Performance of heterosis in tobacco roots and differential expression analysis of related genes

【Objective】To explore the heterosis of tobacco root traits and the differential expression of related genes,so as to provide theoretical basis for in-depth analysis of the formation of heterosis of tobacco root absorption and synthesis of related substances.【Method】Using 12 hybrids and 7 parents with heterosis in nicotine and potassium content traits as materials,the genetic characteristics and heterosis of tobacco root traits were analyzed by measuring root length,quantity and volume,and the differential expression of genes related to tobacco root development was detected by real-time fluorescence quantitative PCR.【Result】The root length of the seven parent materials was 94.80-476.77 cm,the number of roots was 343-820,and the root volume was 0.18-0.61 cm³. The root length of 12 hybrid combinations was 285.56-734.75cm,the number of roots was 576-1184,the root volume was 0.41-1.01 cm³,and the coefficient of variation of the three traits was 19.97%-29.68%. The broad heritability of tobacco root length,quantity and volume was 95.49%,92.12% and 85.76% respectively,and the combination rate of mid-parent dominance was 91.67%,91.67% and 100.00% respectively.The root length is mainly controlled by the additive effect of genes,and the root number and root volume were mainly controlled by the non-additive effect of genes,showing obvious heterosis. There was a certain correlation between the mid-parent expression superiority of different root development-related genes and the root trait heterosis,among which,the midparent expression superiority of NtAUX1 and NtARF16 genes was significantly(P<0.05,the same below) or extremely significantly(P<0.01,the same below) related to the root length heterosis.The mid-parent expression superiority of NtFLA18 gene was significantly or extremely significantly negatively correlated with the heterosis of root quantity and volume. The relative expression of NtFLA18 gene in K326×Jiucaiping No. 2 was down-regulated than that of its parents,NtAUX1 gene was dominant,and NtARF16 gene was up-regulated than that of its parents. The expression pattern of these genes was related to the formation of tobacco root heterosis.【Conclusion】The root length,root quantity and root volume of tobacco have strong heritability and universal heterosis,which can be used to select new tobacco germplasm with developed roots. GDH88,Va116,Nanjiang No. 3 and G70 can be used as excellent parents for root improvement;K326×GDH88,Va116×Bina No.1,G70×Jiucaiping No.2,G70×Nanjiang No.3 and K326×Jiucaiping No.2 can be used as an important reserve materials for cultivating excellent root architecture.