Genetics of maize inflorescence architecture

Maize inflorescences have become a model system for functional genomics from agronomic, developmental, and evolutionary viewpoints. The purpose of this research was to gain deeper insights into genetic control of quantitative variation for maize inflorescence architecture. Two biparental populations with different genetic backgrounds and mating structures were used to identify the locations and effects of quantitative trait loci (QTL) influencing the different components of maize inflorescences. A comprehensive set of maize inflorescence architecture traits were measured in multiple replicates and environments. The use of the intermated B73 x Mo17 (IBM) population revealed a relatively large number of significant QTL for all the inflorescence traits. Tassel architecture showed strong modular development, with traits integrating into modules that are consistent with different orders of meristems involved in tassel development. The central spike of the tassel and kernel row number showed strong positive correlation and also explained most of the common variation between the tassel and ear. Novel methodology was developed for detecting QTL with pleiotropic effects on inflorescence traits that integrated or showed high correlations. The maize nested association mapping (NAM) panel, a tremendous genetic resource developed for genome-wide high-resolution mapping, was used to more precisely understand the genetic architecture of tassel traits. This resource will help considerably to identify the genes underlying the QTL controlling inflorescence architecture. We propose a few candidate genes that underlie inflorescence architecture QTL in all three studies on the basis of positional information and functional relevance. The overall findings indicate that the majority of variation in inflorescence architecture is controlled by many genes, mostly with small effects, and their identity is mostly still unknown. The NAM strategy appears to be a promising tool for high resolution mapping and discovery of candidate genes controlling the development of maize inflorescences.