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Abstract
Maize flowering time is an important agronomic trait, which has been associated with variations in the genome size and heterochromatic knobs content. We integrated three steps to show this association. Firstly, we selected inbred lines varying for heterochromatic knob composition at specific sites in the homozygous state. Then, we produced homozygous and heterozygous hybrids for knobs. Second, we measured the genome size and flowering time for all materials. Knob composition did not affect the genome size and flowering time. Finally, we developed an association study and identified a knob marker on chromosome 9 showing the strongest association with flowering time. Indeed, modelling allele substitution and dominance effects could offer only one heterochromatic knob locus that could affect flowering time, making it earlier rather than the knob composition.
Highlights
The relationship between heterochromatic knobs, genome size, and flowering time (FT) in maize is a long debate
The genome size of the inbred lines and hybrids was measured to test whether knob composition contributes to the DNA content variation
The authors showed that the abundance of transposable elements (TEs) and heterochromatic knobs are significantly correlated with altitude, and the knobs act as significant effect loci in the genome size
Summary
The relationship between heterochromatic knobs, genome size, and flowering time (FT) in maize is a long debate. Knobs have intrigued geneticists for more than 100 years, and since their discovery, their functions remain under investigation. These maize genome regions are constitutive heterochromatin with late replication during the cell cycle (Pryor et al, 1980), extensively composed of two highly repetitive satellite DNA families, 180-kb, and TR-1 (Peacock et al, 1981; Ananiev et al, 1998). The meiotic drive mechanism influences the number of knobs in different species of Zea (Rhoades and Dempsey, 1966; Buckler et al, 1999; Higgins et al, 2018). Associations between heterochromatic knobs and agronomic traits have been reported (Blumenschein, 1964)
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