Michoacan maize presents elevated drought resistance. Under water stress Michoacan plants reduce growth rate, which is restored quickly in the presence of water. This behavior is genetically determined and was designated latente (Miranda et al., MNL 56: 28-30, 1982). The latente gene (ltel) was previously mapped on maize chromosome 2S, 11-49 region (Miranda et al., MNL 56: 28-30, 1982). The phenotype used for mapping was based on physiological studies of plants presenting the latente character. Latente plants present a more efficient mechanism for stomatal closure resulting in a reduced loss of water. This parameter can be measured in the field by using a porometer.

In order to study the effect of the latente characteristic in tropical maize, Michoacan plants were crossed to tropical commercial inbred lines. The segregating population was submitted to water stress conditions and the vapor diffusion resistance (VDR) was measured. A total of 73 F2 plants were analyzed. During the water stress period the F2 plants showed a retardation in their development with respect to the control. VDR of individual F2 and control plants was measured. The absolute VDR values for each F2 plant were subtracted from the VDR value of control plants. Approximately 80% of the F2 plants presented higher VDR values when compared to the control plants. In contrast to the preliminary genetic studies, where latente was considered a monogenic trait (Miranda et al., MNL 56: 28-30, 1982; Miranda et al., MNL 65: 45, 1991), our F2 data presented normal distribution, suggesting a typical quantitative trait. Probably, this normal distribution is due in part to great environmental influence over the phenotype. 

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