Production of virus-free grapevines in New Zealand

Transcription

1 New Zealand Journal of Agricultural Research ISSN: (Print) (Online) Journal homepage: Production of virus-free grapevines in New Zealand A. J. Over de Linden & E. E. Chamberlain To cite this article: A. J. Over de Linden & E. E. Chamberlain (1970) Production of virus-free grapevines in New Zealand, New Zealand Journal of Agricultural Research, 13:4, , DOI: / To link to this article: Published online: 14 Feb Submit your article to this journal Article views: 139 Citing articles: 1 View citing articles Full Terms & Conditions of access and use can be found at

2 991 PRODUCTION OF VIRUS-FREE GRAPEVINES IN NEW ZEALAND By A. J. OVER DE LINDEN* AND E. E. CHAMBERLAIN* (Received 24 June 1970) ABSTRACT Because of the high incidence and serious effect of grapevine fanleaf and leafroll viruses on vines in New Zealand, virus-free material is needed for n::!w plantings and replacement of existing infected vines. Virus-free vines of a number of varieties have been introduced from California, and heat treatment has been applied to all important local varieties. Vines of 18 varieties have been treated at 100 F for periods ranging from 56 to 141 days. Of 167 vines raised from shoot tips of heat-treated plants, 45 have been screened for virus infection. Four were found to be infected with fanleaf and 9 with leafroll virus. Vines of the first variety from which virus was eliminated by heat trcatm::nt were released in Plants of a further 6 varieties will be released next year, and 11 varieties, stili being indexed, should be available for release in 1972 and Eight other varieties are undergoing heat treatment. INTRODUCTION Incidence of grapevine fanleaf and leafroll viruses is very high on grapevines in New Zealand, and in many varieties all vines appear to be infected with one or both viruses (Chamberlain et al. 1970). The only other grapevine viruses found in this country, yellow mosaic and enation disease, are probably both caused by strains of fanleaf virus, and, being of low incidence, are of minor economic importance. Overseas, both fanleaf and leafroll are regarded as serious diseases. The former, which in Europe is considered to be one of the main causes of grapevine degeneration, has been reported to cause yield losses of up to 50 percent (Vuittenez 1966). Leafroll, the effects of which have already been discussed (Over de Linden and Chamberlain 1970), is even more serious, as it causes greater yield reductions, delays ripening of fruit, lowers sugar content of the berries, and, in dark-fruited varieties, reduces pigment concentration of the grapes. When it was found that virus diseases were prevalent throughout our commercial vineyards it was realised that a supply of virus-free vines was required by the grapevine industry. The Department of Agriculture began Plant Diseases Division, DSIR, P.B., Auckland, New Zealand. New Zealand Journal of Agricultural Research (1970), 13:

3 992 Virus-free grapevines to introduce virus-free vines from California, but not all varieties of importance in this country were available. It was decided, therefore, to attempt to secure virus-free plants of such varieties from within Ncw Zealand. Because of the high incidence of virus diseases in our vines, the method of visual selection of plants without symptoms followed by indexing to confirm virus freedom which has been successfully practised in some other countries (Baldacci et al. 1966) was not available to us. Instead we initiated a virus-elimination programme based on the method developed at the University of California, Davis, in which plants are raised from shoot tips taken from vines grown in a heat chamber at 100 F. (Goheen et al. 1966). Since clonal types occur within grapevine cultivars (Rives 1966). selection over a period of years in anyone region tends to establish a clonal type adapted to that region. Many of our most popular European grapevine varieties originate from vines introduced from Australia in 1897 and 1898 (Callender 1898), and most of our important European/ American hybrid varieties were imported from France in 1927 and 1929 (Woodfin 1928, 1929). These same varieties have probably been grown for even longer in California. Selection over many years in these two regions of widely differing climates may therefore have led to the development of different clonal types. To ensure availability of virus-free vines of clonal types found suitable under New Zealand conditions, our virus-elimination programme was expanded to cover all popular varieties whether or not they were available as virus-free vines from California. MATERIALS AND METHODS Heat-treatment cabinets Heat treatment is carried out in two cabinets, one in a partly shaded glasshouse and the other in a coolhouse. The temperature in both is controlled within the range 98 to 101 F, with an average close to 100 F. Natural lighting is supplemented by mercury vapour lamps controlled to provide a total of 18 hours' light per day. Humidity is not controlled, but is maintained through watering of vines, and is usually about percent r.h. Propagation frames The propagation frames for striking shoot tips and for general vine propagation are of standard design filled with coarse sand. A sand temperature of 78 F is maintained by thermostatically controlled buried heating cables, and a fine mist is supplied, when required, from nozzlcs controlled by moisture sensors. Selection of vines for heat treatment To ensure that the varieties were true to name and of a good type, cuttings to raise vines for heat treatment were obtained, when possible, from the Te Kauwhata Viticultural Research Station. Such vines are representative of those grown throughout New Zealand, as most grapevines in commercial vineyards originated from the Te Kauwhata Station. To ascertain their virus status, vines of most varieties were indexed for fanleaf and leafroll viruses.

4 Heat treatment A. J. OVER DE LINDEN AND E. E. CHAMBERLAIN 993 The preparation of vines for heat treatment has undergone a number of changes since the first trials were carried out in The growing medium has ranged from potting soil of the John Innes type through peat/sand mixtures to pure sand, and containers have included clay pots, wooden boxes, and galvanised iron and non-porous plastic pots. The procedure used for much of the early work was based on the method described by Sisto and Martelli (1966). Strong cuttings 40 em long wrapped in polythene were held in cool store for at least 4 and sometimes up to 20 weeks. On removal from coolstore cuttings were buried horizontally, 6 per box, at a depth of about 3.5 cm in coarse sand in wooden boxes. The boxes were held for 2 weeks at o F and then placed in the heat cabinet at F for a further 2 weeks before the temperature was raised to looof. Throughout treatment the sand was watered with half-strength Hoagland's nutrient solution every second day. Although this procedure was successful in providing many shoot tips, there were also many failures, and the method was therefore replaced by one similar to that used by Goheen et ai. (1966). Three 3-node cuttings were placed in 50 percent sand and 50 percent peat mixture in an 8 in. heavy, dark coloured, crude plastic flower pot with approximately 10 g Mag Amp with K fertiliser (N-P-K-Mg = ) mixed into the soil medium near the bottom of the pot. Plants were well established (2-8 months) before being placed in the heat cabinet. Throughout treatment a weak solution (1 g per 2 gal water) of Nitrophoska (Blue) fertiliser (N-P-K = ) was used to water the vines. The variety Dr Hogg Muscat failed under either of these procedures to survive in the heat cabinet for more than 20 days, and not until a six-year-old vine was lifted from the field and established in sand in a wooden box were we able to get this variety to survive for a satisfactory period at loo F. Growing of vines from shoot tips Unless the vines in the heat cabinet were showing signs of collapse. they were maintained at looof for at least 68 days before any shoot tips were removed for propagation under mist. However. if collapse appeared imminent, shoot tips were taken earlier, provided the vines had been grown at loo F for at least 55 days. If vines continued to grow after 68 days, they were left in the heat cabinet and further shoot tips removed as they became available. Shoot tips 3 to 5 cm long were excised from heat-treated vines and dipped in a solution of Captan fungicide (lib Captan per 100 gal water) to avoid infection with fungi. such as Botrytis cinerea, before being cut with a razor blade, preferably at a node, to a length of 2-3 cm. The tips were immediately placed in vermiculite in It in. clay pots. 3 or 4 per pot, and the pots sunk into sand of a mist propagation frame. Although the sand temperature was maintained at 78 F, the temperature of the vermiculite was usually about 76 F. Roots formed in 3 to 4 weeks, and the young rootlings were then transferred to a mixture of

5 994 Virus-free grapevines TABLE I-Production of Virus-free Grapevines by Heat Treatment and Shoot Tip Propagation Virus status of Treatment p:lrent vine before No. treated Length of time of heat treatment vines selected treatment of vine selected for Estimated Variety for indexing vines planted and planting in holding producing year of in holding nursery nucleus of release virus-free Fanleaf Leafroll nursery (days) vines (days) Pinot Meunier Gaillard Girerd Hermitage Pinotage Seibel 4986 NI NI Seibel Seibel Cabernet Sauvignon Cinsaut Dr Hogg Muscat Johann Sieve NI Pedro Ximines Pinot Chardonnay Riesling Sylvaner Albany Surprise Palomino + -I Pinot Noir Bactobel Schuyler = not infected, + = infected, NI = not indexed.

6 TABLE 2-Effectiveness of Heat Treatment and Shoot Tip Propagation in Eliminating Fanleaf and Leafroll Viruses from Grapevines Variety Virus status of parent vine Batch Date Length of Number Number Number shoot tips treatment treated infected infected number Fanleaf I Leafroll removed (days) vines fanleaf leafroll Cabernet Sauvignon +t + QGl 12/11/ Cinsaut + + QG1 12/11/ Gaillard Girerd 157 QEl 9/12/ Gaillard Girerd QD3 15/12/ Gaillard Girerd 157 -t- QD2 24/11/ Gaillard Girerd 157 QD2 2/12/ Gaillard Girerd QD3 1/ 1/ Hermitage QAl 4/ 2/ Hermitage + + QA2 27/ 2/ Pedro Ximines + + QGl 12/11/ Pinotage - QD3 15(12/ Pinotage - QD2 24/11/ Pinotage - QFl 18/ 4.' Pinotage - QD3 20/12( Pinotage + QD3 1/ 1/ Pinotage -.+ QD3 26/ 1/ Pinot Meunier Pinot Meunier / 5/ QCl 25/ 5/ Riesling Sylvaner QD3 15/12/ Riesling Sylvaner + QD3 20/12/ Riesling Sy1vaner -I- QD3 1( 1/ Riesling Sy1vaner + + QD3 26/ 1/ Seibd 5455 QA1 4/ 2/ Seibel QC1 21/ 4/ ~ Virus infection detected either by indexing or from symptoms on treated vines. Some vines indexed or observed over two seasons but others over only one. Virus infection could be present in some apparently virus-free vines tested over one season only. t + = infected, - = not infected. ;» '-< ~ ~ o m t Z g Z > Z o rn rn n :r: > s:: t:a ~ Z \0 \0 VI

7 996 Virus-free grapevines equal quantities of peat and sand in 3 in. clay pots. These were returned to the mist progagation frame for at least 24 hr before being plunged into sand at 78 p without mist. Nutrient was applied by watering with normal-strength Hoagland's solution. Once established the rootlings were transferred to successively larger pots with progressively richer soil media until they were growing in potting soil in 6 in. pots. They were held in the 6 in. pots until they had made sufficient growth to be planted in the field. Indexing of vines for virus infection When vines grown from shoot tips of heat-treated plants had made sufficient cane growth to provide material for grafting, they were indexed on grapevine indicator varieties for detection of virus infection using the procedures already described (Chamberlain et al. 1970). The following indicator varieties were used : St. George: For fanleaf, yellow mosaic, and enation disease viruses. Mission: For leafroll virus. LN 33: For corky bark and leafroll viruses. * RESULTS Virus status of vines before heat treatment Results in Table 1 show that of the 18 varieties heat treated, 16 were indexed for fanleaf and leafroll viruses, one for fanleaf only, and one was not indexed. Of the varieties indexed, 11 were infected with both viruses, three were infected with leafroll but not fanleaf virus, two were free from both viruses, and one was free from fanleaf but was not indexed for leafroll. Heat treatment and propagation of shoot tips Since the virus elimination programme started in 1964, 167 vines have been established from 437 shoot tip cuttings taken from 291 heattreated plants of the 18 varieties listed in Table 1. Of the established vines, 100 have been selected for indexing and planting out in a holding nursery. Details of the number of selected vines of each variety and length of heat treatment of parent vines are given in Table 1. Some vines survived for more than 55 days and produced new growth at p during all seasons of the year and in all soil media and all containers. The influence of season, soil mixture, or container type on vine sllrvival and production of new growth under heat, or on percentage establishment of shoot tip cuttings, was not consistent. However, there was a tendency for vines to survive longer and produce more new shoots and for tip cuttings to establish more readily during the winter, spring, and early summer than in the late summer and autumn. Also, in general, vine survival and shoot growth were better in non-porous pots than in * Experience at this laboratory confitms the observation made by R. H. Taylor, Victoria, Australia (pers. comm.) that the variety LN 33 is an excellent indicator for leafroll virus.

8 A. J. OVER DE LINDEN AND E. E. CHAMBERLAIN 997 clay pots or wooden boxes. Sand or sand/peat mixtures with added fertiliser gave rather better growth than soil. Effectiveness of heat treatment in virus elimination Results in Table 2 show that of 45 plants produced from shoot tips of heat-treated, infected vines, 13 were still infected with either fanleaf or leafroll viruses. However. at least one vine of each of the 9 varieties appears to be free from infection, although in some cases further testing is required to confirm this. Table 2 also shows that in some instances fanleaf virus was eliminated by heat treatment, but leafroll was not, while in others treated vines were free from leafroll, but still infected with fanleaf. Virus was eliminated in some treatment batches, but in others treatment for the same time failed to produce virus-free plants. Also in some batches the vines of one variety were virus-free, but those of another treated for the same length of time were still infected. No infection with corky bark virus was found on any of 23 vines indexed on the LN 33 indicator variety. Vines selected for heat treatment were free from symptoms of yellow mosaic and enation disease, but if either disease had been carried in a latent form and survived heat treatment, it would have been detected on the St. George indicator variety. Growth of vines raised from shoot tips Once rooted, vines raised from shoot tips made rapid growth, and most were ready to transplant to the holding nursery in 6 to 8 months from the time tips were removed from the heattreated vines. In the nursery they continued to make vigorous growth, and by the time they were 2 to 3 years old were producing considerable quantities of cane Fig. I-Vine from heat-treated plant. Three-year-old Seibel 5455 vine showing crop and vigorous cane growth. [Photo A. Underhill

9 998 Virus-free grapevines (Fig 1). Although they were pruned for cane production, many vines bore fruit within 2 to 3 years. Distribution of virus-free grapevines All heat-treated vines found to be still infected with either fanleaf or leafroll viruses are destroyed. When no infection is found during the first year of indexing the indicator vines are retained for a further year's observation and the selected vines re-indexed. No vines are considered for final selection as virus-free until they have indexed negative in two growing seasons. When a vine of any variety has been selected as virus-free the clone is increased as rapidly as possible by propagating from hard- and soft-wood cuttings. As soon as sufficient material is available the variety is released for distribution. Some vines are retained for field testing at this laboratory, and some are sent to the Te Kauwhata Viticultural Research Station, which is establishing a collection of virus-free grapevine varieties for subsequent distribution of cuttings to growers. If the variety is of particular value to the industry, vines are sent also to the Horticultural Department, Massey University, which has undertaken to raise virus-free plants of our most important varieties for sale to vine growers. The estimated year of release of the 18 varieties that have been heat treated so far is given in Table 1. The first variety from which virus was eliminated by heat treatment, Pinot Meunier, was released in Vines of a further 6 varieties have been selected as virus-free this season for release next year. Continuation of the virus-elimination programme. Many of the varieties of importance in New Zealand have been heat treated already, but the following are still undergoing treatment:- Golden Chasselas, Pinot Nair Oberlin, Pinot Nair AM 1O}5, Black Hamburg, Tokay Furmint, Ezereves, Refosco, and S.V DISCUSSION The term "virus-free vines" as used throughout this paper indicates that the vines are free from viruses for which they have been indexed. We have no evidence of the presence in New Zealand of any virus that does not produce symptoms on St. George, Mission, or LN 33 varieties, but it is possible, though unlikely, that the vines designated virus-free could carry latent viruses that do not produce symptoms on any of these indicators. From the information available it is not possible to explain why some shoot tips from heat-treated vines were free from virus infection and others were not. Goheen et at. (1966), who experienced similar discrepancies, suggested that the time lapse between placing vines in the heat cabinet and the commencement of new growth might influence the virus status of shoot tips. Also, rate of growth of new shoots, length of

10 A. 1. OVER DE LINDEN AND E. E. CHAMBERLAIN 999 shoot tips removed, and slight variations in temperature and light intensity during treatment could influence the presence or absense of infection. It is evident from results in our trials that treated vines must be thoroughly indexed before they can be declared virus-free. The popular Baeo 22A variety has not been included in our viruselimination programme, because the main planting at the Te Kauwhata Station is free from virus infection. Also, virus-free vines of this variety introduced from California have been released after testing for agronomic characteristics at the Te Kauwhata station. Since most vines in New Zealand vineyards are infected with both fan leaf and leafroll viruses, the use of virus-free vines for new plantings and replacement of existing infected vines would have a tremendous impact on the wine industry. Grapes would mature earlier, yields would be greatly increased (in some vinifera varieties possibly trebled), the sugar content of the must would be higher, and in dark-fruited varieties the pigment concentration increased (Over de Linden and Chamberlain 1970). Also, in most seasons, the earlier harvesting of fruit would reduce losses from Botrytis rot, which becomes severe after autumn rains. Not only would there be a big increase in wine production through the use of virus-free vines, but wine quality would be improved by the higher sugar content of the must, and red wines would be a deeper colour. As yield increases would be greater in the sensitive vinifera varieties than in the tolerant hybrids, growers would be encouraged to plant greater acreages of the high-quality classical vinifera varieties, thus still further improving the quality of their wines. Acknowledgments The authors acknowledge assistance by members of the Department of Agriculture, particularly Mr P. F. Hitchcock, Manager, Te Kauwhata Viticultural Research Station, who supplied material of named grapevine varieties, and Mr F. Berrysmith, Viticulturist, Horticulture Division, who advised on the relative importance of the different varieties. Also, we are most grateful to Professor W. B. Hewitt and Dr A. C. Goheen, Plant Pathology Department, University of California, Davis, who supplied information on their procedures in the heat treatment and tip propagation of grapevines. REFERENCES BALDACCI, E.; BELLI, G.; REFATII, E.; CESATI, R.; PESSINA, F. 1966: Proc. Intern. Can!. on Virus and Vector on Perennial Hosts. Univ. Calif.. Davis. Sept. 1965: CALLENDER, F. 1898: Rep. Dept. Agric. N.Z CHAMBERLAIN, E. E.; OVER DE LINDEN, A. J.; BERRYSMITH, F. 1970: N.Z. Jl agric. Res. 13: GOHEEN, A. C.; LUHN, C. F.; HEWITT, W. B. 1966: Proc. Intern. Conf. on Virus and Vector on Perennial Hosts. Univ. Cali!. Davis. Sept. 1965: OVER DE LINDEN, A. J.; CHAMBERLAIN, E. E. 1970: N.Z. Jl agric. Res. 13:

11 1000 Virus-free grapevines RIVES, M. 1966: Proc. Intern. Conf. on Virus and Vector on Perennial Hosts, Univ. Calif., Davis, Sept. 1965: 1-9. SISTO, D.; MARTELLI, G. P. 1966: Ibid.: VUIlTENEZ, A. 1966: Ibid.: WOODFIN, J. C. 1928: N.Z. Jl Agric. 36: : Ibid. 39: