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The genus Nicotiana is an important germplasm source for cultivated tobacco varieties improvement, the creation of tobacco interspecific hybrids and their molecular cytological analysis during the meiotic phase will provide the basis for the subsequent efficient transfer and utilization of excellent wild germplasm. Allotriploid interspecific hybrids were created from the parents of Nicotiana sylvestris Q67 and common Nicotiana tabacum L. cv. K326. Their chromosome composition, chromosomal behavior during the meiosis and expression of related genes were investigated by routine cytological observation, genomic in situ hybridization and real-time quantitative PCR. In this study, 68 allotriploid hybrids (SST) with 36 chromosomes were identified by phenotypic and cytological analysis from crossing Nicotiana sylvestris with Nicotiana tabacum. The results of general cytology and genomic in situ hybridization showed that 29.26% of the pollen mother cells of interspecific hybrids were abnormal in meiosis. The main abnormal behavior was the backward chromosomes from the T chromosome group in metaphase I and II, with 1-3 lagging chromosomes. The cells with the most lagging types in metaphase I and II were the cells with 1 and 2 lagging T chromosomes respectively. They accounted for 29.09% and 30.88% of the total number of cells carrying backward chromosomes, respectively. The abnormal types of anaphase I, anaphase II and telophase II were mainly unequal segregation, backward chromosomes and micronucleus. In anaphase I, a variety of abnormal segregation ratios were counted, but the chromosome composition after segregation was still close to 2∶1 (S∶T). The results of RT-qPCR showed that in prophase I, except for the significant up-regulation of CDKA:5319 and CYCA:6720 from S chromosome group, the expressions of other genes were significantly down regulated. From the metaphase I to the telophase II, compared with the control, except that MIS12 and CDKA:0239 from T chromosome group had no significant changes, other genes（CENH3, CDKA:5319, CYCA:0111 and CYCA:6720）were significantly or extremely significantly up-regulated, indicating that the disorder expression of meiosis related genes may be causing the abnormality of meiosis. [ABSTRACT FROM AUTHOR]

【Objective】To solve the problem of large differences in the maturity status of the upper leaves of flue-cured tobacco at one-time harvest, the present experiment explored the effects of gibberellin and potassium nitrate spraying concentration and spraying time on the simultaneous maturation and flue-cured tobacco quality of the upper 6 tobacco leaves of the flue-cured tobacco Zhongchuan 208. The impact was expected to provide a theoretical basis for promoting the one-time harvest of flue-cured tobacco. 【Method】Using the Box-Behnken method in response surface optimization design, the concentration of gibberellin (0, 15, 30 μmol/L) and potassium nitrate (0, 0.5, 1.0 g/L) and the spraying time (20, 25, 30 days) after topping was designed with three factors and three levels, a total of 16 treatments. The physiological indicators related to the maturation of the 1-3 tobacco leaves from top to bottom(denoted as Tup) and the 4-6 tobacco leaves from top to bottom(denoted as Tdown) were measured, and the treatment indexes were calculated. The synchronization maturity value was used as a basis for measuring synchronization maturity. The smaller the value, the better the synchronization maturity state. 【Result】 The synchronous maturity value of each treatment was significantly lower than that of the control, and the appearance quality and total chemical composition of cured tobacco leaf were higher than that of the control. The treatment of spraying 15 μmol/L gibberellin and 0.5 g/L potassium nitrate (T2, T5, T9, T16) had the best synchronous mature state, and the highest total score of appearance quality and chemical composition; The results of response surface showed that gibberellin and potassium nitrate had a very significant impact on the comprehensive score, and the impact curve was similar. The spraying time also had a very significant impact on the comprehensive score. The model validation and optimization results showed that the comprehensive score of flue-cured tobacco was close to the predicted value, indicating that the model was reliable and could predict the comprehensive score of flue-cured tobacco.【Conclusion】Spraying gibberellin and potassium nitrate can promote the uniform maturity of upper leaves and improve the quality of flue-cured tobacco leaves. [ABSTRACT FROM AUTHOR]