Low mycotoxins content at harvest, high in stored maize: harvesting and storages practices implications in two agro ecosystems of Tanzania

Abstract

A survey was conducted to establish association of pre-storage and storage practices on occurrence of multiple mycotoxins in northern highland and eastern lowland maize based agroecosystems in Tanzania. Four hundred (400) households from 80 villages, 40 from each of the two agro-ecosystems were randomly selected for semi structured interviews to establish maize harvesting and storage practices. From each household, approximately 1kg of maize was collected at maize maturity before they were harvested and another 1kg maize collected from at least 6 months storage. The five household samples from each village were reconstituted to make one composite sample representing a village. Standard procedure was used for mycotoxins extraction. Compound quantification was done using Ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOFMS). More than 70% of farmers in the Eastern lowland used grain hardness as an indicator of grain maturity. Delayed harvesting of 4 to 12 weeks after maturity was observed across the two agro-ecosystems. More than 60% farmers shelled maize mechanically by beating on floor, in bags and elevated platforms. Most important storage insect pests were confused flour beetle (Tribolium confusum Jacquelin du Val) (100%), followed by 80% larger grain borer (Prostephanus truncutus L). Fourteen fungal species were detected and only 12 were present in both agroecosystems. Penicillium brevicompactum and F. culmorum were not detected in samples from northern highland while F. tricinctum and F. equiseti were not detected in the eastern lowland zone. With exception of F. graminearum, all other species were more abundant in eastern lowland than northern highland. In eastern lowlands, aflatoxin contamination in samples stored for six months was ten times higher than in samples collected at harvest. Significant (p≤0.05) positive and negative correlations between mycotoxins and storage practices were obtained. The study suggests that pre-storage and storage practices applied by subsistence farmers in the two agro-ecosystems need to be fine-tuned to reduce mycotoxins risk the two maize based agro-ecosystems.