Study On Construction Of AFLP Molecular Genetic Maps And Chromosome Redouble In Sorghum-sudangrass

Sorghum-Sudangrass appears to begreat forage which resulted from hybriding Sorghum bicolor（L.） Moench with Sorghum Sudanese（Piper） Stapf. Sorghum-Sudangras synthesizes parents! eminent traits, which not only includes sorghum characteristics such as cold and drought resistance,lodging resistance and high yield, but also includes sudangrass characteristics like high tillering ability, high nutrition, low cyanide, good palatability and strong disease resistance. However, the hybriding forage generating high content of CN in the stems and leaves, which could poison the livestock. To further explore the potential of security and yield of Sorghum-Sudangras, we analyzed Sorghum-Sudangras F₂ segregation population and F₁ hybrid seed in this study. High-density genetic mapping, the quantitative trait loci（QTL） and double chromosome of hydrocyanic acid agronomic characters were conducted, in order to develop molecular marker to assist breeding of agronomic character such as lowcyanide and create new allotetraploid Sorghum-Sudangrass. The main results were as follows:1. We established the Sorghum-Sudangras F₂ segregation population which could be used for genetic map construction and essential agronomic character QTL localizaiong by crossing Sorghum-Sudangras and Red hull Sudangrass. 253 suitable primers used for AFLP were designed and 825 polymorphic loci were detected by PCR amplification of 240 seedling in Sorghum-Sudangras F₂ segregation population, we detect 127 loci were deviated from 3:1 Mendelian segregation ratio, which accounted for 15.4% of total.3. We constructed a frame map with 10 linkage polulation. 284 genes were markered in the map among 825 AFLP markers, the number of linkage marker in 10 linkage polulation was account for 34.4%, and segregation ratio was account for 13.9% in total.4. The length of genetic linkage population frame map was 940.3cM in 10 genetic linkage polulation, the average length between two markers was 3.52 cM, which belongs to the high density genetic map. The longest linkage polulation LG and the smallest LG! was 139.0cM and 38.5cM, respectively. The average interval of LG "and LG# was 1.46 cM and 7.26 cM, respectively, Which was the highest marker density and the lowest.5. The mesured values of 10 agronomic characters including the content of hydrocyanic acid, plant length and tillering number et al. were continuous distributed with vertical bell curve. These values were appeared in normal distribution by Kolmogorov-Smirnova test and Shapiro-Wilk test, each 10 agronomic characters could be used for QTL localization analysis.6. Correlative analysis showed that 10 agronomic characters including the content of hydrocyanic acid, plant length et al. were postive or negative correlative relationships. The positive correlation have 4 groups in 45 groups, and the negative correlation have 3 groups, the remarkablely positive correlation have 3 groups, the remarkablely negative correlation have 1 group.7. Taking LOD>2.5 for critical value to analyze the localization of activity of 10 agronomic characters by using MapQTL 4.0 software and MQM plotting. The results indicated that there were 24 QTL controlled 10 agronomic characters. The 24 QTL were distributed on the 9 linkage groups outside the linkage group LG#, and each linkage group contains 2.4 QTL on average; Their distribution was uneven. The most distribution was on linkage group LG I with 5 QTL. The least distribution was on LG !with 1 QTL. There was each one QTL controlled leaf number, tiller number and plant dry weight, 2 QTL controlled hydrocyanic acid content, 3 QTL controlled stem diameter, leaf length, leaf width, panicle length and stem-leaf ratio and 4 QTL controlled plant height.8. The results of correlation analysis showed that: there was a positive correlation between leaf length and leaf width, controlling by locus ll3 and lw3,which were both detected on linkage group lgs, aparted 0.1cM from each other. There was a positive correlation between hydrocyanic acid content and gain tillers, panicle length. hydrocyanic acid content and gain tiller number traits were controlled by locus cn1 and tn1 separately, which were both detected on linkage group LGV, aparted 0.18 cM from each other. QTLs cotrolling hydrocyanic acid content and panicle length were not on same linkage group. There was a positive correlation between leaf number and plant height, QTL ln1 controlling leaf number located between ph1 and ph2, setting 35.6 cM and 6.2 cM apart from both ends.9. QTL associated with the control of Panicle length, pl1, pl2, pl3 were located on linkage group LG$, in the interval 6.7cM long between markers P29M93-690 and P28M50-250, the distance was short, form gene clusters; pl1 was less efficient loci, pl2, pl3 were synergistic gene locus, the sum of the three was 4.68, promote the growth of ears when joint action.10. Sorghum-Sudangrass hybrid F₁ was used as materials to research mutagenic effect of colchicines treatment.We have found that the best colchicine treatment combinations for Sorghum redhull sudangrass hybrid F₁ and Sorghum redhull sudangrass hybrid F₁ were 0.10% D24 h and 0.05%D36h, and the mutation rate of F₁ was the best under the two treatment combination.