GENETIC AND BREEDING STUDIES ON AMYLOPECTIN MUTANTS IN RICE

支链淀粉是大米中淀粉的主要组成部分，约占大米淀粉的80%，因此，支链淀粉对大米的食用品质和工业加工特性有很大影响。尽管支链淀粉的重要性很大，但由于支链淀粉结构修饰相关基因的信息和支链淀粉遗传资源的数量有限，支链淀粉在水稻育种中的研究还很少。本研究以水稻受精卵细胞为材料，通过亚硝胺诱变获得支链淀粉突变株，并对其遗传和理化特性进行了鉴定，建立了利用微处理器控制的二极管阵列光谱仪DU 7000分光光度计测淀粉/碘复合体碘含量、淀粉生物合成相关酶蛋白的SDSPAGE分析、支链淀粉生物合成…的Native-PAGE/活性染色的快速简便方法更多与HEIS相关的酶，如淀粉分支酶、淀粉去分支酶、淀粉合成酶和普兰酶，以及用尿素测定淀粉糊化程度。用这些方法筛选了两个粳稻品种金梅泽、台中65和一个籼稻品种IR36的受精卵细胞经MNU处理后产生的突变株，获得了直链淀粉延伸剂(Ae)、粉1(Flo 1)、粉2(Flo 2)、粉3(Flo 3)、粉4(Flo 4)等改变胚乳淀粉支链结构的突变株。对这些突变体中胚乳淀粉的结构和理化分析表明，支链淀粉支链结构的变化比直链淀粉含量对淀粉的糊化或溶胀等加工性质的影响更大，这对煮米饭的蒸煮品质和大米淀粉的工业加工品质有很大影响。这些事实有力地说明了支链淀粉遗传资源在水稻品质改良育种中的重要性。本研究结果不仅为水稻品质改良提供了育种材料，也为深入研究支链淀粉生物合成的遗传和生化调控提供了重要的理论材料。较少

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