Genetic diversity analysis and population structure can estimate genetic variation of diverse materials, and can be used in germplasm management and varietal protection. In this study, the genetic diversity and population structure for tobacco germplasm (78 cultivated tobacco accessions in China) were analyzed by using 28 SSR markers. A total of 127 alleles were detected with an average of 4.5 per locus in 78 accessions, while PIC values ranged from 0.19 to 0.89 with an average of 0.63 per marker. Based on genetic similarity, most of sun-cured and flue-cured tobacco accessions were clustered into group A and group B, respectively. A model-based structure analysis for these accessions detected two subpopulations, which were generally coincident with the clustering analysis and showed the genetic similarities were relative high for these accessions. These results revealed narrow genetic diversity for the tobacco germplasm in China.

The tobacco-specific nitrosamines (TSNAs) are one of the most important groups of carcinoigens in tobacco leaf, knowing the difference of TSNAs contents in tobacco genotypes should be beneficial for breeding low TSNAs cultivars which could decrease the harmfulness to human health in tobacco products. For this purpose, 8 genotypes (include burley, sun-cured and flue-cured tobacco) were selected as materials, the TSNAs contents of uncured and cured leaves were assessed with LC-MS/MS. The results showed that TSNAs contents were significantly increased after curing in all genotypes. The mean TSNAs contents of leaves before and after curing in burley were the highest among three types of tobacco, and the contents in sun-cured tobacco were the lowest. Coefficient of variation (CV) of TSNAs among genotypes in burley was higher than that in flue-cured and sun-cured tobacco, and the CV in sun-cured tobacco was the lowest. The positive correlation was observed in NNN, NAT and total TSNAs contents between uncured and cured leaves in three types of tobacco. Therefore, the TSNAs contents in uncured leaves could be considered as evaluation index to screen tobacco cultivars with the low TSNAs contents.

For the purpose of the population genetics study of the HUMARA locus, the allele, and genotype frequencies were determined in two Chinese population samples (Han-101, Bei-113) using PCR, PAGE, and silver staining. Fourteen alleles were found. The size of amplified fragments were 258 bp-315 bp. The observed heterozygosities were 0.83 in the Han population and 0.73 in the Bei population respectively. The expected heterozygosities were 0.91 in the Han population and 0.97 in the Bei population respectively. Both populations meet Hardy-Weinberg expectation, Han population x2 = 17.7206, df = 11, p > 0.05; Bei population x2 = 7.4268, df = 10, p > 0.05. The discrimination power were 0.95 in females and 0.89 in males in the Han population, 0.94 in females and 0.88 in males in the Bei population. Thus, the allelic frequency data can be used in the personal identification and parentage testing in the forensic science practice. The PCR test established in this study is robust and reproducible.

The exotic Chromolaena odorata is one of the most destructive invasive plant species in South China, and hence an efficient and sustainable control method is urgent. One method, replacement control, which eliminates harmful plants by introducing another competitive plant, is being used increasingly for controlling invasive plants. To test the potential of Pennisetum hydridum to control C. odorata, a series of polyculture experiments with different proportions of the two species was conducted. Competitive indices, plant morphological and physiological traits, and soil nutrient contents were measured to test the impacts of P. hydridum on C. odorata. The presence of P. hydridum significantly suppressed growth of C. odorata, and P. hydridum was not sensitive to the presence of C. odorata. Moreover, increased root/shoot ratios of P. hydridum enhanced its underground competitive ability, and competition between the two species resulted in remarkable reductions of soil nutrient contents which would further decrease the competitiveness of the invasive C. odorata. In summary, our results suggest that P. hydridum is a prospective candidate to control C. odorata.