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Background Amber-like compounds form in tobacco (Nicotiana tabacum) during leaf curing and impact aromatic quality. In particular, cis-abienol, a polycyclic labdane-related diterpenoid, is of research interest as a precursor of these compounds. Glandular trichome cells specifically express copalyl diphosphate synthase (NtCPS2) at high levels in tobacco, which, together with NtABS, are major regulators of cis-abienol biosynthesis in tobacco. Results To identify the genes involved in the biosynthesis of cis-abienol in tobacco, we constructed transgenic tobacco lines based on an NtCPS2 gene-knockdown model using CRISPR/Cas9 genome-editing technology to inhibit NtCPS2 function in vitro. In mutant plants, cis-abienol and labdene diol contents decreased, whereas the gibberellin and abscisic acid (ABA) contents increased compared with those in wild-type tobacco plants. RNA sequencing analysis revealed the presence of 9514 differentially expressed genes (DEGs; 4279 upregulated, 5235 downregulated) when the leaves of wild-type and NtCPS2-knockdown tobacco plants were screened. Among these DEGs, the genes encoding cis-abienol synthase, ent-kaurene oxidase, auxin/ABA-related proteins, and transcription factors were found to be involved in various biological and physiochemical processes, including diterpenoid biosynthesis, plant hormone signal transduction, and plant-pathogen interactions. Conclusions The present study provides insight into the unique transcriptome profile of NtCPS2 knockdown tobacco, allowing for a better understanding of the biosynthesis of cis-abienol in tobacco.

In order to further improve the identification efficiency of tobacco mildew, a rapid identification model of tobacco mildew based on random forest algorithm was proposed in this study. In order to ensure the feasibility and pertinence of the model study, this study takes redried leaf tobacco as the research object, selects high-temperature and high-humidity environment as the experimental conditions, and obtains the sample data of the degree of tobacco mildew under different experimental conditions. At the same time, this paper constructs a rapid identification model of tobacco mildew with the help of random forest algorithm. Through the model experimental results, it is found that the accuracy of the model for the rapid identification of training samples can reach 93.82%, while the accuracy of independent testing is 94.84%. The experimental results fully reflect the availability and efficiency of the random forest algorithm model in the rapid identification of tobacco mildew.

The in vitro culture of unpollinated ovaries is one of the techniques used to induce gynogenesis. To explore the mechanism of lily gynogenesis and obtain haploids to shorten the breeding cycle, the in vitro effects of flower bud sampling time, exogenous plant growth regulators (PGRs), and different concentrations of picloram on embryo formation in unpollinated ovaries of Lilium L. 'Sorbonne' (oriental hybrids) were studied. The results indicated that flower buds ≥8 cm in length were most suitable. The PGRs picloram and 2,4-dichlorophenoxyacetic acid (2,4-D) with 6benzylaminopurine (6-BA) or kinetin were useful in inducing ovule expansion in vitro. However, most ovules did not survive on the media containing 2,4-D, whereas those grown on media containing picloram developed normally. In particular, a lower concentration of picloram (0.5 mg L −1 ) was found to be beneficial to the development of ovules into embryogenic shoots, whereas higher concentrations were more favorable to the development of shoots from the ovary wall. In total, 87 regenerated plants were obtained from unpollinated ovaries of Sorbonne. The chromosome ploidy of 20 of these was determined by counting root tip chromosomes, and eight of the regenerated plants were found to be haploids.