Harrow pears continue to show promise. " The ‘Harrow’ (Ontario, Canada) pear breeding program was initiated in 1962 to develop fire blight resistant pear selections for the fresh and processing markets ." Have never seen anyone attempt to list all 25 varities. It is my feeling we should grow the ones we can and continue to watch for the others to be released. Harrow hw623 & hw624 are now known as Happi & Dew drop pears Harrow hw623 & hw624 Happi & Dew drop pears a follow up
https://www.ars.usda.gov/ARSUserFiles/20721500/catalogs/pyrcult.html
Notes on hw 604 & 605 are found here http://publications.gc.ca/collections/collection_2015/aac-aafc/agrhist/A51-1-1978.pdf
270287.pdf (1.9 MB)
These are the 25 pears from the harrow station.
HW 600 unamed above
HW 601 unamed above
HW 602 harvest queen
HW 603 harrow delight
HW 604 unamed above
HW 605 unamed above
HW 606 bliss
HW 607
HW 608 delicious
HW 609 harrow sweet
HW 610 harrow crisp
HW 611 unreleased
HW 612
HW 613
HW 614 sundown
HW 615 unreleased
HW 616 harrow gold
HW 617 unreleased
HW 618
HW 619 unreleased
HW 620 unamed above
HW 621 unreleased
HW 622 unreleased
HW 623 happi
HW 624 dew drop
Performance-of-New-Fire-Blight-Resistant-Pears-Bill-Shane.pdf (822.1 KB)
"
Introduction
The North American continental climate is sufficiently
moderated by the Great Lakes to allowing the com-
mercial production of cold tender tree fruits
(including peach, nectarine, apricot, and pear) in
southern Ontario, Canada, and adjoining states of the
USA.
In Ontario the major production area is the Niagara
region, which extends ~50 km west from the Niagara
River to the outskirts of Hamilton Ontario, and some
15-20 km south from Lake Ontario towards Lake Erie.
In this area, the combination of soil types and climatic
zones moderated by the interaction of Lake Ontario
and the Niagara Escarpment provide conditions suita-
ble for commercial tender fruit production. Growing
conditions are less favourable elsewhere in Ontario,
but a significant industry has developed along the
north shore of Lake Erie in the southwestern part of
the province, where climatic conditions are typically
more extreme in both summer and winter. Pears can
also be produced in limited areas around Georgian
Bay, and along the St. Lawrence and Ottawa River
valleys where conditions can be favourable.
Pear production in Ontario is concentrated in the
Niagara region (~85% of provincial production) and
southwestern Ontario (~12%) with limited production
elsewhere in the province. Major cultivars are Bartlett
(syn. Williams) and Bosc (~60% and ~25%, respective-
ly). Until 2008, ~60% of the Bartlett crop was pro-
cessed, but this market was lost when the only pro-
cessing plant in eastern North America was closed.
Since 2008, pear production has declined. In 2010,
Ontario produced 2928 T from 407 ha of bearing or-
chard, with a farm gate value of ~CAD 3.6 million
(Statistics Canada, 2012).
Pear breeding activities were initiated by Dr. R.E.C.
Layne in 1962 at the Agriculture and Agri-Food Cana-
da (AAFC) Research Centre at Harrow Ontario, located
in the south-westernmost part of the province (lat.
42° 02’ N, long. 82° 54’ W). Throughout the 1970s, Dr.
H.A. Quamme made a large number of crosses, which
were evaluated by Dr. F. Kappel (1982-1987) and Dr.
D.M. Hunter (from 1988). Starting in 1988, crosses
were made to incorporate resistance to both fire
blight and pear psylla (Cacopsylla pyricola) into high
quality fruiting selections. In the mid-1990s, the pro-
gram was transferred to the AAFC Research Farm at
Vineland Station in the Niagara Region (lat. 43° 11’ N,
long. 79° 24’ W), the transition taking five years to
complete (1996-2000). The Harrow/Vineland program
was the only active pear breeding program in Canada
in the 1990s and 2000s, and crosses were made each
year during this period. AAFC funding for the program
was discontinued in 2009, and an exit strategy was
developed to accelerate seedling evaluation, with an
emphasis on identifying potential introductions while
at the same time removing seedlings which did not
meet selection criteria. Final pollinations were con-
ducted in 2011, primarily for pollen compatibility
purposes. Under the terms of a commercialization
contract completed in 2012 with the Vineland Re-
search and Innovation Centre (VRIC), responsibility for
pear introductions was transferred to VRIC, and cur-
rently (2016), VRIC is evaluating the remaining seed-
ling populations for potential new advanced selec-
tions.
2. Breeding Objectives
The major pear breeding objective was the develop-
ment of selections and cultivars with improved re-
sistance to biotic stresses, especially resistance to fire
blight. Fire blight (a bacterial disease caused by Erwin-
ia amylovora) was, and still is, the major disease con-
straint for pear production in Ontario. The dominant
cultivars, ‘Bartlett’ (syn. ‘Williams’) and ‘Bosc’,
(approx. 60% and 25% of Ontario production, respec-
tively), are both very susceptible to fire blight, and
their continued production is dependent on timely
applications of streptomycin for fire blight control.
Breeding resistant or tolerant cultivars is the long-
term alternative to dependency on chemical control.
Additional objectives included: (1) extending the har-
vest and marketing seasons, thus providing additional
marketing opportunities; (2) improved fruit qualities
such as fruit size, appearance, skin color, flesh firm-
ness, flavor, texture, and processing and storage po-
tential; (3) improved resistance to pear psylla
(Cacopsylla pyricola); (4) improved tree longevity,
good annual productivity with no biennial bearing
habit, vigor, growth habit and precocity; and (5) im-
proved resistance to other faults, such as pre-harvest
drop, non-uniform fruit ripening, and short shelf life.
3. Breeding Strategy
Since it was initiated at AAFC-Harrow in 1962, the
pear breeding program involved controlled hybridiza-
tions between selected parents, primarily Pyrus com-
munis (European pear) cultivars. Crosses were made
each spring from 1963-1968, 1972-1981 and 1988-
2011. Typically, there was a minimum of 200 pollinat-
ed flowers per cross, and up to 80 parental combina-
tions in any one pollinating season. Seedling popula-
tions were generated from which individual seedlings
were selected (based on tree and fruit characteristics)
for further evaluations prior to the introduction of
new cultivars. Typically, this process takes at least 20
years.
A recurrent mass selection breeding strategy was
followed to simultaneously improve disease re-
sistance, cold hardiness, and tree and fruit character-
istics. Modified back-crossing was also used to incor-
porate a greater range of desirable pomological char-
acters while avoiding deleterious effects of inbreeding
associated with repeated back-crossing to a single
parental cultivar. However, ‘Bartlett’ was used exten-
sively in the program, as it was the industry standard,
with many desirable characteristics. Interspecific hy-
bridization was used only to a limited extent, the
benefits of incorporating desirable characteristics
found in other Pyrus species being offset by require-
ments for one to several generations of back-crossing
in order to recover acceptable cultivar characteristics.
Many sources of resistance to fire blight were used,
including fire blight-resistant selections from US
breeding programs (e.g. Rutgers University, NJ; USDA,
Beltsville, MD, and Kearneysville, WV; Purdue Univer-
sity, IN). The fire blight-resistance of advanced selec-
tions and introductions was derived from P. com-
munis cultivars (e.g. ‘Seckel’, ‘Waite’, ‘Maxine’, ‘Old
Home’, ‘Farmingdale’), the interspecific hybrid
‘Kieffer’, or from species selections such as P. ussuri-
ensis ‘76’ and P. pyrifolia ‘NJ-1’. Since the early
1970s, seedling selections from the Harrow program
were also used as both pollen and seed parents. Sev-
eral selections from the Cornell University (Geneva,
NY, USA) program developed from a P. communis x P.
ussuriensis cross back-crossed to P. communis had
good resistance to both fire blight and pear psylla,
and were used as pollen parents in the Harrow pro-
gram during the 1988-1995 period.
4. Screening and Seedling Evaluations
Seedling populations were evaluated, primarily in the
field, for characteristics of the major breeding objec-
tives. Each objective forms part of a multiple trait
selection protocol, and a serious deficiency in any of
the major areas where cultivar improvement was
being sought resulted in that individual seedling being
discarded.
Fire blight screening techniques were developed to
identify fire blight resistance in progeny and potential
parents (Layne and Quamme, 1975). In the green-
house, seedlings ~30-40 cm tall were inoculated near
the actively growing shoot tip with 100 μL of a stand-
ardized suspension of six virulent strains of E. amylo-
vora (108 cfu mL-1
). When evaluated two months later,
seedlings were discarded if the lesion extended beyond ~25-30% of the shoot length, thus reducing the
number of susceptible seedlings planted out for field
evaluations. At Harrow, seedling trees were screened
again when they started to fruit, usually 5-7 years
after planting into seedling orchards. Actively growing
shoot tips (minimum of 10 per tree) were inoculated
in early June with the standardized mixture of six E.
amylovora strains, and the lesion length as a percent
of total shoot length was determined about six weeks
later. In addition, all trees were assessed annually in
the field for incidence and severity of natural fire
blight infections, using a modification of the USDA
scale (van der Zwet et al., 1970). ‘Kieffer’ was used as
the standard reference for this assessment, and the
rating had to be equal to or better than ‘Kieffer’ for
continued evaluations. At Harrow, ‘Bartlett’ had an
average rating of 3.9 on this scale.
Seedling trees were evaluated for horticultural and
fruit characteristics. In order to determine optimum
harvest time (based primarily on appearance and fruit
firmness), fruits were harvested on 2-3 dates each
harvest season, and evaluated after one to several
weeks of cold storage. For seedling screening, fruits
were rated for appearance, flavor and texture, while
advanced selections were subject to more extensive
fruit analysis (including Brix, pH, titratable acidity,
fruit firmness, skin and flesh colour). In addition, oth-
er descriptive data were collected and used for filing
Plant Breeder’s Rights applications. Fruit samples
were also processed as pear halves or puree, and
evaluated by a semi-trained taste panel to assess the
processing potential of these selections; Bartlett sam-
ples were also processed and used as the reference
cultivar.
5. Virus Testing of Selections
When a seedling selection was advanced for further
testing, trees were propagated for planting in repli-
cated second test orchards and in grower trials. When
propagation was initiated, budwood samples from
the original seedling tree were sent to the Agriculture
Canada Plant Quarantine Station [now known as the
Canadian Food Inspection Agency (CFIA) Sidney La-
boratory] in Saanichton, BC, for virus-testing. Woody
host and herbaceous-host biological indicators, to-
gether with serological and molecular methods, were
used to test for the presence or absence “of all known
viruses, virus-like agents, viroids, and phytoplas-
mas” (D. Thompson, pers. comm). This process typi-
cally took about three years to complete, though
preliminary results were usually available within two
years of sample submission. With the development of
new diagnostic methodologies, especially PCR, testing
can now be completed within one year. If test results
were positive, distribution of propagated trees in the
nursery was cancelled to prevent spread of infected
material. Virus-free trees have been maintained in a
repository at the CFIA Sidney Laboratory, and limited
quantities of virus-free budwood can be made availa-
ble for propagation.
6. Second Test and Grower Trials
Trees of advanced selections and standard cultivars
(as reference cultivars) were propagated on either
Bartlett seedling rootstock or on clonally-propagated
rootstocks, usually Old Home x Farmingdale 87
(OHF87), and planted into replicated trials at AAFC-
Harrow (to 1994) or at AAFC-Vineland (starting in
1998), as well as at other research stations across
Canada. In some years, trees were also propagated on
quince rootstocks (Quince A or Quince C). Replicated
trials at Harrow typically consisted of 3-5 selections
and 1-3 reference cultivars, all on the same rootstock,
and planted as single-tree plots in a completely ran-
domized design with 4-6 replicates. Grower members
of testing organizations [from 1964 to 1997: the
Western Ontario Fruit Testing Association (WOFTA);
after 1997: the Ontario Fruit Testing Association
(OFTA)] could obtain limited numbers of trees of ad-
vanced selections, subject to non-propagation agree-
ments, for testing in commercial orchards. By con-
ducting replicated trials and grower evaluations con-
currently, the time required for evaluation and intro-
duction of a new cultivar was reduced. Data from
replicated trials, evaluations of both fresh and pro-
cessed fruit, and annual tree performance cards re-
turned to WOFTA/OFTA were all used to determine
the commercial potential of advanced selections.
The replicated trial orchards at Harrow and Vineland
were also used to collect detailed objective descrip-
tive data required for the Plant Breeder’s Rights (PBR)
applications under the Canadian Plant Breeder’s
Rights Act of 1990.
Advanced test selections were also evaluated by co-
operating researchers in other countries. Commercial-
ization contracts for introductions were developed,
and, where possible, these introductions were pro-
tected under appropriate legislation (e.g. COV, EU
PVR, USPP). In some cases, selections were discarded
in Ontario as they did not meet criteria for introduc-
tion, but evaluations at other locations with less se-
vere conditions [both abiotic (especially climatic) and
biotic (especially disease pressure)] led to naming,
protection and introduction outside of Canada.
7. Cultivar Introductions
To date, 25 selections have been placed in advanced
trials. Of these, six have been named and introduced
for commercial production in Canada. Other selec-
tions (i) are in the final stages of testing prior to nam-
ing; OR (ii) require some further evaluation; OR (iii)
have been discarded from further evaluations in On-
tario. All these selections have good to excellent re-
sistance (but not immunity) to natural fire blight in-
fections, with ratings greater than 8.5 on the USDA
scale; on this scale, Bartlett (a susceptible standard
cultivar) has a rating of 3.9, while Kieffer (a resistant
standard cultivar) is rated at 9.0. Harvest dates for
these cultivars and selections range from about 2
weeks before Bartlett to 4 weeks after Bartlett.
‘Harrow Delight’ and ‘Harvest Queen’ (Quamme and
Spearman, 1983) were introduced into the public
domain in 1981. ‘Harrow Sweet’ (Hunter et al., 1992),
‘AC Harrow Gold’ (Hunter et al., 2002a), ‘AC Harrow
Crisp’ (Hunter et al., 2002b), and ‘Harovin Sun-
down’ (Hunter et al., 2009)] were introduced after the
granting of Plant Breeder’s Rights and are subject to
commercialization contracts. Three additional selec-
tions (HW620, HW623 and HW624) are to be intro-
duced in the near future. HW624 will be the first in-
troduction combining fire blight resistance and psylla
resistance.
In addition, two cultivars [AC Harrow Delicious
(HW608) and ‘Harrow Bliss’ (HW606)] were named,
protected and introduced in Europe.
7.1. Brief Notes On Cultivars
The following are brief notes on introductions and
selections, presented in approximate order of har-
vesting. Harvest dates were determined on trees
grown at Harrow, Ontario, Canada. All these selec-
tions have good to excellent resistance (but not im-
munity) to natural fire blight infections.
7.1.1. Harrow Delight (HW603)
Harvested about August 10 at Harrow, ~2 weeks be-
fore Bartlett. Fruit colour is greenish-yellow with a red
blush. Because it tends to drop heavily as it matures,
fruit should be picked while still green. If left on the
tree until the background colour changes to yellow,
shelf life is also greatly reduced. The tree consistently
produces good crops. Fruit size which is similar to
Bartlett on unthinned trees is improved by thinning.
Even when the skin colour is greener than yellow,
flesh texture is very good, very juicy and free of stone
cells. Fruit flavour is rated as high as Bartlett. When
processed as halves or puree, Harrow Delight has had
better-than-average ratings, but not as high as for
Bartlett. Mature trees have excellent resistance to fire
blight (9.5 rating on the USDA scale), but this cultivar
is susceptible to pear psylla. Harrow Delight is pollen
compatible with Harvest Queen, Bartlett, Bosc and
Anjou. This cultivar was released in 1981 and there-
fore there are no propagation restrictions.
7.1.2. AC Harrow Gold (HW616)
Fruit are picked ~10 days before Bartlett, between
Harrow Delight and Harvest Queen. An attractive
yellow fruit, with good size (larger than Harvest
Queen, similar to Bartlett), smooth skin, fine texture,
very good flavour, and exceptionally juicy. The fresh
fruit quality of AC Harrow Gold is rated similar to
Bartlett. As with many other early season pears, the
fruit will not store for very long (probably no more
than 4-6 weeks), but it is excellent for roadside
stands. The tree is fire blight resistant (9.5 rating).
Pollination of Bartlett by AC Harrow Gold has been
variable: in some years, it does not appear to polli-
nate Bartlett, while in other years, good fruit set has
been obtained with AC Harrow Gold pollen. Bartlett
does appear to consistently pollinate AC Harrow Gold.
Precocity in a second test planting appears to be simi-
lar to that of Bartlett. AC Harrow Gold was introduced
in 2000, and protection under the Plant Breeders
Rights Act was granted in 2003.
7.1.3. Harvest Queen (HW602)
Picked the third week of August, ~1week before Bart-
lett. Fruit keeps on the tree very well and will increase
in size with later picking. Fruit size is usually smaller
than Bartlett, even with thinning which improves fruit
size and reduces the tendency for biennial bearing.
When grown on OHxF-333 rootstock, fruit size is fur-
ther reduced, so that a higher proportion of fruit are
unmarketable. Fruit quality, texture and flavour are as
good as or better than Bartlett, both fresh and pro-
cessed as pear halves. The tree has very good fire
blight resistance (9.1 rating). Harvest Queen is pollen
compatible with Harrow Delight, Bosc and Anjou, but
not with Bartlett. This cultivar was released in 1981
and therefore there are no propagation restrictions.
7.1.4. AC Harrow Crisp (HW610)
A very attractive pear with red blush on smooth yel-
low skin. The cream-white flesh is smooth, grit-free,
firm even when fully ripe, with a mild sweet flavour.
The fruit matures at the end of August or early Sep-
tember, about the same time as Bartlett. It can be
picked over a 2-week period. Early picked fruit can be
stored for about 2 months, but storage life is reduced
with later picking. If kept too long or picked too late,
it will deteriorate internally without external signs.
Fruit size on unthinned trees is slightly larger than
Bartlett. It has a good to very good rating for quality
of both fresh and processed fruit. Tree is medium in
size, conical and upright, annually productive and
hardy. It is a poor pollinator and will not pollinate
5
Bartlett, but Bartlett will pollinate AC Harrow Crisp to
a limited extent. The tree has very good fire blight
resistance (9.4 rating), similar to Harrow Sweet and
Harvest Queen. Precocity of AC Harrow Crisp is similar
to Bartlett, trees coming into production about 4
years after planting. AC Harrow Crisp was introduced
in 2000, and protection under the Plant Breeders
Rights Act was granted in 2003.
7.1.5. HW624
The fruit, which ripens about 7-14 days after Bartlett,
have a light yellow background colour when ripe, with
a very attractive bright red blush on the exposed side.
Flavour and texture are very good. The original seed-
ling had a good first crop in 1997, and yield was also
good in 1998. This selection was advanced in 1998,
and propagated for testing through OFTA in 2000.
HW624 also has field resistance to pear psylla. It is
not directly graft-compatible with Quince rootstocks.
Protection under the Plant Breeders Rights Act was
granted in 2012, and this selection will be introduced
in the near future.
7.1.6. HW623
A late season pear harvested ~3 weeks after Bartlett.
Fruits are yellow-green with a light blush, and a
creamy-white flesh with smooth texture. Fruits have a
long narrow neck, similar to Bosc. Yields have been
moderate, and fruit size is medium-large. Protection
under the Plant Breeders Rights Act was granted in
2010, and this selection will be introduced in the near
future.
7.1.7. Harovin Sundown (HW614)
The fruit ripens about 3 weeks after Bartlett. The orig-
inal seedling tree has been a good perennial yielder
since being selected in 1982. Fruit shape is ovate to
ovate-pyriform, with good size (similar to Bartlett).
The fruit has a smooth yellow-green skin with a light
russet in some years. The flesh is cream-white with
good texture. While flavour is generally good, there
can be some astringency in the skin which is reduced
by storage. Poor fruit flavour due to astringency, even
after storage, has been reported for fruit produced in
cooler-than-normal seasons at Harrow, so this selec-
tion will probably not be adapted to the cooler grow-
ing season conditions in the Atlantic Provinces. This
pear will store very well at -0.5 C for about 10 to 12
weeks (until late December). The tree is fire blight
resistant (9.6 rating). It tends to produce secondary
flower clusters which can lead to the development of
late-ripening second crop. Secondary flowering has
not resulted in increased fire blight infections. It does
not appear to pollinate Bartlett well, but HW614 is
pollinated by Bartlett. In second test plantings, pre-
cocity and productivity have been similar to Bartlett.
Harovin Sundown was introduced in 2008 and protec-
tion under the Plant Breeders Rights Act was granted
in 2010.
7.1.8. Harrow Sweet (HW609)
Harrow Sweet produces annual heavy yields of fruit
ripening about 23-25 days after Bartlett. Fruit has
yellow ground colour with red blush, and fruit size is
comparable to Bartlett. Because it yields heavy crops,
Harrow Sweet should be thinned to maintain fruit size
and productivity. The fruit is very sweet and juicy,
with excellent taste, and keeps well in cold storage
for about 10 weeks (into December) - longer than
Bartlett. It can be gritty around the core but this does
not detract from overall quality. It has received ac-
ceptable ratings in processing trials at Harrow. The
tree is medium in size, pyriform, upright spreading,
hardy and consistently very productive. It has good
fire blight resistance (9.3 rating), similar to Harvest
Queen and Harrow Delight. Harrow Sweet is more
precocious than Bartlett, producing fruit from lateral
buds on one-year wood as well as on spurs, thus com-
ing into production in the second or third year after
planting; however, fruit size may be a problem on
very young trees. Named in 1990, Harrow Sweet was
the first release from the Harrow pear breeding pro-
gram to be protected under Plant Breeders Rights
legislation in Canada and Europe, and a US Plant Pa-
tent has been issued. This cultivar has been commer-
cially available through our agent since 1996.
7.1.9. HW620
Attractive greenish-yellow fruit with no blush, ripen-
ing about 4 weeks after Bartlett. Fruit shape is similar
to Bartlett. The original seedling, which is not thinned,
may have a tendency to biennial bearing: in the light-
er crop years, fruit size is larger than Bartlett, while in
heavier crop years, fruit size is similar to or slightly
smaller than Bartlett. Appropriate orchard manage-
ment practices, especially pruning and thinning, have
reduced this tendency in the early years of a second
test orchard. Fruit texture is smooth and buttery with
a mild pleasant flavour. Fruit will store well for about
12 weeks. The tree has very good fire blight re-
sistance (9.3 rating) but pear scab has been a problem
in some years. Protection under the Plant Breeders
Rights Act was granted in 2012, and this selection will
be introduced in the near future.
8. Commercialization
For information on commercial availability of intro-
ductions, please contact Agriculture and Agri-Food
Canada, Office of Intellectual Property and Commer-
cialization by email at OIPC-BPIC@agr.gc.ca.
Acknowledgements
The support of the Ontario Fruit Producers Marketing
Board, the Western Ontario Fruit Testing Association
and its successor organization, the Ontario Fruit
Testing Association, and the collaboration their grow-
er members, is gratefully appreciated. Also appreciat-
ed is the support of the St. Davids (Ontario) fruit pro-
cessing plant (operated at different times by Canadian
Canners, Nabisco, Kraft and Con Agro) and their col-
laboration in sensory evaluations of processed prod-
ucts from the pear breeding program.
References
Hunter DM, Pinsonneault P, Kappel F, Quamme HA,
Bonn WG, Layne REC, 1992. ‘Harrow Sweet’ Pear.
HortScience 27: 1331-1334.
Hunter DM, Kappel F, Quamme HA, Bonn WG, 2002a.
‘AC Harrow Gold’ Pear. HortScience 37: 224-226.
Hunter DM, Kappel F, Quamme HA, Bonn WG, 2002b.
‘AC Harrow Crisp’ Pear. HortScience 37: 227-229.
Hunter DM, Kappel F, Quamme HA, Bonn WG, Sling-
erland KC, 2009. ‘Harovin Sundown’ Pear. HortScience
44: 1461-1463.
Layne REC, Quamme HA, 1975. Pears. In: Janick J,
Moore JN (Eds), Advances in Fruit Breeding. Purdue
University Press, West Lafayette, IN, USA. 38-70.
Quamme HA, Spearman GA, 1983. ‘Harvest Queen’
and ‘Harrow Delight’ Pear. HortScience 18: 770-772.
Statistics Canada, 2012. Fruit and Vegetable Produc-
tion. http://www.statcan.gc.ca/pub/22-003-x/22-003-x2011002-eng.pdf
Van der Zwet T, Oitto WA, Brooks HA, 1970. Scoring
System for Rating Severity of Fire Blight in Pear. Plant
Disease Reporter 54: 835-839.
New Canadian pear varieties are fire blight tolerant
Pear breeding north of the border
New pear is twice as nice