Detection and characterization of Macluravirus infecting greater yam (Dioscorea alata L)
By: Manasa V G.
Contributor(s): M L Jeeva(Guide).
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KAU Central Library, Thrissur Theses | Reference Book | 660.6 MAN/DE (Browse shelf) | Not For Loan | 173440 |
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MSc(INT)
Yams constitute a group of Dioscorea species cultivated mainly in Asia,
Africa and South America for their edible, underground tubers. Viral pathogens
are one of the most important factors threatening production of this vegetatively
propagated crop. Yam viruses are poorly characterized, which is a hindrance to
the safe movement of germplasm. The overall aim of this study was to detect
Macluravirus infecting greater yam and to characterize the virus at molecular
level. Serological and nucleic acid based methods were employed for the
detection of Macluravirus infecting greater yam, which was not previously
detected in India. Analysis of greater yam leaf and tuber samples by double
antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA), dot
immunobinding assay (DIBA) and reverse transcription polymerase chain reaction
(RT-PCR) followed by sequence analysis revealed the occurrence of
Macluravirus. Novel species specific primers were developed to amplify the full
coat protein gene of the virus. Sequence and phylogenetic analyses, based on the
entire CP- coding region revealed considerable variability and the virus was found
to be more similar to Chinese yam necrotic mosaic virus (ChYNMV) than other
viruses of the genus Macluravirus. The virus coat protein gene exhibited only 65
to 70% nucleotide sequence identity with other macluraviruses indicating that it is
putative new species. Hence the name Yam macluravirus is proposed for the new
sequence reported. Restriction digestion with Mse1 enzyme followed by DNA
polyacrylamide gel electrophoresis (DNA PAGE) showed presence of
intraspecific variation within the virus isolates obtained from CTCRI field.
Mechanical inoculation and insect transmission of the virus on Nicotiana
benthamiana, N. tabaccum and Vigna unguiculata plants yielded negative results.
These results will be useful for reliable virus indexing to facilitate the safe
movement of greater yam planting material and exchange of germplasm within
and outside India.
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