INFLUENCE OF LAND USE ON THE DISTRIBUTION AND DIVERSITY OF PYTHIUM SPP.

Abstract

The distribution of Pythium species across land use gradient was examined in two agroecological zones in Kenya. The two zones were selected owing to their unique characteristics and locations. Soil samples were collected along a transect from the forest through to the cultivated land. The sample plots were established at fixed intervals of a distance of 200m apart to avoid auto-correlation Pythium propagules were activated to germination using baiting techniques, and the mycelium baited was cultured to obtain axenic culture for identification. Based on morphological characteristics, a total of 32 species of Pythium were found at the Embu study site, with soil under Napier having the most diverse population and that under maize the least. The Taita site yielded 12 Pythium species, with the highest diversity in cropped plots and the lowest in Natural forest. Species abundance increased with increasing ecosystem disturbance while diversity increased with decrease in disturbance. All the species isolated from the Taita site were also sampled from the Embu site except P. helicoids, P. periplocum and P. grandisporangium. The common pathogenic species P periplocum, P. hypogynum and P. spinosum were isolated mostly from croplands confirming the effect of host occurrence on the distribution of Pythium species.