Fine Mapping And Functional Verification Of The Clbl Gene With Less Collateral Branches In Watermelon

Lateral branch are affected by multiple factors such as genetic factors,environment and plant hormones,excessive side branches will affect the nutrient distribution between plants,light harvesting,planting density,and ultimately adversely affect crop yield and quality.pruning branches and branches in watermelon cultivation management is a time-consuming and laborious task,and it is difficult to adapt to the needs of high-efficiency and light-simplified cultivation in agricultural production.watermelon with branchless can not only increase the planting density,but also greatly reduce the labor cost of pruning and branching.The analysis of the genetic basis and mechanism of the formation of branchless is the basis and prerequisite for the improvement of watermelon plant type,but so far the regulation network of watermelon formation with branchless and the molecular mechanism is unclear.We use the normal branching material WT20 and the branchless material WCZ as the research materials,separated groups by building six generations,clarified the genetic law of watermelon collateral traits,fine mapping and functional verification of the gene branchless(bl)that controls the development of watermelon Lateral branch,laid a solid foundation for further research on the molecular mechanism of collateral formation,regulatory network and breeding of branching varieties.The main findings are as follows:1.It is clear that the traits of watermelon with few lateral branches are controlled by a recessive single gene.By observing the different growth and development stages of the parents after planting,it is found that the plant height,number of internodes and number of side branches of WT20 material are significantly greater than WCZ in the two periods.Especially in terms of the number of lateral branches,the lateral branches of WT20 are distributed in each internode,while the lateral branches of WCZ are only distributed in the first 3～5 internodes.The phenotypic traits of 10 F1,130 BC1 and 1406 F2 populations were observed.The few lateral branches genes in watermelon are controlled by a recessive single gene,which is named Branchless(Clbl).2.Fine mapping to the Clbl gene that controls the lateral branches of watermelon.According to BSA-seq and SSR molecular marker polymorphism analysis,we finely mapped and cloned the candidate gene Cla018392 that controls the number of watermelon lateral branches.The sequence analysis of Cla018392 showed that there was a SNP(C to A)mutation in the WCZ(less branching)of its CDS region,which resulted in the mutation of alanine(GCA)in the fourth exon to glutamate(GAA).Based on this SNP,a dCAPS marker was developed,which was co-segregated with the phenotypes of recombinant single plants in F2 and 152 normal branch watermelon materials.Sequence alignment and phylogenetic tree showed that Cla018392 belongs to the TFL1 gene family member,and we named it ClTFL1.3.The results of in situ hybridization and RT-PCR showed that the expression of ClTFL1 in the growth point and axillary buds of WT20(normal branching)was higher than that of WCZ(branchless),and the results of subcellular localization showed that the ClTFL1 gene was localized in the nucleus and cell membrane on.4.Ectopic expression of watermelon cltfl1 gene in arabidopsis can increase the number of lateral branch and restore the phenotype of tfl mutant with reduced lateral branches.5.Using WT20(normal branching)as the recipient parent and WCZ(branchless)as the donor parent,a near-isogenic line of the CITFL1 gene in the background of WT20 was constructed using molecular marker-assisted selection.