Plant Virology Laboratory Department of Mycology and Plant Pathology, Dr. Y S Parmar University of Horticulture and Forestry, Nauni, Solan – 173230
National Symposium on Strategic Issues in Plant Pathological Research held at Department of Plant Pathology, CSK HP Krishi Vishvavidayalaya, Palampur on November 24–25, 2011
Bioassay of viruses in vegetatively propagated crops including apple is considered to be an essential component in indexing programmes for the production of virus free propagating material. Woody indicators namely Malus pumila ‘Virginia Crab’, Malus platycarpa, Malus pumila ‘Spy 227’, Malus pumila ‘Russian clone’ and Jay Darling were used for the detection of viruses in an apple tree carrying mixed infection of Apple chlorotic leaf spot trichovirus (ACLSV), Apple stem pitting foveavirus (ASPV), Apple stem grooving capillovirus (ASGV) and Apple mosaic ilarvirus (ApMV) through double grafting, grafting cum budding and double budding indexing methods. These indicators resulted in the detection of the above mentioned viruses by exhibiting typical viral symptoms like excessive callusing and swelling at the graft union between budwood of infected test plant and indicator of Spy 227; swelling and brown line necrosis at the graft union of infected budwood and Virginia Crab indicator; leaf deformation accompanied by peculiar red spotting on the leaves of Jay Darling; mosaic and oak leaf pattern on leaves of Malus platycarpa and chlorotic spots in combination with ring spots on leaves of Russian clone. These symptoms were produced after 90 to 150 days following graft/bud inoculation depending upon the method of indexing. Further, serological detection of viruses in these symptomatic indicator plants by employing double antibody sandwich (DAS) form of enzyme-linked immuno-sorbent assay (ELISA) resulted in finding out the presence of multiple infection of ASGV, ACLSV, ASPV and ApMV in Spy 227, Jay Darling and Malus platycarpa indicators; ASGV, ACLSV and ASPV in Russian clone and Virginia Crab indicators. These studies revealed that the woody indicators tested could serve as potential sources for use in biological indexing in the virus certification programme of apple.
