Genetic Analysis And Molecular Identification Of Maize Dwarf Mutant Gad39

Plant height is one of the most important selection traits in maize breeding,which determines the planting density and lodging resistance of maize,and further affects its yield and quality.Therefore,it is a necessary measure for increasing maize yield to study molecular mechanism of plant height.In this study,a dwarf natural mutant gad39 from maize inbred line Mo17 was selected as the experimental material,and its phenotypic analysis and mapping cloning were performed.The main results are as follows:The plant height of gad39 mutants was significantly lower than that of wild type Mo17 during the whole growth and development stage.For example,the plant height(100.00 cm)and ear position(20.22 cm)of gad39 was 51.92% and 36.76% of those of the wild type(192.60 cm,55.00 cm),respectively.Compared with the wild type,the cell size of gad39 was significantly smaller,and the number of internodes,internode and tassel length were all reduced,while the number of tillers in the mutant was significantly increased.Genetic analysis indicated that the mutant phenotype was regulated by one recessive nuclear gene,and GAD(Gibberellin Associated Dwarf)gene had been mapped between two molecular markers td4 and td6 on the long arm of chromosome 3.The physical distance of this region is 15.34 kb,including a reported dwarf gene D1/Zm GA3ox2,which encodes GA3 oxidase(GA3ox),and is one of the key enzymes in gibberellin(GA)synthesis pathway.Gene Sequencing revealed that there were 10 In Dels and 21 SNPs in the D1 gene of gad39,resulting in aspartic acid mutation at position 40 to glycine,alanine mutation at positions 60 and 61 to proline,and aspartic acid mutation at position 145 to alanine.The dwarf mutant gad39 was sensitive to GA3 treatment,the exogenous gibberellin(GA3,100 μg·m L-1)could recover the same phenotype of plant height as that of the wild type.The results showed that the gad39 mutant was an allelic mutant of D1 gene found in the background of maize inbred line Mo17.Due to the deficiency of active GA synthesis,the number of internodes,internode length and tassel elongation of the mutant were reduced.This study provided a new genetic material of dwarf maize,enriched the dwarf source of maize,and further clarified the molecular mechanism of gibberellin regulating maize plant height,which laid a certain foundation for the study of its function and had the potential value for agricultural production research.