甘蓝型油菜显性核不育系D3A的细胞学研究

为明确甘蓝型油菜显性核不育两型系D3AB的花器官形态差异和不育材料D3A的花药败育时期与特点,并为进一步研究雄性不育机理奠定基础,分别对D3A与D3B不同时期的花蕾进行了形态学观察及细胞学研究.首先通过体视镜观察发现, D3A与D3B外观形态无明显差异,均能正常开花,且在雄蕊发育早期均表现正常,后期D3A雄蕊退化萎缩,花粉囊不能正常开裂;不育材料D3A子房柱头发育速度稍快于D3B.通过扫描电镜观察发现, D3A早期花药基部开始皱缩,表皮细胞排列紧密.随着花蕾发育, D3A花粉囊壁表皮细胞逐渐萎缩,最终塌陷且药室不能正常开裂释放花粉; D3B花粉囊始终呈现出紧致饱满状态,花药正常开裂,同时释放出大量成熟花粉粒.通过石蜡切片观察发现,不育材料D3A和可育材料D3B在花蕾发育早期,都能形成花粉母细胞,但与D3B相比, D3A花粉母细胞结构松散,且绒毡层已开始呈现液泡化状态;进入四分体时期,不育材料D3A的花粉囊中观察到高度液泡化的绒毡层细胞,且无四分体结构出现.实验结果表明:绒毡层细胞提前发生了降解而未向分泌型转化,使四分体时期丧失了发育过程中所必需的营养物质,从而不能形成小孢子并发育为成熟的花粉粒进行释放,因此认为D3A的败育属于绒毡层发育异常类型.

Cytological Studies of Dominant GMS Sterile Line D3A in Brassica napus L.

An experiment was made to detect the vital abortion periods and cytological characteristics of anther development in dominant GMS homozygous two-type line D3AB in Brassica napus L., so as to provide a theoretical basis for further study of the mechanism of male sterility. Stereoscopic examination showed that phenotypically, the flowers and floral development appeared normal in both D3A and D3B, but the development rate of the ovary stigmata of D3A was slightly greater than that of D3B. Meanwhile, the anthers gradually degenerated during the late development of flowers, which resulted in abnormal pollen release. The results of scanning electron microscopy analysis showed that the base anthers shrank and the epidermal cells were tightly arranged at the early development stages of anthers in D3A. However, with the development of flower buds, the pollen wall of D3A shrank obviously until loss of activity. Eventually the anthers of D3A could not normally crack and release pollen whereas the anthers in D3B normally cracked and released a large amount of mature pollen. Paraffin section analysis indicated that pollen mother cells were normally formed at the early flower stages in both D3A and D3B, but the structure of the pollen mother cells in D3A was loose, and a vacuole state began to appear in its tapetum. In the tetrad stage, highly vacuolized tapetum cells were detected in the pollen sacs of D3A, and no tetrad structures were noticed in it. The above-stated results indicated that the tapetum cells in the sterile line degraded prematurely and failed to be transformed to the secretory-type tapetum cells, and thus had no sufficient nutrients for their development at the tetrad stage and microspores were not formed to release pollen, thus leading to the sterility of D3A. In conclusion, the abortion of D3A may be the abnormal type of tapetum.