## 4 Discussion  
In this study, the R-DNA and S-DNA genes of Mozambican BBTV isolates from the Chokwe district of Gaza were sequenced and analyzed for the first time, revealing new information about their classification and possible geographical origin. Figure 6: Phylogenetic tree constructed based on the amino acid sequence of the R-DNA of BBTV isolates collected in the district of Chokwe, Mozambique and isolates from GenBank. Bootstrap values were obtained using the MEGA7.0 neighbor-joining program with 2000 repetitions. The nucleotide identities of the R-DNA among the 40 analyzed isolates revealed that 38 of them presented a difference of at most 2%, showing the high conservation of this gene, which has already been observed by authors from other regions of the world. [PERSON] [37] in Nigeria also found 100% identities among the local isolates. Another study conducted in Cameroon by [PERSON] et al. [38] showed a similar result, that is, 100% homology between nucleotide sequences of the analyzed isolates. In phylogenetic studies performed by [PERSON] et al. [39] and reviewed by [PERSON] et al. [20], the classification of BBTV isolates, based on nucleotide sequences, into two groups, the South Pacific group and the Asian group, was proposed. The Mozambican isolates showed higher identities with isolates from the PIO group, between 97% and 99%, and the lowest identities with the isolates from the SEA group, between 90% and 92%, indicating that the Mozambican isolates belong to the first group. These results were corroborated by the distribution of the isolates in the phylogenetic tree based on nucleotide sequences, which showed a clear subdivision of the isolates into two distinct clades, with all the Mozambican isolates grouped together with the isolates of the PIO group. Other authors studying isolates from different African countries also reported that the isolates belonged to the PIO group [21; 37; 38; 40; 41; 42; 43]. Interestingly, the Mozambican isolates were very similar to isolate JQS20453 from Malawi, which borders Mozambique to the south and west. This demonstrates that there is a high probability that the Mozambican isolates came from this country. [PERSON] et al. [8] had already considered Malawi as an area for the dissemination of BBTV through the exchange of planting material of preferred cultivars among farmers in bordering countries. However, it is necessary to consider that South Africa also has the presence of BBTV and shares a border with southern Mozambique. As there is no information on the complete gene sequences of the R-DNA in GenBank, it could not be included in this study. However, South Africa cannot be ruled out as the origin of the inoculants that reached Malawi and Mozambique, as it is geographically closer to southern Mozambique than Malawi. Research on the introduction of BBTV in sub-Saharan Africa (SSA) indicated that the arrival of BBTV in Africa may have occurred in two ways: in the DRC in 1950, it was probably through infected propagules brought from southern Asia or the South Pacific [44; 45; 46]; in Equatorial Guinea and Gabon, it may have been introduced by infected aphids (_Pentalonia nigronerosa_) brought by migrant workers from the Philippines. Then, it is assumed that it spread to other African countries (Rwanda, Burundi and Central African Republic) [46; 47]. This virus is known to be widely prevalent in Central African countries and in Malawi, Southern Africa [8]. To date, the occurrence of the disease has been reported in 16 countries of Central and Southern Africa (Angola, Benin, Egypt, Nigeria, Gabon, Burundi, Cameroon, Central African Republic, DRC, Congo, Equatorial Guinea, Malawi, Rwanda, Zambia, South Africa and Mozambique) [48]. In the nucleotide sequence analysis of the S gene of the isolates from Mozambique, it was observed that it is also highly conserved, with more than 50% of the isolates being 100% identical, and the lowest identity was 98%.