Cytogenetic studies in the genus Zea : 2. Colchicine-induced multivalents

Area of Science:

• Plant genetics
• Cytology
• Genomics

Background:

• Maize (Zea mays) is an important crop with a complex polyploid genome.
• Understanding the genomic structure of maize and related species is crucial for breeding and evolutionary studies.
• Previous studies suggested maize is an allotetraploid, but detailed evidence on genome pairing and evolution is ongoing.

Purpose of the Study:

• To investigate the genomic structure and evolutionary history of Zea mays and Zea perennis.
• To confirm the allotetraploid nature of maize and elucidate the pairing behavior of its homoeologous genomes.
• To provide evidence for the autoallooctoploid nature of Zea perennis.

Main Methods:

• Premeiotic treatment with colchicine to induce chromosome doubling and quadrivalent formation.
• Analysis of quadrivalent frequencies in meiosis in Zea mays and Zea perennis.
• Comparative genomic analysis based on observed meiotic configurations.

Main Results:

• Colchicine treatment induced 1-5 quadrivalents in Zea mays (2n=20).
• Quadrivalent numbers increased from 5 to 10 in Zea perennis (2n=40).
• Results support maize possessing two non-pairing homoeologous genomes (A2A2 B2B2), likely due to Ph-like genes.

Conclusions:

• The findings confirm the allotetraploid origin of maize.
• The study supports the autoallooctoploid genome formula (A'1A'1 A″1A″1 C1C1 C2C2) for Zea perennis.
• Ph-like genes likely play a role in suppressing homoeologous recombination in maize.