Fluorescence in situ hybridization analysis reveals multiple loci of knob-associated DNA elements in one-knob and knobless maize lines

Fluorescence in situ hybridization analyses were conducted to examine the presence or absence of the 180- and 350-bp knob-associated tandem repeats in maize strains previously defined as "one-knob" or "knobless. " Multiple loci were found to hybridize to these two repeats in all maize lines analyzed. Our results show that the number of 180- and 350-bp repeat loci do not correlate with the number of knobs in maize and that these tandem repeats are not independently sufficient to confer knob heterochromatin, even when present at megabase sizes.