水稻細胞質雄不稔性及有關植物性狀之遺傳

Abstract

前人的研究指出Chinsurah Boro II具有雄不稔性的細胞質和稔性恢復因子，此種特性將可利用於雜交種子的經濟生產。為明瞭其詳細的遺傳行為，在本試驗中使用Chinsurah Boro II與日本型品種高雄10號正反交，分別栽植F1、F2，也將具有Chinsurah Boro II細胞質的F1正反回交於高雄10號，然後調查此等材料的十個性狀，探討其遺傳現象，並利用變方和變積分析法估計遺傳率，外表相關及遺傳相關。同時在F2的族?中，分別逢機選取30個植株作系統繁殖，利用Sakai等所提出的方法，估計株高、正常花粉率等4個性狀受細胞質影響的大小，並以Mather的方法加入母性影響，做雜種後代變方成分的劃分，以估算狹義的遺傳率。茲將所得結果概述如下： (一)花粉率和結實率的分離形式，在回交第一代具有Chinsurah Boro II的細胞質者與反交具有高雄10號的細胞質者有很大的差異。無論是回交第一代或雜交第一代，持有 Chinsurah Boro II的細胞質者其稔性均較反交者為低，此結果確定了Chinsurah Boro II是細胞質雄不稔性的來源。 (二)開花後柱頭外露的性狀，係來自Chinsurah Boro II，對高雄10號柱頭不外露是部分顯性，在回交第一代和雜交第二代此性狀沒有明顯的分離形式。在第二期作，雜交第二代中有許多植株柱頭外露的比率高於Chinsurah Boro II，但在第一期作則否，顯然的此性狀易受季節的影響。 (三)抽穗期可能為受細胞質的影響，雜交後代持有高雄10號的細胞質，抽穗期有延遲的趨勢，且使雜交第二代與第三代未抽穗的株數較反交為多。但統計分析的結果並沒有支持此結論。 (四)在雜交第二代，株高、粒長、柱頭初級角度、柱頭次級角度和花絲長等五個性狀，呈連續性的變異，顯示一般數量性狀的特性。雜交第一代的粒寬平均值約是兩親的中間值，但在F2的分離形式，有很少數的植株具有與高雄10號同樣或較寬的粒幅，且兩期作均有相似的表現。 (五)花粉率、粒寬、結實率之廣義遺傳率為最高，均在0.95以上，其次是柱頭外露，粒長，抽穗期在0.80~0.90之間，株高在0.75左右。然而柱頭初級角度，柱頭次級角度和花絲長之遺傳率均在0.20以下，但由雜交第二代估計者大約在0.40~0.60之間。 (六)抽穗期與花粉率，抽穗期與結實率，花粉率與結實率，柱頭外露與粒長，其外表相關係數均在0.85以上；柱頭外露與粒寬，粒長與粒寬，其外表相關係數均在0.87以下。 (七)抽穗期與花粉率，抽穗期與結實率，抽穗期與柱頭次級角度，抽穗期與花絲長，花粉率與結實率，花粉率與柱頭次級角度，花粉率與花絲長，柱頭外露與粒長，結實率與柱頭次級角度，結實率與花絲長，粒寬與柱頭初級角度，柱頭次級角度與花絲長，其遺傳相關係數在0.95以上，表現高度的正相關；柱頭外露與粒寬，柱頭外露與柱頭初級角度，株高與柱頭次級角度，粒長與粒寬，粒長與柱頭初級角度，其遺傳相關係數在0.95左右，表現高度的負相關。 (八)使用估計細胞質影響的遺傳模式，來估算株高受細胞質影響的程度，其係數m=0.0753，此數字太小，幾乎可以忽略。而抽穗期、花粉率、結實率估計所得的值為負。 (九)雜種族?以變方成分劃分的方法，估計株高的廣義遺傳率為0.64，狹義遺傳率為0.39。 Previous invesitgators indicated that an Indian rice variety, Chinsurah Boro II, possessed the male-sterile cytoplasm and a pair of the fertility-restorer genes. Undoubtedly this well be the important germ plasm for the development of commercial hybrid rice, though its possibility is still considered remote. In order to understand its genetic behaviour in relation to other traits, we made reciprocal crosses between Chinsurah Boro II and a Japonica variety, Koahsiung 10, The F1 and F2 plants, together with the reciprocal BC1's between the F1 possessing Chinsurah Boro II cytoplasm and Kaohsiung 10, were grown for investigating ten plant characteristics including pollen fertility. The analyses of variance and covariance were used to partition their components for estimating the phenotypic and genotypic correlations and the heritability in a broad sense. From each of the F2 populations, 30 plants were taken at random for progeny-testing. The cytoplasmic effects on plant height and other three traits were, thus, estimated by the methods proposed by Sakai and others. The Mather's method, modified by Sakai et al. was used in partioning the components of variation in various hybrid populations for estimating the heritability in the narrow sense. Summarized below are the results of this study. 1. The segregation patterns of pollen and spikelet fertilities in the BC1, possessing the sytoplasm of Chinsurah Boro II, differed greatly from those of the reciprocal BC1 having Kaohsiung 10 cytoplasm. Both of the BC1 and F1 having Chinsurah Boro II cytoplasm were lower in the fertilities than their respective reciprocals. It is, thus, confirmed that Chinsurah Boro II was the source of cytoplasmic male sterility. 2. The stigma exsertion after anthesis, derived from Chinsurah Boro II, was found partially dominant over the non-exertion from Kaohsiung 10 in both F1's Segregation patterns of this trait in the BC1's and F2's were rather obscured and higher percentages of stigma exsertion than that of Chinsurah Boro II were observed in a number of F2 plants in the second crop season, but not in the first crop. Apparently, the trait was easily influenced by seasons. 3. It seems that the date of heading was slightly influenced by cytoplasm, since the hybrid populations in Koahsiung 10 cytoplasm tended to be late in heading and the F2 segregated more unheaded plants than their reciprocals. However, statistical results did not support this conclusion. 4. The heritability estimates of the ten traits in the broad sense were as follows: pollen fertility, spikelet fertility and spikelet width, over 0.95; stigma exsertion, spikelet length and heading date, 0.80~0.90; plant height, about 0.75; the initial angle and final angle of stigmas, and the lenght of filament, below 0.20 from the F1 data and 0.40~0.60 from the F2 data. 5. In the F2, a continuous variation was observed in five traits, they were plant height, spikelet length, initial and final angles of stigmas, and filament length, indicating the quantitative nature of these traits. The average spikelet width of the F1 was about the mid-parent value. However, very few plant similar in the width with the upper limit, Koahsiung 10, occurred in the F2 in both crop seasons. 6. The phenotypic correlation coefficients between stigma exsertion and spikelet length, heading date and pollen fertility, heading date and spikelet fertility, pollen fertility and spikelet fertility, were all over 0.85. On the contrary, stigma exsertion and spikelet width, spikelet length and spikelet width were negatively correalted, the coefficients were lower than -0.87. 7. The important character pairs, showing high genotypic correlation coefficients over 0.95, were stigma exsertion and spikelet length, heading date and pollen fertility, heading date and final angle of stigmas, pollen fertility and final angle of stigmas. On the contrary, the pairs like stigma exsertion and spikelet width, stigma exsertion and initial angle of stigmas, plant height and final angle of stigmas, had highly negative coefficients of genotypic correlaiton about -0.95. Stigma exsertion was negatively correlated with plant height and pollen fertility with moderately high coefficients. 8. Using the methods proposed by Sakai and others, the cytoplasmic effect on plant height was estimated to be m=0.0753, which was almost negligible. The m values for pollen fertility, spikelet fertility and heading date were negative, indicating non-fitness of the formulated hypothesis and genetic model to these three traits in this cross. 9. The heritability of plant height, estimated by the partitioning of variance components in hybrid populations was a value of 0.64 in the broad sense and 0.39 in the narrow sense.