Factors Affected BC1F1 Size for Development of Genome-Wide Introgression Lines

Introgression lines are important genetic materials for genetics study and breeding. Development of those lines involves cross and backcross processes between recipient and donor parents. The population size of BC1F1 is a critical parameter for fully covering donor genome and successfully obtaining desired introgression lines. However, the minimum sufficient number of BC1F1 plants is unknown for each species and cannot be obtained experimentally. A computer program was developed by simulating the recombination process during meiosis to define the ideal BC1F1 population size. The reliability of the program was confirmed by mathematics and experimental data. Three factors including linkage group number, linkage group length, and gene density were analyzed, and all of them had positive relation with the size of BC1F1 population. The population size increased from 6.06 to 9.49 when the linkage number increased from 5 to 40. The population size was 7.14 when the linkage group length was 80 cM, while it became 8.64 when the length was 200 cM. The population size was 7.65 with the density of 20 cM per gene and 8.22 with 10 cM per gene. The BC1F1 population sizes of rice (Oryza sativa L.), wheat (Triticum aestivum L.), maize (Zea mays L.), and soybean (Glycine max L. Merr.) were predicted to be 12, 13, 14–15, and 13, respectively, by the program with 95% confidential level.

摘要全基因组导入系是遗传和育种研究的重要材料。导入系经受体亲本和供体亲本间连续杂交、回交构建而成, BC1F1群体大小是获得理想导入系群体的关键参数。然而, 各物种所需要的最小群体尚不清楚, 并且难以通过试验确定。本研究通过编写程序, 模拟减数分裂时的重组过程研究适宜的群体大小, 并通过数学运算和试验验证程序的可靠性。结果表明, 编程模拟与数学计算和试验结果一致。BC1F1群体大小与连锁群数目、连锁群长度和基因密度之间均为正相关。当模拟连锁群从5个增加到40个时, 群体大小需要由6.06增加到9.49; 当模拟连锁群长度从80 cM增加到200 cM时, 需要的群体大小从7.14增加到8.64; 当模拟基因密度从每基因20 cM缩小到每基因5 cM时, 群体大小从7.65增加到8.22。为测试该程序的应用范围, 对水稻、小麦、玉米、大豆等主要作物进行了BC1F1群体大小模拟,在保证95%的概率覆盖全基因组条件下, 水稻需要的群体最少, 为12个个体, 小麦和大豆均需13个个体, 玉米需要的个体数最多, 为14 ∼ 15个。