Molecular evidence for presence of Manihot esculenta associated virus 1: CG-Nmb and/or CG-Kah isolates in coast, Tanzania: A threat to cassava production

Genetic diversity of Manihot esculenta associated virus type 1 (MEaV-1) species suspected to cause the most destructive Brown Streak of Cassava (CBSD) in Tanzania, has remained elusive since the year 2020 when MY-6mb-4 virus isolate was first identified in Chambezi, Coast region. In this study, two additional isolates (CG-Nmb and CG-Kah) of the MEaV-1 species were characterized in the same area after screening leaf samples collected from 292 Kiroba, 12 Albert and 22 Kikombe varieties of cassava using a Reverse Transcription Polymerase Chain Reaction (RT- PCR) assay. One half of the leaf samples collected from each of the three varieties displayed CBSD-like symptoms whilst the other half were CBSD-asymptomatic. The MEaV-1 infection was detected only in the CBSD-symptomatic Kiroba, Albert and Kikombe varieties by 58%, 100% and 82%, respectively. Since the RT-PCR assay could only detect the two MEaV-1 isolates simultaneously rather than discriminating them, it indicates that either one of the isolates or both of them caused the infection in the CBSD-cases. Detection of additional MEaV-1 isolates, has expanded the genetic diversity knowledge on the MEaV-1 species in Tanzania which is essential for thorough comprehension of CBSD epidemiology and guiding invention of more effective CBSD-control methods using recombinant DNA technology.