Study On Differences Of Agronomic Traits And Potassium Metabolism Genes Expression Of Different Potassium Efficiency Genotypes In Tobacco(Nicotiana Tabacum L.)

There is a significant impact of potassium on the growth, stress resistance, chemical quality, aroma and flammability in tobacco. Low potassium content of tobacco has become an important factor to restrict the further enhance in quality of tobacco leaf in China. Using the characteristics of tobacco plant itself, not only the absorption and utilization of potassium can be improved, but also the quality of tobacco can be improved, and the problem of the shortage of potassium resources in China can be solved. This study was based on the materials of 6 differences potassium efficiency of different genotypes of tobacco which were screened out in our laboratory, using the method which were combining with seedling of nutrient solution culture experiment, pot experiment and field cultivation experiments. In the condition of normal potassium and low potassium (40% level of normal potassium), seedling physiological traits, agronomic traits, potassium element distribution differences, field tobacco yield and output value, chemical quality and potassium metabolism related gene expression were studied. The goal was to provide some basis data in making some improvements on genetic and raising cultivation regulation of tobacco potassium absorption efficiency. The main results were as follows:1. Differeces of seedling physiological traits of different potassium efficiency tobacco genotypesThe results of seedling of nutrient solution culture experiment showed that, compared with the potassium inefficiency genotype, the root length, root surface area, root fresh weight and underground dry weight in potassium efficiency genotype were higher. Especially under low potassium stress, the root of potassium efficiency genotype had a more strong development advantage. The fresh weight, shoot dry weight and leaf potassium content of tobacco seedling shoot of potassium efficiency genotype were higher than that of the potassium inefficiency genotype. Therefore, it was proposed that the better root development was one of the characteristics of potassium efficiency genotype, and also the mechanism of high potassium absorption in potassium efficiency genotype during seedling stage.2. Differences in agronomic traits and potassium distribution of different potassium efficiency genotypes in tobaccoThe results of different potassium levels treatments in pot showed that the agronomic traits and dry matter accumulation of potassium efficient cultivars were better than that of potassium inefficient cultivar. The dynamic change trend of potassium content of potassium efficient varieties was decreasing firstly and then increasing, while the potassium content of potassium inefficient cultivar has always been reduced. At the day after transplanting 65 d, in the case of sufficient potassium supplying, potassium in potassium efficiency genotype varieties priority distributed to leaves, but potassium was transferred from leaf to shoot and root in potassium inefficient cultivars. Under the circumstances of insufficient potassium supplying, although potassium in potassium efficient gene varieties was transferred more to root, potassium distribution ratio to leaf was still the largest. Potassium of potassium inefficient cultivars also finally allocated to root, and the potassium distribution ratio to root was the maximum. During later growth period, high potassium varieties could make full use of the absorption and accumulation of potassium, produce more dry matter and have the better ability of potassium on recycling. The quantity of dry matter, potassium accumulation, potassium bioavailability, and potassium economic utilization of the varieties in high efficiency genotypes of potassium were higher than those of the genotypes in low efficiency genotypes.3. Comparison of yield, output value and chemical quality of tobacco with different potassium efficiency genotypes in fieldThe results of potassium efficiency genotype in the field experiments of different potassium level comparison showed that under low potassium conditions potassium efficiency genotype varieties had a better production potential although output of potassium efficiency genotype varieties did not reflect the advantage compared with potassium inefficiency genotype varieties. Although low potassium would reduce the chemical coordination of tobacco leaves, potassium efficiency genotype varieties was better than that of potassium inefficiency genotype varieties.4. Differences in the expression of potassium metabolism related genes in different potassium efficiency genotypes of tobaccoThe expression of several potassium metabolism related genes in different potassium efficiency genotypes of tobacco was analyzed as follows:(1) The relative expression of the tobacco potassium related genes in different potassium genotypes were different. The relative expression of NtTPK in the stem and root of NC628 were relatively high. In the normal potassium treatment, the relative expression content of NtTPK in middle leaves of NC89, Yunyanl, K326 and NC628 were relatively high; NKC1 and TORK1 relative expression were higher in HB030, Gexin3; NKC1 in NC89 and Yunyanl had a relatively low expression.(2) The relative expression of the tobacco potassium related genes in different parts of the tobacco plant were different. TORK1 and NtTPK in the root of NC628 and NC89 had an higher relative expression, the relative expression of TORK1 in the middle parts of the leaves and stem of NC628 were lower; the relative expression of NKC1 in the root of Gexin3 and HB030 were higher, the relative expression of NKC1 in the middle leaves and stems of NC89 and K326 were lower; the relative expression of TPK1 in the root of Gexin3 and K326 were higher, which relative expression of that in the leaves and stems were lower; TORK1, NKC1 in HB030` and Gexin3` root and middle leaves had a higher amount of relative expression but relatively lower in the stems.(3) The relative expression of tobacco potassium related genes in different tobacco plants were different. Under the treatment of low potassium, TPK1 had a decreasing relatively expression in various parts of NC628, Gexin3 and HB030; the relative expression of NtTPK and NKC1 in various parts of Gexin3 were significantly increasing, indicating that it could promote their expression under low potassium conditions; under low potassium treatment, the relative expression of NKC1 in NC89` stem and root were reduced, NtTPK in HB030 stems and roots of relative expression were also decreasing, NtTPK in middle leaves of K326 and NC89 relative expression were also decreasing, indicating that it could inhibit the expression under the low potassium treatment; there was no difference in the relative expression which under normal potassium and low potassium of TORK1 and NKC1 in HB030` stems, indicating that the relative expression amount was not affected by the external potassium environment.