GENETIC AND BREEDING STUDIES ON AMYLOPECTIN MUTANTS IN RICE

支链淀粉是稻米中淀粉的主要组成部分，约占80%，因此，预计将对米饭的食用品质和工业用途的加工特性产生重大影响。尽管支链淀粉在水稻育种中具有重要意义，但由于有关支链淀粉结构修饰基因的信息和支链淀粉遗传资源的有限，支链淀粉在水稻育种中的应用还很少。本研究尝试通过MNU处理水稻受精卵细胞诱导支链淀粉突变体，并对其遗传和理化性质进行表征，以将其用作育种材料。我们开发并设计了使用微处理器控制的二极管阵列光谱仪DU 7000分光光度计（Beckman）快速、简化的淀粉/碘复合物碘比色测量方法，淀粉生物合成相关酶蛋白的SDS-PAGE分析，支链淀粉生物合成酶蛋白的Native-PAGE/活性染色 关于我们 与淀粉酶相关的酶如淀粉分支酶、淀粉脱支酶、淀粉合成酶和支链淀粉酶，以及使用尿素测量淀粉糊化。利用这些方法，我们对两个粳稻品种Kinmaze和台中65以及一个籼稻品种IR 36的受精卵细胞进行了MNU诱变筛选，获得了直链淀粉扩展剂（ae）、floury 1（flo 1）、floury 2（flo 2）、floury 3（flo 3）、floury 4（flo 4）、sugar 1（sug 1）等。对这些突变体胚乳淀粉的结构和理化分析表明，支链淀粉分支结构的变化比直链淀粉含量的变化对淀粉的糊化或溶胀等加工特性的影响更大，这对米饭的蒸煮质量和大米淀粉的工业加工质量有很大影响。这充分说明了支链淀粉遗传资源在稻米品质改良育种中的重要性。本研究结果不仅可作为水稻品质改良的育种材料，而且可作为了解支链淀粉生物合成的遗传和生化调控的学术研究材料。少

Amylopectin is a major constituent of starch, being about 80%, in rice and therefore, will be expected to affect greatly on the eating quality of cooked rice and the processing properties for industrial use. In spite of this importance, little attention has, so far, put on amylopectin in rice breeding, because of limited numbers of the information for related genes modifying amylopectin structure and of the genetic resources in amylopectin. In this research, we tried to induce the mutants for amylopectin by MNU treatment of fertilized egg cells in rice and to characterize the genetic and physicochemical properties for using them as breeding materials.We developed and devised the speedy and simplified methods for the iodine colorimetric measurement of starch/iodine complex using the microprocessor controlled diode array spectrograph DU 7000 Spectrophotometer (Beckman), SDS-PAGE analysis of starch biosynthesis related enzyme proteins, Native-PAGE/Activity staining for amylopectin biosynt … More hesis related enzymes such as starch branching enzymes, starch debranching enzymes, starch synthase and pullanase, and the measurement of starch gelatinization using urea. Using these methods, we screened the mutant strains induced by MNU treatment of fertilized egg cells of three kinds of two Japonica rice cultivar, Kinmaze and Taichung 65, and a Indica rice cultivar IR36, and obtained various kinds of mutants modifying the amylopectin structure of endosperm starch, such as amylose extender (ae), floury 1(flo 1), floury 2(flo 2), floury 3(flo 3), floury 4(flo 4), sugary 1(sug 1) etc. The structural and physicochemical analyses of endosperm starches in these mutants shows that the changes in branching structure of amylopectin modified more greatly than the amylose content on the processing properties of starch such as the gelatinization or swelling of starch, which greatly affects the cooking quality of boiled rice and the industrial processing quality of rice starch. These facts indicates strongly the great importance of genetic resources for amylopectin in the breeding to improve the grain quality in rice. The results obtained in this research will play the important rolls not only as breeding materials improving the grain quality in rice but also as the materials of academic researches comprehending the genetic and biochemical regulation of amylopectin biosynthesis. Less