Pathogen Dynamism and Variability of Rice Yellow Mottle Virus in Kenya
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Date
2025
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springer
Abstract
Rice yellow mottle disease (RYMD) continues to constrain rice production in Africa. Rice yellow mottle virus (RYMV),
which belongs to the Sobemovirus genus, is the causal agent of RYMD. In Kenya, previous studies on RYMV mostly
focused on western Kenya, ignoring the central and coastal regions, which are also important areas for rice cultivation in the country. This has resulted in incomplete data on RYMD outbreaks. This study aimed to determine
the prevalence of RYMD in the farmers’ felds, and the genetic diversity of the RYMV based on the coat protein
gene. Field surveys were carried out in Kenya’s rice-growing regions between May and July 2023 to determine
disease incidences using the IRRI Standard Evaluation Scale (SES) for rice. Symptom observations and serological
tests confrmed the presence of RYMV in all surveyed rice cultivation areas. The presence of RYMV was detected
in Kirinyaga, Tana River, and Taita Taveta counties of Kenya, representing the feld report of its occurrence in these
regions. Disease incidence and severity analysis using one-way ANOVA showed no signifcant diference in RYMD
incidence among the rice irrigation schemes (F (6,29)=1.838, P=0.1265). Sequencing results of the coat protein
gene (ORF4 region) revealed that the RYMV isolates in this study could be classifed as S4ke, S4ug, and S4mg strains
in the East Africa lineage. The discovery of the RYMV strain S4mg in Kenya runs counter to the gradual strain of breaking up and moving away that has been established in Africa over the past two centuries. Results showed that RYMV
is present in all the rice-growing regions under study and exhibits intra-strain diversity in Kenya. Incorporating resistance genes into extensively grown rice cultivars is crucial for preventing the spread of the rice yellow mottle virus.
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Citation
Kigaru, Antony, et al. "Pathogen dynamism and variability of rice yellow mottle virus in Kenya." Phytopathology Research 7.1 (2025): 43.