| Cotton is the main economic crop, occupy important position in the world and our national economy. Cotton verticillium wilt is one of the main diseases caused serious damage to many countries in the world, seriously affect the yield and fiber quality of cotton, has became a major obstacle for cotton production. Genetic analysis showed that the resistance of cotton to verticillium wilt belongs to the quantitative genetic model under the effect of multiple strains, is controlled by polygene. The genetic research involves in many aspects, such as host parents, pathogen, environment, strain, disease grade classification standard and evaluation method, therefore, it need to synthetically consider more than one method, material, environment to create new materials which are resistant to verticillium wilt. Using molecular marker technology to pyramid assistedly multi-target-trait-genes, can accelerate the genetic improvement process, and greatly improve the efficiency of breeding, have made success in many crop breeding application.5026 and 60182 are two upland cotton accessions which are tolerance to verticillium wilt, come from our laboratory with years of breeding efforts, previously were characterized by method of QTL analysis, then we done the molecular marker assistedlypyramiding research to target resistance QTL in their F2 subsequent high generation group with the method of self-cross breeding, then we got 155 different combination of QTL from F5 group. Based on this, we surveyed the yield and quality traits of 155 combinations for two years, and finished the identification of the resistance to verticillium wilt. Then we selected a batch of materials whose yield, quality, resistance traits were significantly better than that of the donor parent materials.The main results were as follows:1. Based on the results of QTL mappingrelated to verticillium wilt resistance in 5026 and 60182 in the early stage of our laboratory, we screened verticillium wilt resistance QTL from parents using SSR markerswith parents resistance loci. We got 155 different combinations of QTL pure materials to F5generation. When planting the 155 combinations in growth chamber, then, we used the high virulent and defoliating strain V991 to test their resistance to verticillium wilt, investigated the relative disease of cotton leaves and Vascular bundle.The relative disease index of cotton leaves of parents 5026 and 60182 respectively were 25.96,29.67, Vascular bundle respectively were 28.48,22.96, two methods of survey results reached the level of tolerance, and were consistent with the early appraisal results of verticillium wilt resistance of our laboratory. The relative disease index of cotton leaves of of H7124 was 21.96, Vascular bundle was 18.39, closeto the level of resistance, was superior to the parents of 5026 and 60182; the relative disease index of TM-1 as the upland cotton genetic standard and disease sensitive control is standarded as 50.00.The relative resistance index range of 155 combinations was 8.58-65.82, the mean was 29.96. There were 70 materials better than the high verticillium wilt resistant parents, the relative resistance index range was 8.58-25.19; V1 achieved high resistance, relative resistance index was 8.58; there were 41 materials achieve resistance level, relative resistance index range was 11.26-19.83; 67 materials achieved tolerance level, relative resistance index range was 20.23-34.69; and 49 materials achieved sensitive, relative resistance index range was 35.08-65.82.2.When analyzing the 155 materials, we found that it was not that the more QTL pyramided, the better resistance to verticillium wilt, then we finished the confirmation to each QTL for the excellent allelic variation loci, found 4 excellent allelic variation loci: D6-NAU2754-2, All-NAU905-2,A11-NAU4565-1, D7-NAU3053-1, the effect values respectively were:-5.92、-4.69、-3.76、-2.13. And for the materials, themore excellent allelic variation loci material pyramided, the better resistance to disease. The relative resistance index average of the materials which aggregated 4,3,2,1,0 excellent allelic variation loci respectively were 19.82,23.99,28.05,38.37, and 40.22.3. We have found two significant QTL through screening and analyzing QTL associated with the cotton fiber quality:one has been located on D3 chromosome, connected with primer NAU242,significantlyaffect the cotton fiber length and fiberuniformity ratio; another has also been located on D3 chromosome,connected with primer NAU1862,significantly affectthe cotton fiber strength and fiberelongation.Further,106 materials tolerant/resistant diseasewere further evaluated to yield and quality traits. Six materials achieve tolerance, with excellent yield and quality traits, their relative resistance index range from19.11 to 24.57, the yield and quality could reach:LP, 0.35-0.39; LI,6.57-7.48g; BW,5.08-6.11g; FL,30.08-32.85mm; FS,31.60-34.18cN/tex; FMIC,3.81-4.84. There were also some materials achieveresistance, but yield or quality traits was not very good, for example:there were 14 materials whichyield was general, but quality was good, relative resistance index range was 8.58-19.11, FL,30.12-32.92mm;FS, 32.05-36.73cN/tex;FMIC,3.54-4.99. There were 3 materials which qualitywas general, but yield was high, relative resistance index range was 16.38-17.34,LP,0.36-0.39,LI, 6.38-7.58g,BW,5.36-6.01g; And there were 12 materialswhich yield and quality traits were general, but achieved resistance, relative resistance index range was11.91-19.66, could be used as the donors of disease resistance breeding.4. Integrated resistance traits, yield and fiber quality traits, we got 52 excellent materials in comprehensive traits, and the parameters of the various traits more than the average: relative resistance index range was 8.58-29.64;LP,0.33-0.40; LI,4.94-7.94g; BW,4.32-6.80g;FL,27.66-32.96mm;FS,29.55-36.33,cN/tex;FMIC,3.43-3.43;FUR,84.70-88. 15%;and Fe,5.25-6.80%. |
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