Identification of Cassava Mosaic Virus Strains in Zimbabwe Using Nanopore Sequencing

Abstract

Tapiwa Nyakauru and Fiona Robertson

Cassava (Manihot esculenta Crantz: Euphorbiaceae) is the only species in its genus that is grown as a food crop. Africa is the largest centre for cassava production, producing over 100 million tonnes per year. However, cassava is affected by several diseases including Cassava Mosaic Disease (CMD) which is caused by Cassava Mosaic Viruses (CMVs). Symptoms of CMD include distortion of leaf lamina, mottling, unordered growth and malformation of the leaves, formation of chlorotic mosaics, and narrowing of the leaves. Several strains of CMVs that have been recorded include Africa cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV), East African cassava mosaic Malawi virus (EACMMV), East African cassava mosaic Ugandan virus (EACMV-UG), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Zanzibar virus (EACMZV), East African cassava mosaic Kenya virus (EACMKV) and South African cassava mosaic virus (SACMV). However, limited information is available with regards to CMV strains in Zimbabwe. This work focused on identifying specific strains of CMV that are affecting cassava plants in Zimbabwe. Using nanopore sequencing, several strains of CMV including ACMV, EACMV, EACMV-UG, EACMV-K, and SACMV were detected in cassava plants from Zimbabwe. These findings provide the first comprehensive evidence of CMV strain diversity in Zimbabwe and highlight the potential of nanopore sequencing as a rapid and cost-effective tool for virus surveillance, early detection, and management of CMD in cassava production systems.

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