Occurrence and Distribution of Begomoviruses Infecting Cassava in Western Kenya

Abstract

Cassava (<i>Manihot esculenta</i> Cranz) is an important food staple in Busia, Homabay, Siaya, Migori, Kwale, Kilifi and Marakwet Counties and is a secondary food crop for many Kenyans. The current yields of 3-4 tons/ha obtained in Western Kenya are far below world averages and this is largely attributed to pests and diseases. The usual practice of retaining some seed cuttings from the current ware crop or buying them from neighbours, leads to accumulation of viral diseases most important of which are caused by begomovirus infections. A survey for cassava mosaic disease (CMD) was carried out in main cassava growing areas of Western Kenya with a view to determine incidence and distribution of the causal viruses. A total of 33 cassava farms in seven sub-counties in Western Kenya were covered. Leaf samples were collected and analysed serologically and by molecular means. Cassava plants in most farms were severely affected by cassava mosaic disease. Disease incidence in farms ranged between 2% to 54%. Three cassava infecting begomoviruses, African Cassava Mosaic Virus (ACMV), East African Cassava Mosaic Virus (EACMV) and East African Cassava Mosaic Virus – Ugandan variant (EACMV-Ug) were found in the collected samples, with EACMV-Ug being most prevalent followed by EACMV. These are interesting findings given that in the past surveys, ACMV was the most abundant virus in the area. To increase cassava yields, it is recommended that cassava farmers be educated on cassava diseases and their control.