Phenotypic and Genetic Dissection of Maize Internode Length.

Plant height is among the most studied traits in maize, however the genetic architecture of its main components, internode length and node number is not well understood. Node number has been shown to be genetically associated with flowering time. With the growing interest in utilizing maize as a source of biomass for biofuel production, it is desirable to alter the maize ideotype to enhance not only grain yield but also biomass yield, through the development of taller plants, without altering maturity. The objective of this study was to characterize the phenotypic relationships among plant height (PH), internode length (IL), internode length below and above the uppermost ear (BEIL and AEIL, respectively) and node number (NN) and to map quantitative trait loci (QTL) for these traits using phenotypically and genetically diverse maize populations. The study was conducted in field trials grown during 2009-2011 in one environment using two recombinant inbred line (RIL) populations, the intermated B73 x Mo17 (IBM) and Oh43 x W64A, as well as the Nested Association Mapping (NAM) population. Across all of these inbred lines we found a strong Spearman’s rank correlation between PH and IL (r=0.60, p<0.01), PH and BEIL (r=0.63, p<0.01) and BEIL and IL (r=0.78, p<0.01), whereas the correlation between PH and AEIL (r=0.29, p<0.01) and IL and AEIL (r=0.63, p<0.01) were comparatively lower. The correlation between PH and NN was lower (r=0.33, p<0.01) than PH and IL, and the correlation between IL and NN was negative (r=-0.43, p<0.01). Interestingly, we did not find overlapping QTL between IL and NN in any of the populations analyzed. Based on these observations it is possible to hypothesize that plant height could be enhanced through the development of genotypes with longer internodes while maintaining or decreasing the node number and therefore potentially maintaining desirable maturity time.