Analysis of the variety Carioca showed that the sectors were localized in the aleurone. Different levels of pigmentation could be observed, and five classes were characterized as being full, near full, stippled, near colorless and colorless (Fig. 1). Comparing the phenotypes found in the Carioca original population with others described in the literature, we concluded that these phenotypes should be comparable to a paramutation event. All the other varieties are known to be bb;rr. In the summer of 1999-2000 we conducted a field experiment with all varieties without pollination control to analyze the occurrence of colored and stippled kernels.
The wind direction was favorable to lead the pollen grain of the Carioca onto other varieties. The results are presented in Table 1 with only three phenotypic classes. In the class Mot/Stt "near full", "stippled" and "near colorless" are included. The ear with paramutation means that at least one kernel was mottled. Interestingly, no kernel with a stippled phenotype was observed in the Ferrinho variety. Its position in the field was favorable to present at least one kernel with a stippled phenotype. Our hypothesis is that the alleles of color were completely null. These varieties have been analyzed carefully in order to verify why they did not show such a stippled phenotype. We have conducted controlled crosses between Ferrinho and Carioca as a complete diallel to check out possible differences when Ferrinho was used as female or male.
Our results show that the allele was transmitted to other varieties, and the paramutation event was observed by the kernels showing different color levels or reduced expression of the dominant allele. The low level of introgression in some varieties such as IAPAR 50 and Cayano is a result of its position in the field. This low introgression reinforces the hypothesis of a null expression of the alleles, because these varieties were more distant from Carioca in the field than Ferrinho. The detailed analysis was not presented because we are conducting experiments with inbred lines and backcrosses derived from these varieties.
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