Genetic Analysis And Map-based Cloning Of Maize Endosperm Mutant Su5

Maize is an important food crop, as well as an important source of animal feed andindustrial material. However, due to the scarcity of human food and livestock feed,the strong demand of energy for industrial development, it is imperative to improvethe yield and quality of maize. The nutritive value, economic value and energeticvalue of maize are mainly manifested in the maize kernel. Endosperms in grainsaccounted for80-90%of the dry weight. Thus, it is the prerequisite of improving theyield and quality of maize to analyze the functional genes related to the endospermdevelopment in maize.Maize endosperm mutant used in this study is EMS chemical mutated inbred lineMo17. It was determined as homozygote after several generations of geneticidentification. We named it mutant1511. In order to understand the function andmechanism of the mutant gene, we used map-based cloning of the gene for initialpositioning. The main results are as follows:1. Phenotypic identification and genetic analysis of the mutant1511: Through thephenotypic identification of mutant1511, its endosperm showed that testa shrinkage,transparent, volume was significantly smaller than wild type maize endosperm. Someof powder endosperm has serious deficiencies, while the majorities are cutinendosperm. Scanning electron microscopy results showed that the cells of matureendosperms of mutants arranged irregularly and the cell volume was small; the starchgrains had irregular shape, uneven size and irregularly arrangement. In the test ofmain component in the endosperm, it was found that compared with normal inbredlines, the content of soluble polysaccharide increased by50%and content of amylosereduced greatly in mutants. Due to high content of soluble polysaccharides in themutant,1511is considered as a sweet corn.2. Screening polymorphism of SSR: In the screening of polymorphic SSR molecular markers of three kinds of inbred lines B73, Mo17and8902,125pairs of polymorphicprimers in350pairs of SSR primers were found. There were45polymorphic primersbetween B73and8902, only4primers per chromosome on average; there were94polymorphic primers between Mo17and8902,9primers per chromosome on average;there were112polymorphic primers between B73and Mo17,11primers perchromosome on average.3. Primary mapping of mutant gene: F2population built by1511and B73wereanalyzed by BSA (Bulked Segregation Analysis) method. The results showed thatmarkers nc005linked with mutant gene Thus mutant gene are located in maizechromosome4.4. Fine mapping of mutant gene: According to540individuals of F2population,mutant gene was determined between umc2282and bnlg1729of SSR marker onchromosome4. The genetic distance between mutant gene and umc2282isapproximately3.5cM. The genetic distance between mutant gene and bnlg1729isapproximately6.3cM. The physical distance between two SSR markers isapproximately35Mb. This shows that gene is located near the centromere, which hasa low exchange rate. Thus, it caused a great difficulty to conduct the fine mapping ofmutant gene.In conclusion, we found that mutant1511is a sweet corn and located the mutant genesugary5between SSR marker umc2282to bnlg1729on chromosome4. Although thephysical distance between the two markers is long, it is not reported about mutant1511phenotype-related genes between the two markers, so the mutant1511is a newmutant. For the1511is a sweet corn, the mutant gene named sugary5. This study laidthe foundation for acquisition of the gene and further functional identification.