Abstract:
Kenya lies within sorghum centre of diversity. However, information on the relative extent
of diversity patterns within and among genetically defined groups of distinct ecosystems is
lacking. The objective was to assess the structure and phenotypic diversity of wild sorghum
populations across a range of geographical and ecological conditions in the country.
Sixty-two wild sorghum populations (30 individuals per population) sampled from four distinct
sorghum growing regions of Kenya and covering different agroecologies were characterized for
ten qualitative traits. Plant height, number of tillers, panicle sizes and flag leaf dimensions were
also recorded. Frequencies of the phenotypic classes of each character were calculated.
The Shannon diversity index (H0) was used to estimate the magnitude of diversity. Principal
component analysis was used to differentiate populations within and between regions. Wild
sorghum is widely distributed in Kenya, occurring in sympatric ranges with cultivated sorghum,
and both have overlapping flowering windows. All characters considered displayed great
phenotypic diversity. Pooled over characters within regions, the mean H0 ranged between 0.60
and 0.93 in Western and Coast regions, respectively. Wild sorghum was found to show a weak
regional differentiation, probably reflecting the importance of seed-mediated gene flow in
shaping the wild sorghum population structure. Trait distribution was variable among regions,
but there was no conspicuous distribution of the traits studied in any given region. Spontaneous
hybridization and introgression of genes from cultivated to wild sorghum seems to be likely,
and may already have occurred for a long time, although undocumented. Implications for
in situ and ex situ genetic resources conservation are discussed.
