Varieties and Rootstocks –
The California Perspective
Mary Lu Arpaia and John Menge
University of California, Riverside
Why
Why have
have an
an Improvement
Improvement Program
Program
Producing the Crop - Enhancing Productivity
High production of optimally sized fruit
Tolerance to disease, pests
Tolerance to environmental stress
Tree "manageability"
On-tree storage and minimize alternate bearing
Marketing the Crop - Maximizing Fruit Quality
Minimizing physiological disorders
Uniformity of ripening
Tolerance to low storage temperatures
Tolerance to handling "mis-management"
Decreased postharvest fruit decay
Mary Lu Arpaia (September 2004)
1
Requirements/Risks of a
plant improvement program
Long-term venture (10 – 20 years)
9 Requires coordinated effort: academia,
growers, packers, consumers
9 Wide-scale adoption unknown: will
there be a return on the investment?
9 Most current cultivars and rootstocks
are local selections – can improvements
be found?
9
Challenges
Challenges Specific
Specific to
to
Avocado
Avocado Plant
Plant Improvement
Improvement
Avocado is “relatively primitive” –
commercial production <100 years
9 Understanding limited on avocado genetics
9 May be many years to come into production
9 Highly heterozygous – seedling populations
extremely varied
9
Mary Lu Arpaia (September 2004)
2
The goals of an avocado improvement program
can be achieved through varietal and rootstock
manipulation using either traditional breeding
methods or as technology improves, molecular
techniques.
Additionally, an important component for the
future is germplasm conservation.
Characterization and preservation of wild
Persea and related genera is essential in order
to preserve desirable traits useful for future
breeding efforts.
University
University of
of California
California
Avocado
Avocado Improvement
Improvement Program
Program
Rootstock Selection Program
Disease tolerance - J. Menge, G. Zentmyer
Salinity tolerance - D. Crowley, M. L. Arpaia
Field Productivity - M. L. Arpaia, G. Bender, B. Faber
Varietal Improvement - M. L. Arpaia
Genetic Characterization - M. Clegg, T. Chao
Germplasm Conservation - R. Scora, J. Menge, M. L.
Arpaia
Mary Lu Arpaia (September 2004)
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Contributions
Contributions of
of UC
UC Avocado
Avocado Program
Program
Rootstocks
Identification of PRR tolerant material
Rootstock productivity and salinity tolerance
Dwarfing
Cultivars
New varieties for CA growers
Breeding stock shared with international
community and has been the foundation of other
intl. breeding programs
Components
• Testing current selections
• Developing new selections
Mary Lu Arpaia (September 2004)
4
Varietal Selection UC, Riverside
B. O. Bergh: 1964 - 1994
G. W. Witney: 1994 - 1996
M. L. Arpaia: 1996 - present
Technical Support:
Bob Whitsell 1964 - 1989
Gray Martin 1984 – 1997
David Stottlemyer 1997 - present
Varietal
Varietal breeding
breeding in
in California
California
Current major cultivars are "local" or introduced
selections
Released Cultivars to CA industry
Dr. B. O. Bergh and Mr. R. Whitsell
Gwen, Whitsell and Esther - released in 1984
Dr. B. O. Bergh and Mr. G. E. Martin
Lamb Hass and Sir Prize - released in 1996
Released 2003
Dr. Mary Lu Arpaia and Mr. David Stottlemyer
3-29-5 (GEM) and N4 (-) 5 (Harvest)
Mary Lu Arpaia (September 2004)
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Components
Components of
of evaluation
evaluation
•
•
•
•
•
Yield
Fruit characteristics – size, seed size
Maturity and postharvest quality
Tree vigor – growth habit
Flowering, stress tolerance
Mary Lu Arpaia (September 2004)
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Growth Habit Varies
Hass
3=29-5 (GEM)
Gwen
Lamb Hass
N4 (-) 5 (Harvest)
Marvel (BL516)
Leaf Shape - The unreleased varieties are
all ‘Gwen’ offspring. Although the leaves tend
to be similar, there are subtle differences
between the varieties.
Mary Lu Arpaia (September 2004)
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Yield
UC South Coast REC, Topworked Trees
1600
1600
1400
1400
Fruit Count
Fruit Count
1200
1200
1000
1000
2004
2004
2003
2003
2002
2002
2001
2001
2000
2000
1999
1999
800
800
600
600
400
400
200
200
0
0
OA184
OA184
BL667
BL667
(Nobel)
(Nobel)
BL516
BL516
(Marvel)
(Marvel)
Hass
Hass
Harvest
GEM
Harvest
GEM
(N4 (-) 5) (3-29-5)
(N4 (-) 5) (3-29-5)
Sir Prize Lamb Hass
Sir Prize Lamb Hass
Cultivar
Cultivar
Alternate Bearing Tendency
UC South Coast REC, Topworked Trees
Less
More
Lamb Hass
Sir Prize
GEM (3-29-5)
Harvest (N4 (-) 5)
Hass
BL516 (Marvel)
BL667 (Nobel)
OA184
0
25
50
75
100
125
150
175
200
Coefficient of Variation (%)
Mary Lu Arpaia (September 2004)
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Yield
DeBusschere Variety, Clonal Duke 7 RS
Fruit
Fruitcount
Coun
900
800
2004
700
2003
600
2001
2002
500
400
300
200
100
0
BL667
BL516
Lamb Hass
Harvest
Hass
GEM
Cultivar
Flowering at UC South Coast REC in Irvine, CA. for 2002 - 2004
Hass
Lamb
GEM
Harvest
Sir Prize
BL667
BL516
0
20
40
60
80
100
120
140
160
180
Julian Date
2004
2003
2002
Flowering varies from
year to year
Mary Lu Arpaia (September 2004)
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Fruit Maturity
3-29-5 (GEM)
40
40
GEM
Hass
2000
2002
2003
35
Dry Matter Content (%)
Dry Matter Content (%)
35
2001
30
25
20
30
25
20
15
15
1/1 1/15 1/29 2/12 2/26 3/11 3/25 4/8 4/22 5/6 5/20 6/3 6/17 7/1 7/15 7/29 8/12 8/26 9/9 9/23
1/1 1/15 1/29 2/12 2/26 3/11 3/25 4/8 4/22 5/6 5/20 6/3 6/17 7/1 7/15 7/29 8/12 8/26 9/9 9/23 10/710/21
2003
Calendar Date
Similar pattern of
dry matter
accumulation to
Hass
Comparison of dry
matter changes over
season
Fruit Maturity
N4 (-) 5 (Harvest)
35
40
Harvest
Hass
2000
2001
2002
2003
30
Dry Matter Content (%)
Dry Matter Content (%)
35
25
30
25
20
20
15
15
1/1 1/15 1/29 2/12 2/26 3/11 3/25 4/8 4/22 5/6 5/20 6/3 6/17 7/1 7/15 7/29 8/12 8/26 9/9 9/23
2003
Slower pattern of
dry matter
accumulation to
Hass
Mary Lu Arpaia (September 2004)
1/1
1/15 1/29 2/12 2/26 3/11 3/25
4/8
4/22
5/6
5/20
6/3
6/17
7/1
7/15 7/29 8/12 8/26
9/9
9/23 10/7 10/21
Calendar Date
Comparison of dry
matter changes over
season
10
Differences between Hass and Lamb Hass
Lamb Hass maturity season – mid to late summer
Fruit shape – more “square”
Lamb Hass has more upright growth habit
Flexible wood – fruit borne interior of tree; tends to set fruit in
clusters
Lamb Hass is more “tolerant” to Persea mite and other pests (?)
Photosynthetic rate approximately 30% higher than Hass and
higher chlorophyll content
Fruit Maturity – Lamb Hass
40
% Dry Weight
36
Hass '99
Lamb '99
Hass '00
Lamb '00
Hass '01
Lamb '01
32
28
24
20
16
Jan 1
Jan 29
Feb 26
Mar 26
Apr 23
May 21
Jun 18
Jul 16
Aug 13
Sep 10
Delayed dry matter accumulation compared to Hass
Pattern of accumulation similar over seasons
Mary Lu Arpaia (September 2004)
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Growth habit differences between Hass and Lamb Hass
Hass
Lamb Hass
Developing new selections
1. In consultation with U. Lavi
(Israel)
Seed collection:
BL667, BL516, GEM,
Gwen, Lamb Hass, 5-552
2. In consultation with B. Bergh
Isolation Blocks:
BL516 x GEM
Gwen self
Thille x GEM
Lamb x GEM
Sir Prize x Gwen BL667 x Lamb
Mary Lu Arpaia (September 2004)
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Indexing for
disease is a critical
component
Critical to know:
•Relative disease tolerance
•All introduced material
should be tested
Clonal Rootstocks
The California Experience
Mary Lu Arpaia (September 2004)
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Rootstocks can influence many
scion characteristics
Yield
Tree size/vigor
Yield efficiency
Leaf nutrient status
Tolerance to environmental stresses
•
•
•
•
•
Use of clonal rootstocks relatively new
•
•
•
500
Potential for future improvements high
Significant differences due exist
More uniform tree performance possible
Cumulative yield per tree (kg)
2
Years after Planting
4
5
6
7
8
3
9
10
400
300
200
100
0
Borchard
100
Duke
7
Toro
Canyon
Topa
Topa
D9
G755A
G755B
G755C
Canopy volume (cu. meters)
Borchard
Duke 7
Toro
Canyon
Topa
Topa
D9
G755A
G755B
G755C
80
60
40
Rootstock
influences
yield and
tree size
20
4.5
6.5
7.5
8.5
Years after planting
Mary Lu Arpaia (September 2004)
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Tree Size – South Africa
Duke 7
2
G755C
Yield efficiency per cycle (kg/cu. m canopy)
1.5
Duke 7
Toro
Canyon
1
D9
G755C
0.5
0
Year
4-5
Yield efficiency
declines due to
increases in tree size
and loss of productive
canopy surface
Year
6-7
Year
8-9
Table 6 Yield efficiency (kg fruit·m-3) of ‘Hass’ avocado trees
growing on ten clonal rootstocks at the University of California
South Coast Research and Education Center (latitude, 33°44’N;
longitude, 117°49’W) (n=20).
Yield efficiency (kg fruit·m-3)
Rootstock
Significant
differences in
yield efficiency
Not necessarily
associated with
vigorous trees
Mary Lu Arpaia (September 2004)
1991/92
1993/94
1995/96
mean
G755A
G755B
G755C
Topa Topa
Duke 7
Borchard
D9
Toro Canyon
0.60c
0.48cd
0.42d
0.81b
0.97a
0.96ab
0.95ab
0.90ab
0.87c
0.83cd
0.69d
1.06b
1.23a
1.17ab
1.15ab
1.13ab
0.238c
0.182c
0.236c
0.935a
0.958a
0.935a
0.696b
0.948a
0.57c
0.50cd
0.45d
0.93b
1.05a
1.02ab
0.93b
0.99ab
Thomas
G1033
∗∗∗
0.75
0.58
∗∗∗
1.00
0.94
n.s.
∗∗∗
0.50
0.69
∗∗∗
0.75
0.74
n.s.
∗
∗
Mean separation tests within columns non-significant (n.s.), or
significant at the P=0.05 (∗) or 0.001 (∗∗∗) level based on Fisher’s
Protected LSD test.
15
Alternate Bearing can be
influenced by clonal rootstock
140
Weight per tree (kg)
Duke 7
120
Toro Canyon
100
D9
80
G755C
60
40
20
0
2
**
3
**
4
**
5
**
6
**
7
**
8
*
9
**
10
**
Years after planting
Table 2. Alternate bearing index of ‘Hass’ avocado trees
growing on ten clonal rootstocks at the University of
California South Coast Research and Education Center
(latitude, 33°44’N; longitude, 117°49’W). See Materials &
Methods section for calculation.
Significant
differences
detected
Rootstock
Alternate bearing index
G755A
G755B
G755C
Topa Topa
Duke 7
Borchard
D9
Toro Canyon
1.49c
1.25d
1.21d
1.91a
1.61bc
1.70b
1.56bc
1.92a
Thomas
G1033
∗∗∗
1.83
1.63
n.s.
Mean separation tests within columns non-significant (n.s.)
or significant at the P=0.001 (∗∗∗) level based on Fisher’s
Protected LSD test.
Mary Lu Arpaia (September 2004)
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Rootstock can influence leaf nutrient status
Nitrogen
Phosphorus
2.7
0.255
0.235
2.5
0.215
0.195
% dry weight
% dry weight
2.3
G755C
Duke 7
2.1
D9
Toro Canyon
1.9
G755C
0.175
Duke 7
0.155
D9
Toro Canyon
0.135
0.115
1.7
0.095
0.075
1.5
1988
1989
1990
1991
1992
1993
1994
1988
1995
1989
1990
1991
1992
1993
1994
1995
Year
Year
Potassium
1.7
1.6
% dry weight
1.5
G755C
1.4
Duke 7
1.3
D9
Toro Canyon
1.2
1.1
1
1988
1989
1990
1991
1992
1993
1994
1995
Rootstocks affect ‘Hass’ avocado fruit rots
– believed related to calcium uptake
4 wks @ 5C
Flesh volume (%)
Marques, Hofman et al 2001
40
SV
Seedling Velvick
CV
Clonal Velvick
D7
Duke 7
30
b
a
c
20
a
b
10
a
Non-stored
Mary Lu Arpaia (September 2004)
Stored
17
‘Hass’ Avocado Phenology Model
Relative growth rate
“On” year = heavy crop load
“Off” year = light crop load
100
80
shoot
60
root
40
bloom
20
0
Julian date
Are there rootstocks affects?
Root growth rate – No consistent differences
Annual root growth rate of ‘Hass’ avocado on four clonal rootstocks.
Year
Rootstock
1992
1993
1994
-1
mm·day ·root
‘Thomas’
‘Topa Topa’
‘Duke 7’
‘D9’
Sig. of Fx
0.75ab
0.84a
0.60c
0.67bc
*
0.72
0.97
0.69
0.72
0.67a
0.75a
0.47b
0.75a
n.s.
*
1995
1996
0.52a
0.32bc
0.18c
0.38ab
0.38a
0.25b
0.23b
0.24b
-1
**
*
z
Means within a column with no letter(s) in common are significantly different (Fisher’s
Protected Least Significant Difference test at P=0.05).
y
ns, *, **, *** are non-significant, or significant at P≤0.05, P≤0.01, or P≤0.001, respectively.
Mary Lu Arpaia (September 2004)
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Rootstock had no effect of shoot growth rate
Shoot growth ratez (mm·day-1·shoot-1) of ‘Hass’ avocado on one of four rootstocks.
‘Thomas’
‘Topa Topa’
‘Duke 7’
‘D9’
Sig. of Fy
Avg.
1992
1993
1994
1995
1996
springz summer
spring summer
spring summer
spring summer
spring summer
0.68
0.65
0.61
0.63
0.37
0.26
0.27
0.16
3.57
5.71
5.34
5.05
4.57
5.81
6.49
6.59
1.60
1.80
2.00
1.82
0.46
0.36
0.46
0.72
0.83
0.51
0.70
0.86
0.78
0.41
0.92
0.46
1.40
0.97
1.17
1.34
0.37
0.20
0.32
0.26
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.64
0.27
4.92
5.86
1.80
0.50
0.73
0.64
1.22
0.29
z
Spring = average of spring (first) flush; Summer = average of summer (second) flush.
y
ns, *, **, *** are non-significant, or significantly different at P≤0.05, P≤0.01, or P≤0.001, respectively. Statistical analysis
performed using log transformed growth rates (log10 of rate + 1).
Environmental Stress –
Phytophthora root rot
Disease
resistance/tolerance
possible
New selections
Young avocado with root rot
resistant rootstock growing
among older avocados dying from
avocado root rot
Mary Lu Arpaia (September 2004)
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Breeding program
Breeding blocks of
resistant varieties
planted together to
enhance natural
crossing.
Screening and greenhouse
evaluation of rootstocks
Fruit from breeding blocks is
germinated in the greenhouse and
inoculated with Phytophthora cinnamomi
Mary Lu Arpaia (September 2004)
Selected resistant seedlings are
reinoculated each time they are
repotted
20
Resistant varieties are grafted to
stumps in the field to get abundant
budwood for experiments.
Production of clonal
rootstocks for
experiments
Field
Evaluation
Thomas
Steddom
Resistant rootstocks grown in
Phytophthora-infested soil
Uzi
Mary Lu Arpaia (September 2004)
Thomas
21
Environmental Stress –
Salinity
San Diego
County
Stehly
Trial
Duke 7
Latas
Toro Canyon
VC801
VC218
Thomas
PP4
VC256
Zutano
December 2001
Mary Lu Arpaia (September 2004)
22
Condition of surviving trees - July 2002
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
25
VC
2
4
yo
n
PP
To
ro
Ca
n
5
PP
Th
om
as
*
18
VC
2
7
41
Du
ke
VC
2
01
56
VC
2
Ev
st
ro
VC
8
ta
no
uk
e*
D
Ba
rr
Zu
La
ta
s
1.0
Chloride concentration - September 2001
Sodium concentration - September 2001
350.0
0.14
300.0
0.12
250.0
0.10
200.0
0.08
150.0
0.06
100.0
0.04
50.0
0.02
0.00
0.0
Latas Zutano
Barr
Evstro VC801 VC256 Duke 7 VC241* VC218
Duke*
PP5
Thomas
PP4
Toro
Canyon
VC225
Latas Zutano
Barr
Evstro VC801 VC256 Duke 7 VC241* VC218
PP5
Thomas
PP4
Duke*
Toro
VC225
Canyon
What we know - Much yet to be learned
Differences between avocado races needs
to be better understood
Clonals can improve overall tree
performance and potentially postharvest
quality
As with other tree crops; with time we will
find that varying environmental conditions
will require different rootstocks
•
Salinity, Disease, Cold, Soil
Mary Lu Arpaia (September 2004)
23
Greater cultural, harvesting and
water costs coupled with
increasing market competition
Approaches for the future
Enhancing Productivity
Understanding avocado tree
physiology and stress responses
• Light manipulation
• High density plantings
• Rootstocks for disease, salinity
tolerance, dwarfing
• Varieties w/ > productivity, pest
tolerance, suitable for close
spacings
• Pollinizers and Pollinators
•
NEED INTEGRATED
PROGRAM
For
For more
more information
information
www.avocadosource.com
www.avocadosource.com
Variety
Variety information
information
•• Database
Database of
of avocado
avocado varieties
varieties
•• Information
Information on
on rootstocks
rootstocks (ongoing)
(ongoing)
••
Mary Lu Arpaia (September 2004)
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