Creation Of Mutants For Seed Appearance And Components Based On Mnu Mutagenesis Of Amphoteric Germ Cells Of Rice And Their Characterization

Rice(Oryza sativa L.)is a cereal crop of the genus Oryza.Half of the world’s population uses it as a staple food.It is widely used in many fields such as agriculture,food,feed,and energy,and is related to sustainable agricultural development and social stability.With the turn of the life sciences towards the post-genomics era,rice has become a model plant for cereal crops and comparative plant genomics.Functional genomic research of important agronomic traits has become the forefront of plant biology,and rice breeding is also becoming more diverse.The rice genome is about 1/7 of the human genome,contains about 430 million base pairs,and has a total of 12 chromosomes.The whole gene components of rice are Oryza Sativa ssp.indica and Oryza sativa L.ssp.Japonica.Type,which contains46022-55615 genes and 32,000-50000 genes,respectively.The development and utilization of rice mutants has promoted the identification and functional analysis of some genes,and the lack of genetic mutation materials caused by low mutation efficiency has become a key factor in which the biological functions of most rice genes remain unknown.In our laboratory,we have established N-methyl-N-nitrosourea(MNU)mutagenesis technology for amphoteric germ cells in rice.Compared with the reported mutagenesis methods,the method has significantly improved the mutation efficiency of broad-spectrum gene mutations,which can provide efficient technical support for the large-scale development of various mutant materials required for functional genome and breeding research in rice.Rice seed traits directly affect rice grain yield and quality as well as the commercial value of rice-based products.Rice genetic breeding has received widespread attention for a long time.In order to develop various genetic mutation materials for unknown function identification and diversified breeding of rice grain traits,new genetic information related to the expression of relevant grain traits was discovered.In this study,we screened 373 M2 generations and their offspring seed populations obtained from MNUtreatment of wild-type rice varieties(Liaoyan 6),and obtained and characterized the grain appearance and endosperm of 15 homozygous genotype mutants.Nature and stalk type,leaf type,spike type and glume type traits,and named the OSGM series.The resulting mutants include a series of granule type mutants,endosperm mutants,and seed coat mutants.Compared with the wild type,OSGM1 and OSGM2 are grain-type mutants,the size of which shows extremely reduced or increased traits.OSGM1 is accompanied by changes in endosperm traits.OSGM3,OSGM4,OSGM5,OSGM6,OSGM7 and OSGM8 are heart white endosperm mutants,and the endosperm is opaque and white deposits.OSGM9 and OSGM10 are peripheral white endosperm mutants with thin grains,white edges around the edges of the endosperm,white transparent vitreous,and wrinkled epidermis.OSGM11 and OSM12 are silty endosperm mutants with opaque and white endosperm.OSGM13 is a waxy endosperm mutant with an opaque milky white and waxy endosperm.OSGM14 is a dark cloudy endosperm mutant with a dark white endosperm between the wild type and waxy endosperm.OSGM15 is a seed coat mutant with a reddish-brown surface and longitudinal wrinkles on the surface.In order to further explore the possibility of genetic correlation between the grain traits and endosperm properties of various mutants,starch,protein and pigment properties were analyzed for the 15 mutants obtained.Compared with the wild type,OSGM1 as a small-grain mutant,the total starch and amylopectin content are reduced,the starch grains are slightly prismatic,and the anthocyanin content of the seed coat is significantly increased;OSGM2,OSGM3,and OSGM11,respectively As wide-thickness mutants,heart white endosperm mutants and silty endosperm mutants all reduced amylose content,starch granule structure was obviously loosely arranged;OSGM9 and OSGM15 as peripheral white endosperm mutants and red-brown seed coat mutants,The starch granules are all loose and dense in the middle;OSGM13and OSGM14 are waxy endosperm mutants and murky endosperm mutants,and the amylose content of both has dropped sharply.Among them,theendosperm center of OSGM13 contains starch granules with cavity structure.OSGM14 has an irregular,multifaceted prismatic starch granule structure.The 57 k Da gluten precursor content of OSGM2 was significantly increased,and the 40 k Da and 20 k Da components were reduced.OSGM3 is a new 57 H mutant with an increased amount of gluten precursor,mature 40 k D acidic component and 20 k D basic component.;The 13 k Da prolamin component of OSGM9 contains three polypeptide chains;the 13 k Da prolamin component of OSGM11 has a deletion.Both OSGM1 and OSGM2 significantly increased the anthocyanin content of the seed coat;the anthocyanin content of the OSGM9 and OSGM10 seed coats was extremely reduced and the proanthocyanidin content was significantly increased;OSGM15 as a red-brown seed coat mutant,the anthocyanins of the seed coat and Anthocyanin content increased significantly.The changes in endosperm properties of rice grain trait mutants obtained in this study may cause mutations in starch or pigment synthesis and accumulation-related genes,resulting in changes in endosperm quality and nutritional properties.Therefore,the obtained rice grain mutants are genetically modified,Researches on gene identification,cloning,and breeding of new varieties are expected to contribute to the identification of unknown functional genes related to rice grain trait expression and the achievement of the goal of diversified rice nutrition quality.