Genetic Analysis And Fine Mapping Of Watermelon Dwarfing Gene Cldw

Dwarfism is one of the most important commercial traits in watermelon?Citrullus lanatus.?varieties.Dwarf types plants can promote concentrated fruits in high density crops due to maximum intake of light resources for photosynthesis which result the greater yield per unit area,and also improve the economic benefits of farmers.To date,dwarf watermelon has fewer varieties,and excavation and utilization of dwarf materials are of great significan t trait for watermelon breeding.In this study,a six generations?P₁,P₂,F₁,BC₁P₁,BC₁P₂,and F₂?population was constructed by crossing of P₁?long vine type plant,W1-1,female parent line?and P₂?dwarf type plant,‘812',male parent line?,to verify the inherited genetics of dwarfing traits.Three plant hormones?GA₃,IAA,and 6-BA?were used for hormone sensitivity analysis of dwarf‘812'.At the same time,the paraffin sections of the internode of the two parent lines were observed,and the contents of endogenous hormones in internode of tw o parent lines were determined.Based on the re-sequencing data of the two parent lines,the chromosome regions of watermelon dwarf gene were obtained by bulked segregant analysis?BSA?,and further fine mapping for watermelon dwarf genes was also performed.Analysis of expression level of candidate gene and cloning of related coding sequence?with intron?was different for two parent lines.The main findings of study are as follows:?1?The ratio of segregation for six generations population indicated that the watermelon dwarfism trait is inherited and controlled by a single recessive gene.?2?Three plant hormones?GA₃,IAA,and 6-BA?were used for hormone sensitivity analysis and the results showed that the dwarf material‘812'is defective mutant for GA synthesis.?3?The observation results of paraffin sections showed that the dwarf material‘812'treated with exogenous GA₃ had significantly longer internode cells as compared to the water treated.The internode cell length of dwarf material‘812'treated with exogenous GA₃was similar to the internode cells of‘W1-1'.?4?The results of measurement of endogenous GA₃ content at internode of the two parent lines also showed that bioactive GA₃ was existed in‘W1-1'parent,but not exhibited in‘812'parent.?5?Fine mapping of the watermelon dwarf gene by BSA revealed Cla015407 gene located on watermelon chromosome 9 which encodes a GA₃-?hydroxylase protein.The real-time PCR results showed that the expression level of Cla015407 in‘W1-1'was significantly higher than that in‘812'at the internode sites of reproductive growth period.Meanwhile,the cloning of Cla015407 coding sequence?with intron?from two parent lines exposed the splice site mutation of Cla015407 in‘812'parent.