Meiosis in a triploid hybrid of Gossypium: high frequency of secondary bipolar spindles at metaphase II

Abstract

Studies on meiosis in pollen mother cells (PMCs) of a triploid interspecific hybrid (3x = 39 chromosomes, AAD) between tetraploid Gossypium hirsutum (4n = 2x = 52,AADD) and diploid G. arboreum (2n = 2x = 26,AA) are reported. During meiotic metaphase I, 13 AA bivalents and 13 D univalents are expected in the hybrid. However, only 28% of the PMCs had this expected configuration. The rest of the PMCs had between 8 and 12 bivalents and between 12 and 17 univalents. Univalents lagged at anaphase I, and at metaphase II one or a group of univalents remained scattered in the cytoplasm and failed to assemble at a single metaphase plate. Primary bipolar spindles organized around the bivalents and multivalents. In addition to the primary spindle, several secondary and smaller bipolar spindles organized themselves around individual univalents and groups of univalents. Almost all (97%) of the PMCs showed secondary spindles. Each spindle functioned independently and despite their multiple numbers in a cell, meiosis I proceeded normally, with polyad formation. These observations strongly support the view that in plant meiocytes bilateral kinetochore symmetry is not required for establishing a bipolar spindle and that single unpaired chromosomes can initiate and stabilize the formation of a functional bipolar spindle.

Interspecific hybridization in Gossypium L.: characterization of progenies with different ploidy‐confirmed multigenomic backgrounds

“…We observed increased pollen sterility in the hexaploid. Increased pollen sterility in the hexaploid derivates was reported earlier by Brown and Menzel (1952) and Beasley (1942), which might be due to high frequency of secondary bipolar spindles in the PMCs (Vafaie-Tabar and Chandrashekran 2007).…”

Understanding meiosis and the implications for crop improvement

“…The meiotic behaviour of several allopolyploid plant species has been, and continues to be, studied. These include bread wheat (Riley and Chapman 1958;Sears 1982;Martinez-Perez et al 2001;Griffiths et al 2006;Colas et al 2008;Boden et al 2009), oilseed rape (Brassica napus L.) (Attia and Robbelen 1986;Jenczewski et al 2003;Udall et al 2005;Leflon et al 2006;Liu et al 2006;Nicolas et al 2008Nicolas et al , 2009, oats (Avena sativa L.) (Gauthier and McGinnis 1968;Rajhathy and Thomas 1972), cotton (Gossypium hirsutum L.) (Brown 1954;Reyes-Valdés and Stelly 1995;Ji et al 2007;Vafaie-Tabar and Chandrashekaran 2007) and tobacco (Nicotiana tabacum L.) Berbeć2003, 2007). Of all these plant species, the hexaploid genome of bread wheat has provided some of the most useful information to date.…”

Cytogenetic Study on Trispecific Hybrid from Gossypium hirsutum L., G. australe and G. capitis-viridis

“…)，5 个为四倍体棉种(2n = 4x = 52) [1] 。棉属有四个 栽培品种即亚洲棉、草棉、陆地棉、海岛棉，其余 47 个均为野生棉种 [2] 。由于栽培棉种对病虫害及非生物 胁迫较为敏感 [3] [5] ； 绿顶棉也具备优异的纤维品质及抗病、 抗虫性等 [6] 。导致栽培棉与野生棉性状的差异归因于 遗传物质及调控机制的不同，比如，栽培种中棉酚腺 体的形成主要受两个分别位于同源染色体 c12 (Ahgenome)和 c26 (Dh-genome)上 [7] 的基因 Gl 2 和 Gl 3 的控 制，种子棉酚含量受基因 G 1 的控制 [8] ；由于该特性只 存在于一些 C 组和 G 组的野生棉中， 这些澳洲野生棉 在进化系统中又远离陆地棉 [9] ，所以只有通过种质渗 入将澳洲棉的遗传物质导入陆地棉才能使陆地棉得 到改良。如早在 60 年代 Muramoto [10] 将澳洲棉和陆地 棉杂交，F 1 加倍，再对六倍体进行选择，第四代具备 比陆地棉和海岛棉更大的耐寒性，抗根腐病菌，且改 进了纤维品质，六倍体的纤维能纺成高强力棉纱。梁 理民 [11] 等人通过陆地棉和斯特提棉种间杂交育成新 品种秦远号，同时选育出抗病优质、抗病高强、抗病 大铃、抗病高衣分、抗枯黄萎病新种质。迄今为止， 我国已获得陆地棉与 19 个野生棉种及其他栽培种的 高代种间杂种(4 代以上) [12] [24] 。本研究中三元杂种高度不育的直接原因在 于，三元杂种减数分裂紊乱，染色体分离不均等，向 多极移动，最终形成的配子得不到全套染色体，花粉 粒无活力。 Brown [25] 和 Beasley [26] 也曾报道过六倍体杂 种花粉败育的现象，这可能是由于减数分裂中两级纺 锤丝大量出现造成的 [27] 。…”