Approximately 900 plants of commercially grown strawberries of 45 varieties and experimental seedling selections were collected from various parts of the state of Minnesota and indexed for the presence of viruses. Their presence in these plants was demonstrated by the appearance of symptoms in the indicator plant, Fragaria vesca L., after they were inarch-grafted. 93 % of the plants indexed were virus-infected. Based on symptoms, the viruses have been classified into 14 symptomtypes. It was found that mottle and mild yellow-edge were the two dominant viruses, whereas crinkle and vein chlorosis were of rare occurrence. There was no indication that certain symptom-types are associated with particular commercial varieties of strawberries or experimental seedling selections

King, T. H.

Liu, Stephen C.Y.

Skiles, R. L.

English

University of Minnesota, Morris (UMM): Digital Well

Journal of the Minnesota Academy of Science Volume 30 Number 1 Article 10 1962 Occurrence and Severity of the Viruses of Strawberry in Minnesota T. H. King University of Minnesota Stephen C.Y. Liu University of Minnesota R. L. Skiles University of Minnesota Follow this and additional works at: https://digitalcommons.morris.umn.edu/jmas  Part of the Botany Commons Recommended Citation King, T. H., Liu, S. C., & Skiles, R. L. (1962). Occurrence and Severity of the Viruses of Strawberry in Minnesota. Journal of the Minnesota Academy of Science, Vol. 30 No.1, 33-36. Retrieved from https://digitalcommons.morris.umn.edu/jmas/vol30/iss1/10 This Article is brought to you for free and open access by the Journals at University of Minnesota Morris Digital Well. It has been accepted for inclusion in Journal of the Minnesota Academy of Science by an authorized editor of University of Minnesota Morris Digital Well. For more information, please contact skulann@morris.umn.edu. is again different in that the multiple-male groups did not maintain a normal balance and hence dropped out. Another point may be mentioned. Multiple-male groups have been recorded for very few swarming insects. The paucity of records on this factor of intraspecific interfer-ence may be due to the difficulty in observing such inci-dences rather than suggesting that the factor is uncom-mon among swarming insects. In summary, these observations show that a significant proportion of the male midges was involved in unsuccess-ful mating due to interference by other males, and also suggest that the male approached the females entering the swarm almost instantaneously. LITERATURE CITED CHIANG, H. C. 1961. Ecology of Insect Swarms. I. Ex-perimental Studies of the Behavior of Anarete near felti Pritchard in Artificially Induced Swarms. Animal Behavior 9:213-219. DOWNES, J. A. 1950. Habits and Life-Cycle of Culicoides nubeculosus. Nature 166:510-511. GrnsoN, N. H. E. 1945. Mating Swarm in a Chironomid, Spaniotoma minima. Nature 150:268-269. KNAB, F. 1906. The Swarming of Culex pipiens. Psyche 13: 123-133. CAMBOURNAC, F. J. C. AND R. B. HILL. 1940. Observa-tions on the Swarming of Anopheles maculipennis var. atroparvus. Amer. lour. Trop. Med. 20: 133-140. BOTANY Occurrence and severity of the viruses of strawberry in Minnesota T. H. KING, STEPHEN C. Y. LIU and R. L. SKILES 1 University of Minnesota, St. Paul SUMMARY: Approximately 900 plants of commercially grown strawberries of 45 varieties and experimental seedling selections were collected from various parts of the state of Minnesota and indexed for the presence of viruses. Their presence in these plants was demonstrated by the appearance of symptoms in the indicator plant, Fragaria vesca L., after they were inarch-grafted. 93 % of the plants indexed were virus-infected. Based on symp-toms, the viruses have been classified into 14 symptom-types. It was found that mottle and mild yellow-edge were the two dominant viruses, whereas crinkle and vein chlorosis were of rare occurrence. There was no indica-tion that certain symptom-types are associated with par-ticular commercial varieties of strawberries or experi-mental seedling selections. INTRODUCTION: Plakidas (6) first reported diseases of strawberries of a virus nature in the United States in 1926. Harris ( 3) reported the occurrence of a virus dis-ease in England in 1933. Since then many reports on strawberry viruses have been made. which have dealt principally with new diseases, methods of transmission and control measures. A comprehensive review of the literature has been made by Plakidas (7). Investigations on the prevalence of strawberry viruses in commercial varieties grown in 11 eastern states was made by Demaree and Marcus ( 1) . They found all the commercial varieties affected and that nearly all the plants of each variety were contaminated with certain viruses regardless of the states in which the strawberries were grown in the United States. This paper reports the 1 Paper No. 4860, Minnesota Agricultural Experiment Station, St. Paul, Minnesota. Proceedings, Volume Thirty, No. One, 1962 prevalence of viruses in strawberries grown in Minne-sota (1951-57). MATERIALS AND METHODS: In Minnesota commercially grown strawberry varieties which were to be studied were collected by members of the staff or sent to the experi-ment station by nurseries and growers from 19 counties in Minnesota. In addition, clonal plants were also col-lected of potential new varieties from the University Fruit Farm of the Minnesota Experiment Station at Excelsior, Minnesota. Approximately 900 plants from 45 varieties and experimental seedling selections (Tables 1 and 2) were collected and indexed to Fragaria vesca L., an East Malling clone of the indicator species. When one or more stolons had developed on an indicator plant to the stage where the terminal bud was geniculate, it was grafted to a plant of a selected commercial variety. The inarch-grafting of stolon-to-petiole or stolon-to-stolon was used in all the studies ( 4, 5). The petiole selected for graft-ing was the youngest which could be handled with rea-sonable facility and generally was about the same diam-eter as the stolon of F. vesca (indicator plant). Symptoms resulting from virus infection in the indi-cator plants usually began to appear within 4 to 8 weeks after grafting depending on the season of the year. The success of the grafts were determined by severing the grafted petiole or stolon from the test plant 10 to 17 days after the grafts have been made (2). The development of symptoms in the indicator such as epinasty, chlorosis, stunting and crinkle were recorded and grouped together into classes according to a system developed by Skiles (10) (Table 3). 33 TABLE 1. The prevalence of viruses in commercially grown varieties of strawberries in Minnesota.a 2 3 4 5 6 7 8 9 10 11 12 13 14 Tota!•! Armore 2 2 Arrowhead 2 12 4 II 4 4 2 39 Beaver 2 14 2 IO 2 30 Brunes Marvel 4 4 Burgundy 4 7 Catskill 2 2 Dunlap 3 9 5 25 8 2 2 55 Evermore 8 IO 18 Gem 3 IO 4 2 19 Jumbo 2 2 Kellogg Marvel 2 2 4 -Minnesota 6 12 18 Montana Progressive 2 2 4 Premier 6 28 2 65 9 2 3 3 4 122 Redrich 2 4 2 18 6 3 36 Robinson 2 31 4 21 3 4 4 71 Sawyer 2 2 Sparkle 4 4 Streamliner 4 2 4 4 6 20 Temple ,, 2 9 13 .t. Thomas 2 4 6 Wayzata 1 2 4 7 TOTAL 23 126 34 194 26 10 21 6 22 8 10 5 0 0 485 • Based on inarch grafting between plants of commercial varieties and F. vesca. • Results of studies made in Minnesota from 1951-1957. fABLE 2. The prevalence and classes· of viruses occurring in Minnesota experimental seedling selections (1954-1957)" No. of Total Virus Classes Virus- no of Seedling free plants selection 2 3 4 5 6 7 8 9 10 11 12 13 14 plants indexed 1283 10 12 1361 1 4 7 1 13 1363 8 1 10 1393 4 6 1395 2 11 15 1400 5 5 1404 5 2 14 21 1504 2 9 11 1636 1 1 8 2 1 3 16 1643 3 4 1 16 1 1 1 2 5 34 1650 1 4 1 11 2 19 1666 14 3 17 1668 8 1 9 1711 3 2 2 13 4 24 1715 14 1 2 17 1728 1 9 1 11 1731 2 2 4 20 1 8 38 1778 5 1 6 1788 2 8 4 15 1811 2 2 1839 2 8 IO 1844 2 1 3 1864 2 13 2 17 TOTAL 24 19 14 219 0 0 1 0 2 1 6 4 2 38 331 • The experimental seedlings are potentially new strawberry varieties being developed by the Horticulture Department, University of Minnesota for use by growers. In most cases they are not distributed around the state of Minnesota and have only been grown at the University of Minnesota Fruit Farm located near Excelsior, Minnesota. 34 The Minnesota Academy of Science TABLE 3. Basic symptoms or sympt~m-combinations produced in F. vesca when grafted to commercial varieties or strawberries grown in Minnesota.• Minnesota virus class number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Symptoms Epinasty Epinasty and mild chlorosis Epinasty and chlorosis Epinasty, chlorosis and dwarfing Epinasty and chlorotic spotting Chlorotic spotting or streaking Epinasty, chlorosis, and necrotic spotting Ring spot, epinasty and mild chlorosis Chlorotic spotting, dwarfing and chlorosis Dwarfing and chlorosis Crinkle Veinal necrosis and chlorosis Witches' broom Leaf curl • Classes 1-10 were recognized by Skiles (10); whereas the additional classes 11-14 or combinations of symptoms have been recognized in this study. REsUL TS: The results presented in Tables 1 and 2 indi-cate that in commercially grown strawberries in Minne-sota as well as in certain experimental seedling selec-tions viruses or virus complexes occur in nearly every plant. All the viruses were masked in the commercial varieties and their presence was demonstrated by the de-velopment of symptoms in th~ indicat~r plants. In the commercial varieties and seedlmg selections, 93 % of the plants indexed were virus-infected. Epinasty, chlorosis and stunting were the most prevalent symptoms that de-veloped in the indicator host. It was observed that seasonal environmental changes had an effect on the symptom development. As a rule the yellows-types ( chlorosis) develop best during the sum-mer and are less severe when transmitted to the indi-cator host during the winter, whereas many of the crinkle or mosaic type viruses complexes caused the most severe reactions in the indicator plants during the winter months. Moreover, in some plants the yellows-type reacti?n seemed to become less severe 4 to 6 weeks after the m-itial appearance of the symptoms, resulting in only a_mild discoloration and abnormality of the leaves and petioles. It was found that mottle and mild yellow-edge as FIGURE 1: Yellows virus of strawberry in the indicator plant, F. vesca. Yellows consists of epinasty, leaf distortion, stunting and chlorosis. Proceedings, Volume Thirty, No. One, 1962 described by Prentice (8, 9) were the two dominant viruses in Minnesota strawberries, whereas crinkle and vein chlorosis were of rare occurrence (Figures 1 and 2). FIGURE 2. Crinkle virus of strawberry in the indicator plant, F. vesca. Crinkle consists of mottle pattern in the leaf, leaf dis-tortion and vein necrosis. The results indicate that specific viruses or virus com-plexes were not associated with any ·specific commercial variety or seedling selection but are more o_r less ra?-domly distributed throughout the state of Mmnesota _m the numerous strawberry varieties. From the complexity of the symptoms that developed in F. vesca, it seems probable that there are numerous strains of the straw-berry viruses occurring in various combinations that are responsible for the symptoms that developed in F. vesc~. In the 22 varieties tested, virus free plants were found m only the following: Brilliant, Catskill, Dunlap, Evermore, Gem, Premier (Howard 17), Redrich, Robinson and Wayzata. The development of resistant varieties and the elimi-nation of viruses from commercial plantings by isolating virus-free stock, and increasing, distributing, and main-taining a source of this stock by a certification plan, ap-pears to be the most practical and feasible method of control. The development of resistant varieties, after more is known about the strawberry virus complex and its effect on the degeneration of strawberries, is an important goal for the future. LITERATURE CITED 1. DEMAREE, J. B. and C. P. MARCUS. 1951. Virus Diseases of Strawberries in the United States, with Special Reference to Distribution, Indexing, and In-sect Vectors in the East. Plant Dis. Rep tr. 35: 527-537. 2. GOHEEN, A. C. 1955. Methods for Determining the Success of Graft Unions between Plants in Straw-berry Virus Studies. Plant Dis. Reptr. 39: 31-32. 3. HARRIS, R. V. 1933. The Strawberry "Yellow-edge" Disease. J. Pomol. & Horticult. Sci. 11: 56-76. 4. HARRIS, R. B. and A. A. HILDEBRAND. 1942. Stud-ies in Strawberry Diseases. V. the Use of Fragaria vesca L. as an indicator of Yellow-edge Crinkle. J. Pomol. & Horticult. Sci. 19: 227-242. 35 5. MILLER, P. W. 1952. Technique for Indexing Straw-berries for Viruses by Grafting to Fragaria vesca. Plant Dis. Reptr. 36: 94-96. 6. PLAKIDAS, A. G. 1926. Strawberry "Yellows," a Degeneration Disease of the Strawberry. Phytopath. 16: 423-426. 7. PLAKIDAS, A. G. 1955. Virus Diseases of Straw-berry, a Review. Plant Dis. Reptr. 39: 525-541. 8. PRENTICE, I. W. 1952. Resolution of Strawberry BOTANY Virus Complexes. V. Experiments with Viruses 4 and 5. Ann. Appl. Biol. 39: 487-494. 9. PRENTICE, I. w. and T. M. WooLCOMBE. 1951. Resolution of Strawberry Virus Complexes. IV. The Latent Period of Virus 3 in the Vector. Ann. Appl. Biol. 38: 389-494. 10. SKILES, R. L. 1952. The Strawberry Viruses in Min-nesota. Unpublished Ph.D. Thesis, University of Minnesota. The Effect of 0-Phenylphenol on the Growth of Some Fungi Occurring in Wood 1 WILLIAM MERRILL and D. W. FRENCH University of Minnesota, St. Paul INTRODUCTION: It is often difficult or impossible to ob-tain cultures of wood rotting fungi from pieces of de-cayed wood placed on agar media, because other fungi present in the wood grow out rapidly and hide or sup-press the fungus or fungi responsible for the decay. Trich-oderma viride Pers. occurs very commonly in decayed wood, grows rapidly on agar media suitable for the isola-tion of wood-rotting fungi, and makes the isolation of wood decay fungi difficult. Russell (2) reported that O-phenylphenol added to the culture medium at the rate of 0.06 grams per liter would inhibit the growth of Tricho-derma but permit wood rotting fungi to grow, although it did inhibit Merulius lacrymans (Wulf.) Fr., a fungus that causes brown rot. Denyer ( 1) tested 20 species of fungi and found that a medium containing O-phenyl-phenol had little or no inhibitory effect on fungi that cause white rot and on some of those that cause brown rot, but did inhibit some fungi that cause brown cubical rot. Isolations by the authors from decayed wood from buildings, using a medium containing O-phenylphenol, and involving white and brown rots, often failed to yield any wood rotting fungi. For this reason it seemed desir-~ble to determine the effect of O-phenylphenol in the medium upon the growth of some of the common fungi known to cause either white rot or brown rot. MATERIALS AND METHODS: A medium of the following composition was prepared: _malt extract . . . . . . . . . . . . . . . . . . 30 g peptone . . . . . . . . . . . . . . . . . . . . . 5 g agar ........................ 25 g O-phenylphenol ............. 0.06 g water . . . . . . . . . . . . . . . . . . . . . . 1 liter 1 Paper No. 4829, Scientific Journal Series, Minnesota Agri-cultural Experiment Station, St. Paul, Minnesota. 36 The medium was autoclaved, cooled to 50° C., the O-phenylphenol added, the medium poured into petri dishes and allowed to solidify. Pieces of inoculum approximately 5 mm. square from cultures grown 2 weeks on malt agar were transferred to the dishes, the dishes stored 14 days in diffuse light at 25° C., and notes were taken. RESULTS: The fungi which grew on the medium con-taining O-phenylphenol are listed in Table 1; some of these grew more slowly on this medium than on the com-parable medium not containing O-phenylphenol. Those fungi which did not grow on this medium are listed in Table 2. Those which grew very slowly on the medium or which grew only on the block of inoculum are listed in Table 3. DiscussION: The O-phenylphenol completely inhibited (Table 2) or greatly suppressed (Table 3) the growth of about as many species of fungi that cause white rot as those that cause brown rot. None of the Ascomycetes or Fungi Imperfecti tested grew on this medium; both Daldinia concentrica (Bolt.) Ces. and de Not. and Chae-tomium globosum Kunze are common Ascomycetes which can cause white rot of wood. The following fungi produced a red halo, as shown in Figure 1, in the agar around the inoculum block or around the growing col-ony: Asterostroma cervicolor (Berk. and Curt.) Massee, one isolate of Coniophora puteana (Schum. ex Fr.) Karst., Coprinus comatus Fr., Fames applanatus (Pers. ex Wallr.) Gill., Lenzites saepiaria (Wulf. ex Fr.) Fr., Panus rudis Fr., Polyporus compactus Overh., and Poria subacida (Peck) Sacc. CONCLUSION: Ortho-phenylphenol inhibited the growth of both white rotting and brown rotting fungi, and would seem to have limited value as an ingredient of an agar medium used for the isolation of many common fungi that cause decay of wood. The MinnesotaAcademy of Science 

Occurrence and Severity of the Viruses of Strawberry in Minnesota

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Occurrence and Severity of the Viruses of Strawberry in Minnesota

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