| Cotton is not only the most important natural fiber crop in the world, but also an important source of protein and oil. Cotton plays a very important role in our national economy. Due to the existence of cotton glands in cotton, cotton seeds and other organs contain toxic gossypol derive from cotton glands. Cotton seed with toxic gossypol could not be regarded as a kind of food for human and animals because of its toxic, therefore, it becomes vital important to conduct the research of gland in Gossypium hirsutum. From the middle of the last century, breeders began to focus on improving the low gossypol cotton. In order to get excellent varieties can not only ensure the provision of cotton fiber, and can use the protein and fat of cotton.The genus Gossypium comprises of approximate 7 tetraploid species and 45 diploid, including 4 cultivated species, G. hirsutum L., G. barbadense L., G. arboreum L. and G. herbaceum L.. Of the cultivated species, upland cotton(G. hirsutum L.)supplies over 95% cotton fiber production of the world.In the present study, a recombinant inbred line(RIL) population derived from the cross between two upland cotton cultivars, Yumian 1 with toxic gossypol and M11 without toxic gossypol, was used to construct a genetic map and locate the glandless gene in G. hirsutum L.. 1. Screening of polymorphic primersA total of 11449 SSR primer pairs were used to screen the polymorphic primers between mapping parents Yumian1 and M11, and 557 polymorphic primer pairs were obtained, accounting for 4.86% of the total primer pairs. However, the polymorphic proportion is different among different primers. The highest percentage of polymorphic primer is BNL(10.64%), the lowest polymorphism of primer is C2, which is only 2.56%. 2. Genotyping of RIL populationA total of 557 polymorphic primer pairs were used to genotype the 180 individuals of F2:6 RIL population(Yumian1×M11), and 571 loci were obtained. The 571 loci were tested by Chi-square, the result showed that 104 loci distorted from Mendelian segregation ratio 1:1(P﹤0.05), accounting for 18.2% of the total loci. 3. Construction of genetic linkage mapThe genetic linkage analysis was conducted on 571 loci with mapping software Joinmap4.0, and 560 loci are mapped on 26 chromosomes. The genetic linkage map covered 2153.9cM with an average of 4.10 cM between two markers. At-genome contained 221 loci, and spanned 922.1cM with an average distance of 4.17 cM between two markers. Dt-genome contained 304 loci, and spanned1231.8cM with an average distance of 4.05 cM between two markers. 4. Genetic analysis of glandless traitThe F2:6 RIL population has 142 plants with gland, 32 plants with glandless. Chi-square analysis showed that the segregation ratio was 3:1, Which further confirmed that glandless character was controlled by two recessive genes. 5. Localization for glandless geneThe genetic map was used to analyze the localization of the glandless traits. Two genes, gl12 and gl26,were detected on Chr.12 and Chr.26, and explained phenotypic variations were 58.6% and 22.8%, respectively. The alleles(gl12, gl26) of M11 reduced the values of the gland phenotype. The nearest markers were DC40117 and C2-0024. According to the previous study,it is confirmed that gl12 is gl2, and gl26 is gl3. |
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