Flue-cured tobacco (Nicotiana tabacum L.) leaf quality can be improved by grafting with potassium-efficient rootstock

Abstract The low Potassium (K) content in flue-cured tobacco leaves severely restricts the development of China's high-quality cigarette industry. To determine whether the quality of flue-cured tobacco leaves can be improved by grafting, a cross-grafting experiment of two different K-efficiency tobacco strain (Yunyan 87, main cultivar. WuFeng No.2, K-efficient genotype) was carried out. Measurement data from a field experiment with three K supply levels (0,135 and 270 kg K2O ha−1) and four grafting combinations [‘Wufeng No. 2’(W), ‘Yunyan 87’(Y), Y/W (Y grafted onto W) and W/Y (W grafted onto Y)] from 2018 to 2019 were used to evaluate the effect of grafting on flue-cured tobacco quality. The results demonstrated that the average leaf maturity in the grafted tobacco ‘Yunyan 87’ increased by 7.69 %. Meanwhile, maximum accumulation, rapid accumulation duration, and maximum relative accumulation rates of K and biomass in the grafting treatments were all improved over the growth period, and the K levels in the grafted tobacco leaves increased by 95.4 % on average. In addition, when potassium supply level was insufficient, the proportion of K+ in grafted tobacco leaves was higher than that in other treatments. In terms of commercial quality, the chemical and smoking quality of grafted tobacco leaves were 32.2 % and 7.1 % higher than those of ungrafted tobacco leaves. The grafted ‘Yunyan 87’ inherited the advantages of the scion in terms of flavor. At the same time, the combustibility of Y/W was improved by the characteristics of the rootstock, and its total score of quality was highest. The correlation analysis revealed that K accumulation was significantly related to the improvement of tobacco leaf quality. Therefore, increasing the K content and improving the quality of tobacco leaves through grafting is a feasible approach for the production of high quality flue-cured tobacco.