Distribution of Aspergillus and Fusarium ear rot causative fungi in soils under push-pull and maize monocropping system in Western Kenya

It is imperative to establish the distribution and density of soil fungal communities as a requisite for formulating strategies for management of ear rot infections and mycotoxin contamination. In a two seasons study, short (SR) and long rainy (LR) seasons, we investigated the distribution of Aspergillus and Fusarium fungi causing ear rots and producing mycotoxins from 120 soil samples collected from maize fields under push-pull (PP) and maize monocrop (MM) systems in Western Kenya. Cultural methods were used for identification of Aspergillus and Fusarium species, while molecular techniques were used for confirmation of Fusarium section Liseola. Detection of total aflatoxins in cultures of section Flavi isolates was carried out by enzyme-linked immunosorbent assay (ELISA). A total of 338 fungi were isolated; 80% were identified as Aspergillus and 4.4% Fusarium. The distribution of fungi was significant with season but not cropping systems. The frequency of occurrence was higher during the LR (68.4%) than the SR (31.6%). In cropping systems, the frequency of occurrence of Aspergillus flavus was higher in MM (60.2%) than PP (39.8%). However, Aspergillus parasiticus was more frequent in PP (71.4%) than MM (28.6%); and during the SR (78.6%) than the LR (21.4%). Majority (81.3%) of A. flavus and A. parasiticus were toxigenic. There was low recovery of Fusarium species in soil samples. These findings show that soils from both cropping systems are potential for Aspergillus infection and aflatoxins contamination; however, low Fusarium distribution in soil suggest external inoculum source for Fusarium ear rot infections common in most maize fields in Western Kenya.