| As a peculiar reproduction phenomenon in plants, Polyembryony not only contains abundant genetic information, but also contains spontaneous haploids. At present, quite a few haploids from polyembryonic seedlings have been widely applied to crops breeding researches, becoming a precious resource in promoting breeding process and constructing genetic map. Ramie is a kind of monoecism heterozygote crop, whose property of polyembryony has been confirmed. However, the variation of polyembryonic ratio was significant among breeds. This study aimed to obtain polyembryonic varieties and haplobiont. Two ways were adopted in this study:facilitating the germination of polyembryonic seeds and inducing the formation of polyembryony. Meanwhile, this article tentatively explored the characteristics of polyembryonic ramie seedlings from prospectives of morphology, hereditism, ploidy and molecular biology. Main approaches and results are introduced and explored as follows:(1) The optimum germination condition of polyembryonic ramie seeds was defined as: environment temperature controlled to28～30℃, and moist filter paper used as solid substrate. Germination ratio of polyembryonic seeds could be increased by spraying0.8%H2O2liquor. In this study,15cultivars were screened out for their polyembryony percentage above5%o. Meanwhile, by hybridizing and self-crossing samples,8varieties with polyembryony percentages above5%o were cultivated.(2) According to their sizes, structural integrity and whether they are conjoined or not, polyembryonic ramie seedlings can be categorized into5types:semlable, big-small, big-abnormal, both abnormal and siamesed. Further study demonstrated that the categories of polyembryonic ramie seedlings related to its genetic background.(3)09JZ, a group of ramie seedlings, has been cultivated. This group was consisted with21pairs of twin ramie seedlings, a bunch of tri-embryony seedlings and one normal seedling which all screened out from the F1progenies of Jingxi qing x Zhongzhu No.1. SRAP (Sequence Related Amplified Polymorphism) markers were applied in analyzing the genomes of this group and their parents. The results showed that a total of159polymorphic bands were detected with an average of6.6polymorphic bands per primer pair, whose percentage of polymorphic bands were63%. The genetic similarities of all48materials ranged from0.360to0.876. UPGMA method cluster analysis showed that these materials classified into four cluster groups with genetic similarity of0.51. No individual of09JZ has fully consistent polymorphic bands with their parents, so the possibility of individual apomixes excluded.(4) One pair of twin ramie seedlings were obtained by delayedpollination between Zhongzhu No.2and Zhongzhu No.1.The twin seedlings and their parents were detected by SSR markers. The results showed that the twin seedlings were real filial generations.(5) By analyzing the polyembryonic seedlings ratio of filial generation of hybridization and self-crossing, we concluded that polyembryony percentage of filial generation were as same as that of female parents.(6) Chromosome counting and FCM (Flow Cytometry) were both applied to detecting the ploidy of polyembryonic seedlings.2varieties which contained n-2n type were screened out. What’s more,1haplobiont of Yuanjiang Rou was obtained, which was widely different from diploid plants in size, leaf age and growth vigour fields.This study innovatively reveals the fact that polyembryoney property of filial generation is the same as that of the female, which has guiding significance in ramie’s polyembryonic breeding. The feasibility of obtaining haplobiont from twin seedlings can greatly promote the development of ramie breeding research. |
PDF Full Text Request