The Nordic Gene Bank’s Prunus clone archive in Finland II Local races of plum Pauliina Palonen Department ofPlant Production, PO Box 27, FIN-00014 University of Helsinki, Finland, e-mail: pauliina.palonen@helsinki.fi Marjatta Uosukainen Agricultural Research Centre ofFinland, Laukaa Research and Elite Plant Station, Antinniementie I, FIN-41330 Vihtavuori, Finland Eeva Laurinen Agricultural Research Centre ofFinland, Horticulture, Toivonlinnantie 518, FIN-21500 Piikkiö, Finland The morphological variation in 104 local races of plum (Prunus domestica subsp. domestica L.) in the Nordic Gene Bank’s Prunus clone archive in Pälkäne, Southwest Finland was examined. Each tree was described using 37 characteristics. On the basis of fruit characteristics the local races were classified into three main groups. The largest one was the red plum group, the yellow plum group being the second largest. Victoria-type plums, which have not been reported to occur in Finland before and which resemble the English cultivar ‘Victoria’, make up the third group. Victoria-type plums proved to be fully and red plums partly self-compatible, whilst the yellow plums were self- incompatible. All the local races of plum were evaluated for their possible further use. Two of them were selected for commercial propagation. Key words: Prunus domestica, red plum, self-compatibility, Victoria, yellow plum ntroduction European plum (Prunus domestica L.) is usual- ly thought to have been derived from a cross be- tween the cherry plum or myrobalan (P. cerasif- era Ehrh.) and the sloe or blackthorn (P. spino- sa L.) (Nilsson 1989). However, according to Eryomine (1990) several species have partici- pated in the origin of P. domestica, e.g. P. cerasi- fera, P. spinosa, P. salicinaLindley (the Japanese plum), P. armeniaca L. (apricot), P persica (L.) Batsch (peach), and Microcerasus microcarpa. Whereas, Zohary (1992) states that genomically the European plum has nothing to do with P. spinosa, but evolved directly from the variable P. cerasifera stock. Whatever its origins, it is certain that the European plum possesses a rich genetic potential. On the other hand, a narrow genetic base among major cultivars limits major © Agricultural and Food Science inFinland Manuscript received June 1997 401 Voi 7(1998): 401^08. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Palonen, P. et al. Prunus clone archive in Finland: plum plum production to specific areas, and makes plum also susceptible to disease and insect at- tack. On the contrary, great diversity exists in native plum species, and they have wide adapti- bility. (Ramming and Cociu 1990). Plum has been cultivated inFinland for at least 300 years (Webster and Hiirsalmi 1980). In the past plum trees were imported to Finland from Russia, Estonia, Germany and Sweden. In 1929 for exam- ple, in total 36 plum cultivars wereknown to occur in Finland (Collan 1934). Imported cultivars were cultivated on rootstocks, and were often damaged or killed by winter frosts. New races have arisen, however, through their seedlings. Local Finnish plums ‘Yleinen punaluumu’ (‘Common red plum’) and ‘Yleinen keltaluumu’ (‘Common yellow plum’) have been widely cultivated as own-rooted plants. They have been propagated and spread us- ing root suckers, and many slightly different clones of them occur (Collan 1926). Besides being used for fruit production, plum trees are also excellent ornamentals. The com- mercial plum production in Finland is limited to the coastal areas, but in home gardens plums are also grown in Central Finland. Until recently, mainly foreign plum trees have been offered for sale in Finland, and foreign cultivars have been recommended for cultivation. The problem in Finnish plum growing is the insufficient degree of winter hardiness in recommended foreign cul- tivars. The hardiest germplasm and the plant material that is genetically adapted to Nordic conditions, is to be found among the native cul- tivars. The objective of this study was to examine the morphological variation in local races of plum in the Nordic Gene Bank’s Prunus clone archive at the Agricultural Research Centre of Finland, Häme Research Station in Pälkäne. Material and methods The local races ofplum were identified in South- ern and Southeastern Finland, and planted as root suckers on the experimental field in Pälkäne in 1988. No plant protection chemicals were used. More detailed information is given by Palonen et al. (1998). The description and documentation of this plum material was carried out during the sea- sons 1992 and 1993. In 1992, the Prunus clone archive in Pälkäne (61°20’ N. 24°13’E) consist- ed of 178 plum trees representing 104 different local races. Each plum tree was described using the characteristics used by the Nordic Gene Bank. The descriptions were complemented with some further characteristics used by the Inter- national Union for the Protection of New Varie- ties of Plants (UPOV). In total, 37 characteris- tics were used for the description of each tree. Characteristics observed were related to growth habit, flowering, fruit set, as well as external and internal properties of the fruits. The descriptions were made mainly in 1992 and supplemented, using UPOV descreptors, in 1993. They will be saved in the Nordic Gene Bank’s database BIRS. In 1993, the self-compatibility of 20 local plum races was studied. Two branches per tree were isolated before floral anthesis by enclos- ing them in acrylic bags, and two branches were marked and used as open pollinated controls. Self-pollination was aided by brushing the iso- lated flowers carefully with a small clean brush as the pollen was shed. This was carried out dai- ly during the flowering period. The control branches were allowed to be pollinated by in- sects. The number of self-pollinated flowers and the number of open pollinated flowers was count- ed, and later, the number of green fruits was re- corded. Percentage fruit set from both self-pol- lination and open pollination was calculated. The self-compatibility of a local race was estimated by the ratio of percentage fruit set with self-pol- lination to percentage fruit set with open polli- nation. The data on theratios were analyzed with ANOVA- 1-test of MSTAT-C -program (Michi- gan State University 1989). All the local plum races were evaluated for their possible further use. The main criteria were; fruit set, fruit quality, winter-hardiness, resist- ance to diseases and pests, and ornamental val- 402 AGRICULTURAL AND FOOD SCIENCE IN FINLAND ue. Each local race was eitherrecommended for further study or classified to be of no value. Results The trees flowered freely in 1992. The differ- ences in time of flowering were negligible. The fruit set was very high, but cold weather in au- tumn delayed fruit ripening. In 1993, the flow- ering season was very early on account of ex- ceptionally warm weather in May. The period of flowering for all clones varied from 14 to 25 May. No differences in time of flowering were observed. The fruit set was very high and plums were harvested from 6 to 21 September.Also, in several trees fruits were prevented from reach- ing their full maturity by night frosts. Pests were very abundant. Mites (Panonychus uhni), gall mites and aphids were found on most plum trees. Brown rot (Monilia sp.) destroyed a lot of the fruits. Gummosis occurred commonly in the fruits of many plum trees. Beginning in early August, especially with the local races ofred plum types, leaves became greyish, developed some brown spots and then abscissed prematurely. Trees exhibiting these symptoms also shed their fruits just prior to maturity. In early September, many trees were almost leafless even though no diseases were observed. It is thought that the symptoms may have been attributable to physiological disorder, caused by the exceptional weather conditions in conjunction with the abundant fruit set. In the previous autumn 1992, premature fall of snow occurred unexpectedly on 8 October, before the trees had shed their leaves. In the following spring 1993, growth started abruptly, stimulated by a period of extremely warm weather in May. At the beginning of the growing season, plants may also have suffered from drought, whilst in June, on the contrary, it was exceptionally cold and in August the weather was cold and rainy (Figure 1). On the basis of fruit characteristics the local plum races were classified into threemain groups (Table 1). In six cases, two trees representing the same local race proved to be different. Group 1) Red plums. (77 local races) The fruits are have a red skin colour and tree growth habit is erect. Brown rot, gummosis and pest sensitivity occurred commonly. The local races of the red plum type can be grouped further into subgroups, as follows; la) The ground colour in the fruits is greenish, but most of it is covered by red colour. The fruits are round, the fruit length varies from 24 to 27 mm, and the fruit weight from 6.5 to 12.5 g. Fig. I. Mean temperature and pre- cipitation/5 days fromMay to Sep- tember in 1993 and the long term averages in Pälkäne. 403 Vol. 7 (1998): 401-408. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Palonen, P. et al. Prunus clone archive in Finland: plum Table 1.The local plum races in the Prunus clone archive classified into groups. Local races marked with a plus-sign (+) are recommended for further study, e and t indicate the first and the second tree in the field, respectively. Group 1) Group 2) Group 3) Red plums Yellow plums Victoriatype plums la) lb) 1c) 2a) Punaluumu 6 Rymättylä 166Vihti + 84t?+ Häkkisen Victoria + 14Tammela + 9? 206 Joutseno 171 Koski, HL 209 Juva 18? 11, Rymättylä 218 Pukkila + 191 Ruotsinpyhtää 210 Juva + 32?+ 13 Halikko 235 Kangaslampi + 1931Lapinjärvi + 211 Juva 36 Parainen 16 Alastaro 194Lapinjärvi + 213 Mikkeli mlk. + 46 Tuusula 23 Jokioinen 226 Elimäki 229 Hankasalmi + 51 Vantaa + 33 Kemiö Id) 250 Mikkeli mlk. + 230 Hankasalmi + 56 e Nurmijärvi 48 Helsinki Vaarin luumu + 232 Laukaa + 61 Espoo + 57 Siuntio 40 Rymättylä + 233 e Jyväskylä + 621 Espoo 59 Sammatti 50 Tuusula + 2b) 234 Toivakka + 169 Järvenpää 78 Lohja Savion Keltaluumu + 236 Kangasniemi + 170Kärkölä 80 Sammatti 8 Rymättylä + 237 Haukivuori + 179 Kuusankoski 106Porlammi+ le) 22 Halikko 238 Anttola + 181 Valkeala + 129 eAnjalankoski 64 Sammatti + 42 Naantali + 239 Joroinen + 187 t Anjalankoski + 164 Vihti 72 Lohja mlk. + 49 Helsinki + 240 Sulkava + 190Ruotsinpyhtää 165 Vihti + 251 e Janakkala 63, Inkoo + 241 Kerimäki + 192 e Ruotsinpyhtää + 167 Vihti 68?+ 242 Parikkala + 1991 Hamina 168 Vihti 70 Vantaa + 245 e Imatra + 207 Joutseno 175 Orimattila 244 Ruokolahti + 173 Asikkala 248 Anttola + 212 Mikkeli mlk. 178 Orimattila (differs from ali the 177 Orimattila + 290 Hankasalmi 2331 Jyväskylä + 184Elimäki others) 187 e Anjalankoski + 247 Imatra 186Anjalankoski 1881Kotka 249 Hirvensalmi 188 e Kotka 204 Taipalsaari + 300?+ 1921Ruotsinpyhtää 219 Pukkila + 193 Lapinjärvi 220 Sipoo + 195 Porlammi 231 Hauks. + 197 Pyhtää + 222 Perniö + 224 Anjalankoski + 225 Anjalankoski 246 Imatra 251 t Janakkala lb) The fruits are red with a greenish ground colour. They are oblong. The fruit length var- ies from 26 to 32 mm, and the fruit weight from 9 to 16 g. Fruit ripening is the earliest in the whole red plum group. lc) The ground colour of the fruits is yellow, which is partly covered by red colour. The fruits are oblong. The fruit length varies from 27 to 31 mm, and the fruit weight from 10 to 13 g. The taste is delicious. 1d) The fruits are very darkred. They are slightly oblong. The average fruit length is 28 mm and fruit weight 12 g. They resemble the na- tive cultivar ‘Vaarin luumu’ (Uosukainen 1990). le) The fruit colour is dark violet red. The fruits are oblong, the average fruit length being 33 mm, and the average fruit weight 14 g. The fruits ripen distinctly later than the other red plums. Group 2) Yellow plums. (23 local races) The fruit colour is yellow. Yellow plums can be di- vided further into two subgroups, as follows: 404 AGRICULTURAL AND FOOD SCIENCE IN FINLAND 2a) The fruits are oblong. The fruit length var- ies from 28 to 32 mm, and the fruit weight from 11 to 15 g. Fruit ripening is rather late but earlier than in group 2b. 2b) The fruits are typical of the cultivar ‘Ylei- nen keltaluuumu’. They are drop-shaped. The fruit length varies from 35 to 40 mm, and the fruit weight from 15 to 22 g. Fruit ripen- ing is late. The taste is mostly delicious and sweet. The trees are densely-crowned, very healthy and resistant to pests. The leaves are big and leathery. Group 3) Victoria-type plums. (20 local races) Plums of this groupresemble the English cultivar Table 2. The average percent fruit set in each group of local plum races by self-pollination (self) and by open pollina- tion (open), and their ratio (self/open). Percent fruit set (%) self open self/open (%) Red plums 5.0 29.2 18.3b Yellow plums 1.5 16.8 5.3b Victoria-type plums 15.5 19.6 88.0a Overall average 8.2 21.7 41.3 Values followed by the same letter are not significantly dif- ferent at P = 0.05 by Tukey’s test. ‘Victoria’. Fruits are purple with a yellow ground colour. The fruits are oblong, the upper side be- ing slightly narrower. The fruit length varies from 29 to 33 mm, and the fruit weight from 12.5 to 15.0 g. Fruit ripening is late. The branches are typically drooping, and the leaves are big and glossy. The trees are relatively healthy and re- sistant to pests. Two distinct geographical distribution areas were observed. The local races of red plum and yellow plum type were mainly collected from the area south of 61° northern latitude. Victoria-type plums were identified mainly from a triangle shaped distribution area between 61° and 62°20' northern latitude, bordered by Lappeenranta and Kerimäki in east and Laukaa in west. Victoria- type plums have not been reported to occur in Finland before. In all of the plum material examined, the per- centage of fruit set varied; by self-pollination from 0 to 26, the average being 8.2, and by open pollination from 7 to 55, the average being 21.7. The Victoria-type plums proved to be self com- patible, while yellow plums were the least self compatible group (Table 2 and Figure 2.) The local races recommended for further study are marked with a plus sign (+) in Table 1. In the red plum group, 34% of local races were Fig 2. Percentage fruit set of local plum races by self-pollination and open pollination. Local races with- in each group are in the geograph- ical order from west to east. 405 Vol. 7 (1998): 401-408. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Palonen, P. et al. Prunus clone archive in Finland: plum recommended for further study, and in the yel- low plum group and Victoria-type plum group 74% and 85%, respectively. The rest of the local races are considered to be of no value, on ac- count of their poor fruit set, poor fruit quality, their sensitivity to pests, minimal ornamental value, or a bad health status of a tree. Two local races were selected for commercial propagation; a yellow plum from Savio and a Victoria-type plum from Anttola. The plants for sale under names ‘Savion Keltaluumu’ and ‘Anttolanluumu’ will be micropropagated and own-rooted. Discussion A great deal of genetic variation was shown to be present in the local plum races in the Prunus clone archive. This is because both eastern and wertern cultivars have been imported to Finland. Some of these cultivars, or their rootstocks, sur- vived and new progenies have been generated from their seeds and have been distributed through root suckers from garden to garden. ‘Yleinen punaluumu’ is an old local plum, which has been widely cultivated in Finland. Its origin is unknown and many different genotypes occur (Meurman 1947).Five distinctly different groups of red plum types were found to occur in the Prunus clone archive. Some variation also exist- ed within each group. There are contradictory reports concerning the self-compatibility of ‘Yleinen punaluumu’. According to Meurman (1947), Uosukainen (1990) and Laurinen et al. (1992) ‘Yleinen punaluumu’ is self compatible. In contrast, according to Hämet-Ahti et al. (1992) it is self incompatible and needs a pollinator. On the basis of earlier knowledge and our results, local races of red plum types are concluded to be partly self-compatible, but using a pollinator is to be recommended, as it improves yield. The red plum type fruits reached maturity early enough in autumn to avoid frost damage. How- ever, because of the physiological symptoms described above occurring in the trees of this group, and because they are susceptible to pests and diseases, the red plum type local races are not recommended for cultivation. Two different types of yellow plum occurred in the clone archive. The local races of group 2a having an oblong fruit form, may have genes of the cultivar ‘Reine Claude d’Oullins’ in their germplasm. The local races of group 2b are rather typically of the ‘Yleinen keltaluumu’ type. The local races in the yellow plum group proved to be self incompatible, as ‘Yleinen keltaluumu’ has been reported to be (Nilsson 1989, Hämet-Ahti et al. 1992). Suitable pollen donors for ‘Yleinen keltaluumu’ are the cultivars ‘Yleinen punaluu- mu’ and ‘Victoria’ (Laurinen et al. 1992). Yel- low plum trees were healthy and their fruit taste was mostly delicious. The only problems asso- ciated with their culture seem to be their late fruit ripening and the self-incompatibility. The fruits did not reach the full maturity in autumn but were damaged by night frosts in September. Victoria-type plums occur generally in Rus- sia (V. L. Vitkovsky, personal communication, 1993). They are considered to be even hardier than ‘Yleinenpunaluumu’. The local races of this type in the clone archive were registered mainly in Eastern Finland, which supports the hypothe- sis that they have been carried to Finland from Russia. The English cultivar ‘Victoria’ is known to be self compatible (Redalen 1984, Nilsson 1989), as were the Victoria-type local races in the Prunus clone archive. Fruits of this group did not reach their full maturity early enough in au- tumn. Although red plums formed the largest group in the clone archive, most of them were classi- fied to be of no value. Most probably, new culti- vars fit for cultivation in Nordic conditions will be found among yellow plums and Victoria-type plums. Victoria-type plums have not been pre- sented in Finnish literaturebefore. They are con- sidered to be very hardy and the fruits are of good quality. Yellow plum ‘Savion keltaluumu’ and Victoria-type plum ‘Anttolan luumu’ are already in commercial propagation. Surprisingly, there were no blue fruited plum 406 AGRICULTURAL AND FOOD SCIENCE IN FINLAND races in the Prunus clone archive. In addition to the ‘Common red plum’ and the ‘Common yel- low plum’, a ‘Common blue plum’ has also oc- curred in Finland (Meurman 1947, Salonen and Jaatinen 1961). It is mentioned to be not as har- dy as red and yellow ones, and that may be the reason for it not occurring any more. In Swe- den (Fernqvist 1993), and in Estonia (Jaama 1971), several blue fruited plum cultivars occur. A new Finnish plum cultivar ‘Sinikka’, which is a progeny of ‘Czar’, also has blue-colouredfruits (Takala et al. 1990). The general problem and a restricting factor toFinnish plum growing is that only in the most favourable growing seasons can the fruits reach full maturity in autumn. Based on the results of this study, local races do not possess potential germplasm for accelerated fruit ripening. Acknowledgments. Financial support from the Nordic Gene Bank is gratefully acknowledged. References Collan, O, 1926. Hedelmä- ja marjalaatumme. Otava. Helsinki. 144 p. - 1934. Suomen hedelmänviljelys hedelmätarhojamme v. 1929 kohdanneen tuhon valossa. Valtion maata- louskoetoiminnan Julkaisuja n;o 60. Helsinki. 68 p. Eryomine, G. V. 1990. New data on origin of Prunus do- mestica L. Acta Horticulturae. 283: 27-29. Fernqvist, 1.1993. Katalog över fruktsorter i svenska klon- arkivoch sortsamlingar 1992. Report. Nordiska Gen- banken. 12 p. (Available at the Nordic Gene Bank, Alnarp). Hämet-Ahti, L., Palmén, A., Alanko, P. & Tigerstedt, P. M. A. 1992. Suomenpuu- ja pensaskasvio. Dendro- logian seura. Helsinki. 373 p. Jaama, A. 1971. Ploomid. Kirjastus Valgus. Tallinn. 100 p. Laurinen, E., Lehmushovi, A. & Kinnanen, H. 1992. Hedelmä- ja marjalajikkeita ammattiviljelyyn ja ko- tipuutarhoihin. Puutarhaliitto. Helsinki. Puutarhaka- lenteri 51: 8-21. Meurman, O. 1947. Suomen hedelmäpuut ja viljellyt marjat. Il Päärynät, luumut, kirsikat ja marjat. Oy Suomen kirja. Helsinki. 351 p. Michigan State University. 1989. User's guideto MSTAT-C. Michigan. Nilsson, A. 1989. Våra päron-, plommon- och körsbär- sorter. Nordiska Genbanken. Örebro. 370 p. Palonen, P, Uosukainen, M., Laurinen, E., Parikka, P. & Kankila, J. 1998. The Nordic Gene Bank’s Prunus clone archive in Finland. I Local races of sour cher- ry. Agriculturaland Food Science in Finland 7: 391 - 399. Ramming, D. W. & Cociu, V. 1990. Plums (Prunus). Acta Horticulturae 290: 235-287. Redalen, G. 1984. Pollinering av plomme og surkirse- baer. Gartneryrket7A\ 446-450. Salonen, F. & Jaatinen, K. 1961. Kodin puutarha. WSOY. Porvoo. 541 p. Takala, M., Uosukainen, M. & Aaltonen, M. 1990, Tum- mansininen ‘Sinikka’. Puutarha 93: 861-862. Uosukainen, M. 1990. Tervetaimiasemalla tuotannossa olevat ja lajikekokeita varten lisätyt luumulajikkeet. Maatalouden tutkimuskeskus, Tiedote 11/90. p, 1- 30. Webster, A. D. & Hiirsalmi, H. 1980, Luumu. In: Kasvien maailma - Otavan suuri tietosanakirja 3:1196-1197. Zohary, D. 1992. Is the European plum, Prunus domesti- ca L., a P. cerasifera Ehrh. ' P. spinosa L. allo-poly- ploid? Euphytica 60: 75-77. 407 Vol. 7 (1998): 401-408. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Palonen, P. et al. Prunus clone archive in Finland: plum SELOSTUS Pohjoismaisen geenipankin Prunus-kokoelma Suomessa Il Luumukannat Pauliina Palonen, Marjatta Uosukainen ja Eeva Laurinen Maatalouden tutkimuskeskus ja Helsingin yliopisto MTT:n Hämeen tutkimusasemalla sijaitsevan Pohjois- maisen Geenipankin Prunui-kokoelman luumukan- noissa (Prunus domestica L.) esiintyvää geneettistä muuntelua kartoitettiin arvioimalla morfologisia omi- naisuuksia. Vuonna 1993 oli elossa 177 luumupuuta, jotka edustivat 104 eri maatiaiskantaa. Jokaisesta puusta laadittiin 37 ominaisuutta sisältävä kuvaus, joka tallennettiin Pohjoismaisen geenipankin BlRS- tietokantaan. Ominaisuuksiensa perusteella luumukannat jaet- tiin kolmeen ryhmään. Suurimman ryhmän muodos- tavat punaluumut, jotka on kerätty pääosin eteläisim- mästä Suomesta. Ne jaettiin edelleen viiteen alaryh- mään. Toiseksi suurin ryhmä oli niinikään Etelä-Suo- mesta kerätyt keltaluumut, jotka jaettiin vielä kahteen alaryhmään. Kolmannen ryhmän luumut, Victoria- tyyppiset, muistuttavat englantilaista ‘Victoria’ laji- ketta ja ne on kerätty Mikkelin läänistä ja Jyväsky- län ympäristöstä. Victoria-tyyppiset luumut osoittau- tuivat itsepölytyskykyisiksi. Punaluumut olivat osit- tain itsepölytyskykyisiä ja keltaluumut itsepölytysky- vyttömiä. Kartoituksen yhteydessä kaikkien luumukantojen mahdollinen käyttöarvo arvioitiin käyttäen kriteerei- nä puun koristearvoa, satoisuutta, sadon laatua ja tau- ti- ja tuholaiskestävyyttä. Keltaluumukanta Saviolta ja Victoria-tyyppinen kanta Anttolasta on otettu tai- mituotantoon MTT:n Laukaan tutkimus- ja valiotai- miasemalle. 408 AGRICULTURAL AND FOOD SCIENCE IN FINLAND