Meiotic observation on ‘Bartzella’, an intersectional hybrid of Paeonia
2024
RONG Qi | MA Xiaoyan | JI Runze | GUAN Ziheng | CHENG Fangyun | ZHONG Yuan
Abstract [Objective] Most intersectional hybrids in Paeonia are triploids and generally sterile, producing a small number of hybrid offspring. Observing the meiotic chromosome behaviors of ‘Bartzella’, an intersectional hybrid with high ornamental value and several hybrid offspring, can provide insight into the formation mechanism of its low fertility. [Methods] The study utilized the anthers of ‘Bartzella’ as materials to observe the meiotic chromosome behaviors of pollen mother cells (PMCs) through the squash method. [Results] (1) In metaphase Ⅰ, a significant number of univalents were formed in ‘Bartzella’ PMCs. In anaphase Ⅰ, various types of chromosomal aneuploid segregation were observed, accounting for up to 89.13%. (2) During the first meiotic division, chromosome bridges and fragments were found in 27.20% of the PMCs; during the second meiotic division, this percentage was increased to 47.68%. (3) In metaphase Ⅱ, spindle positioning abnormalities were relatively common, with fused spindles accounting for 27.06% and tripolar spindles accounting for 12.84%. The meiotic products included up to 72.41% of dyads and 13.43% of triads, which could generate unreduced gametes accounting for about 67%. [Conclusion] Chromosome aneuploidy segregation and loss of chromosome segments during meiosis may be the primary causes of the high sterility of ‘Bartzella’. Fused spindles, tripolar spindles, and abnormal cytokinesis at the end of second meiotic division may result in the production of unreduced gametes. The significant number of unreduced gametes might give ‘Bartzella’ the potential polyploid breeding. However, interploidy hybridization barriers could restrict its hybrid affinity.
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