary
• Few differences between the Zinfandel
selections tested
• Primitivo selections generally were better
• Earlier maturing
• Similar or higher yield
• Similar or less sour rot

31. Acknowledgements
• Thanks to L. Peter Christensen, Kimberley
Cathline, Jorge Aguilar Osorio, Don
Katayama, & Karin Kawagoe
• Viticulture Consortium & American
Vineyard Foundation

32. For more details…
• Email mwf@uckac.edu