Niche partitioning association of fungal genera correlated with lower Fusarium and fumonisin-B1 levels in maize

Abstract

Through partitioning of ecological niches, several fungi are able to coexist on the same host crop. In (partial) absence of niche partitioning, competitive exclusion among fungi can occur. Competitive exclusion is one of the bases for biocontrol. We investigated fungal correlations, in terms of relative abundance of the fungi, in pre-harvest maize, as a natural ecosystem model. Internal mycobiome fungal relative abundance of maize was used to establish correlations. The maize had been harvested from dry and wet agro-ecological zones of Zambia. The relative abundances of the fungal genera were determined using DNA amplicon sequencing. For this study, positive or absence of correlations between fungal genera signified good niche partitioning (co-existence), whereas negative correlations signified poor niche partitioning and potential for competitive exclusion. When species compete within one niche (competitive exclusion), we may expect to detect higher levels of mycotoxins—since mycotoxins are considered antagonistic agents aimed at defending or invading an ecological niche. To estimate the importance of mycotoxins in competitive exclusion, we measured the influence of the fungal correlations on levels of fumonisin-B1 (FB1) in the maize. FB1 data were derived from a previous study on the maize, determined by HPLC. Results showed that Sarocladium and Stenocarpella had the strongest significant negative correlation with Fusarium, suggesting poor niche partitioning and potential for antagonism of these genera with Fusarium. Furthermore, higher levels of Stenocarpella resonated with lower levels of FB1 and vice versa. It was also observed that, when Sarocladium was in low abundance (< 10%), the frequency of detection of higher levels of FB1 (> 100 µg kg−1) in the pre-harvest maize was highest.