Genetic And Hormone Sensitive Analysis Of Dwarf Mutant In Maize

Dwarfing genetic resource is not only the base of dwarf breeding, but the important material in study of hormone sensitive, metabolic pathways, cytology and biological study. Preliminary study is conducted on the new-found dwarf mutant from genetic, metabolic, and histological aspects. Principal results are as follows:1.comparative results between tall plant and short plant in F2 from crossing by dwarf mutant with seven maize inbred lines which represent the different genetic background shows that plant height, leaf length, male branch and interval days from breeding to silking have the significant difference between mutant and wild type, but stem diameter, leaf number, leaf width, interval during spinning to pollinating have no significant difference. Plant height of mutant is about 45 cm, leaf length is about 30 cm and tassel branch number of mutant are only 2 to 3, for 24%, 35% and 26.39% of wild type respectively. Inteaval days from sowing to spinning of mutant is longer than wild type about 10 to 15 days.2.analysis results of six generations which come from crossing dwarf mutant with seven different inberd lines represented different genetic background of maize showed that plant in F1 is normal, and plant height have no significant difference in experiment both direct cross and reciprocal cross. Segregation ratio of tall plant and short plant in F2 and BC1 is 3:1 and 1:1 respectively. Therefore, there no cytoplasm effect on dwarf character of mutant, it belong to nuclearinheritance and dwarf character is controlled by a recessive gene.3.hormone sensitive test with dwarf mutant and three lines of wild type have showed that plant height have no significant difference between mutant and wild type by spraying with GA3 after 30 days, but plant heigth of mutant can not restore to same leval with wild type by spraying with IAA. Result shows that the mutant is gibberellin sensitive and the dwarf is due to the variation of enzyme which involved in early steps of gibberellin biosynthetic pathway. Auxin also has certain recovery effect on plant height of dwarf mutant, but it is not the main reason to dwarf.4.the third internode in base of mutant and wild type was used to make conventional paraffin sections, the comparative result of cytology shows that cauline bundle in transverse section of mutant plant stalk is more obviously, but the number and cross-sectional area of cell is roughly similar with wild type. In longitudinal section, the cell length of mutant plant stalk is significantly shorter than the length in wild type. These results suggest that internodes cell growth inhibition of mutant is the primary reason cause dwarfing of plant height.