Study On Potassium Nutrition Characteristics Of Different Genotypes Of Flue-cured Tobacco And Their Heredity

Tobacco(Nicotiana tabacum)has a relatively high requirement for potassium(K),which requires a greater amount of K than other crops.Flue-cured tobacco with different genotypes have different K-absorbing ability and different demand of K.It is of great significance for breeding high-K genotype flue-cured tobacco and improving utilization of K fertilizer through deeply research on the mechanism of K-absorbing and K-accumulating abilities of different genotypes of flue-cured tobacco as well as their hereditary character.This research studied the potassium nutritive peculiarity and root peculiarity of high-K flue-cured tobacco under different K-supplying conditions by applying three homozygous lines of At NHX1-expressing transgenic tobacco and four genotypes Flue-cured tobaccowith different K content in leaves.The hereditary regulation high-K genotype which not endure the physical manifestation of low K was discussed preliminarily.The K content of leaves,root volume,root activity,ATPase activity and root cation exchange capacity were also studied through diallel cross design.The aim is to supply the evidence for nutrional fertilization and the high-K variety breeding.Main findings are as follows:Potassium content in tobacco leaf,root morphology and physiological characteristics were investigated using positive At NHX1 gene homozygous strain N7,N9,N10,and nontransgenic control K326 under field and hydroponic condition.These results show that At NHX1-expressing tobacco lines accumulated more potassium in leaf as compared with the control atthe leaf age of 10-70 d under filed condition.The K content of tobacco leaf at maturity(at the leaf age of 70 d)of the three transgenic strains were namely 2.09 times,1.85 times and 1.41 times to nontransgenic control K326.Moreover,transgenic tobaccos overexpressing At NHX1 exhibited higher potassium absorption capability and larger maximum absorption rate of potassium under hydroponic,and in consistent with this,it was found that overexpression also increased roots morphology,root activity,cation exchange capacity and ATPase activity in the transgenic lines.Vmax of the three transgenic strains were namely 1.71 times,1.62 times and 1.40 times to nontransgenic control K326.Taken together,these results provide evidence that At NHX1 might be involved in the K uptake in tobacco,and low K affinity could be the reason for low K intolerance.In order to study K nutrient characteristics of Flue-cured tobacco in depth,The characteristics of mineral K activation,absorption,transport and accumulation of different flue-cured tobacco genotypeswere studied under normalpotassiumsupply(K+)and non-potassiumsupply(K-)conditions to.The results showed that,the efficiency of K absorption,K responsivity and K content of high-K genotypes is higher than low-K genotypes,while the efficiency of K utilization is lower than low K genotypes under K+ condition.The absorbing ability of root,potassium content and dry matter accumulation of high K genotypes was significantly decreased under K-condition.The low K tolerance ability of high K genotypes is lower than low K genotypes.High K genotypes would increase the activation of mineral K in growth medium to meet their own needs through increasing the root volume and the root-shoot ratio under Kcondition,but the K content of plant was significantly decreased because the lowest K absorption concentration is higher.High K genotypes is sensitive to K,the ability of absorption,transport and accumulation of K and the utilization ratio of K fertilizer are high,but the low K tolerance ability is low.K content and root character vary greatly among different genotypes of flue-cured tobaccos during fast-growing term,the variance of general combining ability and special combining ability were also at a significant level,the broad-sense heritability were over 60% and these variance of traits were mainly controlled by genetic factors.The heritability of K content,root activity and ATPase activity of flue-cured tobacco were mainly controlled by dominance effect,and the heterosis of F1 generation is also stronger.High-K content,high-vigor and high-activity ATPase could be gottenthrough heterosis utilization.The heritability of root volume and CEC of flue-cured tobacco were mainly controlled by additive effect,and their narrow-sense heritability is higher,namely 54.81% and 46.18% respectively.Root volume and root CEC wereshould to selected at earlier generation in order to breeding high-volume and high-CEC tobacco cultivars.General combining ability of Nongda 202,Nongda 203 and Qinyan 96 were higher,and they were ideal parents to increase the K-absorbing ability of root.Apart from that the general combining ability of Qinyan 96 in heredity of root volume was negative,Qinyan 96,Nongda 202 and Nongda 203 all had positive general combining ability in the heredity of K content,root volume,root activity,root ATPase activity and CEC,while the general combining ability of Yunyan 85 and NC628 is negative.Special combining ability of Nongda 203×NC628 and Yunyan 85×NC628 in F1 hybridized combination were higher,and have a good comprehensive performance in K content and root physiological property,which could be selected as materials to breed high K efficient flue-cured tobacco varieties.