Importance of different pathways for maize kernel infection by Fusarium moniliforme.
The relative importance of several infection pathways (silks, stalks and seed) leading to kernel infection of maize hybrids by F. moniliforme [Gibberella fujikuroi] was investigated in field experiments in 1993 and 1994. Systemic movement of specific fungal strains within plants was detected using vegetative compatibility as a marker. Transmission of G. fujikuroi from inoculated seed to stalks and developing kernels was detected in 2 of 3 field experiments; the seed-inoculated strain was detected in kernels on c. 10% of ears. The percentage of kernels infected with the seed-inoculated strain ranged from 0 to 70%, with a mean of 0 to 2.5% (0 to 8.3% of G. fujikuroi-infected kernels). Other pathways to kernel infection were more effective than seed transmission and systemic infection. G. fujikuroi strains inoculated into the crowns and stalks of plants were found throughout the stalks and in up to 95% of the kernels in individual plants. Infection through the silks was clearly the most effective pathway to kernel infection. This was the only inoculation method that significantly increased overall incidence of G. fujikuroi infection in kernels; the silk-inoculated strain infected up to 100% of the kernels in individual ears, with a treatment mean as high as 83.7% of kernels. When plants were silk-inoculated, the percentage of kernels infected by other G. fujikuroi strains from the seed or stalk was reduced, apparently due to competition among strains. This study provided evidence that systemic development of G. fujikuroi from maize seed and stalk infections can contribute to kernel infection, but silk infection is a more important pathway for this fungus to reach the kernels.