Nutrient Characteristics Of Different Flue-cured Tobacco Genotypes

The flue-cured tobacco is an important economic crop in China, where has a largest tobacco plants are grown in the world. The main varieties of flue-cured tobacco for cultivation are less than10whereby seriously limiting the productivity. Therefore, breeding flue-cured tobacco materials with optimum production, superior quality, highly resistance and high efficient nutrient utilization are very urgent. Nitrogen (N), phosphorus (P) and potassium (K) are the essential major mineral elements for flue-cured tobacco growth, which are mainly supplied through fertilization. In order to select flue-cured cultivars with high NPK utilization efficiencies, it is necessary to understand the differences in nutrient characteristics of various flue-cured tobacco genotypes, which could also provide information for rational fertilization in flue-cured tobacco cultivation. In current experiments,20genotypes were selected to study the growth, physiology, absorption and utilization of nutrients, yields and qualities of different flue-cured tobacco genotypes in seedling and field stages. These genotypes included commercial cultivars, hybrid tobacco cultivars bred by Zunyi Tobacco Company and their parents. The influences of fertilization on nutrient characteristics were also investigated. The main results are as follows:(1)The agronomic traits and biomass of different flue-cured tobacco genotypes varied significantly in young seedling stage. The root length and shoot height ranged from4.90to6.91cm and from17.85to28.50cm, respectively. The biomass changed between0.053g-dw/plant to0.236g-dw/plant.(2)The uptake and utilization of NPK also vatried among different flue-cured tobacco genotypes in young seedling stage. The NPK contents of tobacco seedlings ranged from38.81g/kg to55.50g/kg,5.45g/kg to7.72g/kg, and37.44g/kg to64.67g/kg, respectively.The plants uptaked more K (from3.05to8.84mg/plant), followed by N (from2.83to9.16mg/plant) and P (from0.37to1.29mg/plant). The dry matter production efficiency of N ranged from18.02to25.77g-dw/g, P ranged from129.46to183.46g-dw/g, K ranged from15.46to26.71g-dw/g, respectively. The NPK uptakes positively correlated with each others, which were also positively correlated with fresh and dry weight. Therefore, in young seedling stage of flue-cured tobacco, it is necessary to pay more attention on NPK ratio of different genotypes for their nutrient demand and seedling cultivation. (3)The root vigor, NR activity and chlorophyll content were significantly different among genotypes in young seedling stage, the variation coefficients were0.25,0.28, and0.20, respectively. The root vigor was positive correlated with N uptakes, dry weight. The chlorophyll content was positively correlated with fresh weight and dry weight.(4) The NR activity of F1generation had significant positive correlation with female parent. The chlorophyll content of Fl generation correlated significantly with male parent, mid-parent and low-parent. The NR activity, chlorophyll content, root vigor, dry matter accumulation of flue-cured tobacco in seedling stage had mid-parent heterosis. The NR activity, root vigor, dry matter accumulation had over high-parent heterosis. The NPK uptakes had no significant heterosis, but some cross combinations had mid-parent heterosis and over high-parent heterosis.(5)Within same fertilization conditions, the growth of flue-cured tobacco was significantly different between genotypes. The agronomic traits (plant height, maximum leaf length and width, leaf number) were significantly different between plants of different genotypes in each growth stage. The main economic properties of different genotypes had remarkable differences, the yields ranged from1644.71kg/hm2to3358.17kg/hm2,the supper tobacco leaves rate ranged from55.00%to88.35%, the prices ranged from11.71yuan/kg to13.65yuan/kg, the output value ranged from20149.04yuan/hm2to45174.04yuan/hm2. The chemical component contents in tobacco leaves were different between leaf positions and showed great variations among genotypes. Among the20flue-cured tobacco genotypes, the difference of nicotine contents between the lowest and the highest were2.01times for upper leaves,2.66times for middle leaves, and3.37times for lower leaves; the difference of total nitrogen contents were1.72times,1.64times, and1.67times,respectively; the difference of total sugar contents were3.23times,2.70times, and2.44times, respectively; the difference of reducing sugar contents were3.23times,2.53times, and2.30times, respectively; the difference of K contents were5.42times,2.04times, and3.55times, respectively; the difference of chlorine content were7.44times,5.30times, and6.50times, respectively; the difference of protein contents were1.48times,1.47times, and1.50times, respectively. Among the20flue-cured tobacco genotypes, the nicotine content of40%genotypes was in suitable scope, the total nitrogen content of85%genotypes was in suitable scope, the total sugar content of75%genotypes was in suitable range, the reducing sugar contents of70%genotypes was greater than suitable scope, the K contents of25%genotypes was in suitable scope. The chlorine content is low and the protein contents were all lower than10%. The chemical component coordination were also different between leaf positions and showed great variations among genotypes. The difference of shmuck value between the lowest and the highest were4.07times for upper leaves,2.84times for middle leaves, and2.75times for lower leaves; the difference of nitrogen to nicotine were1.92times,2.77times, and2.34times, respectively; the difference of sugar to nicotine were6.87times,5.37times, and5.47times, respectively; the difference between reducing sugar and total sugar were6.24times,7.10times and6.94times, respectively. The chemical component coordination in middle tobacco leaves of20genotypes showed that the shmuck value were too large, the ratio of nitrogen to nicotine were too small, the ratio of sugar to nicotine were not coordination, the difference between reducing sugar and total sugar were suitable.(6) The root vigor decreased gradually with the development. The NR activity and the contents of chlorophyll and carotenoids reached the peak60d after transplanted. The root vigor, NR activity, contents of chlorophyll and carotenoids were significantly different between the genotypes60d and90d after transplanted. The dry matter accumulation was significantly different between different genotypes, which changed from244.01g/plant to363.73g/plant. The dry matter accumulation were mainly happened after transplanted60-90d.(7) The K content and uptakes of tobacco plant were higher than N content and uptakes of tobacco plant, the P content and uptakes of tobacco plant were lower in all growth period. The N uptakes of tobacco plant was mainly concentrated during30to60d after transplanted. The P and K uptakes were mainly concentrated after transplanted60to90d. The N,P,K uptakes were mainly distributed in the leaf and stem, the proportions in root were lower. The NPK dry matter production efficiency was significantly different among genotypes.(8) Correlation analysis showed that the leaf number was positively correlated with yield, supper tobacco leaves rate, average price and output value.The path analysis showed that the direct path coefficients of leaf number to yield, supper tobacco leaves rate, average price and output value were higer. The root vigor was positively correlated with yield, output value, supper tobacco leaves rate. The chlorophyll content was positively correlated with yield, output value, high direct action to yield and output value. The plant height was positively correlated with leaf length and width, the root vigor was positively correlated with carotenoids content, the root vigor of seedling was positively correlated with yield and output value. The N uptakes of tobacco plant after transplanted30～60d,60～90d,90～120d were positively correlated with yield, the P uptakes of tobacco plant after transplanted60-90d,90～120d were positively correlated with yield, the K uptakes of tobacco plant after transplanted30-60d,90～120d were positively correlated with yield.(9) The cluster analysis showed that the classification of different flue-cured tobacco genotypes' growth, physiology, yield, output value were different. The genotypes ZYH-4and Wanhua K326grew well in seedling and field stages, of which the yield and quality were good and the nutrient uptakes were high. The genotypes CZ-1and Nanjiang3grew well in field stage, of which the yield and quality were good and the nutrient uptakes were high. The nutrients of T202were higher. The NDMPE and KDMPE of683were the highest, but it's yield and NK uptakes were the lowest.(10) Within0～90kg/hm2(pure nitrogen) application rates, the plant height, leaf number, chlorophyll and carotenoids contents, NR activity, dry matter accumulation, NPK uptakes, yield, supper tobacco leaves rate, average price and output value of Nanjiang3(high quality varietie) increased with increasing amounts of applied nitrogen. No further improvement was obtained when application rate increased to105kg/hm2N. Negative effects were found for some indexes at105kg/hm2N.(11) Compared with the application of chemical fertilizer, the yield, supper tobacco leaves rate, average price and output value with combined application of35%organic nitrogen and65%chemical nitrogen increased by9.71%,2.30%,2.51%, and12.47%, respectively. The chemical component contents and coordination were the best with combined application of35%organic nitrogen and65%chemical nitrogen.The combined application of35%organic nitrogen and65%chemical nitrogen can significantly improve the availability of soil NPK nutrients at later period, increase the effective leaf number and dry matter accumulation, and the chlorophyll and carotenoids contents. Combined application of organic and chemical nitrogen can significantly improve the organic matter, total nitrogen (N) and phosphorus (P) and potassium (K) contents of tobacco-growing soils. The organic matter content of soil increased with increasing application rate of organic nitrogen.