GENETIC AND BREEDING STUDIES ON AMYLOPECTIN MUTANTS IN RICE

支链淀粉是淀粉的主要成分，约占大米中淀粉的80%，因此，支链淀粉将对煮熟大米的食用质量和工业用途的加工性能产生重大影响。尽管支链淀粉具有如此重要的作用，但由于修饰支链淀粉结构的相关基因的信息有限，以及支链淀粉的遗传资源有限，目前对支链淀粉在水稻育种中的应用还很少。在本研究中，我们尝试用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，以便作为选育材料。采用Beckman公司的微处理器控制二极管阵列光谱仪DU 7000分光光度计，对淀粉生物合成相关酶蛋白进行SDS-PAGE分析，对支链淀粉生物合成相关酶蛋白进行Native-PAGE/Activity染色，建立了快速、简便的淀粉/碘复合物碘比色测定方法。用尿素测定了淀粉糊化的效果。利用这些方法，我们筛选了两种粳稻品种金麦和台中65以及一种籼稻品种IR36的受精卵细胞经MNU处理后诱导的突变株，得到了多种修饰胚乳淀粉支链淀粉结构的突变体，如直链淀粉扩展体（ae）、flo1 （flo1）、flo2 （flo2）、flo3 （flo3）、flo4 （flo4）、sugar 1（sug1）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对淀粉糊化或膨化等加工性能的影响大于直链淀粉含量的变化，从而极大地影响了煮熟大米的蒸煮品质和大米淀粉的工业加工品质。这些事实充分说明了支链淀粉遗传资源在水稻品质改良育种中的重要作用。本研究成果不仅可作为改良稻米品质的育种材料，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