Influence of heterochromatin on chiasma localization and terminalization in maize

SUMMARYMicrosporocytes of two maize cultivars were submitted to C banding in order to determine the effect of heterochromatin on chiasma localization and terminalization. Chiasma position was evaluated during diplotene and diakinesis in 14437 bivalents, 2993 of which were heterozygous for bands. Chiasma frequency was higher during diplotene in both cultivars, with a predominance of interstitial chiasmata located in euchromatin. During diakinesis there was a reduction in chiasma frequency in euchromatin, with a consequent increase in the heterochromatin region, suggesting chiasma terminalization. The chiasmata localized in euchromatin appear to move to the region of the heterochromatin blocks. The heterochromatin, however, seem to serve as a barrier against terminalization since terminalization beyond the bands was not observed in any heteromorphic bivalent.