Meiotic analysis of haploid and doubled haploid forms of Nicotiana otophora and N. tabacum

Detailed meiotic studies were conducted on anther-derived haploids of Nicotiana otophora (n = 12) and N. tabacum (n = 24). At midpachytene stages the non-homologous chromosomes apparently remain unpaired. However, since the spreading of chromosomes at this stage was poor, the possible partial pairing, if any, between non-homologues could not be determined with certainty. One to two univalents rarely exhibited partial foldback pairing involving a single arm or the intercalary regions of the same chromosome. — At diakinesis the bivalent-like structures ranged from 0–2 in Otophora and 0–7 per cell in Tabacum haploids. The bivalent-like configurations (mostly rod types with chromatin connections of varying thickness) observed at meta-anaphase I varied from 0 to 1 and 0 to 5 per cell in haploids of Otophora and Tabacum respectively. The various types of secondary associations of univalents at meta-anaphase I were also studied in different haploids. — The probable origin and significance of bivalent-like configurations and secondary associations observed in Nicotiana haploids is briefly discussed. Based on our results, it is concluded that there is very little intra- or intergenomic pairing, if any, in Nicotiana haploids studied. — The meiotic behavior of chromosomes in doubled haploids (N. tabacum) obtained by leaf mid-rib culture, root culture and spontaneous chromosome doubling was remarkably regular with a stable chromosome number of 2n = 48. The meiotic stability of the doubled haploids permits using these materials directly in the breeding program.Contribution from the Department of Agronomy, University of Kentucky. The investigation reported in this paper (72-3-51) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.