ISHS Acta Horticulturae 129: III International Symposium on Small Fruit Virus Diseases
ELIMINATION OF A HEAT-STABLE RASPBERRY VIRUS BY COMBINING HEAT TREATMENT AND MERISTEM CULTURE |
| Author: | G. Baumann |
| Abstract:
From raspberry stock plants infected with the heat-stable raspberry vein chlorosis virus (RVCV) healthy plants were obtained by combination of heat treatment and meristem culture. Root cuttings of "Baumforth's seedling B". a cultivar of red raspberry being totally infected with RVCV were kept in a heat chamber at 38–40°C for 8 weeks. Thereafter meristem tips about 0.2 mm in size were excised from apical and lateral leaf buds of the heat treated plants. The plantlets were cultured in vitro for 5 months on media recommended by vom Berge (Auswirkungen von Viruskrankheiten auf Himbeere (Rubus idaeus L.) und Möglichkeiten ihrer Eliminierung aus infizierten Pflanzen. Diss. Bonn, 1982). The basic medium used for explanting and shoot multiplication consisted of inorganic nutrients (Murashige and Skoog, 1962), 2% saccharose, 0.8% agar (Difco-Bacto), 20 ppm Fe-Na-EDTA, 0.2 ppm N-6-benzylaminopurine (Sigma). For rooting, benzylaminopurine in this media was replaced by 0.2 ppm indole-3-butyric acid. Explants were kept in darkness at 20°C for 5 days after excising. The culture jars were then maintained at 16 h artificial light (cool white fluorescent light) per 24 h cycle at 22–24°C. Plantlets were transferred to fresh media every four weeks and grown on multiplication media for 3 months. They were kept on the rooting media for another 2 months and then transferred to sterilized soil consisting of peat and sand (1:1). From 35 meristems which had been excised from the heat treated "Baumforth" plants 18 had developed to transferable plants including those which did not yet show root formation at the time of transplanting to the soil. All plants survived and were grown in an aphid-proof glasshouse. The indexing for freedom from RVCV was started 8 months after transference to the soil. All 18 plants of "Baumforth's seedling B" which were derived from heat treatment and meristem culture were well established at that time and approximately 25 cm in height. They did not show any leaf symptoms and appeared to be virus-free. To confirm this, young shoots from each of these plants were bottle-grafted to "Norfolk Giant" a sensitive indicator for RVCV. None of the indicator plants developed symptoms whereas plants of "Norfolk Giant" to which shoots of infected "Baumforth's seedling B" had been grafted showed distinct symptoms of RVCV 10 months after inoculation. Furthermore, five of the "Baumforth's seedling B" plants that were rendered virus-free were re-infected with the original source of RVCV by bottle-grafting. Leaf symptoms of RVCV developed on the re-infected "Baumforth's seedling B" which is most sensitive to RVCV within 6 weeks, further confirming that the treated plants were in fact virus-free. These findings confirm results reported by van der Meer (Heat therapy as a tool for the elimination of plant viruses. Semaine d'étude agriculture et hygiène des plantes, Gembloux 1975, 109–117) on eradication | |
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