| Tobacco (Nicotiana tabacum) is an important economic crop in the world. The genusNicotiana comprises66species, while Nicotiana tabacum L. is the only tetraploid (2n=48)in Tabacum subgenus, which is a cultivar for commercial production. Study shows that theancestor of Nicotiana tabacum L.(2n=24II SSTT) may be chromosome doubling fromN.sylvestris (2n=12II SS) crossing with N.tomentosiformis (2n=12II TT) or N.otophora(2n=12II TT). The genetic map of tobacco (Nicotiana tabacum L.) is an important genetictool to study tobacco genome,such as gene mapping, gene clone, comparative genomics,marker assisted breeding and function research. However, only few tobacco geneticlinkage maps were reported, which were mainly focused on cultivated varieties, what’s theworse, the coverage and the density of these maps were too low to application. A F2geneticmapping population was obtained by the cross between N.otophora and N.tomentosiformiswhich are taxonomically belong to the same section Tomentosae. To the best of ourknowledge, it is the first genetic linkage map of Tomentosae section all over the worldbased on SSR markers. The major results were as follows:(1) A total of213F2plants, derived from a single plant (F1) from the cross betweenN.otophora and N.tomentosiformis, were used as the mapping population, and F1plant wasself-fertilized.(2)1,568SSR primer pairs which showed clear, stable polymorphism in femaleparent N.otophora, male parent N.tomentosiformis and Flfrom a total of10,005tobaccoSSR primer pairs by6%non-denatured polyacrylamide gel electrophoresis.(3) Totally627ideal SSR primer pairs were generated from700polymorphic primer pairs selected randomly from the1,568polymorphic primer pairs in PCR amplification ofthe F2population, which finally produced661polymorphic markers (loci), and some ofwhich produced two or more markers (loci). Chi-square test was used to evaluate661SSRmarkers, whereas336(50.83%) showed significantly deviation(P=0.01). Of them,130(19.67%) markers deviated toward N.otophora and88(13.31%) markers distorted toN.tomentosiformis, but118(17.85%) markers distorted to heterozygote (F1).(4) After elimination of the feeble data, a genetic linkage map of tobacco consisted of609SSR markers (loci) was constructed by using JionMap version4.0.The map covered12linkage groups, spanned a total length of1417.20cM with average distance of2.33cM.The number of makers in each linkage group was ranged from39to76, the length of eachlinkage group was varied from82.76to164.24cM and the average length between adjacentmarkers was1.09~3.37cM. All the SSR markers distributed evenly among the linkagegroups without large gap (Gap>30.0cM). It is the fist relatively saturated genetic map ofTomentosae section based on SSR markers at the home and abroad.(5) The genetic linkage map comprised325(53.37%,325/609) distorted markers,which mainly clustered on six linkage groups. Of them,47markers on LG1were distortedto F1;24and22markers of LG2were distorted to female parent N.otophora and F1,respectively;36and48markers belonging to LG4and LG10, respectively, were onlydistorted to female parent N.otophora;20and14markers of LG5distorted toward maleparent N.tomentosiformis and F1, respectively;37markers of LG11were distorted to maleparent N.tomentosiformis. Five segregation distortion regions (SDR) were found on thewhole genome, which were located on LG1(SDR1:13.979cM~26.931cM)、LG4(SDR2:51.473cM~78.597cM)、LG5(SDR3:34.908cM~52.822cM)、LG10(SDR4:90.936cM~104.283cM) and LG11(SDR5:55.331cM~72.216cM), respectively. |
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