The Nordic Gene Bank’s Prunus clone archive in Finland
I Local races of sour cherry
Pauliina Palonen
DepartmentofPlantProduction,POBox27,FIN-00014 UniversityofHelsinki,
Finland,e-mail:pauliina.palonen@helsinki.fi Marjatta Uosukainen
AgriculturalResearch CentreofFinland,Laukaa Research and Elite PlantStation, Antinniementie I, FIN-41330Vihtavuori,Finland
Eeva Laurinen
AgriculturalResearch CentreofFinland, Horticulture, Toivonlinnantie 518,FIN-21500Piikkiö, Finland
Päivi Parikka
AgriculturalResearch CentreofFinland,PlantProtection,FIN-31600Jokioinen.Finland JyriKankila
DepartmentofPlantBiology,POBox27,FIN-00014 UniversityofHelsinki.Finland
Morphological variation among78localraces ofsourcherry(Prunus cerasusL.) inthe Nordic Gene Bank’s Prunus clone archiveinPälkäne inSouthwesternFinland was examined. Each treewasde- scribed using 42 characteristics. On the basis of fruitcharacteristics, 32samples wereclassifiedas morellos, 40samplesasamarelles,and5 samplesdistinct from the other amarellesareproposed tobe calledRymättylä-type cherries. One sample wasfound to be Prunus avium. Amarelle type cherries proved tobe more selfcompatiblethan morello type cherries. In order to find hardy sourcherry cultivars with fruits ofgoodflavour and fit for cultivation inNordic conditions,the mostpromising localraces from each groupwereselected foracomparativetrial.Additionally, somelocalraceswere selected for further use inplant breeding. In 1994-1996,an increasing amountofsevere bacterial canker symptoms wasobservedinthe clone achive.
Key words', amarelle, morello,Prunus cerasus,Rymättylä, self-compatibility
ntroduction
able agricultural and horticultural plant materi- al in the Nordic countries. The horticultural crops are mainly vegetatively propagated, and must, therefore, be preserved on their original grow- ing sites(in situ),orin Gene Bank clone archives The Nordic GeneBank(NGB),founded in 1979,records and preserves genetic variation in valu-
©Agriculturaland Food Science inFinland Manuscriptreceived June 1997
Vol 7(1998):391-
(exsitu)(Trajkovski etal. 1992).The aim of the Prunus project of the Nordic Gene Bank is to find sour cherry, plum and damson plum culti- vars adaptedto Nordic conditions, and to find localraces, which could be cultivated as such, orused in breeding. Besides being used in fruit production, cherry, plum and damson plumtrees arealso excellent ornamentals.
Sour cherry (Prunus cerasus L.) has been cultivated in Finland since the 17thcentury(Col- lan 1929).In 1929, after anexceptionally hard winter,itwasfound that in total21 cherry culti- varsexisted in Finland (Collan 1934). In thepast, cherrytreeswereimportedtoFinland from Rus- sia, Estonia, Germany and Sweden (Collan
1929).The oldest known cultivars in Finlandare
‘Yleinen kuulasmarja’ (‘Common amarelle’),
‘lso kuulasmarja’ (‘Big amarelle’) and ‘Varjo- morelli’(known as ‘Schattenmorelle’ in Germa- ny and ‘Skuggmorell’ in Sweden) (Meurman
1947).Thetreeshave been open pollinated free- ly, and newoffspring generated from seedshave
been propagated and distributed throughroot suckers. Due tothe decades of long natural se- lection and adaptation to harshconditions, the hardiest germplasm available is mostprobably tobe found among the native cultivars.
Anunderstandingofphenotypic and genetic variation in sourcherry is important for cultivar development, future germplasm collection, and setting of priorities for germplasm maintenance (Hillig and lezzoni 1988). The objective of this studywas toexamine the morphological varia- tion in local racesofsour cherry in the Nordic Gene Bank’s Prunus clone archive at the Agri- cultural Research Centre ofFinland, Häme Re- search Station inPälkäne, andtoselect themost promising local races for a comparative trial, starting in 1994.
Material and methods
The local races ofsour cherry, plum and dam- son plumwereregistered during 1982-85, main-
ly in Southern and Southeastern Finland includ- ing the Åland Islands. From every individual Prunustree,registeredonthe Finnishmainland, atleast two root suckers were taken and trans- ported to the Agricultural Research Centre of Finland, Institute of Horticulture in Piikkiö, where they were planted in a temporary loca- tion.In 1988, duplicates of each localrace were
sent toPälkäne(61°2o’ N,24° 13’E), wheretrees wereplantedon anexperimental field with sandy soilata spacing of 3 metreswithin and4metres betweenrows.The localracesoriginating in the Åland Islandswereplaced inaPrunus clonear- chive atÅland Experiment Station in Jomala.
InPälkäne,diseasesymptoms were observed, butno plant protection chemicalswere used in the Prunus orchard. 300 kg of compound ferti- lizer (NPK 7-5-15)per hectare wasappliedan- nually. Every tree was protected against mead- ow voles withaplastic shield. Weedingwas car- ried outby mowingorharrowing, when needed.
Root suckers wereremoved annually. The trees were notpruned.
Documentation of cherry material in the Pru-
nus clone archive in Pälkäne was carried out during each seasonbetween 1992 and 1993. In 1992, the Prunus clone archive consisted of 122 sour cherry trees,representing 79 different lo- cal races, and in 1993, of 118trees, represent- ing 78 different local races. Each tree was de- scribed by the characteristics used by the Nor- dic Gene Bank. The descriptionswere comple- mented with some further characteristics used by the International Union for the Protection of New Varieties ofPlants(UPOV). In total42 char- acteristicswere used for the description of each tree. Characteristics observed were related to growth habit, flowering, fruitset, as wellasthe external and internal properties of the fruits. The descriptionsweremade mainly in 1992 andcom- plemented in 1993. The descriptions will be saved in the Nordic Gene Bank’s database BIRS.
In 1992 and 1993, the self-compatibility of localraces ofsour cherrywas studied. In 1992, 30 local races were selected for the self-com- patibility studies. Three branches pertree were isolated before floral anthesis by enclosing them
in acrylic bags. Additionally, some branches were collected from each tree, and forced to flower. Pollen was collected and the isolated flowerswereself-pollinated.Also,three branch- es per tree were marked and allowed to open pollinate.
In 1993, the pollination experiments were limitedto20 localraces selected in the previous year. Two branches per tree were isolated with acrylic bags, andtwobranchesweremarked and used as open pollinated controls. Self-pollina- tionwas aided by brushing the isolated flowers carefully withasmall clean brush, asthe pollen was dehisced. This wascarriedoutdaily during the flowering period.
The number ofself-pollinated flowers and the number of open-pollinated flowers werecount- ed, and in early July, the number of green fruits was recorded. The percentages of fruitset on self-pollinated andonopenpollinated branches werecalculated. The self-compatibility compar- isons were made in two different ways; based on the geographic origin of the localraces, and basedontheir fruittype classification. The self- compatibility of Eastern and Western localraces was compared in 1992, and the self-compatibil- ity of local races, belonging to different main groups,in 1993.The ratio ofpercentage fruitset with self-pollination to that with open pollina- tion describes the self-compatibility of each lo- cal race. The data on the ratios were analysed with ANOVA- 1-test of MSTAT-C -program (Michigan State University 1989).
Allthe localraces ofsour cherrywereeval- uated for their possible further use. The main criteria were: ornamental value, fruitset, fruit quality, winter-hardiness and resistance todis- eases and pests.Each localrace waseitherrec- ommended for further studyordeterminedtobe ofnovalue.In orderto find hardy sour cherry cultivars with fruits of good flavour and fit for cultivation in Nordicconditions,themostprom- ising localraces from each groupwere selected for a comparative trial and some for possible further usein plant breeding.
Results
Although treesflowered freely in 1992, the yield was low, and the harvesting periodwas length- ened because of the cool weather. In 1993, the flowering season wasvery early because of the extremely warm weather in May and the period of flowering varied from 12Mayto29 May. The differences in earliness of flowering werenegli- gible among the clones. On average, the yield was very high and the fruits were of good qual- ity. The fruitswereharvested from28 Julyto 13 August.
Onthe basis of their fruit characteristics the
local races of sour cherry were classified into three main groups(Table 1).One localrace was foundtobe Prunus avium.
Group 1. Morello cherries. Fruits are very dark, nearly black when mature. The mean weight of the fruitswas2.4 g in 1993. The stalk is fairly long. Fruit flesh and juicearedark red.
The cherries are very aromatic but mostly ex- tremely bitter. The trees have long and weak branches, with bare parts on them. Because of their high contentofacids, intense juice colour and strong aroma,the fruitsaresuitable forcon- serving and for use in the food processing in- dustry.
Group2. Amarelle cherries. Fruit colour is red ordark red. The mean weight of the fruits was2.5 g in 1993. The stalk is ofmedium length.
Fruit flesh is yellowish pink and juice is colour- less or pink. At maturity, the fruit skin is often nearly translucent. The cherries arerelatively sweet or slightlybitter, and less aromatic than morellos. The fruitsare suitable for fresh con- sumption. Thetrees may bebig and bush-likeor small withadecorative form.
Group 3.Rymättylä-type cherries. The sour cherry races of this group resemble amarelle cherries, exceptthat the fruits tendtobe bigger and flatter. The stalk is typically short,thick and rather stiff. Themean weight of the fruits was 2.8 g in 1993. Fruit colour is red. The cherries areproposedtobe called Rymättylä-type,asthey have been registered in Rymättylä or its sur- Vol. 7(1998):391-399.
Table I.Localraces ofsourcherry,selected for furtherstudy.Theraces aredivided into the three main groups of the Finnish sourcherry.
Morello cherries Amarelle cherries Rymättylätype
7 Rymättylä Myttäälän hapankirsikka 4 Rymättylä
35Parainen 12Tammela 5 Rymättylä
87Laukaa 19Somero 10?
107Mäntsälä 24Masku 37Turku
110 Virojoki 30Tenhola 66Sammatti
112Vehkalahti 43Kustavi
114 Lappeenranta 52Tuusula
116Joutseno 54Vantaa
121Juva 74e,Lohja mlk
122Juva 85?
123Juva 86?
125Pertunmaa 91 Nurmijärvi
129Anjalankoski 92 Loppi
134Pertunmaa 93Kärkölä
141Anttola 95Hollola
142Puumala 96Hollola
98Asikkala 101Kuusankoski 102Koria 104Kotka 105Lapinjärvi 108Mäntsälä 109Pyhtää 124Mikkelimlk.
131Lahti 133Pertunmaa 137Laukaa 139Toivakka 140 Kangasniemi 143Anttola 144,Anttola 146Joroinen 160Mikkelimlk.
301?
roundings in Southwestern Finland. Their ori- gins arenotknown.
The local races of morello cherries were found growing mainly in Eastern Finland. The distribution of local races of amarelle cherries ismorewestern.Thesetwotypesmeeteach other in the area between 26° and 21° ofeastern lon- gitude. In the clone archive, the mostnorthern samples of both types were found growing in Laukaa(62°20’ N). However,after the NGB col-
lectionwas completed in 1988,two more sam-
pieswereregistered evenfurther north. The most northern morello sample wasfound from Tuus- niemi (62°45’N) (R.Teravuo, personalcommu- nication, 1993),and themost northern amarelle sample from Pihtipudas(63° 15’N) (M.Raatikai- nen,personalcommunication, 1992). Thesetwo sampleswereaddedtothe clone archive in 1995.
In 1992, the percentage of fruit set varied with self-pollination from 0 to 18, the average being 4.3, and with open pollination from 3 to 24, the average being 10.7(Table 2 and Fig-
ure 1). It was found that the local races from Western Finland yielded higherpercentages of fruit set, both by self-pollination and by open pollination, than the local races from Eastern
Table2.Percentagefruit sets ofsourcherrybyself-polli- nation (self) andby openpollination (open) in 1992and
1993,and theirratio in 1993,
Percentagefruitset
Local 1992 1993 self/open
self open self open (%) race no.
Morellos 1.3 14.1 5.2 34.3 15.5
Amarelles 4.9 9.1 23.1 27.4 94.3
Rymättylä-type 10.5 10.5 38.5 38.5 102.0 Total average 4.3 10.7 19.3 30.6 71.4
Finland. Because of highly random variation in the results it is impossible to say which local races are self-compatible (Saarimäki 1994). In general, thepercentage fruit setswere in 1993 higher than in 1992. They varied with self-polli- nation from2 to39, the average being 19.3, and with open pollination from 13to43, the average being 30.6. Amarelle cherries and Rymättylä- typecherries provedtobemore self compatible than morello cherries (P=0.001).
Localraces recommended for further study are indicated in Table 1 and the local races se- lected for a comparative trial are presented in Table 3. Both Tuusniemi and Pihtipudas local races, whichwere addedtothe clone archive in 1995,were also selected foracomparative trial.
Additionally,somelocalraces were selected for furtherusein plant breeding (Table 4).
FigI. Self-compatibilityof local sourcherryracesindifferent main groups presented aspercentage fruit set by self-pollinationand openpollination in 1992and 1993.
Within each group, localraces are ingeographicalorder from west to east.
Vol. 7(1998): 391-399.
Table3.Localraces ofsourcherryselected foracomparativetrial.
No. Origin Seasonof Fruit set*' Seasonof Form**' Weight Colour Stalk Pit% Soluble
flowering 1-9 ripening 1-5 g 1-9 mm solids%
Morellos
7 Rymättylä medium 7 late I 2.7 8-9 35 11.1 14.7
122 Juva medium 7 late I 2.7 8-9 40 10.0 14.8
Amarelles
24 Masku early 7 early 1-2 2.3 6 30 7.9 17.5
85 ? early 9 early 2 3.1 5 30 7.1 14.2
91 Nurmijärvi early 7 early 1 2.4 5 35 8.8 16.4
93 Kärkölä medium 7 medium 1-2 2.8 6 35 7.1 14.4
96 Hollola late 9 med.-late 2 2.6 1 29 8.8 11.9
101 Kuusankoski medium 9 medium 1-2 2.5 4 35 10.0 13.7
104 Kotka medium 8 medium 2 2.8 4 30 7.6 13.2
109 Pyhtää medium 9 medium 1-2 2.5 4 35 10.0 13.2
137 Laukaa medium 8 medium 1 2.6 6-7 30 8.1 15.1
301 ? early 8 early 2 2.3 7 30 9.8 15.0
Rymättylä-type
10 Rymättylä early 9 medium 2 2.6 4 25 7.7 13.2
37 Turku early 9 medium 2 2.6 5 25 7.5 15.0
*' Fruit set ranges from Ito9, 1=nofruit set,9=veryhigh yielding
**' Form: 1=kidney,2=flat-round,3=round,4=elongated,5=heart
*"
)Colour rangesfrom 1to9, 1 being the mostlight-coloured (brightred) and9 beingthe darkest (black red).
During the documentation period no pests weredetected.However,brownrot(Monilia sp.) destroyed some sour cherry fruits and in 1994,
bacterial canker (Pseudomonas sp.) symptoms were observed insometrees. In 1995 and 1996, symptoms, including leaf necroses, shoot die- back and even dying of individual trees, had spread throughout P. cerasus material. Symp- tomsindicated either Pseudomonassyringaepv.
syringae orP. s. pv. morsprunorum infection (Bech 1992, Sobiczewski and Jones 1992).The identification of these pathogens has sofar not been succesful.
Discussion
Evaluation ofsourcherry fruits is greatly affect- ed by their degree of maturity. The optimumrip- ening date is difficulttoassess visually, as sour cherries reach full maturity upto two weeks af- terthey seem tobe mature, based on fruit col-
Table4.Localracesofsourcherryselected for furtheruse inplant breeding, and thespecial properties of each.
No. Origin Special properties
66 Sammatti Fruit set is veryhigh.The fruitsarebig but tasteless andsour.
139Toivakka The tree is verydecorative,bothin floweringand at harvest. Fruit set is high,but the fruitsaresmall and without flavour.
144Anttola The fruitsarebig,sweetand havean exceptionallygoodaroma.Fruit setis poor.
146 Joroinen The fruitsarerather sweet and well tasting.Fruit set is poor.
158 Imatra TheonlyPrunus aviuminthe clone archive. The fruitsaresmall and sweet.
Fruit set is poor.
our. During this time many of their properties, such as taste, aroma, content of soluble solids and even fruit size continue to change signifi- cantly (Nyman 1990).
Because of wide geneticvariation,differences between the threesourcherry groups in the clone archive arenotdistinct. Diversity is continuous, and alot of variationoccurswithin each group.
This is duetothe factthat,historically,newprog- enies have arisen from seeds, and have been spread through propagatingroot suckers. A clear difference in geographical distribution between morellos and amarelles in Finlandwas observed, morelles being ofeasternand amarelles ofwest- ern origin. Thismostlikely reflects their differ- ent ways ofentry into the country, and is in agreement with findings of Kolesnikova (1975) (Ref. lezzonietal. 1990), who dividedsourcher- ry cultivars intotwoecotypesbasedonmorpho- logical differences and cold-hardiness: i.e.west- ernEuropean and middle-Russianecotypes. In Southern andWestern Europe amarelletypecher- ries have been favoured, while in Eastern and Northern Europe and Russia more cold hardy morello type cherries have been favoured(Yu- shev 1975, 1977,Ref. lezzoni etal. 1990).
On the basis of ourresults from 1993, the morello typelocalraces wereregarded aspartly self-compatible, theirpercent fruitsetby self- pollination varying between 1.5 and 15(Redalen
1984a). The small fruit size ofmostmorellos in the Prunus clone archive is evidence of them being mainly forms of ‘Yleinen ruskeakirsikka’
(‘Common brown cherry’), which is self-incom- patible, and has been widely cultivated in Fin-
land because of its hardiness (Collan 1929, 1934).The othercommonmorello type cultivar is ‘Varjomorelli’. It isoneof the oldestsourcher- ry cultivarsin Finland and totally self-compati-
ble(Meurman 1947, Nilsson 1989).
Amarelletypelocalracesin the clone archive provedtobe self-compatible. Theyaresupposed to be mainly forms of ‘Yleinen kuulasmarja’
(‘Common amarelle’), which has been widely cultivated in Finland, as far as the northern boundary of cherry cultivation (Collan 1929,
Meurman 1947). In amarelle type local races,
especially in Rymättylä type cherries,alsosome characteristics of Duke cherry cultivar ‘lso kuu- lasmarja’ (‘Big amarelle’) wereobserved.
In comparison withsourcherries from other Nordiccountries,nativesourcherries in Finland have relatively small fruits. The fruit size is, however, greatly affected by growing conditions.
Inourstudy, themeanweight of fruitswas 2.4 g for morellos, 2.5 g for amarelles and 2.8 g for Rymättylä type cherries. In a cultivar trial in Sweden, the average fruit weight ofsourcherry cultivars was 4.7 g(Hintze 1976).In Denmark the average fruit weight was 4.3 g for morello cultivars,and4.6 g for amarelle cultivars (Chris- tensen 1990),and in Norway 4.08 g and 4.32 g for morellos andamarelles,respectively (Vestr- heim 1986).
Based on the results of this study, native morello type cherries in Finland are less self- compatible than morello cultivars in Norway. In contrast, the Finnish amarelletype cherries are more self compatible than those in Norway. For morellos, the averagepercents fruitsetby self- pollination were in our study 1.3, and 5.2, in
1992 and 1993, respectively, and in Norway it was 14.7(Redalen 1984b).The averagepercents final fruit setby self-pollination were for am- arelles 4.9 and 23.1, in 1992 and in 1993,re- spectively. For Norwegian amarelle cultivars it was 5.0. The average content of soluble solids in localracesselected foracomparative trialwas
14.5%. It is equal to the threshold value deter- mined by Vangdal (1980) forsweetcherries.
In regard to its annual growth rhythm, sour cherry is apotential new fruit crop in Finland.
The cherries ripen early enough, and can thus be cultivated also further north, if only winter hardiness is secured. In ordertofind new com- mercial sourcherry cultivars adapted to Nordic conditions, themostpromising localracesfrom each groupwere selected for a comparative tri- al. The aim is toselecta few cultivars suitable for fresh fruit production, home gardens andeven for industrial production. For example, in Den- mark, wheresour cherry is the largest fruit crop next to apple, the production has mostly been concentrated on clones of local seedlings, the Vol. 7(1998): 391-399.
mostimportant of thembeing ‘Stevnsbär’(Chris- tensen 1990).Through micro-propagation it is possibletoproduce own-rootedsourcherrytrees.
The advantage of this is that own-rootedtrees are capable of regrowth even after severe win-
ters, when the trunk of thetree is damagedor died.
Acknowledgments.Financial support from the Nordic Gene Bank isgreatfully acknowledged.
References
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SELOSTUS
Pohjoismaisen geenipankin Prunus-kokoelma Suomessa
I Hapankirsikkakannat
PauliinaPalonen,Marjatta Uosukainen,EevaLaurinen,Päivi Parikkaja JyriKankila Maatalouden tutkimuskeskus ja Helsingin yliopisto
Maatalouden tutkimuskeskuksen Hämeen tutkimus- asemallasijaitsevan Pohjoismaisen geenipankinPru- m/s-kokoelman hapankirsikkakannoissa (Prunus ce- rasus L.) esiintyvää geneettistä muuntelua kartoitet-
tiin arvioimallakantojen morfologisiaominaisuuksia.
Vuonna 1993oli elossa 118 kirsikkapuuta, jotka edustivat 78eripaikalliskantaa. Jokaisesta puusta laa- dittiin42ominaisuuttasisältäväkuvaus, jokatallen-
nettiin Pohjoismaisen geenipankin BIRS-tietokan- taan.
Perinnöllistä vaihtelua esiintyirunsaasti,Ominai- suuksiensa perusteella kirsikkakannat jaettiinkol- meenryhmään. 32kantaa olipääasiassa itäsuomalais- taalkuperääoleviamorelleja, joidenhedelmämehu on tummanpunaista. 40 kantaa olikuulasmarjatyyppisiä, joiden hedelmämehu on vaaleaa. Kuulasmarjat oli kerätty pääasiassa eteläisimmästä Suomesta. Viisi Rymättylästä, Turusta jaSammatista rekisteröityä
kuulasmarjakantaaerosivat muista kuulasmarjoista, ja
niilleehdotetaan annettavan nimeksirymättylätyyp- piset hapankirsikat. Vain yksi kokoelman kannoista oli imeläkirsikka. Kuulasmarjat ja rymättylätyyppi- set hapankirsikat osoittautuivat itsepölytyskykyisik- sijamorellit osittain itsepölytyskykyisiksi.
Kartoituksen yhteydessä kaikkien kirsikkakanto- jen mahdollinenkäyttöarvo arvioitiin. Tärkeimpiä kriteereitä olivat puun koristearvo, satoisuus, sadon laatu,tauti-ja tuholaiskestävyys ja talvenkestävyys.
Lupaavimmatkirsikkakannat valittiin kantavertailu- kokeeseen,jonkatavoitteena oli löytääSuomenoloi- hinsoveltuvia lajikkeita. Lisäksijoitakin kantoja va- littiin jonkin hyvänominaisuutensa vuoksikäytettä- väksi jalostuksessa. Hapankirsikan käyttöähedelmän- viljelyssä saattaarajoittaa alttiusPseudomonas-syrin- gae pv. syringae ja P. s. pv, mor.sprwnorwm-baktee- reille.
Voi7(1998): 391-399.
