Cob and Kernel Infection by Aspergillus flavus and Fusarium moniliforme in Inoculated, Field-grown Maize Ears

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Abstract
Significantly more pedicel than apical portions of transversely cut maize (Zea mays) kernels were infected with Fusarium moniliforme. In contrast, Aspergillus flavus was detected more frequently in apical sections. In addition, A. flavus was isolated more frequently from the middle portions of inoculated kernels than from the predicel end. Some ears (needle-inoculated with A. flavus) contained profuse fungal growth and sporulation on silk residues and kernel surfaces, but there was little penetration of uninjured kernels. The recovery of A. flavus and F. moniliforme from apical and pedicel portions of kernels was not affected by genotype or method of inoculation with A. flavus (pinbar or needle inoculation). A. flavus colonized a high percentage (83%)of the cobs in both inoculated and control ears of all maize genotypes. The fungus was recovered from a higher percentage of placental and sclerenchymatous tissue segments with pith tissue segments. F. moniliforme was isolated from cobs less frequently than A. flavus but appeared to be more uniformly distributed throughout them. Although the correlation (r values) of kernel infection by A. flavus with colonization of the placenta and sclerenchyma in the cob was statistically significant, the r values were quite low. The relatively low level of pedicel infection of kernels by A. flavus (7%) compared to combined infection of other kernel segments (45%) leads us to conclude that A. flavus penetrates maize kernels mainly through the pericarp.