Apple Replant Disease Theory versus practice, a n overview of known controlling methods [600497]

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma
Contents
1. Background of apple replant disease (ARD) ………………………….. ………………………….. …………………… 2
2. Control methods applied for ARD ………………………….. ………………………….. ………………………….. ……. 2
2.2 Swapping the soil ………………………….. ………………………….. ………………………….. ………………………… 2
2.3 Applying fertilizers ………………………….. ………………………….. ………………………….. ………………………. 2
2.4 Using resistant strains ………………………….. ………………………….. ………………………….. ………………….. 3
2.5 Testing the soil ………………………….. ………………………….. ………………………….. ………………………….. .. 3
2.6 Removing old plant matter ………………………….. ………………………….. ………………………….. …………… 3
2.7 Growing ‘Break Crops’ ………………………….. ………………………….. ………………………….. …………………. 3
2.8 Fumigating the soil ………………………….. ………………………….. ………………………….. ………………………. 3
2.9 Alternative methods on fighting ARD ………………………….. ………………………….. ………………………….. 3
3. Experiments and their outcome s ………………………….. ………………………….. ………………………….. …….. 4
3.1 A closer look over microbial community development ………………………….. ………………………….. ….. 4
3.2 Wheat – the chief mediator ………………………….. ………………………….. ………………………….. …………… 5
3.2 Brassica seed meal amendments as alternative to soil fumigation ………………………….. ………………. 6
3.3 Herbie – an efficient fighter against soil borne pathogens ………………………….. …………………………. 7
4. Conclusion and recommendations ………………………….. ………………………….. ………………………….. ………. 9
4. Annex 1 ………………………….. ………………………….. ………………………….. ………………………….. …………. 13
5.References ………………………….. ………………………….. ………………………….. ………………………….. …………. 19

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma
“Innovation is not just technology, but is rather a comprehensive vision of what the future
should look like and which requires changes in many ambits. Innovation is driven by people’s
needs, ambitions and dreams, and requires that people at different pos itions in society change
the way they work and live.” ( Klerkx et al, 2012)

1. Background of apple replant disease (ARD)

Replant disease is a debilitating soil problem affecting most orchards when they are replanted.
Symptoms normally affect the entire orcha rd and include slow, uneven growth and poor tree
performance. Due to the general nature of replant disease, it is easy to be unaware that it is present, or
to blame the rootstock or nursery for poor tree performance. Replant disease affects most fruit crop s
including both Pome and Stone fruit (Brown,2013). During the life of an orchard, soil -borne
pathogens belonging to the genera Rhizoctonia , Pythium , Phytophthora, Cylindrocarpon and
Pratylenchus become prevalent in the tree root zone, but they generally d o not appreciably
affect the health or productivity of mature trees (Mazzola, 1998; Mazzola, 1999) . To this date,
previous studies categorized replant disease as having two forms – specific and non -specific. It is
assumed that specific apple replant diseas e only affects apples when they are planted after apples,
while non -specific replant disease affects apples that are replacing other fruit crops, such as stone fruit
or vice versa (Brown,2013). The severity of replant effects can vary from site to site (Ho estra, 1968;
Mazzola, 1998). The symptoms mentioned above include reduction in tree vigor and yield (Traquiar,
1984), and the fact that affected trees start bearing fruit 2 –3 years later than unaffected trees.
According to Mazzola (2004;2009;2015), in app le replant disease, an important aspect to be taken into
account is the microorganisms variety built -up in the root zone of the trees , while applying prevention
and control strategies .

2. Control methods applied for ARD

When it comes to prevention methods and treatments of ARD, opinions vary, as it is a complex
disease involving different causal factors. However, we will briefly list the most common
measures found in the literature and further discuss some of them more in depth in the latter
part of the ar ticle.

2.2 Swapping the s oil

When is needed to replant apple trees in the same location – or if planting in a new location isn’t viable
– then soil replacement can be an effective method for smaller sites. It’s important to ensure that high
quality soil will be used and moreover, it doesn’t come from any fruit tree planting source . Specialists
recommend that the replacing soil should be spread on an area larger than the tree’s roots coverage,
while any old soil will be disposed.

2.3 Applying fertilizers

When pl anting new fruit trees, it is recommended to apply Nitrogen rich fertilizers.

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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2.4 Using resistant strains

It is known that many strains of fruit trees like M27 apples, ‘Colt’ cherries or Myrobalan B plums are
more resistant to replant disease than others.

2.5 Testing the soil

Soil tests could provide vital informati on on Ph levels, soil fertility and microbial communities . It is
recommended that the soil testing and analysis be carried out a year before planting. This will allow the
grower s ufficient time to d etermine fertilizer requirements as well as whether any specific adjustments
are required to the soil Ph levels. At the same time, an overview of the soil -borne pathogens present in
the tested area would give valuable insights on grower’s future decisions.

2.6 Removing old plant m atter

It is advised to e nsure the removal of old plant material as soon – and as thoroughly – as possible, while
taking special care to remove all traces of roots during this process.

2.7 Grow ing ‘Break Crops’

When possible, avoid ing replanting similar species in the same spot might be helpful . For many, this may
not be practical, but growing a ‘break crop’ can often play a vital role in prevention, as Stelljes (2000)
argues. Following the ‘Pomes and Stones’ rule can also prove effectiv e, meaning that instead of
following a ‘Pome’ fruit with a fruit from the same group, a ‘Stone’ fruit should be a good replacement
crop . This method is not guaranteed, as these trees can still be susceptible t o non -specific replant
disease (w hich affects P omes trees that are planted after Stone crops, and vice -versa ).

2.8 Fumigat ing the soil

Apparently, s oil fumigation lead s the fight agains t ARD, with several treatment options available on the
market, depending on the crop in question. Methyl Bromide was on ce commonly used to control apple
replant disease in the 90’s, but has since been phased out for years now (due to environmental
concerns), leaving the role to other alternative products such as Chloropicrin , the most used one . This
specific fumigant prov ed to be e ffectiv e combatant in the war against ARD as studies shown (Line,2005) .
But pre -plant fumigation has also its disadvantages as it negatively impacts on the health and
diversity of soil biological communities (Hoagland et al,2012). Another example of “two faced”
product is metam -sodium, a fumigant commonly used also to treat apple replant disease, which
has been found to disrupt beneficial free -living nematodes, mycorrhizae, and beneficial
bacteria and fungi that cycle nitrogen (Cox, 2006). Additio nally, this chemical is a carcinogen
that can negatively impact farm worker health (Cox, 2006).

2.9 Alternative methods on fighting ARD

The need to find effective strategies in combating apple replant disease emerged over years, as
continuum research takes p lace. Through the lab and field trials, different lessons have been
learnt in time and related reports were published to share the knowledge. For instance,
methods like d igging holes and filling them with imported soil that is free of the causal

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma
pathogens is not cost -effective in a large orchard, and proved to only control disease symptoms
for the first year or two (Anonymous, 2001). At the same time, l eaving soil fallow for an
extended period of time has also been ineffective in controlling the causal path ogen complex
(Mazzola and Mullinix, 2005; Fuller, personnel communication).

3. Experiments and their outcomes

In the past decades, many scientists conducted laboratory and field trials , experimenting ways to
prevent and control ARD. From testing the efficie ncy of chemical products to exploring eco -friendly
alternatives, all those initiatives came to their very own conclusions. Further, we will summarize and
review the experiments we consider to be relevant for our topic.

3.1 A closer look over microbial communi ty development

Rumberger et al (2007) conducted their research on an orchard site that was originally planted with
apple trees around 1910 and then replanted in 1981 with trees grafted on M.9/M.106 and M.9/M.111
rootstocks (M.111 and M.106 roots with an M.9 interstem). The second planting established poorly and
exhibited many symptoms of ARD (Mai et al., 1994). Rumberger et al (2007) argue that using ARD –
tolerant rootstocks is an emerging control strategy. Therefore, they studied the bacterial, fungal, an d
oomycetes populations in the rhizosphere of five rootstock cultivars (M.7, M.26, G.16, G.30 and
CG.6210) “planted into the old tree row or grass lanes
of a previous orchard in Ithaca, NY, to better
understand the role of rhizosphere microbial
communities in the prevalence and control of ARD ”.
Their observations after a period of 3 years, revealed
that microbial densities were highest in July, lower in
May and lowest in September. Moreover, the study
showed that the composition of bacterial and fungal
comm unities in the rhizosphere was highly variable and
changed over seasons and years, as assessed by
terminal restriction fragment length polymorphism (T –
RFLP) analyses (Rumberger et al, 2007) . Their research
paid attention at the changes in terms of fungal
rhizosphere communities , which from initial differences
between the planting positions 2 years later , after the
trees were replanted , they converged. At the same
time , the bacterial rhizosphere community maintained
its difference in numbers between the plan ting
positions, even 3 years after the orchard was replanted.
Figure 1 – fingerprints of the bacterial community in
rhizosphere soil (reproduced from Rumberger et al, 2007)

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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In their study, Rumberger et al( 2007) observed that just as mentioned before by Catska et al.(1982), the
densities of Pseudomonas in the apple rhizosphere decreased over years after replantin g, whereas
population shifts may be related to changes in soil moisture, soil temperature, rhizodeposition and/or
root turnover (Yao et al., 2006b).
Their conclusion was that tree growth and yield data obtained from the studied orchard (Rumberger et
al., 2004; Leinfelder and Merwin, 2006) suggest that “avoiding replanting into the old tree rows coupled
with the use of tolerant rootstocks are useful strategies for reducing ARD in replanted orchards ”.
Furthermore, they found that t he susceptible rootstocks, M.26 and M.7, supported higher densities of
culturable bacteria and fungi in their rhizosphere than the rootstocks G.16, G.30 and CG.6210 .

3.2 Wheat – the chief mediator

Apple replant disease proved to be a major
impediment to organic orchard production
systems. (Hoagland et al,2011). Because studies
shown that it might be caused by soil-borne
pathogens and parasites that are built in the soil
of an orchard over time and due to the
consequences of this dieses, many orchardists
withdrawn their organic cert ification and used
pre-plant fumigation to remediate soil -borne
pathogens prior to planting new apple trees
(Hoagland et al,2012). As an a lternative to
chemical products, research over the positive
effects of planting wheat prior to planting apple
trees wa s conducted.1 Trials revealed that
“beneficial soil microbial communities” were increased after wheat was planted in the orchard
soils, which resulted in suppressing soil -borne pathogens and visible improvements in apple
seedling health. Wheat varieties br ed under
organic conditions had the best results, as
Hoagland et al (2011) noted upon their
research .
The conclusion of their trials was that
“including only one year of annual wheat
cultivation after removal of an existing apple
orchard can increase bene ficial soil microbial
species, suppress soil -borne pathogens and
parasites, and improve the establishment
and productivity of newly apple planted

1 Hoagland, L., Mazzola, M., Murphy, K.M., Jones, S.S., 2012. Wheat varietal selection and annual vs. perennial growth habit impact soil
microbial community and apple replant disease
suppression. Organic Seed Alliance Confere nce, Port Townsend, WA. pp. 13 -15
Figure 3-Impact of wheat cultivation on (reproduced from
Hoagla nd et al,2011)
Figure 2 – Apple growth in pot previously planted to wheat
(control left, organic wheat cultivar right) (July,2009); reproduced
from Hoagland et al (2011)

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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trees. These results support the hypothesis that modification of soil microbial community
composition likely p lays a role in disease suppression following cover crop cultivation ”.

3.2 Brassica seed meal amendments as alternative to soil fumigation

In the early ‘90s, Dr. Mark Mazzola joined the Agricultural Research Laboratory in Wenatchee,
Washington to focus his research on control methods of the ARD2. Over years, he conducted several
field trials using and comparing different strategies to fight replant disease. He noticed that fumigation
with chemical s, such as Telone C -17, only provides short -lived control of h armful soil organisms , while
there are other alternatives for” longer lasting effects and even greater benefits than fumigation in
terms of both tree growth and fruit yields ”.
One of the solution Dr. Mazzola found to be effective is Brassica seed meal amen dment ( SM) that can
provide control of numerous plant pests through generation of biologically active glucosinolate
hydrolysis products or indirectly via t ransformation and activity of the resident soil biology
(Mazzola&Zhao, 2010) . In Mazzola et al. (2014 ) it is described how field trials were conducted to
determine the effect of SM formulation, moment of application and apple rootstock on their efficiency
against ARD. In their study, they used treatment plots of 10,7m/2m, with five replicates per treatmen t,
comparing preplant soil fumigation ( using Telone -C17) with Brassica SM formulations.

2 http://www.goodfruit.co m/new -replant -disease -treatment

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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As presented by Mazzola et al. (2014), tree performance in SM -amended soil was “commonly superior
to that in fumigated soil at the end of four
seasons”. Moreover, they observed an
increased resistance to reinfestation in SM –
amended soils and that the rhizosphere
microbiome gained “unique bacterial and
fungal profiles, including microbial elements
previously associated with suppression of
plant pathogens”
The study conc luded that using Brassica SM
formulations apple replant disease can be
fought as shown by the growth of the trees
and increased yields. Mazzola’s research also
showed that the SM applications can provide
weed control, as well as (like the metagenome
analys es revealed) generating higher
populations of bacteria that can metabolize
toxic organic compounds (this may enable
degradation of pesticides applied to the
orchard ).

3.3 Herbie – an efficient fighter against soil borne pathogens

Between 2004 and 2009 the D utch company Thatchtec developed, in collaboration with
Wageningen UR, a new method for biological soil decontamination(sRset). The method consists
of the introduction of 100% plant -based Herbie -granulates (or liquid) into the soil, followed by
covering th e soil with foil for 3 to 4 weeks. According to the tests the company made, it was
shown that after this period, the ground is usually free of nasty diseases caused by damaging
nematodes, molds and insects (in Annex 1 are described the conditions and resul ts of the field
tests on apple trees, conducted by Laimburg Research Centre for Agriculture and Forestry, Italy in
2016 ; the trials included the use of different methods and products such as steaming, solarisation,
chemical and biofumigants – including Her bie).
Ing. H enk Meints, head of Soil Resetting , started in 2014 a close collaboration with Fleuren Tree Nursery
in Kessel Limburg province (The Netherlands) , conducting a field trial with a duration of two years. The
aim of the experiment was to reproduce the tests described by Mazzola (2010;2014;2015) using Herbie
as mediation product in apple replant disease control. Plant behavior was closely observed and the
results were visible positive in the areas where the soil was amended.

reproduced from Mazzola et al. ( 2014) 1

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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picture of apple trial 2014 -2016 1- photo summer 2016 by H.Mei nts

In March 2017 , a new field trial was agreed for the same location but with more ambitious objectives. In
the following two years, a total surface of 990m2 wil l be divided into eight lots of 8m per 15m, with an
added buffer zone of 2m per 15m , while the dosage of Herbie per treatment plot will be 322 kg, plus a
half dosage plot . The control area will be left untreated. Comparing with the reported figures in Mazz ola
(2014), the selected surface for testing plots at Fleuren Boon, is by far larger. It was decided on purpose
to use these bigger scales aiming at an increased validity for the future test results, as Meints reported.
Furthermore, a closer attention will be paid at the soil biology and tree performance (growth and yields)
during different seasons. The hypothesis is that creating the proper anaerobic condition s in the soil
depends on the outside temperature , period of the year and the moment of replanting. Therefore, the
first planting moment(PL1) will take place four weeks after removing the sealing foil3 . However, the
second moment of planting (PL2) has been chosen for April 2018.

3 The trial will use foil covering periods of 4,8 and 12 weeks

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma

One of the questions that th is research is willing to answer according to Henk Meints is when can the
previous test results be obtained along the trial period (in relation with the timeframe and external
factors)?

4. Conclusion and recommendations

In the past decades, several researc hers focused their attention on identifying the causes of Apple
Replant Disease, along with finding new strategies to prevent and control this important threat to fruit
production. From leaving the land fallow, using rotation and control crops to soil fumi gation and organic
amendments, all has been considered over time. Nowadays, there is a visible tendency on using
environmental friendly solutions, along with an increase in banning regulation regarding the chemical satellite pictures of the tested area 1- Meints (2017)

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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Field trial 2017 -2019 1 – photo Toma (2017) products used in EU agriculture sector. Therefore, solutions such as Brassica seed meal soil amendments
developed by Mark Mazzola, or Herbie invented by Thatchtec in The Netherlands are the proof that
alternatives exist and can be efficient. However, like any other practice, they all have limita tions in terms
of knowledge and it is mandatory to conduct further research in order to improve their approach. Both
Mazzola and Meints aim at increasing the performance of SM and respectively Herbie, when it comes to
dosage, waiting time (till removing th e sealing foil) and moment of planting the trees. By using larger
surfaces for the field trials, as well as testing the method in different times of the year, together with
multi -DNA tests (to monitor the soil biodiversity), all these give a valuable insig ht over the complexity of
replant disease. Thus, for fighting it we need the proper (and as complete as possible) knowledge, which
can only be gained by exploring, experimenting, (re)inventing till the field tests reach saturation.

Field trial 2017 -2019 2 – applying and incorporating Herbie – photo Toma (2017)

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma
Field trial 2017 -2019 3 – testing the i ncorporation level, digging and covering with foil – photo Toma
(2017)

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
A. Toma
4. Annex 14

Field test results over apple tree performance and soil analysis in the Northern part of Italy.

Department of Ecological Agriculture – VZ Laimburg – 2016

File: BioIncrop
Year of experiment : 2016
Subject : Ground fatigue field test
Test facility : Block 93
Variety / Subsistence : Pink Lady M9
Planting distance 3,2 x 1 m
Experiment Design : 12 variants, 4 replicates of 13 -15 trees per 2 edge trees
A soil – weary experimental plant (previous variety: Braeburn on M 9, planting distance 3,2 x 1 m,
planting year 1998) was carried out with different measures and different products.

Test subjects:

4 All the data and graphics in the current annex were translated and reproduced from the original repo rt provided by Laimburg
Research Centre for Agriculture and Forestry , Italy to Thatchtec BV

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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Description:

Compost analyzes :

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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The c ompost was made of organic material and wood shavings – 3 kg / t ree and was added to the plant
hole during planting .

Fertilizing the plant 2016 :
04.04.2016 Nitramoncal 29 N kg/ha
04.05.2016 Fertigonia 18 -18-18 10,3 N kg/ha
20.06.2016 Fertigonia 18 -18-18 3,4 N kg/ha

Product description : Herbie 82 (dry plant -based pro duct)
It was used for introducing it into the moist soil and hermetically covered with foil upon proper mixing .
The expected result was to create anaerobic conditions and enable fermentation process into the soil .

Dates from Thatchtec B.V over Herbie : Analyzes of Laimburg Agricultural Chemistry Laboratory :

Ash: 4 -5% Trockenmasse (%) 89,6
Dry weight: 90 -95% Feuchtigkeit (%) 10,4
Protein: 20 -26% Asche (% FM) 6,5
Fiber: >10% Organische Substanz (% FM) 83,1
Sugars: 4 -6% Stickstoff (N) (% m/m) 2,58
Starches: 2 -3% C/N-Verhätlnis 19
Ph: 4,5 -5 Wasserlösliche Salze (mg/100 g) 810
Arsen (As) (mg/kg FM) 1,1
Eisen (Fe) (g/kg FM) 0,07
Aluminium (Al) (g/kg FM) 0,02
Mangan (Mn) (mg/kg FM) 31,07
Kupfer (Cu) (mg/kg FM) 6,31
Zink (Zn) (mg/kg FM) 29,06
Chrom (Cr) (mg/kg FM) 1,17
Nickel (Ni) (mg/kg FM) 0,62
Blei (Pb) (mg/kg FM) < 0.01
Cobalt (Co) (mg/kg FM) < 0.01
Cadmi um (Cd) (mg/kg FM) 0,07
Quecksilber (Hg) (mg/kg FM) 0,005

What has been done:
– 1 month before planting, 3.4 kg / m² of Herbie was incorporated in the tree strip in the damp soil

– The soil was covered with film and well -sealed

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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In 2015, the 2nd planting was carrie d out on the solarized area and in the control area .

Table soil analysis on 11.03.2015 :

Evaluations:
Figure 3:
Drive length measurement in cm in the open air
1. Measurement: 14.01.2015
2. Measurement: 10.11.2015

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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Figure 4:
Stem growth measurements (diameter) in mm in the open air
1. Measurement after planting: 20.06.2014
2. Measurement in autumn: 19.11.2014
3. Measurement in the autumn: 10.11.2015
4. Measurement in autumn: 06.12.2016

Figure 5:
Harvest 03.1 1.2016 Number of apples / tree

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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Figure 6:
Harvest 03.11.2016 KG Apples / tree

Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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5.References

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Hoagland et al., 2011 .Biological Mediation of Apple Replant Disease in Organic Apple Orchards

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annual vs. perennial growth habit impact soil microbial community and apple replant disease
suppression. Organic Seed Alliance Conference, Port Townsend, WA. pp. 13 -15
Hoestra H 1968 Replant diseases of apple in The Netherlands. Meded. Landbouwhogesch. Wageningen
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Mazzola, M., 1998. Elucidation of the microbial complex having a causal role in the development of
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Mazzola, M., 1999. Transformation of soil microbial community structure and Rhizoctonia suppressive
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Mazzola, M., Gu, Y. -H., 2002. Wheat genotype -specific induction of soil microbial communit ies
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Apple Replant Disease – Theory versus practice, a n overview of known controlling methods
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Mazzola, M., Funnell, D.L., Raaijmakers, J.M., 2004. Wheat cultivarspecific
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Rumberger, A., Yao, S., Merwin, I.A., Nelson, E.B., Thies, J.E., 2004. Rootstock genotype and orchard
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