Update Of Genetic Map Of G. Hirsutum L × G. Darwinii L And Analysis Of Chromosome Structural Variation

Cotton is one of the leading fiber crops in the world.It is not only a source of natural fiber in spinning industry,but also a significant resource for high-quality plant protein and oil.Upland cotton,charactering with extensive adaptability and high production,is widely planted all over the world.It produced approximately 95%of the world's cotton production.However,the quality of upland cotton could not meet the demand of spinning industry.Therefore,it is necessary to improve the fiber quality of upland cotton.Marker-assisted selection?MAS?is one of the most effective methods to improve the fiber quality of upland cotton.Compared with upland cotton,the wild species have many good characters,such as drought resistance,fine fiber and verticillium wilt resistance,which could be used to improve the quality of upland cotton.Genetic maps constructed between Upland cotton and G.darwinii would laid the foundation for the fine mapping of QTLs and candidate genes identifying for cotton traits such as fiber quality.In the present study,SSR markers were used to update the genetic map of?CCRI35×G.darwinii?BC₁ population.Subsequently,the chromosome structure variation of the cotton genome was analyzed by comparing this map with the genetic map of G.barbadense,the physical map of the G.hirsutum and G.raimondii.The results shows as follow:1.Polymorphism of primersIn the present study,a total of 14957 SSR primer pairs were utilized to screen the polymorphism between CCRI35 and G.darwinii.And 1154 polymorphic SSR primers were obtained with a polymorphism ratio of 7.78%.Among these primers,the highest polymorism ratio of polymorphic primer was NAU,with a polymorphism ratio of17.75%.2.Population genotyping and segregation distortion analysisA total of 1303 loci were obtained in this study.Combined with 996 loci of previous study,2309 loci were used for segregation distortion analysis.The result revealed that 178 loci deviated from the mendelian segregation ratio?b:h=1:1?,accounts for 7.71%of all loci.Among them,65 loci distributed on A subgenome and113 on D subgenome.3.Update of the genetic linkage mapIn this study,a genetic linkage map including 2309 marker loci was constructed.The total length of this map was 4002.16 cM,with an average distance of 1.73 cM between two adjacent markers,covering 98.47%of the upland cotton genome.Among these loci,1006 loci located on the A subgenome.The spanning length of A subgenome is 2094.06 cM,and the mean distance between the two adjacent markers is 2.08 cM.The D subgenome has 1303 loci,covering a length of 1908.10 cM,and with a mean distance of 1.46 cM.4.Collinear analysis between genetic maps and physical mapsPhysical maps were constructed by blasting the sequence of polymorphic loci in the genome of G.hirsutum,G.raimondii.A good collinearity was showed between the genetic map and physical maps.However,compared with the physical map of G.hirsutum,five inversion were identified on Chr07,Chr08,Chr15,Chr22,Chr25.Compared with the physical map of Gossypium raimondii,two major reciprocal translocations on A02/A03,A04/A05,eight simple translocation on Chr02,Chr04,Chr11,Chr13,Chr18,Chr21,Chr22 and eight inverted position on Chr08,Chr11,Chr12,Chr15,Chr17,Chr18 were detected.5.Relationship between genetic mapsThe genetic map constructed in this study was compared with the genetic map of Gossypium hirsutum×Gossypium barbadense by using their common markers.Most markers showed good collinearity between two genetic maps.However,four inversions were found on Chr01,Chr03,Chr07 and Chr08.