Meiosis in pollen mother cells of 15 Cryptomeria japonica clones with special emphasis on the behavior of the 6th chromosome pair heteromorphic to chromomycin A3 band.

Abstract

Meioses in pollen mother cells (PMCs) were examined by the conventional staining and the CMA-staining methods in 15 clones of Cryptomeria japonica D. Don carrying three different karyotypes identified and classified by the characteristics of interstitial chromomycin A3 (CMA)-band or secondary constriction on the 6th chromosome pair. Before fixation of PMCs, a newly developed hypotonic treatment was applied for easy and constant preparation of well-spread meiotic chromosomes. At meiotic metaphase I 11 bivalents were observed, which possessed chiasmata at the interstitial region and/or the distal end. Although the CMA-bands were clearly observed on meiotic chromosomes, no chiasma was formed involving these bands. Most of the clones exhibited normal meiotic progression, but two clones (Syusou 5 and 11) showed some abnormal meioses. In Syusou 5 the heteromorphic 6th chromosome pair was involved in univalent formation more frequently than the other chromosome pairs. The normal meiosis in most clones with the heteromorphic 6th chromosome pair indicates that the heteromorphic chromosomes do not affect meiotic process.