冰草属中B染色体在减数分裂期的遗传行为研究

STUDY ON GENETIC BEHAVIOUR OF B CHROMOSOMES AT MEIOSIS IN AGROPYRON GAERTN

对分布于我国不同地区的冰草属(Agropyron Gaertn.)4个种的33份材料进行了花粉母细胞减数分裂期染色体行为观察。发现含 B 染色体的材料主要集中在沙芦草(A.mongolicumKeng,2n=2x=14)中。在沙生冰草(A.deseriorum〈Fi sch.〉Schult.,2n=4x=28)中有40%的材料含 B 染色体。而在四倍体冰草(A.cristatum〈L.〉Gaertn.,2n=4x=28)和根茎冰草(A.michnoi Roshev.,2n=4x=28)中未找到含 B 染色体的材料。偶数 B 染色体间的配对通常发生在终变期,而奇数 B 染色体间的配对通常在中期 I。B 染色体在后期 I的分离是随机的。落后 B 染色体的分离,一般是通过本身的提前分裂以染色单体的形式趋向两极。含有较高数目的 B 染色体有提高 A 染色体间配对和交叉频率的作用。讨论了 B 染色体的存在与倍性水平间的关系以及 B 染色体间的同源性等问题。

The chromosomal behaviour at meiosis' in pollen mother cells of 33 sample materials from 4 species in Agropyron Gaertn. distributed over various regions in China were observed. We found that B chromosomes were mainly present in A. mongolicum Keng (2n = 2x = 14) and were absent in the tetraploid A. cristatum (L.) Gaertn. (2n = 4x = 28) and A. michnot Roshev. (2n = 4x = 28). Of all A. desertorum (Fisch.) Schult. (2n = 4x = 28) populations, they were present in 40%. The pairing between even numbers of B chromosomes usually occured at diakinesis where as uneven numbers of B chromosomes at metaphase I. B chromosomes at ana phase I separated at random. The lagging Bs tended to reach two poles by chromatids through precocious division of Bs. The pairing and chiasma frequencies between A chromosomes were increased by the larger numbers of Bs. The relationship between B chromosomes and species ploidy, the homeology among Bs, etc were discussed.