Phenotypic Traits Identification And Fine Mapping Of Dwarf Mutant Gene In Cotton

In the past four years,the total cotton yield of Xinjiang has been maintained at more than 5 million tons,accounting for more than 80 percent of the country’s total output.It can be seen that cotton industry is playing an irreplaceable role in Xinjiang’s economic development.In cotton production,the plant height is an important agronomic traits,people often through chemical regulation and artificial multi-topping to shape plant type,in order to improve the yield,but it virtually raised planting cost and the intensity of labor,and to control the time and dosage of grasp is not accurate,therefore,mining new dwarfism gene and then breeding dwarf varieties is a new direction.In the study,dwarf mutant AZ,Xinhai 18 and Xinhai43 were used as materials,which are nulliplex-branch.And the phenotype of dwarf mutant was described and analyzed in detail,A hybrid F₂population was configured with AZ mutant and Xinhai 18 as parents,The DNA mixing pools were constructed from 30 crinkled and extremely dwarf plants and 30 plants with normal leaf and plant height,and BSA-seq sequencing was performed on the two mixing pools and their parents.In order to accurately map this locus,two isolated large populations of F₂（AZ mutant×Xinhai 18and AZ mutant×9078N）were established,According to the SNP/Indel information in the preliminary mapping result,A total of 9604 F₂plants from two F₂population were used to genetic and maker analysis.In order to further narrow the range,combining the genotyping to fine mapping gene localization,and determine the dwarf mutant gene on cotton genome,Providing certain basis for gene cloning and breeding for the future.The main results were as follows:1.The phenotypic characters of different island cotton materials were described,it can be concluded that:（1）The hypocotyl and root length of AZ mutant were shorter than Xinhai 18 under light condition.Under dark condition,the hypocotyl length of AZ mutant was longer than Xinhai 18 in the first 6 days,and there was a significant difference between them on the fourth day.Their roots are much longer than their hypocotyls in both light and darkness.（2）Plant height and daily growth of main stem were analyzed,Compared with the control,the plant height and daily growth of dwarf mutant were significantly different in the early bud stage.The maximum daily growth of main stem of AZ mutant was 0.69 cm/d from June 2 to June 7.Xinhai 18 and Xinhai 43both reached 1.61 cm/d and 1.36 cm/d from June 22 to June 27,respectively.The final plant height of the dwarf mutant was less than half of the control,and the difference between the dwarf mutant and the control was extremely significant.（3）According to the analysis of internode number and internode length,the internode length of main stem of Xinhai 18 and Xinhai 43 was longer than AZ mutant from the second node,and they were significantly different from AZ mutant.The internode length of the main stem of the AZ mutant reached the maximum 2.98 cm at the sixth node,Xinhai 18 and Xinhai 43 reached the maximum 6.41 cm and 6.54 cm at the eighth node,respectively,which were significantly different from AZ mutant.The number of internodes of dwarf mutant was always lower than that of controls.（4）The comparison of the boll traits of three materials,the dwarf mutant AZ had the lowest boll length and boll width,xinhai 43 was the highest,then Xinhai 18.Among the three,AZ mutant had the longest bell hilt length,the largest bell hilt thickness was Xinhai 43.xinhai 18 and Xinhai 43 had 18.9 and 16.9 bolls per plant.AZ mutant had 6.1 bolls,the number of bolls per plant of dwarf mutant was significantly lower than that of control,and the bolls of dwarf mutant were concentrated in true leaf 4-9.（5）The comparison of growth period and other traits among different materials showed that AZ mutant had the shortest growth period,which was early maturing,and had the smallest stem,which was significantly different from the control.AZ was the highest at the first node of fruit branch,and the difference was significant.The hundred seed weight,single boll weight and lint percentage of AZ mutants were the lowest.2.Genetic analysis and gene mapping of dwarfing mutants were performed（1）In the F₂population of AZ×Xinhai 18,only segregation of glossy leaf fit a single-recessive-locus mode.Based on the single-recessive-locus mode,the number of crinkled leaf mutants exceeded expectation,but for dwarf the number was much less.In a population of 9078N×NAM,only segregation of dwarf fit a single-recessive-locus mode.Again,the number of crinkled leaf plants exceeded expectation,but for glossy leaf the number was much less.（2）Preliminary positioning was carried out by BSA-Seq method,and the research results showed that:Only a significant interval was found at the end of chromosome D03,with a peak of（44.2-51 Mb）（using the 2019 HAU version of 3-79 as the reference genome）,and the peak of SNP index in AZ pool was found in the interval of 49-49.5 Mb on chromosome D03.（3）In order to further narrow the range,according to the result of preliminary location,the F₂individual plant in the population was labeled.For the population of 9078N×AZ,351 AZ and 1365 WT plants were detected,and the AZ locus was finally located in the range of 49.12-50.16 Mb.However,no additional polymorphism was found between the AZ mutant and 9078N.In the F₂population of Xinhai18×AZ mutant from Xinhai,840 AZ and 3924 WT plants were identified,which were further narrowed down to the interval of 180 kb.There were 84 recombinant plants between the two closest markers.In this interval,four SNPs were used to detect these recombinant plants,and F_2:3families were used.The dwarfing gene was pinpointed in the 35.8 kb region of chromosome D03.