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Cytological and Morphological Studies on Newly Synthetic Hexaploid Wheats

Author: YeYaQing
Tutor: LiuDengCai
School: Sichuan Agricultural University
Course: Botany
Keywords: Synthetic wheat Cytology Agronomic traits T. t. dicoccon Spontaneous Chromosome Doubling
CLC: S512.1
Type: Master's thesis
Year: 2009
Downloads: 56
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Abstract


Common wheat (Triticum aestivum L., 2n=42) is a typical allopolyploid species, which has undergone two allopolyploidization processes during its evolution. The formation of unreduced gametes leads to spontaneous chromosome doubling, which has a great significance in the origin of common wheat. In the origins of common wheat, there is "evolutionary bottleneck" since only a few number of tetraploid T. turgidum wheat and Aegilops tauschii were involved in this process. Compared to its donor species, tetraploid wheat and Ae. tauschii, the genetic diversity of common wheat has been decreased drastically. Previous studies have made it clear that the existing donor species of common wheat have a great deal of genetic resources useful for wheat breeding. The genetic materials from the donor species can be simultaneously transferred into synthetic hexaploid wheat (SHW). SHW provides a permanent "bridge" beween donor speciers and commercial wheat cultivars. The useful genes in donor speciers can be easily introgressed into commercial wheat cultivars via the "bridge", which gives an effecitve strategy to overcome "evolutionary bottleneck" of common wheat.In this study, the chromosome number of root-tip-cells was observed in the S3-generation seeds of SHW-L1 between T. turgidum L. ssp. turgidum AS2255 and Ae. tauschii ssp. typica AS60, which was derived from the chromosome doubling induced by colchicine-treatment. Meanwhile, the meiosis and agronomy were observed in the S1-generation plants of nine SHWs between T. turgidum L. ssp. dicoccon and Ae. tauschii, which were produced from spontaneous chromosome doubling by the union of unreduced gametes. The main results are as follows:1. Among the observed 15 SHW-L1 S3-generation seeds, 12 had 42, one had 39, and two had 41 chromosomes. This meant that aneuploid accounted for 80%, while aneuploid took up 20% among the 15 seeds. These results suggested that the cytology in early gerneration of newly synthetic wheat was instability.2. The S1-generation plants of SHWs showed the agronomic traits of both parents and inherited the high tillering from Ae. tauschii. However, the height of the plants was more similar to that of female parent, T. turgidum ssp. dicoccon. The agronomic traits were varied among SHWs as following: plant height from 99.67cm to 129.70cm, tiller number from 20.70 to 43.33, main spike length from 9.94cm to 14.35cm, spikelet number froml3.11 to 19.60, and 1000-seed weight from 13.33g to 27.33g. Further data analysis showed that different T. turgidum ssp. dicoccon parents may have more significant influence on these agronomic traits in SHW backgrounds than Ae. tauschii parent. In the situation of same T. turgidum ssp. dicoccon, different Ae. tauschii did not lead to significant variations under SHW background. However, in the situation of same Ae. tauschii, the different T. turgidum ssp. dicoccon lead to significant variations .3. The chromosomes in pollen-mother-cells of SHW Syn-SAU-37 during meiotic metaphase I only showed 21 ring bivalents, while the remaining eight SHWs showed both bivalents and univalents with varied number that indicated their abnormal meiotic behaviors.

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CLC: > Agricultural Sciences > Crop > Cereal crops > Wheat > Wheat
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