Genetic analysis and molecular characterization of <italic>dwarf</italic> mutant <italic>gad39</italic> in maize

Abstract

<p id="C3">Plant height is one of the important selection characters in maize breeding, which determines planting density and lodging resistance, and further affects yield and quality. Therefore, it is of great significance to study the genetic and molecular mechanism of related genes controlling plant height in maize. We performed phenotypic identification, cytological observation, genetic analysis, gene mapping, and gibberellin (GA₃) treatment of dwarf mutant <italic>gad39</italic>, which is derived from maize inbred line Mo17. At silking stage, the plant height of <italic>gad39</italic> was only 100.00 cm, significantly shorter than 192.60 cm of wild type Mo17, resulting in a decrease of 48.08%. Morphological identification showed that tassel length, internode number, and cell size of <italic>gad39</italic> mutant were significantly reduced, which might be the main cause of <italic>gad39</italic> dwarfism. In addition to plant dwarfness of <italic>gad39</italic>, the number of tillers increased, ear position decreased, stem became thinner, leaf length became shorter and ear length became shorter. Genetic analysis showed that a single recessive nuclear gene regulated the <italic>gad39 </italic>mutant phenotype, and gene controlling dwarf trait was mapped between markers td4 and td6 on the long arm of chromosome 3. The physical distance between the two markers was 15.34 kb, which contained a dwarf gene <italic>D1</italic>/<italic>ZmGA3ox2</italic>. Sequence analysis also revealed that <italic>D1</italic> allele gene in <italic>gad39</italic> had 10 InDels and 21 SNPs, resulting in the variations of four amino acids in exons. Mutation sites of <italic>gad39</italic> differed from the previously reported sites of mutant<italic> dwarf1</italic>,<italic> d1-4</italic>, <italic>d1-6016</italic>, and <italic>d1-3286</italic>. In conclusion, <italic>gad39</italic> was a novel allelic mutant of <italic>D1</italic>, which encoded GA3-oxidase (GA3ox), a key enzyme involved in the bioactive GA biosynthesis. The seedling height of <italic>gad39</italic> was restored to the level of wild types by GA₃ treatment. In this study, we detected a new dwarfing allelic mutant, which laid a foundation for further analyzing the genetic mechanism of plant height in maize.