Commercially available transgenic maize hybrids (Bt hybrids) offer excellent resistance to European corn borer (ECB) feeding. European corn borer larvae act as wounding agents and vectors for pathogenic, fumonisin-producing Fusarium species, and we have demonstrated that manual infestation of nontransgenic maize plants with ECB larvae enhances both symptomatic and symptomless infection of kernels by F. moniliforme, F. proliferatum, and F. subglutinans. Bt maize hybrids disrupt the usual interactions between ECB and Fusarium species through resistance to ECB feeding and mortality of larvae. With either natural or manual ECB infestation, Bt hybrids that express Cry proteins in all plant tissues consistently experienced reduced kernel infection by Fusarium species compared to near-isogenic, non-Bt hybrids. Bt hybrids that express Cry proteins only in leaf tissue and pollen did not consistently differ from non-Bt hybrids. When non-Bt hybrids were manually infested with ECB larvae, increased Fusarium infection was accompanied by a significant increase in fumonisin concentrations in kernels. Conversely, manually infested Bt hybrids with Cry protein expression in kernels did not experience increased infection or fumonisin concentrations. Therefore, when ECB populations are high, it appears that these Bt hybrids can contain lower levels of fumonisins than traditional hybrids. Symptoms of stalk rot caused by Fusarium species were significantly less severe in some Bt hybrids in some locations, but this effect was not consistent.

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