Maize Stover in Relation to Fusarium Inoculum and Mycotoxins in Maize Grains of Two Agro-ecological Zones in Tanzania

Abstract

Fusarium infection and the contamination of mycotoxins in maize are an important source of yield loss and deterioration of maize grain quality produced in Tanzania. This research aimed to establish information about which type of maize stover is the most important source of Fusarium inoculum. Three components of stover: straw, husks and litter (mix of silk, leaves and tassels) were randomly sampled in maize fields. Parallel to sampling maize stover, maize kernels were collected from the same fields. A molecular approach was employed to determine the toxigenic Fusarium species. This survey showed that the type of stover, the ecosystem and the mutual interaction strongly influenced the occurrence of F. verticillioides, F. graminearum and F. poae. Both F. verticillioides and F. graminearum were abundantly present in grains, husks and litter. However, F. poae occurred in lower frequencies. In regard to mycotoxins in maize kernels, Fumonisins (FBs) were predominantly present in almost 90% of the samples, the incidence of deoxynivalenol and zearalenone was rather low with 19% and less than 5%, respectively. Remarkably, fumonisin concentrations in maize from the Northern highlands exceeded legal threshold values (1000 μg/kg) more often than samples from Eastern lowland. Significant positive correlations between contamination of Fusarium in stover and maize grains were observed. Occurrence of Fusarium species in stover correlated positively with occurrence of fumonisins and deoxynivalenol in maize grains. These results showed convincingly that both ecosystem and stove type influence contamination of F. verticillioides, F. graminearum and F. poae. Appropriate management options for husks and litter in these areas are needed to minimize mycotoxin contamination.

Keywords: Maize stover, Inoculum source, Fusarium, mycotoxins