Assessing The Genetic Diversity Of Germplasm In Tobacco

The genetic diversity among 119 tobacco varieties/lines including flue-cured tobacco, sun/air cured tobacco, burly tobacco, oriental tobacco, rustica tobacco and wild tobacco was assessed by ISSR and IRAP markers. 14 agronomic traits in 59 flue-cured tobacco varieties/lines were analyzed using correlative analysis, principal components analysis (PCA) and cluster analysis. Main results were as follows:The tobacco varieties/lines were amplified by 100 JSSR primers and 10 IRAP primers. In the 119 tobacco varieties/lines, 1206 bands amplified by 34 primers were polymorphic, and the average for per-primer was 35.47 bands, 1800~2600bp for each fragment. The ratio of polymorphic bands (PPB) could be 100%. 651 bands were identified using 24 ISSR primers (24%) and 5 IRAP primers (50%) among the 59 flue-cured tobacco varieties, of which 467 bands were polymorphic, and the ratio of polymorphic bands (PPB) was 71.71%. ISSR and IRAP markers were, hence, suitable for the study of germplasm.Ratio of polymorphic primers and bands of IRAP markers was more than ISSR markers, and the stability and definition of bands amplified by IRAP primers were better than those by ISSR primers. Therefore, the IRAP marker was more suitable for the assessent of the genetic diversity than ISSR markers. The polyacrylamide gel electrophoresis and silver staining can enhance the veracity of assessing genetic diversity.119 tobacco varieties/lines were analyzed by clustering method. There were considerable genetic differences among different types of tobacco germplasm, which the largest distance was between rustica and wild tobacco (GD>0.404) and others were smaller (GD<0.300). The results showed that there was low genetic diversity among the flue-cured tobacco, sun/air tobacco, hurley tobacco, rustica tobacco and oriental tobacco. The varieties/lines from the same type could almost be clustered into the same group or sub-group. There was little genetic differentiation among different types of tobacco (Fst = 0.3243). The value of average heterozygosity (He = 0.2185) and percentage polymorphic loci (P = 25.43%) in the wild tobacco were highest, and the values for the oriental tobacco were lowest (He = 0.0837 and P = 25.43%). The GI values were from 0.9773 to 0.9895 among flue-cured tobacco, sun/air tobacco, burly tobacco and oriental tobacco, which showed low genetic diversity. And the GI values (0.6485-0.7929) suggested that there were high genetic differentiation between rustic tobacco or wild tobacco and others.