Among 80 dent corn inbreds of commercial importance, chromosome knob numbers range from 2 to 8 with a frequency distribution as follows;
The nodal knob number is 4 with 3 and 5 as the two next most frequent classes. Knob number is strongly associated with at least two morphological characters ‑ number of rows of kernels and development of husk leaf blades (flag leaves). As knob numbers decrease, row numbers decrease and flag leaves become more pronounced. It is assumed that low knob numbers, low row numbers and long flag leaves were introduced into Corn Belt dent corn from Northern flint varieties. It is interesting and perhaps significant that these characters are so strongly linked that even after a century of breeding they still remain together in dent corn inbreds.
Although exceptions hsve been observed, there is also an overall correlation between high knob number and shape of ear. For example, those inbreds which approach Mexican Pyramidal in ear shape usually fall into the higher chromosome knob groups.
William L. Brown