Characterization of virus species associated with sweetpotato virus diseases in Burkina Faso

Abstract

Sweetpotato (Ipomoea batatas) production in sub-Saharan Africa is severely affected by viral diseases caused by several interacting viruses, including sweet potato feathery mottle virus (SPFMV), sweet potato chlorotic stunt virus (SPCSV), and sweet potato leaf curl virus (SPLCV). However, the aetiology of viral symptoms on sweetpotato is rarely established in most countries in Africa. Here, we aimed to investigate and characterize the incidence of sweetpotato viruses in Burkina Faso. We performed a countrywide survey in 18 districts of Burkina Faso and collected 600 plants, with and without symptoms, from 80 fields. Viral strains were identified using nitrocellulose membrane-ELISA, PCR, and reverse transcription-PCR. Three scions from each of 50 selected plants with symptoms were grafted to healthy Ipomoea setosa and then serological and molecular tests were performed on the 150 recorded samples. Three viruses were detected: 24% of samples were positive for SPFMV, 18% for SPLCV, and 2% for SPCSV. Across all diagnostic tests, 40% of all plant samples were virus-negative. Coinfections were found in 16% of samples. Partial sequences were obtained, including 13 that matched SPFMV, one that matched SPLCV, and one that matched SPCSV. All identified SPFMV isolates belonged to either phylogroup B or A-II. The SPCSV-positive isolates had 98% gene sequence homology with SPCSV-West Africa for the coat protein. Begomovirus-positive isolates clustered with SPLCV-United States. This first study of sweetpotato viral diseases in Burkina Faso indicates widespread occurrence and suggests a need for further epidemiological investigations, breeding programmes focused on virus-resistant varieties, and improved farming practices to control disease spread.