Genome size variation accompanies the diversification and evolution of many plant species. Relationships between DNA amount and phenotypic and cytological characteristics form the basis of most hypotheses that ascribe a biological role to genome size. The goal of the present research was to investigate the intra-specific variation of the DNA content in maize populations from NE Argentina and further explore the relationship between the genome size and the phenotypic traits seed weight and length of vegetative cycle. Moreover, cytological parameters such as the percentage of heterochromatin as well as the number, position and sequence composition of knobs were analyzed and their relationships with 2C DNA values were explored. The populations analyzed presented significant differences in 2C DNA amount, from 4.62pg to 6.29pg, representing 36.15% of the inter-populational variation. Moreover intra-populational genome size variation was found, varying from 1.08-fold to 1.63-fold. Variation in the percentage of knob heterochromatin as well as in the number, chromosome position and sequence composition of the knobs was detected among and within the populations. Although a positive relationship between genome size and percentage of heterochromatin was observed, a significant correlation was not found. This confirms that other non-coding repetitive DNA sequences are contributing to the genome size variation. While a positive relationship between DNA amount and seed weight have been reported in a large number of species, this relationship was not found in the populations here studied. The length of the vegetative cycle showed a positive correlation with the percentage of heterochromatin. This result allowed attributing an adaptive effect to heterochromatin, since the vegetative cycle length would be optimized via selection for an appropriate percentage of heterochromatin.
Realini, M. F., Poggio, L., Cámara-Hernández, J., & González, G. E. (2016). Intra-specific variation in genome size in maize: Cytological and phenotypic correlates. AoB PLANTS, 8. https://doi.org/10.1093/aobpla/plv138