ISHS Acta Horticulturae 129: III International Symposium on Small Fruit Virus Diseases
PURIFICATION, SOME PROPERTIES, AND SEROLOGY OF STRAWBERRY MILD YELLOW-EDGE VIRUS |
| Authors: | R.R. Martin, R.H. Converse |
| Abstract:
Mild yellow-edge virus (MYEW), a persistent, aphid-borne virus transmitted by several Chaetosiphon spp., is common and serious in cultivated strawberries in western North America. Oregon MYEV isolate MY-18 is readily transmitted by the colony of C. fragaefolii derived from the single aphid originally collected with MY-18 from field-grown strawberry and transferred to Fragaria vesca var. sempperflorens 'Alphine' seedlingd in the greenhooouse. This isolate was increased in Fragaria in the greenhouse for partial purification and study. MY-18 has a thermal inactivatioon point between 45 amd 50°C as determined by apphid and graft transmission from detached leaves that had been immersed in water fot 10 minutes at various temperetures. MY-18 was purified from chronically infected strawberries including the cultivar 'Hood', Fragaria virginaia clone 'UC-10', and 'Alphine' and from 'Alpine' and F. vesca clone 'UC-4' at early stages of symptom development. After comminution in liquid nitrogen, extraction in 0.1 M phosphate buffer with 0.01 M DIECA and 1% thioglycollic acid (pH 7.0) and differential and rate-zonal density gradient (dg) centrifugation, an ultraviolet absorbing dg band (A254), not seen in control preparations, was detected in extracts from MY-18 infected plants. Comparosooon of virus yiekds from roots and leaves of 'UC-4' and 'Alphine' plants exhibiting early stages of MYE symptomalogy showed tnat greater than 50% of the virus yields was recored from the root tissues. Preparations from roots contained mostly 23 nm-diamete, isometric, virus-llike paricles, whilw leag tissues contained predominantly 28 nm-diameter particles. In bitht cases the particles were associated with their correspooonding dg bands and were noninfectious when rubbed onto C. guinoa plants. It is possible that the particles from leaf tissues are partially degraded during purification by phenolic compounds that are known to be present in large quantities in strawberry leaf tissues. In ELISA tests rabbit antisera against MY-18 differntiated between crude MYEV-infected and healthy root extracts and between partially purified MYEV-infected and healthy leaf extracts. A405 readings of infected samples were about 3 times higher than healthy background. However, the same antisera could not differentiate between healthy and MY-18-infected crude leaf extracts in ELISA tests. ELISA tests with crude root estracts of four other isolates of SMYEV gave A405 readings between 2 and 3 times healthy background. Our data support the generally held hypothesus that SMEV is a member of the luteovirus group. However, in ISEM tests using antisera against SMYE, potato leafroll, beet western yellows, legume yellows, pea leafroll, and tobacco necrotic dwarf viruses we were unable to detect virus-like paricles in MY-18 infected F. vesca leaf sap. | |
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