Advances in Plant Pathology Research

ABSTRACT

Cassava mosaic disease (CMD) is among key threats to cassava (Manihot esculenta Crantz) production in Sierra Leone. A diagnostic survey was conducted in 2022 to determine the status of cassava mosaic begomoviruses, whitefly abundance and alternate hosts in cassava field surveys of Sierra Leone. A total of 278 cassava farms were surveyed following the harmonized protocol of the Central and West African Virus Epidemiology program. Findings revealed that, of the 278 farms visited, 10 (3.5%) had no visible symptom of the disease. Of the 8,281 cassava leaf samples assessed, 7981 had symptoms. Average CMD incidence was 90.5%, with the Western Area region recording the highest severity score (3.7), followed by the Northern region (3.2), and the Southern region had the lowest of 2.4. Cutting-borne infection was identified as the primary source of CMD infection. The average whitefly count per field was 5.17. The relationship between CMD incidence and whitefly abundance was significantly negative, while the relationship between CMD severity and incidence was significantly positive. Most farms had ACMV in single and in mixed infections with EACMV and EACMCMV. Most doubly infected plants showed severe symptoms. The ACMV and EACMV were also detected in putative natural hosts Centrosema pubescens, Senna occidentalis, Carica papaya, and Manihot glaziovii of the viruses. The occurrence of variants of ACMV and a high proportion of mixed infections by ACMV, EACMV and EACMCMV, could result in recombination events, suggesting appropriate measures to safe guard cassava production in Sierra Leone.

Keywords: Begomoviruses Status; Distribution and Spread; Damage; whitefly Abundance; Natural hosts; Manihot esculenta