Karyological studies of Iranian Allium (Amaryllidaceae) species with a focus on sect. Acanthoprason. 2. Meiotic chromosomes

Meiosis in pollen mother cells (PMCs) was studied of 23 Iranian Allium species (33 accessions, 105 individuals) that belong to two subgenera and six sections. Materials of 13 species were sampled from (near) type locations. Gametic chromosome numbers, chromosome configurations at metaphase I, chiasma frequency, as well as type and percentages of abnormalities were recognized. The basic chromosome number for all taxa investigated was x = 8. Most taxa were diploid and showed eight bivalents or in rare cases two or four pairs of univalents, but in A. subakaka, A. ubipetrense and A. zagricum tetravalents also occurred. Meiosis in less than 10% of PMCs of diploid accessions was disturbed displaying lagging chromosomes, chromatid bridges, micronuclei, or unbalanced chromosome segregations, but very rarely more than one kind of irregularities were found within one dividing cell. One to three B chromosomes were found in 11 accessions, and were recognized for the first time in A. alamutense, A. elburzense and A. iranshahrii. Our data showed no correlation between the occurrence of B chromosomes and the chiasma frequency, and also no noticeable effect of habitat factors on meiotic chromosome behavior. The studied accessions of A. atroviolaceum and A. sabalense were tetraploid (n = 16) showing irregular meiosis in 20-69% of the PMCs which is regarded as sign of autopolyploidy. Since only two out of 31 investigated accessions belonging to subg. Melanocrommyum were tetraploid, we may suggest a trivial role of polyploidy in the evolution of this subgenus.

Automated summary

Meiosis in 105 individuals from 33 accessions of 23 Iranian Allium species was studied, revealing the chromosome number, configurations, chiasma frequency, and abnormalities. The results showed that the basic chromosome number was x = 8 and most species were diploid with eight bivalents. Some species also exhibited tetravalents. Less than 10% of diploid accessions showed meiotic abnormalities, including lagging chromosomes, chromatid bridges, micronuclei, or unbalanced chromosome segregations. B chromosomes were found in 11 accessions, and were newly recognized in three species. No correlation between B chromosomes and chiasma frequency or habitat factors was observed.