Screening of cultivars against cassava brown streak disease and molecular identification of the phytopathogenic infection-associated viruses

Abstract

Cassava brown streak disease (CBSD) has been reported as a serious and significant constraint on the cassava crop in Democratic Republic of the Congo (DRC), especially in its eastern part, South Kivu, where cassava has exceedingly high socio-economic value in small-holder farming systems. The recent rapid spread and damage of CBSD are alarming. Compared to cassava mosaic disease (CMD) which causes yield losses of up to 70% in very susceptible cassava cultivars, CBSD destroys whole the field causing 100% crop loss, including immediate and direct losses of tuberous roots, planting material, and quality of leaves. The study gathered information on the circulation of viral species present in the region, and screening of cassava cultivars against CBSD. Here we evaluated the disease incidence (DI) and severity (DS), whitefly vector Bemisia tabaci parameters including number of nymphs and adults. Thereat, the work consisted of quantifying the pressure of the disease to find performing cassava cultivars, which may still be recommendable for farmers. Thirty-one improved and local Congolese cassava cultivars were selected. Disease assessment focused more specifically on morphological, epidemiologic studies, and advanced molecular diagnostic techniques for virus detection. The mean extreme values of disease incidence and severity ranged respectively from 0.0 to 59.44%, and 1 to 2.86, root infection up to 100%, whiteflies up to 2 adults, and 68 nymphs per plant. Accordingly, the viral species identified in circulation are Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) (picornalike (+) ssRNA viruses, Ipomovirus, Potyviridae). Varieties like Cibongoyoka, Dorothea, Kamegere, Korengo, Liyayi, M’Bailo, Nabana, Rav, and Siri showed no symptoms of necrosis on the roots. Some cultivars are even less susceptible or not to the disease and may be recommended in this time of the lack of planting material for farmers.

Keywords:

• Cassava brown streak disease
• genotypes
• susceptibility
• Ipomovirus
• Bemisia tabaci

Acknowledgments

The authors directly thank all members of the VLIR-UOS program of the Catholic University of Bukavu (UCB) for funding this work.

Author contributions

Conceptualization, methodology, field experiments, software, and data analysis, writing-original draft preparation and writing-review and editing, formal analysis, B.N. Shukuru; Incorporated some necessary corrections throughout the manuscript editing process until final submission, B.N. Shukuru, T.S. Archana, S. Sharma, and J.A. Kurian; validation and resources, B.N. Shukuru, E.B. Bisimwa, and D.R. Birindwa; data curation, B.N. Shukuru, and D.R. Birindwa; visualization, B.N. Shukuru; supervision, E.B. Bisimwa, C.M. Casinga, and T.S. Archana.

All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data supporting the findings of the study are available upon request from only the corresponding author. The data are not publicly available due to privacy and ethical restrictions.

Additional information

Funding

This research received funds from VLIR-UOS program of the Catholic University of Bukavu (UCB), Bukavu, DRC, in partnership with Flemish universities, Flanders, Belgium.