Inheritance of the morphological differences between maize and teosinte: comparison of results for two F2 populations.

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Abstract
Molecular marker loci (MMLs) were employed to map quantitative trait loci (QTLs) in an F2 population derived from a cross of maize (Zea mays ssp. mays) and its probable progenitor, teosinte (Z. mays ssp. parviglumis). A total of 50 significant associations (putative QTLs) between the MMLs and nine key traits that distinguish maize and teosinte were identified. Results from this analysis are compared with our previous analysis of an F2 population derived from a cross of a different variety of maize and another subspecies of teosinte (Z. mays ssp. mexicana). For traits that measure the architectural differences between maize and teosinte, the two F2 populations possessed similar suites of QTLs. For traits that measure components of yield, substantially different suites of QTLs were identified in the two populations. QTLs that control about 20% or more of the phenotypic variance for a trait in one population were detected in the other population 81% of the time, while QTLs that control less than 10% of the variance in one population were detected in the other population only 28% of the time. In our previously published analysis of the maize x ssp. mexicana population, we identified five regions of the genome that control most of the key morphological differences between maize and teosinte. These same five regions also control most of the differences in the maize x ssp. parviglumis population. Results from both populations support the hypothesis that a relatively small number of loci with large effects were involved in the early evolution of the key traits that distinguish maize and teosinte. It is suggested that loci with large effects on morphology may not be a specific feature of crop evolution, but rather a common phenomenon in plant evolution whenever a species invades a new niche with reduced competition.