Compositions and methods for reducing the level of nornicotine and N-nitrosonornicotine (NNN) in Nicotiana plants and plant parts thereof are provided. The compositions comprise isolated polynucleotides and polypeptides for cytochrome P450s that are involved in the metabolic conversion of nicotine to nornicotine in these plants. Expression cassettes, vectors, plants, and plant parts thereof comprising inhibitory sequences that target expression or function of the disclosed cytochrome P450 polypeptides are also provided. Methods for the use of these novel sequences to inhibit expression or function of cytochrome P450 polypeptides involved in this metabolic conversion are also provided. The methods find use in the production of tobacco products that have reduced levels of nornicotine and its carcinogenic metabolite, NNN, and thus reduced carcinogenic potential for individuals consuming these tobacco products or exposed to secondary smoke derived from these products.

Compositions and methods for reducing the level of nornicotine and N-nitrosonornicotine (NNN) in Nicotiana plants and plant parts thereof are provided. The compositions comprise isolated polynucleotides and polypeptides for cytochrome P450s that are involved in the metabolic conversion of nicotine to nornicotine in these plants. Expression cassettes, vectors, plants, and plant parts thereof comprising inhibitory sequences that target expression or function of the disclosed cytochrome P450 polypeptides are also provided. Methods for the use of these novel sequences to inhibit expression or function of cytochrome P450 polypeptides involved in this metabolic conversion are also provided. The methods find use in the production of tobacco products that have reduced levels of nornicotine and its carcinogenic metabolite, NNN, and thus reduced carcinogenic potential for individuals consuming these tobacco products or exposed to secondary smoke derived from these products.

The present disclosure provides tobacco inbred plants TND950 (phph) SRC, Narrow Leaf Madole (phph) SRC, Narrow Leaf Madole SRC, CMS TND950 SRC, CMS Narrow Leaf Madole SRC, and CMS KY171 SRC, and hybrids PD7305 SRC, PD7309 SRC, PD7312 SRC, PD7318 SRC, and PD7319 SRC. The present disclosure also provides parts of such plants and products made from those parts. The present disclosure also includes progeny of the provided plants including hybrids.

The invention relates to the field of tobacco breeding, particularly to a tobacco plant resistant to TSWD without linkage drag and a method for breeding the same. Provided is a tobacco plant or germplasm resistant to TSWD, which comprises a short RTSW introgressed segment, wherein at least part or entire of the sequence set forth in SEQ ID No.34 is deleted in the short RTSW introgressed segment as compared to the RTSW introgressed segment of tobacco Polalta. Also provided is a method for screening said tobacco plant or germplasm, in which a tobacco plant or germplasm resistant to TSWD carrying a short RTSW introgressed segment is obtained by detecting NaChr4_2M, NaChr4_8M, NaChr3_62.6M and NaChr3_64.6M linkage drag locus markers. Compared with Polalta, the tobacco plant or germplasm provided by the invention not only has TSWD resistance, but also reduces or removes linkage drag.

The present disclosure provides approaches for reducing nicotine. Also provided are tobacco plants with decreased tobacco-specific nitrosamines (TSNAs). The present disclosure further provides modified tobacco plants with low nicotine and increased antioxidant capacity. Further provided are tobacco plants or material with low nicotine and low TSNAs. Also provided is cured tobacco material of the tobacco plants provided herein and tobacco products comprising this cured tobacco material.

The present invention provides a method for modulating the alkaloid content of a plant (e.g. a tobacco plant), the method comprising modifying said plant by modulating the activity or expression of at least one Nic1 ERF gene. The present invention also provides for the use of at least one Nic1 ERF gene for modulating the alkaloid content of a plant, as well as tobacco cells, plants, plant propagation materials, harvested leaves, processed tobaccos, or tobacco products obtainable in accordance with the invention.

The present disclosure provides tobacco Nic1b locus and associated genes. Also provided are tobacco plants with altered total alkaloid and nicotine levels and commercially acceptable leaf grade, their development via breeding or transgenic approaches, and production of tobacco products from these tobacco plants. Further provided are compositions and methods for producing tobacco plants having novel mutations or alleles to reduce nicotine levels. Further provided are sequence polymorphisms and molecular markers for breeding tobacco with reduced nicotine or alkaloids while maintaining tobacco leaf grade and tobacco product quality.

The present disclosure provides approaches for reducing tobacco-specific nitrosamines (TSNAs) in tobacco. Some of these approaches include genetically engineering tobacco plants to increase one or more antioxidants, increase oxygen radicle absorbance capacity (ORAC), increase phenylalanine, or reduce nitrite. Also provided are methods and compositions for producing modified tobacco plants and tobacco products therefrom comprising reduced TSNAs.

Compositions and methods for reducing the level of nornicotine and N-nitrosonornicotine (NNN) in Nicotiana plants and plant parts thereof are provided. The compositions comprise isolated polynucleotides and polypeptides for cytochrome P450s that are involved in the metabolic conversion of nicotine to nornicotine in these plants. Expression cassettes, vectors, plants, and plant parts thereof comprising inhibitory sequences that target expression or function of the disclosed cytochrome P450 polypeptides are also provided. Methods for the use of these novel sequences to inhibit expression or function of cytochrome P450 polypeptides involved in this metabolic conversion are also provided. The methods find use in the production of tobacco products that have reduced levels of nornicotine and its carcinogenic metabolite, NNN, and thus reduced carcinogenic potential for individuals consuming these tobacco products or exposed to secondary smoke derived from these products.

The invention relates to the isolation and the cloning and breeding application of a tobacco mosaic virus (TMV) resistant N'au gene. The invention discloses the nucleotide sequence of the TMV resistant N'au gene shown as SEQ ID NO.1. The amino acids of polypeptide encoded by the TMV resistant N'au gene are shown as SEQ ID NO.2. A non-transgenic TMV resistant tobacco variety can be obtained by transferring an N'au gene which is contained by germplasm resources into a TMV infected popular tobacco variety by conventional breeding means. The N'au gene of the invention has a homologous sequence with high identity rate of nucleotides in the popular tobacco variety, so that it is easy to obtain a shorter introgression segment single plant carrying the N'au gene by conventional breeding, and thereby to obtain a TMV resistant variety with lower linkage drag. The gene can resist both U1 strain and Cg strain of TMV. The novel antiviral gene N'au of the invention has great application prospect in cultivation of a TMV resistant tobacco.