Fine Mapping Of The Dominant Glandless Gene Gl₂～e In Sea Island Cotton (Gossypium Barbadense L.)

Cotton is not only the leading natural fiber resource, but also an excellent resource of oil and protein that are stored in its seeds. Dark-colored gland containing gossypol is an important agronomic trait in cotton. Cotton plants with toxic gossypol could protect them from both insects and pathogens. However, cotton seed with toxic gossypol could not be regarded as a kind of food for human and monogastric animals due to its toxic. In China, cotton was planted more than 5 million hectare every year and could product 6 million ton cottonseeds which contain about 1 million ton oils and 1.5 million ton proteins. Therefore, a large number of plant oil and protein were wasted rather than applied efficiently. Owing to these defects above mentioned, breeders have been effort and attempted to cultivate a novel cotton line with high content gossypol in plant vegetative tissue instead of existing in cotton seed or very low content gossypol.Gl₂^e is a gene controlling glandless traits in cotton plant and seed, which is an important gene resource for gossypol-free cottonseed breeding. Classical genetic analysis suggested that Gl₂ was located in the chromosome 12, therefore Gl₂^e as its multiple alleles also located in the Chr 12 in cotton. In this present study, we constructed a F₂ segregating population containing 1599 individuals using upland cotton genetic standard line TM-1 and sea island glandless mutant line Hai-1 as parents. Thereafter, Gl₂^e gene was finely mapped via this population. The objectives of this study was that providing ground foundation for mapped-based gene cloning and further cultivating cotton variety with high content gossypol in plant vegetative tissue instead of existing in cotton seed or very low content gossypol by gene engineering. The mainly results of this work are as follows:1. To determine the genetic characterize of Gl₂^e gene, we investigated the different positions and stages of 1599 F₂ segregating plants. The results showed that 441 plants had dark-colored glands; 427 glandless plants and 761 plants with low-glands respectively. The data byχ² were consistent with the separation ratio as 1: 2: 1 (χ²=4.028＜χ_0.05,2²=5.99), which further conformed that glandless character was controlled by a incomplete dominance gene, Gl₂^e.2. SSR markers every about 5cM were selected in the chromosome 12 of our lab genetic linkage map to screen the parent plants. The markers with the polymorphism were used to amplify the DNA of 210 F₂ segregating plants selected randomly and recorded the marker genotypes. After eliminating the segregation distortion markers byχ² test, other SSR markers were detected by linkage analysis. The results showed that Gl₂^e was located between CIR362 and NAU5079. Further analysis was performed using the markers between CIR362 and NAU5079. Ultimately, Gl₂^e was located between CIR362 and NAU2251b, NAU3860b, STV033 and the genetic distance was 11.03cM and 1.19cM respectively.3. According to the preliminary results above, the further screening of 1599 plants of the F₂ segregating population was carried out using the markers highly linkage with Gl₂^e. The results showed that NAU3778 and CIR362 were located on the same side of Gl₂^e with genetic distances of 11.25cM and 9.27cM respectively; NAU2251b (NAU3860b,STV033 with the same locus), NAU445 and CIR302 were located on the other side with genetic distances of 0.96cM, 5.29cM and 7.11cM respectively.4. New PCR markers were exploited according to the conservative regions of cDNA or DNA of some key genes in the gossypol biosynthesis pathway. The location results of these markers indicated that the genetic distance of fps1 gene relatively to BNL3836 and NAU3921 markers was 4.4cM and 2.2cM respectively, but far away with the Gl₂^e gene although fps1 gene was also located on the chromosome 12.