.". In:
. J Hum Ecol, 26(3): 163-173 (2009).; 2006.
Seven hundred and fifty bean plant samples with root rot symptoms were
collected from farmers' fields during two surreys carried out in Embu district,
Kenya. Various fungal pathogens were isolated in the laboratory from these
samples; among them were 50 isolates of Rhizoctonia solani, which were
subjected to pathogenicity tests in a glasshouse. Thirty-six isolates of R. solani
obtained from beans with root rots were subjected to DNA microsatellite analysis.
Five isolates of R. solani that cause black scarf of potatoes (Solanum tuberosum
L.) were also analysed alongside those from the beans. A total of 50 alleles were
detected when six microsatellite loci were typed in the 41 samples, with the mean
of 8.33 and a range of 3 at locus RB23 to 19 at locus AF513014. The smallest
allele size was 129 basepair at locus RE102 and the largest was 297 basepair at
locus AY212027. Microsatellite analysis showed a moderate variation among the
isolates from different agro-ecological zones and administrative boundaries
(divisions). Phylogenetic analysis revealed 3 major clusters within the population
of 41 isolates of R. solani from Kenya. Clusters 1, 2 and 3 had 15, 10 and 75%
isolates, respectively. However, cluster 3 had 4 sub-clusters and cluster 1 had 2
sub-clusters, while cluster 2 did not have a sub-cluster. There was no relationship
between microsatellites and geographical origin of the isolates. This is the first
study on the genetic diversity of R. solani using DNA microsatellite analysis in
Kenya.