Low genetic diversity of Banana bunchy top virus, with a sub-regional pattern of variation, in Democratic Republic of Congo.

Banana bunchy top virus (BBTV), belonging to the genus Babuvirus, is the most devastating and widespread banana virus. Banana and plantain are major crops in terms of household income and food security in Democratic Republic of Congo (DRC). Despite the large area under banana and plantain cultivation in the country, before this study, the genetic characterization of BBTV isolates had only been undertaken for two provinces. In the study presented here, genetic variation in BBTV was assessed from 52 BBTV isolates collected in five out of 11 provinces in DRC (Bandundu, Bas-Congo, Katanga, Kinshasa and Kasaï Oriental) and in two provinces using sequences previously described in databases. Full genome sequencing of DNA-R components was performed, revealing low genetic variation (98-100 % nucleotide identity) among the BBTV isolates detected. The phylogenetic analyses showed that all the DRC isolates were clustered in the South Pacific clade of BBTV. Based on the coding region for the replication initiator protein, haplotype diversity was estimated to be 0.944 ± 0.013, with 30 haplotypes from 68 isolates in DRC. Such diversity shows a haplotype distribution mainly at the sub-regional level in DRC. In addition, the sequence determination from the whole genome of selected isolates confirmed low genetic variation among isolates from seven DRC provinces (97-100 % nucleotide identity). This study strengthened the hypothesis of a single BBTV introduction some time ago, followed by the spread of the virus in the country.