Time to flowering in brown midrib mutants of maize: an alternative approach to the analysis of developmental traits.

The brown midrib (bm) mutations of maize affect the biosynthesis of lignin, resulting in reddish-brown vascular tissue in the stem, the leaf blade and sheath. Investigating the effects of the change in lignin content and composition on other phenotypic traits in bm mutants is important in increasing the understanding of how secondary metabolism affects plant development. We examined the time to flowering of inbred A619 and near-isogenic lines of bm2, bm1-bm2 and a segregating population with wild-type and bm1 heterozygotes in a controlled experimental design (Latin square) in two locations. Survival analysis was used to describe the distribution of the time to flowering and compare differences between genotypic classes. Survival analysis is a readily accessible technique that can improve inferences in cases where distributions are skewed, or where data are missing or incomplete. The basic approach to survival analysis as well as its specific application to these data is described. After controlling for the effects of the locations, the time to flowering of the bm2 and segregating populations was found to be significantly different from the wild-type and bm1-bm2 populations.