Chromosomal Behavior during Meiosis in the Progeny of <i>Triticum timopheevii</i> × Hexaploid Wild Oat

The meiotic behavior of pollen mother cells (PMCs) of the F2 and F3 progeny from Triticum timopheevii × hexaploid wild oat was investigated by cytological analysis and sequential C-banding-genomic in situ hybridization (GISH) in the present study. A cytological analysis showed that the chromosome numbers of the F2 and F3 progeny ranged from 28 to 41. A large number of univalents, lagging chromosomes, chromosome bridges and micronuclei were found at the metaphase I, anaphase I, anaphase II and tetrad stages in the F2 and F3 progeny. The averages of univalents were 3.50 and 2.73 per cell, and those of lagging chromosomes were 3.37 and 1.87 in the F2 and F3 progeny, respectively. The PMC meiotic indices of the F2 and F3 progeny were 12.22 and 20.34, respectively, indicating considerable genetic instability. A sequential C-banding-GISH analysis revealed that some chromosomes and fragments from the hexaploid wild oat were detected at metaphase I and anaphase I in the progeny, showing that the progeny were of true intergeneric hybrid origin. The alien chromosomes 6A, 7A, 3C and 2D were lost during transmission from F2 to F3. In addition, partial T. timopheevii chromosomes appeared in the form of univalents or lagging chromosomes, which might result from large genome differences between the parents, and the wild oat chromosome introgression interfered with the wheat homologues’ normally pairing.本研究通过细胞学分析结合顺序C分带-基因组原位杂交（genomic in situ hybridization，GISH）技术，对提莫菲维小麦（Triticum timopheevii）与六倍体野燕麦（hexaploid wild oat）杂交获得的子二代（F2）及子三代（F3）群体的花粉母细胞（pollen mother cells，PMCs）减数分裂行为开展了研究。细胞学分析结果表明，F2及F3群体的染色体数目范围为28至41条。在F2和F3群体的减数分裂中期I、后期I、后期II及四分体时期，可观测到大量单价体、落后染色体、染色体桥与微核。其中F2群体每细胞内单价体平均数量为3.50个，落后染色体平均数量为3.37个；F3群体每细胞内单价体平均数量为2.73个，落后染色体平均数量为1.87个。F2和F3群体的花粉母细胞减数分裂指数分别为12.22与20.34，提示其存在显著的遗传不稳定性。顺序C分带-GISH分析显示，子代群体的中期I与后期I阶段可检测到源自六倍体野燕麦的部分染色体及染色体片段，证实该子代确为属间杂种来源。在从F2到F3的世代传递过程中，外源染色体6A、7A、3C及2D发生了丢失。此外，部分提莫菲维小麦染色体以单价体或落后染色体的形式出现，这一现象可能源于亲本间巨大的基因组差异，且野燕麦染色体的渗入干扰了小麦同源染色体的正常配对。