Abstract:
Cassava mosaic Begomoviruses (CMBs) and
cassava brown streak viruses (CBSVs) respectively cause
cassava mosaic disease (CMD) and cassava brown streak
disease (CBSD). Transmitted by whitefly vector (Bemisia
tabaci), both diseases significantly inhibit cassava
production in Kenya. This study examined the prevalence
and distribution of CMD and CBSD in different agroecological
zones (AEZ) of lower Eastern Kenya through a
multi-stage sampling survey. Sampling involved stopping
at regular pre-determined intervals of about 15 to 20km
between farmers’ fields along transect in each zone. Thirty
plants were randomly sampled along diagonals of each
field to determine both disease incidences. General results
revealed 73% CMD and 53% CBSD prevalence in lower
Eastern Kenya. Specifically, both disease incidences were
high in LM4 (68% CMD and 26% CBSD), followed by
UM4 (55% CMD and 19% CBSD) and least in LM5 (30%
CMD and 8% CBSD). Whitefly (Bemisia tabaci)
infestation significantly and positively correlated with
CMD and CBSD incidences further indicating
considerable contribution of the vector in spreading both
diseases. Molecular diagnostics performed on leaves of
randomly selected plants detected ACMV that cause CMD
and CBSV that causes CBSD. High distribution of CBSD
and CMD in lower Eastern Kenya as assessed in this study
could potentially be integrated in future CMD and CBSD
resistance breeding or virus management programs within
the region.
