MOLECULAR CHARACTERIZATION OF APPLE STEM GROOVING VIRUS
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Date
2015
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Abstract
ABSTRACT
Surveys conducted during 2012 and 2013 in 84 apple orchards of Shimla and Kinnaur districts of
Himachal Pradesh revealed viral incidence ranging between 0 to 80 per cent. Chlorotic spots coupled with
necrotic lesions on apple leaves were the predominant symptoms. Regional Horticultural Research Station
(RHRS), Mashobra, Shimla was selected for conducting biological and serological detection of apple stem
grooving virus (ASGV) and other apple viruses. Serological detection through DAC and DAS-ELISA
resulted in the detection of Apple stem grooving virus (ASGV), Apple chlorotic leaf spot virus (ACLSV),
Apple stem pitting virus (ASPV) and Apple mosaic virus (ApMV) in the form of mixed infection in all the
samples marked for assays. Biological detection of one of the isolates carrying infection of ASGV,
ACLSV, ASPV and ApMV on herbaceous hosts resulted in the production of symptoms on Chenopodium
quinoa, Nicotiana glutinosa, N. tabacum and few other hosts. Detection on woody indicators (Virginia
crab, M. platycarpa, Spy 227, Jay Darling and Russian Clone) under field conditions through double
grafting, grafting cum budding and double budding of inoculators and indicator budwood resulted in
production of typical viral symptoms on leaves in M. platycarpa, Spy 227, Jay Darling and Russian Clone
besides swelling of the graft union in case of Spy 227 indicator. Leaf samples drawn during April and May
months were found suitable for the ELISA of ASGV, ACLSV and ASPV whereas petals were the best
source for detection of these viruses. Association of ASGV with viral symptoms in apple was also
confirmed by RT-PCR assay. Molecular characterization and sequencing of ASGV isolates followed by
phylogenetic studies revealed the homology of two identified isolates with other isolates of ASGV from
other parts of India. Serological indexing resulted in the selection of 13 trees of 7 cultivars free from
infection of ASGV, ACLSV, ASPV and ApMV in ELISA test of 36 symptomless trees of 12 cultivars.
Serological studies of different cultivars and rootstocks revealed the viral infection status of different
cultivars and rootstocks screened.
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Keywords
---, APPLE STEM GROOVING