Genetic Analysis Of The Corn Endosperm Mutants Induced By Space Environment

Mutation technique by space flight was an effective way to create new germplasm resource and cultivate new varieties of crops. In2006, maize inbred lines08-641,18-599and one yellow maize inbred line were carried into space. Shrunken opaque seeds, shrunken transparent seeds and white grain seeds were selected from the offspring. In this study, identification and genetic analysis of these three types of mutant were conducted in morphological characteristics, physiological and biochemical characteristics and molecular level. The results are as follows:1) After continuous selfing of multiple generations, the mutants of shrunken kernels can stably inherited. It can be found by detecting the soluble sugar content of the shrunken opaque kernels and shrunken transparent kernels endosperm mutants in10days,15days,20days,25days and30days after pollination. The soluble sugar content of the mutants was higher than that of normal corn in15days after pollination. The soluble sugar content of the mutants kept increasing after15days until the maximum at the certain time, and then declined along with the period of pollination. This was basically the same with the previously study in sweet corn.The sugar content of C1091, C1092was10%to18%in the milky stage. It could be concluded that C1091and C1092belong to normal sweet corn. The sugar content of C1093, C1095, C1096was20%to25%in the milky stage. They probably belong to super sweet corn. The sugar content of C1094was10%to14%in the milky stage, which was higher than that of normal corn. Whether C1094belonged to the super sweet corn needed to be further confirmed. Through allelic test with the normal sweet corn which has been identified, it can be infered that C1091, C1092belong to the normal sweet corn controlled by sul gene. Through allelic test with the super sweet corn which has been identified, it was infered that C1093, C1094, C1095, C1096belong to the super sweet corn.2) Comparing the agronomic characters of white maize mutant with CK yellow maize. There were no significant differences in plant type, leaf number, grain shape, panicle, the number of spike rows and shaft color. The endosperm color changed. The plant height, ear height, branch number of tassel and branch length of the mutants performanced to reduce compared with CK. Genetic analysis on the white endosperm mutant was conducted. All the individuals in F1presented yellow endosperm. The segregation ratio of yellow endosperm and white endosperm of F2fit into3:1. The segregation ratio of yellow endosperm and white endosperm of BC population fit into1:1, indicating that the white endosperm mutant was controlled by a single recessive gene. Using near-infrared spectrometer to analyze the quality of the white endosperm mutant seeds and the control seeds, it could be found that there were no significant differences in crude protein, crude fat, lysine, total starch, amylose and amylopectin between the white endosperm mutant seeds and the control seeds.3) According to the reported Sul gene sequences, by designing the overlapping primers, gene Sul were amplified from the mutant lines and the control. The amplified fragments were recycled, sequenced and blasted. The mutation in exon2and exon13of gene Sulwhich lead to the changes of amino acid were detected in the normal sweet mutant lines C1091, C1092. Gene Sul encodes starch de-branching enzyme. The mutantion caused the starch de-branching enzyme inactivation. The amylopectin biosynthesis was significantly reduced in the endosperm, and the sugar content was significantly increasing.4) According to the reported Sh2gene, by designing the overlapping primers, gene Sh2were amplified from the mutant lines and the control. The amplified fragments were recycled, sequenced and blasted. The mutation in exon1of gene Sh2which lead to the changes of amino acid were detected in the super sweet mutant lines C1093, C1094, C1095, C1096. Gene Sh2encodes the large subunit of ADP-glucose pyrophosphorylase.ADP-glucose pyrophosphorylase was the key and the rate-limiting enzyme in the maize starch biosynthetic pathway. The mutation of gene Sh2led to inactivation of AGPase. The starch synthesis was blocked.5) According to the reported Y1gene by designing the overlapping primers, gene Y1were amplified from the mutant line and the control. The amplified fragments were recycled, sequenced and blasted. The mutation in exon1of gene Y1which lead to the changes of amino acid were detected in the mutant.By the molecular detection, single base mutations were detected in these three mutants, some of them can lead to the changes of amino acid. These results suggested that the space flight may lead to DNA sequence variation of the maize genome in mutants.