Studies On Molecular Markers And QTLs Of Verticillium Wilt Resistance In Cotton

Cotton plays important role in our country and the world as one of the main cashcrops. Verticillum wilt is one of the most serious diseases in cotton, which influences theyield and quality of cotton severely. Since the 1990s, Verticillum wilt has been spreadingcontinuously. In our country it has became the chief obstacle, which effects high andstable yield of cotton seriously. So, it is called for the cancer of cotton. At present, thefundamental research for cotton Verticillum wilt'virulence differentiation, resistancemechanism, resistance inheritance and virulence mechanism is studied by scholars ofhome and abroad mostly, but this does not meet cotton production. Molecular biology isfor a good method for studying many crops traits, but it begins late in cotton.In the reseach, a G.. barbadense and G. hirsutum are crossed and produce a F₂population. The G. hirsutum parent is Handanl4, which is high yield but susceptible toVerticillum wilt. The G. barbadense parent is Hai7124, which is low yield, poor qualityand resistant to Verticillum wilt. Simple sequence repeat, a molecular marker technique, isapplied in our test, in which polymorphic primer is selected by parents genomes and F₂population is detected. Resistance identification is acted in field and seedling stage,combining with marker analysis, and then quantitative traits loci(QTLs) resistance toVerticillum wilt is located. The purpose is studying the resistance to Verticillum wilt of F₂population, finding QTLs to resistance, comparing field with seedling identification.Zhong G8 is constructed in winter, in 2003 and gained 184 F₂ individuals. In thisstudy, 296 pairs polymorphic primers are selected from 2865 primers, of which 163 pairsare identified in F₂ group and 193 polymorphic sites are got. Partial separation is analysedto polymorphic markers and 46 markers is significant partial separation, accoucting for23.8%, in which 4 markers are related to resistance. With Joinmap 3.0 software, 30linkage groups are constructed consisting of 142 sites and spanning 1169.6cM with anaverage distance of 8.24 cM. In single linkage group, 2 is the least number of marker and24 is most. According to public linkage map, 30 linkage groups is located in 21chromosome. With WinCart2.5 software, QTLs related to resistance have been found byCIM method, and phenotypic variance is from 4.97% to 22.30ï¼…. In July 3 lth and Aug31 th, there is a common QTL, in linkage group 02(chromosome10), and the closet markeris NAU1221d. QTL detection to rate of infected plants of three periods of field andseedling stage is carried and ten QTLs have been found. The phenotypic variance is from5.14% to 22.73%. Comparing resistance identification of field with seedling stage, we can see thatseedling stage is more susceptible than field experiment, and field result is more extensivethan seedling stage. The reasons are as fallows. Firstly, cotton root is badly hurt wheninoculated, so resistance mechanism is damaged seriously. Secondly, isolates is notequable in the field, while mensurable in the seedling stage. At last, in the greenhouse,there is single isolate and hardly any other disease. In the contrary, lots of isolates andother plant diseases and insect pests except Verticillum wilt may turn up in the field.In the study, F₂ population is perennial, so it is good material to deepen research. F_2:3family is applied to resistance identification, so the result is more reliable. Simplesequence repeat is used to find molecular markers related to Verticillum wilt, and it hasreached a basis to reseach Verticillum wilt for the future.