Tobacco Varieties Research Articles

Unveiling the variability in cadmium accumulation and tolerance characteristics: a comparative study of Basma and Yunyan 87 tobacco varieties

ABSTRACT Tobacco (Nicotiana tabacum L.) shows promise for remediating Cd-contaminated soil due to its significant Cd accumulation capabilities. Although various tobacco varieties exhibit distinct Cd bioaccumulation capacities, a comprehensive understanding of the underlying mechanisms is lacking. This study, conducted using hydroponics, explores differences in Cd accumulation and tolerance mechanisms between two tobacco varieties, Basma and Yunyan 87. The results showed that Cd stress reduced the dry weight, tolerance index, and root morphology for both varieties. Basma exhibited a relatively smaller decline in these indices compared to Yunyan 87. Moreover, Basma demonstrated a higher Cd bioconcentration factor (BCF), concentration, and accumulated content, signifying its superior tolerance and bioaccumulation capacity to Cd compared to Yunyan 87. The Carbonyl Cyanide3-ChloroPhenylhydrazone (CCCP) addition resulted in reduced Cd accumulation and BCFs in both tobacco species. This effect was more pronounced in Basma, suggesting that Basma relies more on an active transport process than Yunyan 87. This could potentially explain its enhanced bioaccumulation ability. Subcellular Cd distribution analysis revealed Basma's preference for distributing Cd in soluble fractions, while Yunyan 87 favoured the cell wall fractions. Transmission electron microscope showed that Basma's organelles were less damaged than Yunyan 87's under Cd stress, possibly contributing to the superior tolerance of Basma. Therefore, these results provided a theoretical foundation for development of Cd-contaminated soil tobacco remediation technology.

Transcriptome analysis reveals the mechanism of NaHCO3 promoting tobacco leaf maturation.

NaHCO3 accelerates the aging of tobacco leaves; however, the underlying molecular mechanisms have not been elucidated. This study aimed to explore the mechanism of NaHCO3 in the promotion of tobacco leaf maturation using transcriptome analysis. Leaves on plants or detached leaves of the tobacco variety, Honghua Dajinyuan, were sprayed with or without 1% NaHCO3. The leaf yellowing was observed, the pigment content and enzyme activities were determined and RNA sequencing (RNA-seq) was performed. Spraying NaHCO3 onto detached leaves was found to promote leaf yellowing. Pigment content, catalase activity, and superoxide dismutase activity significantly decreased, whereas peroxidase activity and malondialdehyde content significantly increased. RNA-seq demonstrated that spraying with NaHCO3 upregulated genes associated with cysteine and methionine metabolism; alpha-linolenic acid metabolism; and phenylalanine, tyrosine, and tryptophan biosynthesis and downregulated genes related to photosynthesis and carotenoid biosynthesis. Genes correlated with autophagy-other, valine, leucine, and isoleucine degradation, and the MAPK signaling pathway were upregulated while those correlated with DNA replication, phenylalanine, and tyrosine and tryptophan biosynthesis were downregulated in detached leaves sprayed with NaHCO3 compared with the plant leaves sprayed with NaHCO3. Overall, this study is the first to elucidate the molecular and metabolic mechanisms of NaHCO3 in the promotion of tobacco leaf maturation.

A 2‐year, multi‐county survey of plant‐parasitic nematodes in North Carolina flue‐cured tobacco

AbstractNorth Carolina is the leading producer of flue‐cured tobacco (Nicotiana tabacum L.) in the United States. Production in the state is threatened by numerous plant‐parasitic nematodes, including Meloidogyne spp. (root‐knot), Globodera tabacum (tobacco cyst), Pratylenchus spp. (lesion), Rotylenchulus reniformis (reniform), and Tylenchorhynchus spp. (stunt) nematodes. The invasive Meloidogyne enterolobii is also a major threat as it can infect tobacco varieties carrying the Rk gene, which conditions resistance to other Meloidogyne species. To gain an updated understanding of which nematode taxa are present in tobacco production and investigate distribution of M. enterolobii in North Carolina, a 2‐year survey was conducted. From 2021 to 2022, 188 fields were sampled across 24 tobacco‐growing counties. Samples were assayed for identification and quantification of nematodes at the genus level; where Meloidogyne spp. was identified, molecular testing was used to determine the species. Data were also collected on the previous crop and tobacco variety grown. In both years, lesion, root‐knot, dagger, and stunt nematodes were found in the highest incidence among samples. In 2022, M. enterolobii was identified in a single sample each from Granville and Pitt counties; this is the first report of M. enterolobii from Granville County. Tobacco variety NC 196 and soybean were the most common variety and previous crop grown, respectively, in both years of the survey. Tobacco variety did not have an effect on nematode population density. The previous crop had a significant effect on root‐knot and spiral nematodes in 2021, and lesion and stubby root nematodes in 2022.

A Poor but Efficient Crop: Supply-Side Responses in the Greek Tobacco Sector, 1953-64

We analyzed the price elasticities of the Greek tobacco supply at three different levels of analysis (cross-varietal, cross-regional, and two-dimensional) using secondary-level data published by the Greek National Tobacco Board for the years 1953 to 1964. Our panel suggest that the development of postwar Greece’s tobacco sector was largely determined by market forces rather than by state-led purchasing programs. However, market pressures impacted production and sales volume to varying degrees, depending on the tobacco varieties grown in different parts of the country. Given that tobacco was postwar Greece’s most important export crop, and that it was the object of considerable state support, the often-made claim that state interventionism has disincentivized the adaptation of the Greek agricultural sector to evolving markets needs to be revised. Our findings support Shultz’s poor-but-efficient hypothesis regarding farmers.

Distinct microbiota assembly and functional patterns in disease-resistant and susceptible varieties of tobacco.

The plant microbiota is believed to be an accessory genome that extends plant functions, forming holobionts together with the host plant. Plant disease resistance, therefore, is inextricably linked with plant microbiota, which play important roles in plant growth and health. To explore the relationship between plant microbiota and disease resistance, we investigated the tobacco microbiome of two varieties with contrasting disease-resistance levels to bacterial wilt and black shank diseases. Comparative microbiome analysis indicated that the resistant variety assembled a distinct microbiota with higher network complexity and diversity. While Pseudomonas and Ensifer, which contain biocontrol and beneficial members, were enriched in the rhizosphere of the resistant variety, Ralstonia, a genus including the known causative pathogen, was enriched in the susceptible variety. Metagenome sequencing revealed that biocontrol functions, such as hydrogen cyanide synthase, pyochelin biosynthesis, and arthrofactin-type cyclic lipopeptide synthetase, were more abundant in the resistant variety. Further analysis indicated that contigs encoding the corresponding genes were mostly assigned to Pseudomonas. Among all the metagenome-assembled genomes, positive selection was suggested in the genome assigned to Pseudomonas only in the rhizosphere of the resistant variety. The search of biosynthetic gene clusters in the Pseudomonas genome revealed a non-ribosomal peptide synthetase, the compound of which was brabantamide A, with known antimicrobial activity. Collectively, our study suggests that the plant microbiota might be involved in microbe-mediated disease resistance. Particularly, our results highlight Pseudomonas in the rhizosphere of the disease-resistant variety as a promising biocontrol candidate. Our study may facilitate further screening of bacterial isolates and the targeted design of microbial communities.

APPLICATION OF BIOLOGICAL GROWTH STIMULATOR IZABION AND INSECTICIDE LUX MAXI IN ADAPTIVE TECHNOLOGY OF GROWING AND PROTECTING TOBACCO

Purpose. The purpose of the article is to develop the elements of the adaptive technology of cultivation and protection of new varieties of tobacco of Ukrainian selection and to carry out the economic substantiation of the obtained results. Methodology of research. General scientific and special methods were used in the work: bibliographic and method of theoretical analysis of scientific literary sources – for studying and processing of scientific works related to the technology of tobacco cultivation; agronomic, field and biometric – to study the norms of introduction of experimental drugs, measurement of biometric indicators of tobacco plants in experimental plots; computational and constructive, mathematical and statistical, method of comparative analysis and economic method – when processing the results of scientific research for 2021-2023 and for evaluating the economic effectiveness of elements of adaptive technology of tobacco cultivation. Findings. An economic evaluation of the adaptive technology of growing and protecting tobacco from diseases and pests with elements of the use of new chemical preparations has been developed and carried out: Izabion growth biostimulator and Lux Maxi insecticide, as effective preparations for increasing the yield and quality of tobacco raw materials of the new variety of Ukrainian selection tobacco Berley 46 in the agro-climatic conditions of Transnistria of Ukraine. Their use significantly increases the level of profitability of the process of growing tobacco raw materials by improving the resistance of plants to adverse environmental factors and contributes to the growth of the competitiveness of the tobacco industry of our country on the world market. Originality. New elements of the adaptive technology of growing and protecting tobacco from diseases and pests have been developed using new environmentally safe drugs – the growth stimulator Izabion and the insecticide Lux Maxi on tobacco fields of the Berley 46 variety in the Transnistrian region of Ukraine. Indicators of economic efficiency of new elements of technology are substantiated. Practical value. The scope of application – agricultural enterprises of Transnistria of Ukraine of all organizational and legal forms, engaged in tobacco cultivation. Key words: tobacco, sort, technology, immunity, diseases, pests, growth stimulants, insecticides, cost, price, profit, profitability level, economic efficiency.

Tobacco introduced Perilla frutescens and Ocimum basilicum genes attenuates neutrophilic inflammation in lung tissues of COPD rats

The new-type tobacco varieties “Zisu” and “Luole” were obtained by distant hybridization between N. tabacum L. var. HHY and Perilla frutescens and Ocimum basilicum, with obviously different chemical composition. Smoking is the major risk factor for COPD, characterized by neutrophil-dominant inflammation. In the present study, rat COPD model was established by cigarette exposure, and the health hazard of three varieties was compared by general condition observation, pathological and morphological evaluation, total and differential cell numeration, and characterization of major inflammatory mediators and MAPK/NF-κB pathway, etc. Rats in “HHY” group developed obvious symptoms such as cough, dyspnea, mental fatigue, etc., but these symptoms were obviously mitigated in “Zisu” and “Luole” groups. H&E staining analysis, including score, MLI, MAN, wt% and WA%, showed that “Zisu” and “Luole” significantly alleviated lung injury and the degree of airway remodeling and emphysema compared to “HHY”. In BALF, the number of total leukocyte and the percent neutrophils in “Zisu” and “Luole” groups were evidently lower than “HHY” group. The levels of inflammatory mediators, such as IL-8, MPO, MIP-2, LTB4, TNF-α and neutrophil elastase, in “HHY” group were obviously higher than “Zisu” and “Luole” groups. The ROS-mediated NF-κB p65 and p38MAPK pathways may play an important role. Results indicated that tobacco introduced perilla and basil genes could remarkably attenuate recruitment, infiltration and activation of neutrophils and intervene in airway inflammation, retarding disease progression, especially “Zisu”. Changes in chemical composition via breeding techniques may be a novel way for tobacco harm reduction.

Population genetic diversity of tomato spotted wilt orthotospovirus isolates from tobacco in Yunnan Province, China

We explored the genetic diversity and molecular evolutionary characteristics of tomato spotted wilt orthotospovirus (TSWV) on tobacco in Yunnan. In this study, 523 diseased tobacco leaf samples with suspected TSWV infection from nine different geographical sources in Yunnan were tested, and nucleocapsid protein (NP) of some isolates was amplified and cloned by reverse transcription-polymerase chain reaction (RT‒PCR). Bioinformatics tools were used to analyze the population genetic structure and molecular evolutionary relationships of the tobacco TSWV population. TSWV was detected in 284 of 523 samples, with an average positivity rate of 54.3%. NP gene sequences of the 159 tobacco TSWV isolates obtained were all 777 bp, with 265 nucleic acid polymorphic sites, with 197 variant sites, including 66 parsimony informative and 131 single variant sites. Results for virus consistency and variation analysis based on the NP gene showed that the nucleotide sequence consistency of Yunnan TSWV isolates was 96∼100%, the haplotype diversity 0.963, and the nucleic acid diversity 0.006. Phylogenetic analysis revealed that Yunnan tobacco TSWV isolates belong to the same group, with lower genetic differentiation and more frequent gene exchange among tobacco isolates of different geographical origins; their geographical characteristics were not obvious, and significant recombination signals were detected in the gene sequences of the DL-20 and DL-42 isolates. Many of the NP gene mutations of tobacco TSWV isolates from different geographic origins were deleterious in the nine different planting regions of Yunnan tobacco TSWV isolates, with only the population in the QJ planting region experiencing past population expansion events. The findings suggest that genetic recombination, mutation, and negative selection pressure are major drivers of the genetic diversity of tobacco TSWV in Yunnan. This study report of genetic variation in populations of TSWV isolates from various tobacco regions in Yunnan and provides information on the population structure of Yunnan tobacco TSWV isolates, which can help to prevent and control TSWV on Yunnan tobacco and provide a reference for research of disease-resistant varieties of tobacco.

Transcriptomics and virus-induced gene silencing identify defence-related genes during Ralstonia solanacearum infection in resistant and susceptible tobacco

Bacterial wilt (BW) caused by Ralstonia solanacearum is a globally prevalent bacterial soil-borne disease. In this study, transcriptome sequencing were subjected to roots after infection with the R. solanacearum in the resistant and susceptible tobacco variety. DEGs that responded to R. solanacearum infection in both resistant and susceptible tobacco contributed to pectinase and peroxidase development and were enriched in plant hormone signal transduction, signal transduction and MAPK signalling pathway KEGG terms. Core DEGs in the resistant tobacco response to R. solanacearum infection were enriched in cell wall, membrane, abscisic acid and ethylene terms. qRT-PCR indicated that Nitab4.5_0004899g0110, Nitab4.5_0004234g0080 and Nitab4.5_0001439g0050 contributed to the response to R. solanacearum infection in different resistant and susceptible tobacco. Silencing the p450 gene Nitab4.5_0001439g0050 reduced tobacco resistance to bacterial wilt. These results improve our understanding of the molecular mechanism of BW resistance in tobacco and solanaceous plants.

Evaluation of growth, physiological response, and drought resistance of different flue-cured tobacco varieties under drought stress.

In recent years, more severe droughts have occurred frequently in many parts of the world, drought stress is the primary abiotic stress factor restricting the growth and quality of flue-cured tobacco. Therefore, screening dryland cultivation-compatible flue-cured tobacco varieties will help reduce the negative impact of drought. Tobacco varieties were selected: Qinyan 96 (Q96), Zhongyan 101 (Z101), Yunyan 87 (Y87), and Yunyan 116 (Y116). A pot experiment was conducted with four water supply gradients: sufficient, mild stress, moderate stress, and severe stress. The aim was to analyze inter-varietal differences in agronomic traits, photosynthetic traits, reactive oxygen species (ROS) metabolism, and antioxidant enzyme system under drought stress. Additionally, the drought resistance of four flue-cured tobacco varieties was evaluated using principal component analysis and membership function analysis. The results showed that drought intensification inhibited seedling growth and development across all varieties, with Q96 showing the least decrease and Y116 the greatest. With the increasing degree of drought stress, photosynthetic rates (Pn), transpiration rate (Tr), and stomatal conduction (Gs) have shown gradually decreasing trends, while substomatal cavity CO2 concentration (Ci) showed a growing trend. Severe drought corresponded with lower chlorophyll content and decreased the maximal photochemical efficiency (Fv/Fm), photosystem II (PSII), and photochemical quenching coefficient (qP) in all varieties, while steady-state non-photochemical quenching (NPQ) increased. Increased drought stress led to significantly higher reactive oxygen species (ROS) and malondialdehyde (MDA) content accumulation in tobacco seedlings. The antioxidant enzyme activities in, Q96, Z101, and Y87 increased under mild drought stress, whereas Y116 showed decreased activity. The drought resistance ranking among the four varieties is as follows: Q96 > Z101 > Y87 > Y116. Therefore, Q96 is a promising drought-tolerant breeding material that can be used as a reference for dryland cultivation of flue-cured tobacco.

Polyphenol content in tobacco (N. tabacum L.) and antioxidant activity

The aim of the present work is to determine the content of polyphenols in tobacco varieties and to investigate the antioxidant activity in tobacco extracts. Bulgarian tobacco varieties from the Basmi and Kabakulak variety groups produced conventionally and biologically, were used. Two types of extracts were investigated - crude extracts obtained by four solvents - 100% CH3OH, 60% CH3OH, H2O, and 96% C2H5OH, and purified extracts obtained by further purification of crude 60% methanolic extract using two techniques - solid phase extraction (SPE) and resin purification, Tobaccos from the variety group Basmi, conventionally grown, have a higher polyphenol content compared to the tobaccos from variety group Kabakulak. No significant difference was observed in the polyphenol contents of in conventionally and organically grown tobaccos of the same variety. The content of phenolic compounds in crude extracts by various solvents decreased in the following order: 60% CH3OH>H2O>100% CH3OH>96% C2H5OH. The crude and purified tobacco extracts showed high antioxidant activity determined by ABTS, FRAP and DPPH assays. The total phenolic content and antioxidant activity of 60% crude methanolic extracts were close to the SPE purified and resinpurified tobacco extracts

Comparative Technological Assessment of the Quality Formation of Local and Introduced Varieties of Virginia Flue-cured and Burley Tobaccos

The production of “marketable” tobacco is decisive in the pReferences of local farmers towards certain varieties of Virginia and Burley tobaccos. The aim of the study was to complete a comparative technological evaluation of the quality potential of introduced and local varieties of Virginia flue-cured and Burley air-cured tobaccos in Bulgaria. The investigation was conducted with tobaccos from 2018 crop year and included 4 varieties of Virginia flue-cured and 2 varieties of Burley tobacco (local and introduced), grown in different regions of Southern and Northern Bulgaria. The complex assessment of tobacco quality was based on leaf and smoke chemical indicators, external leaf quality elements and smoking performance of the studied tobaccos. The final rating was achieved by referring to the value of the calculated “quality indices”. Two of the local varieties, V 0454 from region Parvomay and PVH 19 from Central Northern Bulgaria were rated the best in the complex evaluation of the FCV tobaccos. A better complex expression of quality was found in the introduced (trial) variety Burley N compared to the local Burley 1317 in Southern Bulgaria region.

Identification of CNN hyper-parameters for tobacco leaf quality classification on Nvidia Jetson Nano

At the moment, there are some inaccuracies in manual classification for tobacco leaf quality selection, which are influenced by some factors, such as human fatigue or poor lighting. These cases lead to the need for another method that is more consistent, faster and reliable. This research is an implementation of CNN (Convolutional Neural Network) in the classification of fresh tobacco leaves in terms of maturity grades. The primary objective is to develop an efficient CNN model capable to automize the classification of tobacco leaves into three maturity criteria: immature, mature, and old. This methodology consists of some key factors, including color thresholding strategies to purge the noise from the background, Basic Image Manipulation approaches, the systemized screening of different input sizes, and CNN models to enhance the results. The result of this research proves that the developed CNN model has 97.9 % accuracy achieved following 200 training sessions. The model is trained on a dataset comprising 1,249 fresh leaf photos, with a balanced 80:10:10 for train, validation and test ratio. However, the study emphasizes that the CNN model has successfully supported the tobacco leaf discrimination on a Jetson Nano Single-Board Computer with a Graphic Processing Unit (GPU). The study extends beyond the mere theoretical contribution to practical applications in sorting “Gagang Rejeb Sidi” tobacco leaf, the highest quality tobacco variety in South Malang, East Java, Indonesia. Classification using a webcam as an input device shows the fastest processing time of 203.17 ms and the maximum is 1,363 ms. This CNN model algorithm will be applied to a tobacco leaf selector machine, which has a high-speed conveyor and a three-position selector arm. The machine will be operated close to the field in post-harvest time under uniform lighting conditions. Overall, the result of this research is highly relevant in terms of the short duration and accuracy for understanding the commodity classification. It provides a new angle toward speeding up the classification process and improving Indonesian tobacco quality

Изследване на морфологични и качествени показатели на нови линии ориенталски тютюн от екотип Крумовград

In recent years, oriental tobacco varieties from the Krumovgrad ecotype have been among the most preferred by commercial companies in Bulgaria. The creating and study of genetic material with their participation is important to meet the needs and requirements of the sector. During a three-year period in the conditions of experimental field (EF) - Markovo were studied biometric (number of leaves, plant height, length and width of 14 and 21 leaves) and quality (yield and distribution by classes) indicators of four lines of oriental tobacco, created with the Krumovgrad ecotype participation. As control was used variety Krumovgrad 90. As a result of the studied biometric and qualitative indicators, it was established, that according to the indicators plant height, the studied lines are in the oriental tobacco range, but form a greater number of leaves from the control variety (the largest numbers of leaves and smaller by size in line 72). Line 71 has a statistically proven longest length on the 14th and 21st leaves. Lines 71 and 73 have the highest average yield (kg/da) for the three years and exceed the yield of the control variety by 10-15%. The class distribution results show, that lines 72 and 73 have the highest percentage of I-st class, and line 71 has the highest percentage of II-nd class and the lowest percentage of III- rd class. From the assessment made lines 71 and 73 have the best values of the biometric and quality indicators.

Loss function of NtGA3ox1 delays flowering through impairing gibberellins metabolite synthesis in Nicotiana tabacum.

Flowering time, plays a crucial role in tobacco ecological adaptation besides its substantial influence on tobacco production and leaf quality. Meanwhile, it is sensitive to biotic or abiotic challenges. The plant hormones Gibberellins (GAs), controlling a number of metabolic processes, govern plants growth and development. In this study, we created a late flowering mutant HG14 through knocking out NtGA3ox1 by CRISPR/Cas9. It took around 13.0 and 12.1 days longer to budding and flowering compared to wild type Honghuadajinyuan. Nearly all of the evaluated agronomic characters deteriorated in HG14, showing slower growth and noticeably shorter and narrower leaves. We found that NtGA3ox was more prevalent in flowers through quantitative reverse transcription PCR analysis. Transcriptome profiling detected 4449, 2147, and 4567 differently expressed genes at the budding, flowering, and mature stages, respectively. The KEGG pathway enrichment analysis identified the plant-pathogen interaction, plant hormone signal transduction pathway, and MAPK signaling pathway are the major clusters controlled by NtGA3ox1 throughout the budding and flowering stages. Together with the abovementioned signaling pathway, biosynthesis of monobactam, metabolism of carbon, pentose, starch, and sucrose were enriched at the mature stage. Interestingly, 108 up- and 73 down- regulated DEGs, impairing sugar metabolism, diterpenoid biosynthesis, linoleic and alpha-linolenic acid metabolism pathway, were continuously detected accompanied with the development of HG14. This was further evidenced by the decreasing content of GA metabolites such as GA4 and GA7, routine chemicals, alkaloids, amino acids, and organic acids Therefore, we discovered a novel tobacco flowering time gene NtGA3ox1 and resolved its regulatory network, which will be beneficial to the improvement of tobacco varieties.

Overexpression of NtLHT1 affects the development of leaf morphology and abiotic tolerance in tobacco

LYSINE HISTIDINE TRANSPORTER1 (LHT1) is a crucial broad-specificity and high-affinity amino acid transporter affecting the uptake of nitrogen and probably the tolerance to abiotic stress in plants. However, little is known about the phenotypic functions of LHT1 in plant growth and development and abiotic stress tolerance. In this study, we identified the NtLHT1 gene from the tobacco variety Honghuadajinyuan (HD) and determined its important roles in leaf morphological development and plant resistance to abiotic stress. Comprehensive functional analyses using knockout and overexpression transgenic lines (ntlht1 and OE) revealed overexpression of NtLHT1 accelerated leave senescence and increased plant height, leaf number and plant tolerance under cold, salt and drought stresses. In addition, NtLHT1 overexpression significantly decreased the leaf elongation of HD, causing the leaves to change from a long-elliptical shape to an elliptical shape. However silencing NtLHT1 decreased the seed germination rate under NaCl and PEG stresses. Moreover, NtLHT1 significantly affected the contents of various amino acids, such as the neutral, acidic, non-polar and aromatic amino acids, ethylene precursor (ACC), GA3 and IAA in tobacco. These results suggested that the amino acid and ethylene precursor ACC transport activities of NtLHT1 provide fine regulatory function for plant growth and development and plant tolerance to abiotic stress.

Overexpression of Nta-miR6155 confers resistance to Phytophthora nicotianae and regulates growth in tobacco (Nicotiana tabacum L.).

Tobacco black shank induced by Phytophthora nicotianae causes significant yield losses in tobacco plants. MicroRNAs (miRNAs) play a pivotal role in plant biotic stress responses and have great potential in tobacco breeding for disease resistance. However, the roles of miRNAs in tobacco plants in response to P. nicotianae infection has not been well characterized. In this study, we found that Nta-miR6155, a miRNA specific to Solanaceae crops, was significantly induced in P. nicotianae infected tobacco. Some of predicted target genes of Nta-miR6155 were also observed to be involved in disease resistance. To further investigate the function of miR6155 in tobacco during P. nicotianae infection, Nta-miR6155 overexpression plants (miR6155-OE) were generated in the Honghua Dajinyuan tobacco variety (HD, the main cultivated tobacco variety in China). We found that the Nta-miR6155 overexpression enhanced the resistance in tobacco towards P. nicotianae infections. The level of reactive oxygen species (ROS) was significantly lower and antioxidant enzyme activities were significantly higher in miR6155-OE plants than those in control HD plants during P. nicotianae infection. In addition, we found that the accumulation of salicylic acid and the expression of salicylic acid biosynthesis and signal transduction-related genes is significantly higher in miR6155-OE plants in comparison to the control HD plants. Furthermore, we found that Nta-miR6155 cleaved target genes NtCIPK18 to modulate resistance towards P. nicotianae in tobacco plants. Additionally, phenotypic analysis of miR6155-OE plants showed that Nta-miR6155 could inhibit the growth of tobacco by suppressing nitrogen uptake and photosynthesis. In conclusion, our findings indicated that miR6155 plays a crucial role in the regulation of growth and resistance against P. nicotianae infections in tobacco plants.

Pepper vein mottling virus (PVMV) – нов вирус по тютюна в България

The aim of the present study is to trace the emergence and development of TEV and PVMV, new viruses for tobacco in Bulgaria, in the three varietal groups of Burley, Virginia and Basmi tobacco grown in the central part of southern Bulgaria. During the period 2017-2019, immunological studies were carried out to prove new viruses for tobacco in Bulgaria from the group of potyviruses PVMV and TEV. A kit for serological identification of the French company SEDIAG S.A.S. was used to prove the viruses. To detect TEV, TAS-ELISA was performed with IgG dilution of 1:100 and DAS-ELISA - to detect PVMV with IgG dilution of 1:100. In Virginia and Basmi tobacco variety groups, the potyvirus PVMV was serologically proven, and the virus was identified for the first time in tobacco in Bulgaria. PVMV was demonstrated in monoinfection and in complex with TEV in isolates from the cultivar group Virginia and Basmi. TEV and PVMV were not detected in isolates from the Burley cultivar group. In tobacco, the two potyviruses cannot be distinguished based on symptoms alone. Accurate diagnosis is possible by applying an ELISA or PCR test

Tobacco roots increasing diameter and secondary lateral density in response to drought stress

Exploring the responses of root morphology and its physiological mechanisms under drought stress is significant for further improving water and nutrient absorption in roots. Here, we simulated drought through hydroponics combined with PEG treatments in tobacco to characterize the changes in tobacco root architecture. Our results showed the total root length, first lateral root number, and first lateral root length were significantly reduced upon increasing drought severity, but the average root diameter and secondary lateral root density increased under certain drought conditions. The change of auxin content in roots under drought stress was correlated with the root diameter and second lateral root density responses. Exogenous addition of the auxin analog (NAA) and the auxin transport inhibitor (NPA), as well as DR5:GUS staining experiments further demonstrated that auxin participated in this physiological process. Meanwhile, brassinolide (BR) exhibited a similar trend. Exogenous addition of BR (EBR) and the BR synthesis inhibitor BRZ experiments demonstrated that BR may participate upstream of auxin under drought stress. PEG treatment significantly up-regulated NtBRI1 at 9–24 h, and promoted the up-regulation of NtBSK2 and NtBSK3 at 48 h and 24 h, respectively, these genes may contribute to the change in root morphology under drought stress. This study shows that auxin and BR are involved in the changes in root morphology in tobacco exposed to drought stress. The elucidation of the molecular mechanism at play thus represents a future target for breeding drought-tolerant tobacco varieties.

Tobacco resistance gene expression levels in response to the infection of Phytophthora nicotianae

One of the main obstacles often encountered in efforts to increase productivity and quality of tobacco (Nicotiana tabacum) yields is the attack of black shank disease by the oomycetes Phytophthora nicotianae. So far, what has been done mainly by tobacco cultivators is the observation of resistance through calculating the rate of death or disease of plants due to pathogen attack, so research is needed to determine the resistance profile of local varieties of tobacco to black shank disease in molecular stage to speed up the screening process of tobacco varieties. This study aim to determine the gene expression profile related to resistance in tobacco varieties Beinhart 1000, Hick Broadleaf, and two local varieties, namely Dark 302 and Dark 314, in response to black shank disease. The research consisted of preparing tobacco and P. nicotianae inoculum, artificial inoculation, followed by semi-quantitative analysis of gene expression related to tobacco resistance, PR1, PR4, PLP2, and PUB24. Tobacco resistant variety, Beinhart 1000, expressed a relatively 285% higher PR1 significantly than the control. The length of time of infection showed that PR1, PR4, PLP2, and PUB24 genes were expressed temporally, and the dynamics of expression of each test gene affected the development of pathological conditions.