Sugarcane bacilliform viruses in Ethiopia: genetic diversity and transmission by pink sugarcane mealybug

Badnaviruses infecting sugarcane, collectively called sugarcane bacilliform viruses (SCBVs), are reported worldwide and are responsible for causing leaf fleck disease in sugarcane. SCBVs are genetically heterogeneous members of the badnavirus species complex. The objective of this study was to evaluate the genetic diversity of sugarcane bacilliform viruses (SCBVs) in four distinct sugarcane growing sites in Ethiopia. Additionally, the study aimed to examine the transmission of SCBV through vectors. A total of 270 sugarcane leaf samples, including both virus-suspected (symptomatic) and asymptomatic leaves, were collected and tested using a PCR assay with SCBV-F and SCBV-R primer pairs. Out of these samples, 67 (24.8%) were found to be SCBV-positive. Phylogenetic analysis and pairwise sequence comparisons based on the partial RT-RNase H coding region showed that the SCBVs in Ethiopia are genetically diverse. The phylogenetic analysis revealed that isolates from the current study formed four clusters together with SCBV-G, L, Q and S isolates reported from different parts of the world. This suggests that the introduction of SCBV to Ethiopia may have occurred in multiple countries. The glasshouse experiments demonstrated the efficient transmission of SCBV from infected to healthy sugarcane plants by pink sugarcane mealybugs (Saccharicoccus sacchari), which are associated with the sugarcane crop in the field. These findings contribute to the current understanding of the genetic diversity of SCBVs in Ethiopia.