Improvement of Nicotiana tabacum L. for low conversion of nicotine to nornicotine and its effect on morphological traits and chemical composition | Improvement of Nicotiana tabacum L. for low conversion of nicotine to nornicotine and its effect on morphological traits and chemical composition

إنجليزي. Nornicotine is a secondary metabolite formed in tobacco leaves by the oxidative N-demethylation (conversion) of nicotine. Its high level is undesirable because this alkaloid is a precursor of N-nitrosonornicotine, which has been shown to have carcinogenic properties. The aim of the study was to assess the nicotine and nornicotine content in four successive generations of ten tobacco cultivars/breeding lines. The possibility of reducing potentially harmful compounds in the cultivars/breeding lines was also determined. The study was conducted as field experiments between the years 2014 and 2018. The alkaloid content in the leaves was determined by the gas chromatography/ mass spectrometry (GC/MS) method. The systematic assessment of the alkaloid profile of tobacco and eliminating converter plants in four successive generations, particularly within breeding lines characterized by a wide conversion range, made it possible to reduce the nornicotine content and, thus, the potentially carcinogenic compounds in the leaves. Three lines, ZD2, TNX1, and WGLB with a stable conversion rate of ≤3% and low content of nornicotine were obtained. Furthermore, the morphological traits of the isogenic lines ZD2, TNX1 and WGLB, which exhibit markedly different conversion capacity were evaluated. The greenhouse experiment showed that there were significant differences in some morphological traits. The non-converting lines TNX1 and ZD2 produced longer and wider 9th and 15th leaves than the converting analogues. A relationship has been identified between the traits that determine the phenotype of tobacco cultivars/lines and their ability to convert nicotine to nornicotine.

تلميع. Nornicotine is a secondary metabolite formed in tobacco leaves by the oxidative N-demethylation (conversion) of nicotine. Its high level is undesirable because this alkaloid is a precursor of N-nitrosonornicotine, which has been shown to have carcinogenic properties. The aim of the study was to assess the nicotine and nornicotine content in four successive generations of ten tobacco cultivars/breeding lines. The possibility of reducing potentially harmful compounds in the cultivars/breeding lines was also determined. The study was conducted as field experiments between the years 2014 and 2018. The alkaloid content in the leaves was determined by the gas chromatography/ mass spectrometry (GC/MS) method. The systematic assessment of the alkaloid profile of tobacco and eliminating converter plants in four successive generations, particularly within breeding lines characterized by a wide conversion range, made it possible to reduce the nornicotine content and, thus, the potentially carcinogenic compounds in the leaves. Three lines, ZD2, TNX1, and WGLB with a stable conversion rate of ≤3% and low content of nornicotine were obtained. Furthermore, the morphological traits of the isogenic lines ZD2, TNX1 and WGLB, which exhibit markedly different conversion capacity were evaluated. The greenhouse experiment showed that there were significant differences in some morphological traits. The non-converting lines TNX1 and ZD2 produced longer and wider 9th and 15th leaves than the converting analogues. A relationship has been identified between the traits that determine the phenotype of tobacco cultivars/lines and their ability to convert nicotine to nornicotine.