Submitted to: Illinois Corn Breeders School Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/15/2006
Publication Date: 3/6/2006
Citation: Lauter, N.C., Moose, S.P. 2006. Functional and positional dissection of a novel QTL affecting the duration of juvenility in maize. 42nd Annual Illinois Corn Breeders School Proceedings. 42:64-82.
Technical Abstract: The regulation of vegetative phase change is particularly amenable to genetic dissection in maize because the boundary between juvenile and adult tissue is discretely delineated by a suite of epidermal markers. Like the reproductive phase change wherein plants switch from producing leaves to flowers, the transition from producing leaves with juvenile identity to those with adult identity is mediated by changes in the shoot apical meristem and is subject to genetic regulation. We have used the intermated B73 X Mo17 recombinant inbred lines (IBMRILs) to identify QTL that affect when the meristem identity switches according to two different macroscopic measures, the onset of adult pubescence and the loss of juvenile wax. Although the duration of the juvenile phase is essentially the same in B73 and Mo17, substantial transgressive segregation among the IBMRILs allowed the detection of several QTL for each trait, including two loci that appear to pleiotropically affect both markers of juvenility. One of these, Leaf identity regulator1 (Lir1), co-localizes with glossy15, a gene known to regulate all epidermal markers of vegetative phase change. Since glossy15 has been shown to be necessary and sufficient to extend juvenility, the detection of the Lir2 QTL on chromosome 7 was a surprise. Here we report on efforts to characterize and localize Lir2. For both the wax and pubescence characters, the B73 allele of Lir2 extends juvenility in a dosage-dependent manner that is not altered by the genotype at Lir1 or any of the other detected QTL. To establish a non-parametric confidence interval for the position of Lir2, the full analysis protocol for composite interval mapping was implemented to analyze 1000 bootstrap resamplings of our data. We compare this analysis protocol with the commonly used shortcut and evaluate the strengths and weaknesses of each.