Mapping Kernel Row Number in Maize and Teosinte

Elucidating the genetic basis of the evolution of morphological differences between populations is a fundamental goal of evolutionary biology. The process of crop domestication, which involved intense artificial selection over a relatively short period of time, provides an opportunity to investigate the genetics behind morphological divergence. In maize (Zea mays ssp. mays) and its wild progenitor teosinte (Zea mays ssp. parviglumis), selection during domestication increased in the number of rows of kernels per ear from two rows in teosinte to the many rows typical of maize ears. The increase in kernel row number was most likely due to selection for improved grain yield. QTL mapping in four populations was used to identify regions controlling kernel row number in maize and teosinte across the genome. Between five and eight QTL were detected in each of the three maize teosinte backcross population. In addition, twenty-three QTL and eight significant interactions were detected using a population of RILs. A QTL with high LOD support on the short arm of chromosome 10 was detected in all populations. The QTL region on chromosome 10 also controls tassel branch number, culm diameter, and flowering time. The region contains a homolog of the highly pleiotropic rice gene ghd7, which is a strong candidate for a gene contributing to the difference in kernel row number as well as other measured traits between maize and teosinte.