| Summary: | 碩士 === 國立嘉義大學 === 農藝學系研究所 === 100 === Two hybrid crosses with lowland and upland rice initiated from Tainan District Agricultural Research and Extension Station, Taiwan, were used in this study. All F2 generation seeds divide two parts. One part is continues to propagate in the field via mass selection until F5 generation (M1F5) without extra selection. The other one is screened with 24% polyethylene glycol (PEG) during seed germination. The germinated seedling then transplant into the field and propagated to F3 generation (P1F3). Some P1F3 seeds propagated to F5 generation via mass selection continuously (M2F5) and the others screened by PEG at germination stage as above and propagated to F4 generation (P2F4). The P2F5 was generated by plant-to-row trial in the field. Result summarized as following:
1.From the seed germination rate, the cross 1 is inherited from similar native upland rice, Cha-Shan, have higher potential to enhance drought tolerance. Besides, the selection efficiency through mass selection method is increased significantly and is benefit for rice breeding program.
2.From the plant height frequency, two crosses have high influence of plant height genetic variation by different generation and select method, plant height showed exceeding to the parental distributions in two crosses.
3.From the 1000-grain weight frequency showed exceeding to the parental distributions in two crosses. Cross 1 not the same trend by different generation and select method, however cross 2 have increase trend.
4.From the analysis of variance , two crosses the plant height genetic variation rate have decrease trend in different generation and selection method, showed plant height of the smaller genetic variation rate performance stabilized by human and drought tolerance characteristic selection; 1000-grain weight genetic variation rate more than 90% except cross2 F3 generation, comparison of two crosses the 1000-grain weight higher than plant height of genetic variation rate, showed 1000-grain weight genetic variation rate have small effect by selection methods and drought tolerance selection, mainly effect by genes.
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