Phenotypic and molecular screening for resistance in elite cassava clones against cassava brown streak disease (CBSD) in Kenya

Cassava production in East Africa is severely constrained by viral diseases, particularly Cassava Brown Streak Disease (CBSD), which can cause yield losses of up to 100%. This study evaluated the response of elite cassava clones to CBSD under high natural disease pressure to identify superior genotypes for breeding. Five elite genotypes (08/363, F10-30-R2, Nl, Tajirika, and Ex-Mariakani), a susceptible check (Kibanda Meno), and a local control (Shibe) were grown at KALRO-Mtwapa. Whitefly vector (Bemisia tabaci) populations and CBSD incidence were monitored at 3, 6, and 9 months after planting. Disease severity, incidence, and Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) analyses were used to assess infection in symptomatic and asymptomatic samples. CBSD incidence exceeded 70% in Kibanda Meno but was lowest in Shibe and Tajirika. Mean disease severity was highest in Kibanda Meno (>1.5). RT-PCR confirmed the presence of CBSD in both symptomatic and asymptomatic plants, with a positive correlation between whitefly abundance and disease incidence. Clones 08/363 and F10-30-R2 exhibited low disease severity and infection rates, indicating superior tolerance to CBSD, whereas Kibanda Meno and Ex-Mariakani were highly susceptible. These findings suggest that 08/363 and F10-30-R2 are promising candidates for CBSD management and resistance breeding. Their deployment could enhance cassava resilience, safeguard yields, and strengthen food security in regions affected by the disease.