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T.M. HEMALATHA*, B.V. BHASKARA REDDY, R. SARADA JAYALAKSHMI,
S.R. KOTESWARA RAO, M. HEMANTH KUMAR AND G. MOHAN NAIDU
Agricultural Research Station, ANGRAU, Perumallapallae – 517 505
Sugarcane Yellow Leaf Disease caused by Sugarcane Yellow Leaf Virus (SCYLV) is a serious viral disease affecting production and productivity in many ruling sugarcane varieties in Andhra Pradesh. SCYLV is a single stranded, positive sense, RNA genome, with six open reading frames (ORFs 0-5) and three un-translated regions (UTRs) consisting of 5.8 kb nucleotides. The losses due to the disease range from 60 per cent in the main crop to 100 per cent in the ratoon crop. Twenty five SCYLV infected leaf samples were collected from major sugarcane growing regions and amplified the ORF 1& 2 regions of the genome of the virus coding for RNA dependent RNA polymerase gene (RdRp) using the primer pair (SCYLV-F3 and SCYLV-R3). Positive amplifications of 1110 bp obtained from twelve samples were sequenced and analyzed for sequence identities, sequence variations and phylogenetic relationships with the SCYLV isolates reported earlier from India and other countries with the view to determine the variability among the SCYLV isolates reported from India and abroad. The nucleotide (nt) and amino acid (aa) sequence comparison in the RdRp coding regions showed a significant variation between Indian isolates (SCYLVIND) and other SCYLV isolates reported worldwide. The multiple sequence analysis of the isolates under the study with 22 similar sequences of SYLCV isolates reported from India and worldwide revealed 90.6 – 100% identities with IND, REU, BRA, CHN, HAW, CUB, COL and PER isolates reported from other countries. The nucleotide identities were 95.7 – 100 per cent with other SCYLV isolates reported from India. There was greater similarity in amino acid sequences i.e., up to 94.2 – 99.2 per cent between the Indian isolates and the CUB, COL isolates while the similarity was about 90.0 – 96.1 per cent with other genotypes. This was further confirmed from the phylogenetic analysis where the CUB and COL isolates clustered with the isolates reported from India while the other genotypes (HAW, CHN, REU, PER, BRA) clustered into a separate group. The Indian isolates showed close relationship with the CUB and COL isolates. Hence it was confirmed from the study that SCYLV isolates collected from major sugarcane growing regions of Andhra Pradesh are closely related to SCYLV-CUB and SCYLV-COL isolates from Cuba and Columbia respectively.
Sugarcane, Sugarcane yellow leaf virus, Molecular Characterization, Movement, Protein, Phylogenetic analysis.