Genome size variation in Zea mays ssp. mays adapted to different altitudes

Previous studies have indicated a positive correlation between genome size and altitude among plant species. It has been hypothesized that increasing genome size occurs due to increasing C-banded heterochromatin. In corn, increasing altitude has been correlated with decreasing knob (C-banded) heterochromatin, suggesting that DNA content may decrease with increasing altitude. In this study, nuclear DNA content of 12 southwestern United States Indian maize populations, collected at various altitudes, was determined. The significant positive correlation observed between genome size and altitude suggests that corn follows the trend of increasing DNA content with increasing altitude observed in other plant species. Whether this correlation is due to increasing knob heterochromatin or additional intra- or supernumerary chromosomal DNA sequences has yet to be determined.