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Fig. 1. Best linear unbiased predictors (BLUPs ± SE) for phenotypic performance of three traits, (a) grain yield (hybrids grown at three densities, 30, 54, and 79 thousand plants/ha, and yield per hybrid is for the density giving the highest average yield), (b) percentage of plants not root-lodged, (c) anthesis to silking interval, measured in experiments conducted from 1990 to 2002, for a sequence of commercially successful Pioneer corn hybrids taken from an ERA study (unpublished data), and (d) a plot of the inbred scores on the first two principal components from analysis of SSR molecular marker profiles of the parents of the hybrids. (OPV = open pollinated variety, DC = double cross, TC = three parent cross, TC-MSC = three parent modified single cross, SC = single cross, SC-T = single cross transgenic; SS = Stiff Stalk Synthetic inbred line, NSS = non-Stiff Stalk Synthetic inbred line). The large boundaries distinguish three main groups of lines; Old = the old inbred lines used before the formation of the heterotic groups and the other two groups represent SS and NSS inbred lines. The arrows indicate the direction of the progression of inbred improvement in the SS and NSS heterotic groups.
