| Summary: | 碩士 === 臺灣大學 === 農藝學研究所 === 98 === Segregation distortion is the deviation of the segregation ratio of a locus from the expected Mendelian ratio. Ｍany causes will lead to segregation distortion, and they could be classified into gametic effect and zygotic effect.
In order to understand this phenomenon, a F2 and four reciprocal backcross populations from a cross between Taichung Sen 10 (indica) and Taikeng 2 (japonica) rice were created. Chi-square goodness-of-fit tests were used to determine whether the segregation ratios of backcross populations were deviated from expection. The EM algorithm was employed to obtain the maximum likelihood estimators of different populations. The results show that there are SDL of gametic effect in the backcross, but they have different effects on different mating types. When F1 was served as paternal parent in the backcross populations (TCS10/F1、TK2/F1), SDL were detected on the interval between RD0306 and RD0307 of chromosome 3 and RD0612 of chromosome 6. Both of the viabilities of SDL were nearly 0. When F1 was used as maternal parent in the backcross populations (F1/TCS10、F1/TK2), SDL was detected on the interval between RD0603 and RD0605 of chromosome 6. The viabilities of SDL was 0.69 in F1/TCS10 population, and 0.46 in F1/TK2 population. Additional SDL was detected on the interval between RD1101 and RD1102 of chromosome 11 in the backcross population from a cross between F1 and TCS10. The viability of this SDL was 0.59.The four SDL both deviated toward indica allele. However, no zygotic effect in four backcross populations was found. The genotypic frequencies of F2 appeared to be a combination of gametic effects without additional zygotic effect.
In the meanwhile, to understand how SDL affect the genetic distance、QTL detection and the accuracy of EM algorithm, simulation experiments were carried out. According to the simulation result, the genetic distance、QTL detection and the accuracy of EM algorithm will not affect by either one SDL nor two SDL on different chromosomes.The only way that the genetic distance is affected by two SDL on the same chromosome. While the effect of two SDL are the same, the genetic distance will reduce. Otherwise, the genetic distance will increase by the two SDL with different direction.
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