Genetic Map Construction From Interspecific Hybridation BC₁ Population?Gossypium Hirsutum L.×Gossypium Tomentosum L.?

Cotton is the vital important natural fiber crop,as well as a source crop of plant oil and plant protein.At present,there are 52 species of cotton in the world,of which 4 are cultivated and 48 are wild.The cultivated area of upland cotton is the largest among the cultivated species.The cotton yield of upland cotton is more than 95%of total production in the world.The genetic basis of the cultivar in Gossypium hirsutum is relatively narrow,and it is necessary to expand its genetic resources in order to improve the characteristics of Gossypium hirsutum.Wild cotton has been went through natural selection and bred under conditions of salinity,drought,barrenness,diseases and insects in the long time,and so it has naturally formed a genetic advantage in these aspects and obtained a rich genetic basis.Gossypium tomentosum is a species of tetraploid wild cotton.It was first discovered in the Hawaiian of the United States.It is characterized by trichomes,no nectaries,drought resistance,salt and alkali resistance,pest resistance,and high fiber strength.Gossypium tomentosum can be crossed with Gossypium hirsutum to obtain heritable offspring,so it can be used as a material to enrich and improve the genetic traits of upland cotton.In this study,the BC₁ population was derived from the parents of Gossypium hirsutum CCRI35 and Gossypium tomentosum P0601211.The results of the study are as follows:1.Primer polymorphismIn this experiment,4536 pairs of SSR primers were used to screen the polymorphism of their parents,CCRI35 and P0601211.A total of 968 polymorphic primers were obtained with a polymorphism ratio of 21.34%.2.Genotyping BC₁ populationUse CCRI35?P0601211 as parents was crossed to obtain the F₁ generation.F₁ was then backcrossed with CCRI35 to obtain the BC₁ population.From the BC₁population,92 individual plants were randomly selected and the polymorphic primers of 968 pairs were used to screen polymorphic loci in the 92 individuals.A total of 1023markers were obtained,of which 55 primers were double-site marker primes.According to the?2 testing,there were 119 marker loci deviating from the Mendelian genetic segregation ratio,and the ratio of partial segregation reached 11.63%.3.Construction of genetic mapThe genetic linkage analysis of the above-mentioned 1023 polymorphic marker loci was performed using JoinMap to construct interspecific genetic linkage maps of upland cotton and Gossypium tomentosum.The genetic map contained 28 linkage groups and 1021 marker loci covering a length of 4110.7 cM.The average distance between markers is 4.0 cM.Among them,the A genome contains 521 markers,covers a length of 2079.2 cM,and the average distance between markers is 4.0 cM.D genome contains 500 markers,covering a length of 2031.5 cM,and the average distance between markers is 4.1 cM.4.Collinearity Analysis between genetic map and physical mapThe interspecific genetic linkage maps in this study were collinearized with the physical maps of Gossypium hirsutum and Gossypium raimondii,respectively.The genomic sequences showing most of the marker sites and physical maps are well-colinear.Among the 1021 marker loci on 26 chromosomes,880 marker loci found corresponding positions in the upland cotton genome,covering 95.4%of the upland cotton genome.In the A subgenome,2079.2 cM corresponded to 1.29 GB and the coverage span was 96.0%.In the D subgenome,2031.5 cM corresponds to 783 MB with a span of 94.4%.