Li Z, Heneen W K
Department of Agronomy, Huazhong Agricultural University, 430070, Wuhan, China, CN.
Theor Appl Genet. 1999 Aug;99(3-4):694-704. doi: 10.1007/s001220051286.
It has been proposed that both complete and partial separation of the parental genomes during mitosis and meiosis occurs in the intergeneric hybrids between Orychophragmus violaceus (2n=24) and the three cultivated Brassica tetraploids (B. napus, B. carinata and B. juncea). The hypothesis has been that this and the variations in chromosome numbers of these hybrids and their progenies result from the different roles of the A, B and C genomes originating from Brassica. To test this hypothesis, we produced hybrids between O. violaceus and the cultivated Brassica diploids. The hybrids with B. oleracea (2n=18, CC) had an intermediate morphology, but their petals were purple like those of O. violaceus. They were sterile and had the expected chromosome number (2n=21) in their mitotic and meiotic cells. The hybrid with B. campestris (2n=20, AA) was morphologically intermediate, except for its partial fertility and its yellow petals, which were similar to those of B. campestris. It was mixoploid (2n=23-42), and cells with 2n=34 were most frequent. Partial separation of parental genomes during mitosis, leading to the addition of O. violaceus chromosomes to the B. campestris complement, was proposed to explain the findings in the mitotic and meiotic cells of the hybrid and its progeny. In crosses with B. nigra (2n=16, BB), the majority of the F(1) plants were of the maternal type (2n=16), a small fraction had B. nigra morphology but were mixoploids (2n=16-18), predominantly with 2n=16 cells and three plants, each with a specific morphology, were mixoploids consisting of cells with varying ranges of chromosome numbers (2n=17-26, 11-17 and 14-17). The origin of these different types of plants was inferred to be a result of the complete and partial separation of parental genomes and the loss of O. violaceus chromosomes. Our findings in the three crosses suggest that the A genome was more influential than the C genome with respect to complete genome separation during mitosis and meiosis of the hybrids with B. napus. Possible complete and partial genome separation during mitotic divisions of the hybrids with B. carinata was mainly attributed to the role of the B genome. The combined roles of the A and B genomes would thus contribute to the most variable chromosome numbers of mitotic and meiotic cells in the hybrids with B. juncea and their progenies. The possible cytological mechanisms pertaining to these hybrids and the potential of genome separation in the production of Brassica aneuploids and homozygous plants are discussed.
有人提出，诸葛菜（2n = 24）与三种栽培四倍体芸苔属植物（甘蓝型油菜、埃塞俄比亚芥和芥菜型油菜）的属间杂种在有丝分裂和减数分裂过程中会发生亲本基因组的完全和部分分离。假说是，这些杂种及其后代染色体数目的这种情况和变异是由源自芸苔属的A、B和C基因组的不同作用导致的。为了验证这一假说，我们培育了诸葛菜与栽培二倍体芸苔属植物的杂种。与甘蓝（2n = 18，CC）的杂种具有中间形态，但其花瓣像诸葛菜一样是紫色的。它们不育，有丝分裂和减数分裂细胞中的染色体数符合预期（2n = 21）。与白菜（2n = 20，AA）的杂种在形态上是中间型，只是部分可育，其黄色花瓣与白菜的相似。它是混倍体（2n = 23 - 42），2n = 34的细胞最为常见。有人提出，在有丝分裂过程中亲本基因组的部分分离导致诸葛菜染色体添加到白菜的染色体组中，以此来解释该杂种及其后代有丝分裂和减数分裂细胞中的发现。在与黑芥（2n = 16，BB）的杂交中，大多数F(1)植株是母本类型（2n = 16），一小部分具有黑芥形态但为混倍体（2n = 16 - 18），主要是2n = 16的细胞，还有三株具有特定形态，是由染色体数范围不同的细胞组成的混倍体（2n = 17 - 26、11 - 17和14 - 17）。推断这些不同类型植株的起源是亲本基因组完全和部分分离以及诸葛菜染色体丢失的结果。我们在这三个杂交中的发现表明，在与甘蓝型油菜的杂种有丝分裂和减数分裂过程中基因组完全分离方面，A基因组比C基因组更具影响力。与埃塞俄比亚芥的杂种有丝分裂过程中可能的完全和部分基因组分离主要归因于B基因组的作用。因此，A和B基因组的共同作用会导致与芥菜型油菜的杂种及其后代有丝分裂和减数分裂细胞中染色体数变化最大。讨论了与这些杂种相关的可能细胞学机制以及基因组分离在芸苔属非整倍体和纯合植物生产中的潜力。
