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Capilloviruses represents an important genus of the family Betaflexiviridae and are plant infecting pathogens. They include several agriculturally important viruses encompassing RNA genomes. Apple stem grooving virus (ASGV) is an important virus of this genus. In recent years, reports are accumulating about its expanding host range breadth (HRB) to affect various other plant species. Increased multiple host adaptability of ASGV could be associated with factors like genetic variability, recombination, genome expression strategy, virus transmission and infection biology. The evolution in the viral genome is driving this virus to increased genome variability resulting in infection of different hosts. This review article focuses on recent advances made in understanding ASGV genome biology and possible disease mechanism that may help unravel the complexities of this viral infection conferring multiple host adaptability. Contrarily, this virus also has an immense potential to be used as vector to unveil viral pathogenicity mechanism, its use as Virus Induced Gene Silencing (VIGS)/Virus-Induced Genome Editing (VIGE) vector, and for the enhancement of plant resistance. These features may allow deciphering functional genomics of important crops, enhancement of plant disease resistance ability, ultimately benefiting agriculture, has also been discussed. [ABSTRACT FROM AUTHOR]

The complete nucleotide sequence of an Indian isolate of Apple chlorotic leaf spot virus ( ACLSV) was determined and found to be 7,525 nt in length. The genome organization was similar to known isolates of ACLSV, encoding three ORFs. Comparisons indicated high sequence variability among known isolates with overall nucleotide sequence identities of 80 to 84%. A striking variable region was identified among the replicase protein upstream of the RNA-dependent RNA polymerase (aa 1510-1590), which showed a 41-43% match with the corresponding region in other isolates. Phylogenetic analysis at the nucleotide level clustered the isolates into three groups, without any relation to geographical origin. Recombination analysis showed that the isolate is a recombinant with recombination sites spread throughout the genome, especially in the polymerase gene region (nt 4700-5400). Most recombination sites were bordered by an upstream region (5′) of GC-rich and downstream region (3′) of AU-rich sequences of similar length. Correlation of recombination site with host type is discussed, and it was found that there were more interlineage recombinations in the apple host compared with intralineage recombinations. [ABSTRACT FROM AUTHOR]