Fungal ear rot pathogens in maize cropping systems: A comparative analysis of push-pull and monocropping systems in Western Kenya

Abstract

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