Molecular Marker-assisted Selection For Resistance To Verticillium Wilt In Cotton Breeding

This study used G. barbadense, G. hirsutum, sea-land hybrid and upland hybrid offspring as experimental material, including M4,10Q, M37 and M44 strains, with 58 varying degree of resistance to Verticillium wilt. The cottons were planted in artificial disease nursery and inoculated Verticillium wilt fungus in seedling period. Also, the study recorded degrees of bacteria infection and disease index in different growth stage. Then measured agronomic characters and yield traits of field germplasm and did correlation analysis on the two index and the resistance of each type cotton. Used 11 SSR polymorphisms primers having chain relationship with resistance to Verticillium wilt gene to do SSR-PCR amplification analysis on 20 G. barbadense and G. hirsutum with different disease resistance and disease infection cultivars. Calculated the consistent degree of the disease-resistant cultivars'amplified bands and the resistance properties. The results were as follows:1.58 cotton cultivars (strains) were tested among which relative disease index of G. barbadense refers to between 11.59?44.10, average of 18.54, and seven of the G. barbadense resistant to diseases, account for 38.89% of the determination of cotton; relative disease index of G. hirsutum refers to between 15.21?50.00, average of 33.32. Analysis results showed that G. barbadense's disease resistance higher than G. hirsutum's. In population of land-sea hybrid descendants, the M4 strain relative disease index refers to the mean value of 22.31, no high disease-resistance strain; the 10Q relative disease index refers to the mean value of 20.51, including strain have not infected, which came to the conclusion that 10Q groups had slightly stronger Verticillium wilt resistance than the M4 groups. M37 strain relative disease index refers to between 0-41.50, average of 24.49 and its high disease-resistance strain accounts for 15.00% of the tested samples; land-land hybrids'M44 had more infected strains and relative disease refers to between 15.52?54.60, average of 39.23, which lead to the conclusion that M37 groups had slightly stronger Verticillium wilt resistance than the M44 groups.2. G hirsutum's relative disease index had negative correlation with number of per plant cotton boll and had significant negative correlation with plant height, and number of effective per pant cotton boll. G. barbadense's relative disease index had negative correlation with number of effective per pant cotton boll only, with others' agronomic characters was no correlation. M4 strain's relative disease index had negative correlation with plant height and had significant negative correlation with number of effective per pant cotton boll.10Q strain's relative disease index had significant negative correlation with number of effective per pant cotton boll. M37 strain's relative disease index had negative correlation with plant height, and number of per plant cotton boll. The findings were consistent with sea island cotton. M37 strain's relative disease index had negative correlation with plant height and had significant negative correlation with number of effective per pant cotton boll.3. G hirsutum's relative disease index had negative correlation with fibre weight per boll and had significant negative correlation with lint percentage. G. barbadense's relative disease index had no correlation with yield traits. M4 strain's yield traits had significant correlation with lint percentage.10Q groups' relative disease index had significant negative correlation with fibre weight per boll, and lint percentage. M37 groups' relative disease index had significant negative correlation with lint percentage. M44 groups' relative disease index had negative correlation with fibre weight per boll, and had significant negative correlation with lint percentage. The results showed that the degree of disease impact lint percentage, and fibre weight per boll significantly.4. Results screened out VM15, VM18, VM22, VM23, VM32 five pairs of primers could amplify differences polymorphic bands, these primers originated from mRNA sequence, Protein gene sequence and genomic sequence. Calculated the consistent degree of VM32, VM15, VM23 primers' amplified bands and the resistance properties, the result was 1.000, 0.857,0.857, average higher than 0.800. So, the six specific bands contained resistance genes.