Means comparison showed that no genotype had a significant decrease of CN under N limitation (Fig. 4B), but ANOVA grouping of genotypes into the two categories of high CN or low CN showed a significant reduction of CN by N limitation (P , 0.05), with high-CN genotypes having 10 more crown roots than low-CN genotypes under low-N conditions. A different set of genotypes was planted at the field site in South Africa in 2012 (SA2012). In 2012, the CN ranged from 30 to 46.5 under low-N conditions. There was no significant effect of N stress on the average CN of these genotypes. N limitation affected CN in only one genotype, IBM165, and in this instance actually increased CN (Fig. 4C).