THE RESISTANCE OF SOME POTATO VARIETIES TO SPRAING CAUSED BY TOBACCO RATTLE VIRUS Esko Seppänen Department of Plant Pathology, Agricultural Research Centre Received March 7, 1972 Abstract. TRY was detected and identified for the first time in Finland. According to the information available rattle is an uncommon potato disease in our country. Spraing symptoms were detected in tubers grown in a trial field at Tikkurila in 1968, and during the following years it was possible to make observations on the resistance of 10 varieties to the disease. Sieglinde and Pito were most susceptible followed by Jaakko, Eigenheimer, Olympia and Valtti. Amyla, Record and Realta were fairly resistant and Bintje most resistant. According to Calvert and Harrison (1966) there are 2 viruses which cause spraing in potato tubers: tobacco rattle virus (TRY) and potato mop top virus (PMTV). The former is transmitted by nematodes of the genus Trichodorus and the latter by a fungus Spongospora subterranea (Wallr.) Lagerh., the causal agent of powdery scab. To the present, PMTV has occurred chielfly in Great Britain where, according to Calvert (1970), it is widespread. The occurrence of TRY either under the name »rattle» or its synonyms is more common. In addition to its occurrence in Great Britain (e.g. Cadman and Harri- son 1959, Todd 1965) it has been detected in the Netherlands (Roozendaal 1947, Roo- zendaal and van der Want 1948), in Denmark (Hansen 1962, Kristensen 1962, Kris- tensen and Engsbro 1966), in Norway (Bjornstad 1962, cf. Bjornstad 1969), in Sweden (Lihnell 1958, Persson 1968) and in the USA (Walkinshaw and Larson 1959). This paper is the first report on the occurrence ofTRY in Finland and also summarizes observations of varietal resistance to spraing. Materials and methods Identification of TRY. Tobacco rattle virus was identified by means of test plants Nicoliana tabacum L. (Samsun) and Chenopodium amaranticolor Coste and Reyn, with which TRY can be distinguished from PMTV (Calvert and Harrison 1966, Todd 1967). It was transmitted directly to leaves by rubbing with cut surfaces of tubers having spraing symptoms and by means of juice from infected tobacco roots. The symp- toms in test plants were similar to these described by Calvert and Harrison (1966), https://www.c-info.fi/en/info/?token=h25WM_X6cjAUzXbD.ll3lj0MheiOX3_mzYgbz-w.EORjK3AwnLj2SwDLCXt72SZo_r7fZYkw8tkLihC2uk1oG7AHeKaRGmpvqxNjhywqQgZvBOMs6a3n4hUV_o1jOpEr4KFrg3-e-KPRzxBQNt9FAhnH2rpHRCEkPyU2f1OxUJkdESwo9zXWcgklQjHaYzSTLCMD6a0OQC7nF8yaay4 77 Kristensen and Engsbro (1966), Todd (1967), i.e. necrotic spots in tobacco and chlorotic spots (1 —2 mm in diameter) in C. amaranticolor (Fig. 1). Soil samples from the trial field were examined by Mr. O. Roivainen of the Department of Pest Investigation. The nema- tode Trichodoruspachydermus Seinhorst, a vector of TRV (SOL et al 1960), was detected. Resistance to spraing. During 1968—71 ten table potato varieties com- monly grown in Finland: Amyla, Bintje, Eigenheimer, Jaakko, Olympia, Pito, Realta, Record, Sieglinde and Valtti were grown in sandy soil at Tikkurila to test the resistance of their tubers to mechanical damage. From 1968 through 1970 all the seed potatoes originated from the South Savo Exp. Station, where seed potatoes for trials are propagated under disease-controlled conditions, and they were free from viruses except for virus S in some varieties. In 1971 part of the seed potatoes used were saved from the previous crop and were infected with TRV. The first spraing symptoms were detected in 1968 in the varieties Eigenheimer, Jaakko and Pito. Valid comparisons of varietal susceptibility were not possible until 1970—71. Only secondary symptoms in the haulm of a few plants were detected in 1971. The leaves and partly also the stems were deformed and dwarfed (Fig. 2). Yellowish mottled leaves were present, but the crop suffered from drought and therefore it was not possible to get any detailed records regarding the varietal responses of the haulms to TRY. Strikingly deformed leaves were present in Amyla, Eigenheimer, Jaakko, Olympia, Pito, Sieglinde and Valtti. Fig. 1. Local lesions on the leaves of Nicotiana tabacum (Samsun), and Chenopodium amaranticolor, 9 days after inoculation with TRV. Kuva 1, Rattle-viruksen aiheuttamat primäärioireet Nico- tiana tabacum'in (Samsun) ja Chenopodium amaranti- color'in lehdissä 9 vrk inokuloinnin jälkeen. 78 Tubers were harvested normally each year starting in 1968 and examined the follow- ing spring (in February in 1972). Tubers were halved through their largest diameter and the extent of necrosis was rated as follows: 0 = no necrosis present 1 = I—l 2 % of cut surface with severe necrosis 2 = 13—37 » » » » » » » 3 = 38—62 » » » » » » » 4 = 63—87 » » » » » » » 5 = 87—100 » » » » » » » Percentages of tubers affected and mean values ofthe extent ofnecrosis were calculated. This assesment method is not as exact as those used by Harrison (1968) and Alonso and Preece (1970) but is proper for comparing varieties. Furthermore, if tuber necrosis is common and the samples large enough, differences in assessment methods have little or no effect on the results. TRY in Finland TRY has probably existed tens of years here without being detected until spraing symptoms were seen in potato tubers grown in a trial field in which potatoes had been grown for a number of years successively. In addition to this, spraing symptoms were recognized in ten samples of tubers sent by growers to the Department of Plant Pathology Fig. 2. Severe secondary symptoms in the variety Sieglinde. Kuva 2. Voimakkaat sekundäärioireet Siiklissä. 79 during the years 1968—71 (Fig. 3). Probably the occurrence of TRY (and PMTV) is more widespread than is indicated in the figure but, in any case, TRY is of no importance in commercial potato production in our country. First, most of the tubers sent in were grown in gardens where potatoes had been grown year after year in the same plot. This has not been done in commercial cropping. Second, in the course ofstudies concerning the quality of table potatoes and ring rot, attention was paid to the occurrence of spraing, but in more than one thousand samples examined no tubers with spraing were detected even though the susceptible varieties Eigenheimer and Pito made up the majority of the lots (Fig. 4). Resistance of varieties Varieties have been examined for the presence of spraing since 1968 but because the field was not uniformly infected the first reliable results were not obtained until 1970. Fig. 3. Dots indicate the origins of tubers with spraing sent to the Department of Plant Pathology. Kuva 3. Paikkakunnat, joilta lähetetyissä näytteissä todettiin viruksen aiheuttamaa mukulanekroosia. 80 The results in Table 1 show the great variation between varieties. Most susceptible were Sieglinde and Pito; rather susceptible were Jaakko, Eigenheimer, Olympia and Valtti. Amyla, Realta and Record were fairly resistant and Bintje very resistant. About a fourth of the tubers of Sieglinde and Pito showed necrosis and most of the necrosis was severe (2—5 rating). Table 1. The incidence ofspraing symptoms in ten varieties. Means of results obtained in 1970 and 1971. Variety Percentage of tubers having different severities of spraing (See text) Index 1 ) 12 3 4 5 Total Yhteensä Sieglinde 8 5 4 7 2 26 11 Pito 11 11 7 2 1 32 9 Jaakko 10 4 4 3 1 22 7 Eigenheimer 5 4 3 3 1 16 6 Olympia 4 4 6 2 1 17 6 Valtti 12 6 3 2 0 23 5 Amyla 4 110 0 6 1 Record 2 10 0 0 3 0.4 Realta 110 0 0 2 0.3 Bintje 0 0 0 0 0 0 0 *) The index was obtained by using the mid-point values of % necrosis in each of the rating classes (i.e. 6, 25, 50, 75 and 94 % for the ratings 1,2, 3, 4 and 5, respectively), multiplying the number of tubers in each rating class by its respective % necrosis, and dividing by 100. Fig. 4. Spraing symptoms of TRY in tubers of Eigenheimer. Kuva 4. TRV:n aiheuttamaa mukulanekroosia Eigenheimerin mukuloissa. 81 Discussion The results obtained concerning varietal resistance to spraing caused by TRY are fairly similar to those reported elsewhere. According to Kostein (1962) Amyla, Olympia and Sieglinde are susceptible. The susceptibility of Sieglinde has also been reported by Kristensen and Engsbro (1966) and that of Eigenheimer by van Hoof (1964). The resistance ofBintje was established by van Hoof (1964), Kristensen and Engsbro (1966), and Harrison (1968). It was stated earlier that rattle is very uncommon in Finland. This is fairly surprising because according to Lihnell (1958) spraing is rather common in Sweden (cf. Persson 1968). It is rather common also in Denmark (Hansen 1962, Kristensen 1962, Kristensen and Engsbro 1966). Although rattle is of no present importance in our country attention has to be paid to its occurrence. Because the number of farmers specializing in potato growing is increasing the probability that all soil borne diseases will increase becomes greater. REFERENCES Alonso, A. B. & Preece, T. F. 1970. Assesment of spraing caused by tobacco rattle virus in potato tubers. PI. Path. 19: 25—28. Bjornstad, A. 1962. Stengelbont pä potet. Bondevennen 1962: 594—596, 622—624. Bjonstad, A. 1969. Spredning av Potet-mopp-topp-virus (PMTV) med settepoteter. Jord og Avl. 1969, 2: I—4. Brandenburg, E. & Eibner, R. & Tostman, R. 1959. Untersuchungen iiber die Eisenfleckigkeit-Propfen- bildung der Kartoffel als bodengebundene Viruskrankeit. Mitt. biol. Bundesanst. 97: 36—51. Cadman, G. H. & Harrison, B. D. 1959. Studies on the properties of soil-borne viruses of the tobacco- rattle type occurring in Scotland. Ann. appi. Biol. 47; 542—-556. Calvert, E. L. 1970. Mop Top Virus. Agr. North. Ire. 45: 82—85. Calvert, E. L. & Harrison, B. D. 1966. Potato mop-top, a soil-borne virus. PI. Path. 15: 134—139. Eibner, R. 1961. Untersuchungen iiber das vorkommen von Tabak-mauche-bzw. Ratelvirus in West- deutschland. Nachrbl. Deut. Pfl.schutzd. (Braunschweig) 13: 104—105. Hansen, S. E. 1962. Rattlevirus i kartofler. Statens Plantepatologiske Forsog, Mancdovcrsigt 394: 20—24. Harrison, B. D. 1968. Reactions of some old and new British potato cultivars to tobacco rattle virus. Eur. Potato J. 11: 165—176. Hoof, H. A. van 1964. Het tijdstip van infectie en veranderingen in de concentratie van Ratelvirus (Kringerigheit) in de aardappelknol. Meded. Landb. hogesch. Opzoekingssta. Staat Gent 29: 944—955. Kristensen, H. R. 1962. Jordbärne plantevira. Tidsskr. for Planteavl 66: 75—-148. Kristensen, H. R.& Engsbro, B. 1966. Undersogelser og forsog vedroende jordbärne vira. I. Rattle-virus. Tidsskr. for Planteavl 70: 353—379. Kostein, H. 1962. Weitere Untersuchungen iiber das bodengebundene Ratelvirus an Kartoffeln. Diss, Giessen. (Ref. Steck, U. 1971.) Lihnell, D. 1958. Investigations on spraing. Proc. 3rd Conf. Potato Virus Dis. 1957, Lisse-Wageningen 184—188. Persson, S. 1968. Nematoder av släktet Trichodorus i syd-svenska äkerjordar och deras förraäga att över- föra rattelvirus. Nat. Swe. Inst. Plant Prot. Contr. 14: 163—199. Roozendaal, A. 1947. Ziekten van het stengelbont-type bij de aardappel. Tijdschr. Pl.zickt. 53: 93— 101. 82 Roozendaal, A.& van der Want, J. P. H. 1948. Over de identiteit van het ratelvirus van de tabak en het stengelbontvirus van de aardappel. Tijdschr. Pl.ziekt. 54; 113—133. Sol, H. H. & Heuven, J. C. van & Seinhorst, J. W. 1960. Transmission of rattle virus and Airopa belladonna mosaic virus by nematodes. Ibid. 66: 228. Steck, U. 1971. Zur Biologic, Ökologie und Bekämpfung des Tabak-Rattle-Virus (TRV) im Kartoffel- bau. (Eine Literaturstudie) Bayerisches landw. Jahrb. 48: 867—891. Todd, J. M. 1965. Soil-borne virus diseases of potato. Scott. PI. Breed. Sta. Rec. 1965; 209—235. Todd, J. M. 1967. Soil-borne virus diseases of potato. N.A.A.S. Quat Rev. 77: 21 —29. Wai.kishaw, C. H. & Larson, R .H. 1959. Corky ringspot of potato. Univ. Wis. Res. Bull. 217: I—3l.1 —31. SELOSTUS TUPAKAN RATTLE-VIRUS SUOMESSA JA 10 PERUNALAJIKKEEN KESTÄVYYS SEN AIHEUTTAMAA MUKULANEKROOSIA VASTAAN Esko Seppänen Kasvitautien tutkimuslaitos, Maatalouden tutkimuskeskus Vuonna 1968 todettiin Tikkurilassa erään koelohkon perunoissa mukulanekroosia (kuva 4), joka osoitettiin tupakan rattle-viruksen (TRV) aiheuttamaksi (kuva 1). Vastaavanlaisia mukuloita on Kasvi- tautien tutkimuslaitokselle lähetetty useilta paikkakunnilta Etelä-Suomesta (kuva 3). Taudin merkitys on meillä ainakin perunassa vähäinen, sillä äskettäin suoritettujen ruokaperunan laatua ja rengasmädän levinneisyyttäkoskevien tutkimusten yhteydessä kiinnitettiin huomiota myös tämän taudin esiintymiseen, mutta ainoassakaan mukulassa ei todettu taudin oireita. Taudin levittäjiä ovat meillä harvinaisen anke- roissuvun Trichodorus lajit. Perunanviljelyn erikoistumisen yleistyessä on kiinnitettävä huomiota myös tähän tautiin. Tikkurilassa taudin saastuttamassa maassa kasvaneiden 10 meillä yleisesti viljellyn lajikkeen muku- loiden kestävyydestä tehdyt havainnot on esitetty taulukossa 1. Eigenheimer, Pito ja Siikli (Sieglinde) olivat altteimmat, melko alttiita olivat Amyla, Jaakko, Olympia ja Valtti. Realta ja Rekord olivat melko kestäviä ja Bintje kestävä. Ulkomaisissa tutkimuksissa esitetyt tiedot Eigenheimerin, Siiklin, Araylan, Olympian ja Bintjen kestävyydestä ovat yhtäpitäviä nyt saatujen tulosten kanssa. Muiden lajikkeiden kestävyydestä ei aikaisempia tuloksia ole käytettävissä.