Cembranoids produced by tobacco glandular trichomes have bioactivities in resistance to insect pests and pathogens. Cembratrien-ol synthase (CBTS) plays a key role in the biosynthesis of cembranoids and directly determines the cembranoid content in tobacco. This study examined the effect of changing CBTS1 expression on tobacco resistance to the insect pest Spodoptera frugiperda and oomycete pathogen Phytophthora nicotianae. The CDS sequence of CBTS1 was cloned into gene overexpression and silencing vectors and introduced into tobacco (Nicotiana tabacum L. cv. TN90) to obtain CBTS1-overexpression plants (CBTS1-OE) and CBTS1-silenced plants (CBTS1-RI). Compared with control plants, the content of cembratrien-ol (CBT-ol) was increased 4.48 times in the CBTS1-OE plants but decreased by 68% in the CBTS1-RI plants, while that of cembratrien-diol (CBT-diol) was increased 3.17 times in the CBTS1-OE plants but decreased by 76% in the CBTS1-RI plants. The S. frugiperda resistance of transgenic tobacco plants was evaluated by in vitro toxicity test, and the results showed that the resistance of CBTS1-OE plants to S. frugiperda was significantly improved but that of CBTS1-RI plants was reduced. The P. nicotianae resistance of transgenic tobacco plants was assessed by the detached leaf assay, and the results showed that the resistance of CBTS1-OE plants to P. nicotianae was enhanced, while that of CBTS1-RI plants was attenuated. Further gene expression analysis showed that overexpression of CBTS1 increased the expression of the pathogen-related gene PR-1a, while silencing of CBTS1 decreased its expression. This study demonstrated that manipulating the expression of CBTS1 could change the cembranoid content in tobacco plants and alter their resistance to both insect pests and oomycete pathogens.

Solanesol, which accumulates predominantly in the leaves of tobacco plants, has medically important bioactive properties. To investigate the genetic basis of solanesol in tobacco (Nicotiana tabacum), the solanesol contents of 222 accessions, 206 individuals from an N. tabacum Maryland609 (low-solanesol) × K326 (high-solanesol) F2 population and their corresponding F1 self-pollinations, were determined using ultra-performance liquid chromatography. Genome-wide quantitative trait locus (QTL) and association analysis were performed to identify QTLs and markers associated with solanesol content based on simple sequence repeat molecular markers. A total of 12 QTLs underlying solanesol content were mapped to seven linkage groups (LGs), with three of the QTLs (QTL3-1, QTL21-6, and QTL23-3) explaining 5.19–10.05% of the phenotypic variation. Association analysis revealed 38 significant marker-trait associations in at least one environment. The associations confirmed the QTLs located on LG3, LG10, LG14, LG21, and LG23, while new elite makers were located on 11 additional LGs, each explaining, respectively, 5.16–20.07% of the phenotypic variation. The markers LG14-PT54448, LG10-PT60114-2, LG10-PT60510, LG10-PT61061, and LG-21PT20388 may be useful for molecular-assisted selection of solanesol content in tobacco leaves. These results increase our understanding of the inheritance of solanesol-associated genes and will contribute to molecular-assisted breeding and further isolation of regulatory genes involved in solanesol biosynthesis in tobacco leaves.