Genetic characterization of the origin of offtype plants in maize inbred lines

In inbred lines plants with morphological differences are called offtypes. The appearance of offtypes can be explained by the influence of foreign pollination (genetic contamination), by contaminations with foreign seeds (mechanical contamination), or by environmental factors such as effects on the growth of seedlings. In this paper offtypes were analyzed using 16 microsatellite markers. It is shown that 5% are originated from mechanical contamination, 90% from genetic contamination and 5% are due to environmental factors. The average inbreeding coefficient of the lines was 0.91. The evaluation of the microsatellites was performed with agarose as well as with acrylamide gels. In comparison to acrylamide gels, just 25.4% of the differences between offtypes and inbred lines could be detected on agarose gels. The characterization of heterozygous offtype samples was also less accurate with agarose gels, as in only 15.2% of cases heterozygosity could be seen in comparison to an acrylamide gel based analysis.