Genetic Diversity Analysis Of Tobacco Germplasm And Evaluation Of Tobacco Local Germplasm

Tobacco (Nicotiana tabacum L.) is one of the important economic crops. In recent years, the rich tobacco germaplasm has been formed by introducing from abroad and local breeding in China. There are a number of problems which restrict the development of the domestic tobacco industry, including the limited cultivated varieties, narrow and weak genetic basis, aging of some tobacco varieties and lack of local varieties.In this study,81 accessions of tobacco germplasm were collected,which included local tobacco varieties, flue-cured tobacco, burley, oriental tobacco, restic tobacco and aircured tobacco.70 accessions from the tobacco germplasm were used to analyze the genetic diversity and genetic relationship of the tobacco germplasm, according to a comparative study on their quality-related agronomic traits and chemical constituents, and the results of SSR molecular marker. The results were as follows:1. Through the primer screening, there were amplification products of 57 primers that had the clear bands and rich diversity. The average Nei’s index and Shannon’s index of the 57 primers were 0.1894 and 0.3037, which indicate the primers had good discrimination. The genetic distance of materials was 0.02-1.99, the average genetic distance is 0.66, the average genetic distance of all varieties breed at home and abroad is 0.48, and local tobacco materials was 0.98.The most of introductive varieties from overseas had formed the family, such as K326 series and Coker series, and the local germplasm resources had more abundant genetic variation degree and obvious regional characteristic.2. According to the UPGMA cluster analysis based on SSR data,70 tested germplasm could be classified into three types. The main components of the first type is flue-cured tobacco, the main germplas of second type is the collected local resources, restic tobacco is the third type.In the first groups,there were a small amount of local tobacco,aircured tobacco and oriental tobacco samsun. Clustering results distinguished local variety and the existing promotional cultivars from the genetic level, and the genetic relation of the existing promotional cultivars was relatively close. Some collected local germplasm had the same genetic basis for existing promotional cultivars.3. In the selected 7 agronomic characters, stem, leave layer width and the longest leaf length had the biggest diversity index, and all of then more than 1.90. There were significant differences in the agronomic traits among the different types of tobacco materials. Flue-cured tobacco, burley tobacco and aircured tobacco had the biggest number in plant height, available leaf number, the longest leaf length and the max leaf width. Local tobacco germplasm had shorter field growth period than flue-cured tobacco and oriental tobacco, and similar with oriental tobacco in the longest leaf length and the max leaf width and leave layer width. The number of Restic tobacco agronomic characters was the lowest of all kind tobacco. The traits of clustering results is roughly same with molecular marker clustering, and can will clearly divided 81 different tobacco materials into three categories.The first group included most of flue-cured tobacco and burley tobacco, the second group included most of the local varieties, the third group included restic tobacco, but some of the varieties didn’t agree with molecular marker experimental results.4. According to the chemical quality testing of different types of tobacco germplasm resources, there were differences in the chemical quality of all kinds of tobacco germplasm resources, in content of reducing sugar, nicotine, potassium, chlorine and total nitrogen. From the comparative analysis of potassium to chloride ration and sugar to nicotine ration, it could found that the potassium to chloride ration of flue-cured tobacco was 11.12 and the highest, burley tobacco was 2.32 and minimum; oriental tobacco have the highest ratio of sugar to nicotine, and higher than flue-cured tobacco. Therefore, oriental tobacco as the important aroma sources of cigarette usually, flue-cured tobacco was also the most widely in the cigarette products. And the sugar to nicotine ration of local germplasm and burley tobacco and aircured tobacco were minimum and far lower than oriental tobacco and flue-cured tobacco.5. There was greater genetic difference between Local tobacco and existing promotion of cultivation in the genetic relationship and genetic background analysis, and genetic background differences were related with region local germplasm has strong adaptability. In the agronomic characters, local germplasm effective leaf number at least, average 7.63% less than tobacco field growth period. The related properties such as the biggest leaf length, maximum leaf width, leave layer width and so on, were lower than flue-cured tobacco the nearly 50%.Agronomic characters diversity and nicotine content are the highest index in tested type material, burning is good than burley tobacco, sugar to nicotine ration are roughly equal to burley tobacco and aircured smoke, the quality and consistence of aroma is less than flue-cured tobacco.