The Effect of Aspergillus flavus on Seedling Development in Maize

Plant growth and its interaction with microorganisms change yearly. High temperature and humidity have characterized recent seasons in the north of Italy and around the world, increasing the parasitic ability of Aspergillus flavus to colonize maize kernels and aflatoxin levels. These molecules have the highest acute and chronic toxicity of all mycotoxins; the maximal concentration in agricultural food and feed products, and their commodities, are regulated worldwide. In this study we suggest a simple methodology to test the susceptibility of candidate maize varieties to A. flavus before their release onto the market. A panel of 92 inbred lines and 14 hybrids were analysed, disease phenotypes were scored on artificially inoculated kernels using a rolled towel assay, and therefore we observed different responses to fungal infection on the kernels, outlining a high variability among the tested lines characterized by a different effect of the pathogen on seedling development. Even the hybrids responded differently on a statistical basis to A. flavus with regard to the development of coleoptile, allowing their categorization into classes of susceptibility to be used for the varietal registration. Interestingly, the hybrid 6a-A was less susceptible to A. flavus compared to its reciprocal in terms of the length of the coleoptile. The comparison of breeding lines released on the market in different years suggested a poor improvement in genetic resistance against A. flavus in maize so far, opening up a possible topic for future research aimed at mitigating the impact of climate change on agriculture.