Study of Quantitative Trait Polymorphisms Emerging from Doubled Haploids Maize Lines.

Doubled haploids are useful in plant breeding because they are expected to be completely homozygous. Except for rare mutations, their progeny should show no genetic diversity. Even so, over 50 years ago George Sprague and his associates demonstrated that heritable variation in quantitative traits quickly emerged among the progeny of doubled-haploids. The rate of variation was demonstrated to be greater than the rate of spontaneous mutations. The means to determine the cause of that variation was not possible at that time, but we believe it is today. We have established ten separate lineages that have descended from a single doubled-haploid B73 plant. In the summer of 2014 we planted seed for two sequential self-fertilized generations from each of these lineages. These were planted in triplicate in a randomized complete block design (RCBD). The resulting plants were evaluated for 14 quantitative traits (plant height, number of tassel branches, 100 grains weight, etc.). A heritable polymorphism for any particular trait is indicated if there is no significant difference between the two generations of a lineage but the lineage is significantly different from other lineages. An analysis of variance (ANOVA) indicates that out of 14 quantitative traits, eight are found to be significantly different. To further test the heritability of these quantitative traits, seeds obtained from self-fertilized plants that were found to be polymorphic in 2014 were sown in summer 2015. Traits are being analyzed and compared with the 2014 observations. Confirmation of Sprague’s results will encourage us to pursue molecular analysis.