Yield Response, Quality Traits, and Nitrogen-Use Efficiency of a Burley Tobacco Crop Grown in Mediterranean Areas (Southern Italy) as Affected by Intensive N Management

Tobacco is an annual cash crop widely cultivated over the world, which generally needs great amounts (N) of nitrogen to achieve the best yield and quality. However, with a view to sustainable and environmentally friendly agriculture, also for this crop, the reduction in N fertilization is a priority, but without negatively affecting the yield and quality of the cured product. Therefore, field experiments were conducted during 2002 and 2003 on light air-cured (Burley) tobacco at three different locations of the Campania region (Southern Italy) where high-quality light air-cured (Burley) tobacco is traditionally cultivated. At each location, the following six N fertilization treatments were compared with four replications (blocks): (i) a not fertilized control (N0); (ii) 50 kg N ha−1 (N50); 90 kg N ha−1 (N90); 130 kg N ha−1 (N130); 170 kg N ha−1 (N170); 210 kg N ha−1 (N210). The yield of cured leaves appeared positively influenced by N fertilization but not at a rate higher than 170 kg ha−1. N fertilization directly influenced nitrates and the total N content of cured leaves at all locations. The greater values of both parameters were reached at N130 or N90, respectively, at Vitulazio (CE), N170 at Bellizzi (SA), and N90 at San Giorgio del Sannio (BN). The fire holding capacity increased with N fertilization up to N170 treatment (12–13 s at CE and BN but just 8 s at SA). L* (brightness) decreased with increasing N fertilization giving cured leaves less bright and opaquer. The a/b ratio (a*, green/red; b*, blue/yellow) increased with N treatments producing cured leaves of dark hazelnut. The best scores were assigned to cured products obtained by plants fertilized with 170 kg N ha−1. N-use efficiencies were negatively influenced by N fertilization. The best NUE and N-uptake efficiency was recorded in 2002 at Vitulazio (CE), in spite of a higher NO3-N before N fertilization than other locations.

RNA-Seq, physiological, and biochemical analysis of burley tobacco response to nitrogen deficiency

To explore the effects of nitrogen deficiency in burley tobacco, two varieties were cultivated and subjected to conditions of sufficient and deficient nitrogen. The natural characteristics of varieties TN90 and TN86 during tobacco cultivation were similar for nitrogen metabolism. Both carbon and nitrogen metabolism were significantly affected by reducing amounts of applied nitrogen. Under nitrogen-deficient conditions, average leaf biomass, root weight, photosynthetic rate (Pn), pigment levels, total nitrogen, and nitrate content of TN86 and TN90 were significantly decreased by 52.88%, 69.19%, 22.65%, 46.80%, 37.42%, and 79.15%, respectively (p < 0.01). Nicotine and soluble reducing sugar contents were significantly decreased by 96.67% and 95.12%, respectively, in TN86 roots (p < 0.01), which was consistent with the reductions in root surf area, average diameter, and root volume. Nitrogen deficiency induced 6318 differentially expressed genes in both TN90 and TN86, which were highly expressed. In total, 428 upregulated genes were analysed and found to be mainly enriched in the MAPK signalling pathway, sesquiterpenoid and triterpenoid biosynthesis, and arginine and proline metabolism. Meanwhile, 213 downregulated genes were analysed and found to be mainly enriched in photosynthesis, nitrogen metabolism, and amino acid biosynthesis. Reduced pigment content and Pn may result in low carbohydrate formation and decreased leaf biomass in burley tobacco under nitrogen-deficient conditions.

Reducing the nitrate content of burley tobacco by grafting with flue-cured tobacco

Background: Nitrosition of tobacco pyridine alkaloids by nitrate-derived NOx is the origin of tobacco-specifc nitrosamines (TSNAs) formed in tobacco, which are among the most notable toxicants present in tobacco products and smoke. Burley tobacco is particularly susceptible to TSNA formation because the cultivars exhibit a chloroplast-deficient and nitrogen-use-defciency phenotype which results in high accumulation of nitrate. Strategies to lower nitrate levels in tobacco could produce a corresponding decrease in TSNAs accumulation in leaves. Previous studies have showed that grafting with high nitrogen use efficiency rootstock was able to improve the nitrogen utilization of flue-cured tobacco. In this study, a reciprocativel grafting experiment has been conducted with two varieties of different tobacco types (burley tobacco ‘Eyan No.1’ and flue-cured tobacco ‘K326’) to investigate whether replacing burley tobacco root with flue-cured tobacco by grafting can enhance pigment biosynthesis and photosynthesis parameters and reduce nitrate content of burley tobacco leaves, and to explore the corresponding mechanism. Results: The results showed that compared with the self-rooted burley tobacco seedlings, grafting significantly increased the pigment content, net photosynthesis, biomass, total soluble sugar, reducing sugar, nitrate reductase activity, glutamine synthetase activities, NH4-N and soluble protein content of the leaves of Eyan No.1 while decreased the nitrate content and NO3-N/TN. Interestingly, transcription level analysis suggested that replacing burley tobacco root with flue-cured tobacco by grafting was able to up-regulate the genes involved in starch and sucrose metabolism, porphyrin and chlorophyll metabolism, carbon fixation in photosynthetic organism metabolism, carotenoid biosynthesis and nitrogen metabolism of burley tobacco leaves. In addition, the PPI network revealed gene_68511, gene_35043 and gene_77508 had higher degrees via replacing burley tobacco root with flue-cured tobacco, which might be hub proteins to reduce nitrate accumulation. Conclusions: In conclusion, grafting with high nitrogen use efficiency rootstock provided an exceptionally promising means of nitrate reduction in burley tobacco leaf , which is a principle precursor of TSNAs, due to the improvement of photosynthesis and nitrogen metabolism in the scion.

Constitutive activation of nitrate reductase in tobacco alters flowering time and plant biomass

Pyridine alkaloids produced in tobacco can react with nitrosating agents such as nitrite to form tobacco-specific nitrosamines (TSNA), which are among the most notable toxicants present in tobacco smoke. The market type known as burley tobacco is particularly susceptible to TSNA formation because its corresponding cultivars exhibit a nitrogen-use-deficiency phenotype which results in high accumulation of nitrate, which, in turn, is converted to nitrite by leaf surface microbes. We have previously shown that expression of a constitutively activated nitrate reductase (NR) enzyme dramatically decreases leaf nitrate levels in burley tobacco, resulting in substantial TSNA reductions without altering the alkaloid profile. Here, we show that plants expressing a constitutively active NR construct, designated 35S:S523D-NR, display an early-flowering phenotype that is also associated with a substantial reduction in plant biomass. We hypothesized that crossing 35S:S523D-NR tobaccos with burley cultivars that flower later than normal would help mitigate the undesirable early-flowering/reduced-biomass traits while maintaining the desirable low-nitrate/TSNA phenotype. To test this, 35S:S523D-NR plants were crossed with two late-flowering cultivars, NC 775 and NC 645WZ. In both cases, the plant biomass at harvest was restored to levels similar to those in the original cultivar used for transformation while the low-nitrate/TSNA trait was maintained. Interestingly, the mechanism by which yield was restored differed markedly between the two crosses. Biomass restoration in F1 hybrids using NC 645WZ as a parent was associated with delayed flowering, as originally hypothesized. Unexpectedly, however, crosses with NC 775 displayed enhanced biomass despite maintaining the early-flowering trait of the 35S:S523D-NR parent.

Effect of climate change on burley tobacco crop calendars

In Colombia, tobacco cultivation is an important generator of employment and income for farmers; however it faces different problems as low crop yield compared to other countries; specifically, in the north of the country, where the climatic conditions are less favorable and the productivity is lower than other areas of the country due to low mechanization. In order to improve the tobacco yield per hectare in the municipality of Ovejas, this research aimed to determine the water requirements of burley tobacco cultivation under conditions of climate variability to obtain optimal information for crop calendars. Water requirements of burley tobacco were determined using the crop water requirement equation. This calculation ethod was programmed in Python to automate the generation of maps, developing a tool that allowed a detailed analysis per unit area per week. Based on the results obtained, weeks 17 and 18 of the year (last week of April and first week of May, respectively) are proposed as optimal planting times, since the cycles of crops planted in this period showed precipitation surplus in the initial phase of cultivation, which is a critical phase for their development. Climate change simulation showed that crops must be continuously monitored in order to adapt to new weather conditions.

Leaf area estimation of Burley tobacco

ABSTRACT: Leaf area is an important growth variable in agricultural crops and the leaf is the main variable of interest in the tobacco industry. So, the aim of this scientific research was to estimate the Burley tobacco leaf area by linear dimensions of the leaves and to determine which mathematical model is more adequate for this purpose. Two experiments were carried out with Burley tobacco, cultivar DBH 2252, in 2016/2017 and 2018/2019 agricultural years, respectively, in the municipalities of Itaqui and Vanini - RS - Brazil. In 600 leaves were measured length (L), width (W), length×width product (LW), length/width ratio (L/W) and determined the real leaf area (LA). Four hundred and fifty leaves were separated to generate models of the leaf area as a function of linear dimension and the other 150 leaves were used for model’s validation. The power model LA = 0.5037LW1.04435 (R² = 0.9960) is the most adequate for Burley tobacco ‘DBH 2252’ leaf area estimation. Alternatively, the models LA=2.0369W1.8619 (R²=0.9796) and LA=0.1222L2.2771 (R²=0.9738) based on width and length, respectively, can be used when only one leaf dimension is measured.

Characterization of Phn15.1, a Newly Identified Phytophthora nicotianae Resistance QTL in Nicotiana tabacum

Phytophthora nicotianae is an oomycete that causes black shank, one of the most economically important diseases affecting tobacco production worldwide. Identification and introgression of novel genetic variability affecting partial genetic resistance to this pathogen is important because of the increased durability of partial resistance over time as compared with genes conferring immunity. A previous mapping study identified a quantitative trait locus (QTL), hereafter designated as Phn15.1, with a major effect on P. nicotianae resistance in tobacco. In this research, we describe significantly improved resistance of nearly isogenic lines (NILs) of flue-cured tobacco carrying the introgressed Phn15.1 region derived from highly resistant cigar tobacco cultivar Beinhart 1000. The Phn15.1 region appeared to act in an additive or partially dominant manner to positively affect resistance. To more finely resolve the position of the gene or genes underlying the Phn15.1 effect, the QTL was mapped with an increased number of molecular markers (single-nucleotide polymorphisms) identified to reside within the region. Development and evaluation of subNILs containing varying amounts of Beinhart 1000-derived Phn15.1-associated genetic material permitted the localization of the QTL to a genetic interval of approximately 2.7 centimorgans. Importantly, we were able to disassociate the Beinhart 1000 Phn15.1 resistance alleles from a functional NtCPS2 allele(s) which contributes to the accumulation of a diterpene leaf surface exudate considered undesirable for flue-cured and burley tobacco. Information from this research should be of value for marker-assisted introgression of Beinhart 1000-derived partial black shank resistance into flue-cured and burley tobacco breeding programs.

Socio-environmental risks associated with the green tobacco sickness in farmers: a case-control study

ABSTRACT Objective: to determine the presence of socio-environmental risk factors for the development of Green Tobacco Sickness in workers who grow Burley tobacco. Method: matched case-control study. The data collection took place in two moments: from December 2016 to January 2017 and December 2017, when the Burley tobacco was collected, through a household survey with interview application and urine collection for urinary cotinine. Results: the socio-environmental risk factors that remained associated with the disease were: bundling tobacco (p=0.047) and wearing socks (p=0.011); with protective effect were found sticking tobacco seeding of the day (p=0.006) and number of tobacco harvested per day (p=0.021). Conclusion: the steps in the Burley tobacco work process increase the exposure and risk of developing the disease. By identifying these factors, it is possible to address interdisciplinary control and prevention measures.