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Pythium is a water mould fungus which survive as a parasite, saprophyte or both. Pythium
spp. play important ecological services like recycling of both Carbon and mineral
nutrients for continued plant growth. Members of this genus are ubiquitous and found in
soil, water, plants and animal substrate. Spatial distribution and species diversity of
Pythium were studied with aim of determining the effects of intensive agricultural
practices on distribution and diversity. Agricultural intensification interferes with the
natural processes occurring within the soil and destroys useful bacteria and fungi, and
other organisms leading to increase in parasitic species like Pythium. Application of
agrochemicals like fertilizers, pesticides and fungicides as well as continuous cropping
interferes with natural processes in the soil ecosystem leading to change in the number of
Pythium species in the soil (Burge, 1988). The possibility of using Pythium as
environmental quality indicator is considered as one important aspect of the study since
their distribution is associated with a particular environmental condition, that the presence
or absence of such condition means its presence or absence (Paoletti et al.,1991).
Land use practices in the two benchmark sites form a gradient of land use intensities
drawn from the inputs which is perfect for testing the significance on the difference in
distribution and diversity.
Each benchmark site was divided into windows, sampling plots and sampling points
where soil samples were collected. Using the soil samples collected from Embu in lrangi
forest and Taita in Ngangao forest, the presence of Pythium species propagules were
tested by attempting to isolate species of the genera using baiting techniques. The
growing mycelium were verified directly by water mounts in a Microscope or transferred
from the bait to the isolation media CMA (Com Meal Agar) amended with antibiotic
Chloramphenicol (20mg/L) and Benomyl (10mg/L). To get data on distribution of
Pythium at each sampling point, soil was collected at different depths. The isolates were
characterized using morphological features in order to identify them tospecies level as
guided by 'Monograph of genus Pythium' (Van Der Plaats - Niterink 1983).
Eighteen Pythium species were collected in Embu and ten species in Taita. This shows
that Embu has a richer diversity than Taita. Over 20 morpho species whose identification
was not certain were isolated also in both Embu and Taita. ANa VA analysis of deviance
table shows that dispersion of Pythium in Taita based on land use system is significant at
p~0.04927 at a=O.05. Also, it was found that Chances of encountering Pythium increases
significantly ith increase in carbon in Embu (p ~0.01830) (fig.7), and nitrogen
concentration (~0.0003518).
