Assessing white maize resistance to fumonisin contamination
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Genetic improvement is an emerging method to reduce the levels of fumonisin (FB) contamination in maize, but breeding advances depend on the development of suitable methods to accurately assess the performance of different cultivars. Our study focused on characterizing a local isolate of Fusarium verticillioides; comparing artificial inoculation techniques with this isolate (injection into kernels and down the silk channel); and assessing white maize resistance under artificial vs. natural inoculation. The fungal growth rate significantly increased with temperature and water activity aw. The optimum growth rate, corresponding with the shortest phase of initial growth, occurred at 25–30 °C and 0.99 aw. Under silk inoculation with this isolate, the hybrid EP10 × EC22 accumulated significantly less FBs than the other hybrids, whereas, under kernel inoculation, differences among hybrids were not significant (P ≤ 0.05). The local isolate of F. verticillioides produced FBs and responded to the usual environmental conditions during maize kernel ripening in northwestern Spain. Inoculation with this isolate is recommended because it is aggressive, toxigenic, and adapted to the local environment. Silk inoculation was the only method that allowed a clear distinction among genotypes based on differences in resistance to FB accumulation. Resistance to natural and artificial inoculations was confirmed for the hybrid EP10 × EC22.