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Introduction: French bean (Phaseolus vulgaris L.) holds global significance as one of themost consumed legumes, with commercial value surpassing that of all other legume crops combined. In India, the consumption of French beans has grown steadily, especially in the North Eastern region, driven by heightened consumer interest in its nutritional benefits. Considering these factors,we initiated an induced mutagenesis program to enhance the genetic diversity of locally grown French bean genotypes, traditionally cultivated for their superior adaptability. Methods: To achieve this, we initiated an induced mutagenesis program. Seeds from the village seed stock were subjected to treatments with varying doses of ethyl methane sulfonate (EMS) ranging from 0.1% to 0.4% and sodium azide (SA) from 0.1% to 0.4%. The objective was to increase yield potential and enhance genetic diversity. Results: The treatment with EMS and SA led to a non-specific, dosage-independent reduction in biophysiological characteristics in French bean mutants. Notably, the 0.4% SA treatment significantly inhibited germination and fertility, causing a decrease in chlorophyll (10.02 mg. g-1 FW) and carotenoid (1.57 mg. g-1 FW) levels. This suggests a disruption in genes associated with chlorophyll and carotenoid synthesis. However, in the M2 generation, the mutagenic treatments substantially improved yield and associated traits. The highest pod yield per plant was recorded at 79.50 gm for the 0.2% EMS treatment. A character association study revealed strong correlations (0.217 to 0.995) between pod yield and other agronomic traits. Discussion: The results indicate that selecting mutants based on these traits in populations treated with EMS and SA can significantly increase crop yield. The 0.2% SA and 0.2% EMS M2 mutant populations exhibited the highest induced variability, making them ideal for selecting higher-yielding mutant lines for further breeding generations. The increased yields in these mutant lines, derived from a local cultivar, show promise for meeting the growing demand for French bean production through their widespread cultivation. [ABSTRACT FROM AUTHOR]

Microsatellite markers were used for the assessment of genetic diversity and genetic structure in a germplasm collection of yellow mustard, Sinapis alba L. The comprehensive collection of genetic resources represented 187 registered varieties, landraces, and breeding materials. Microsatellites generated 44 polymorphic alleles in 15 loci. Eleven of them were medium to highly polymorphic, and the high levels of observed heterozygosity (0.12–0.83) and Nei's gene diversity index (0.11–0.68) indicated a high level of polymorphism. Based on PCoA and neighbor joining analyses, the genetic resources were divided into two groups. The range of genetic dissimilarity in the analysed collection was in the range of 0.00–1.00. The high level of dissimilarity between the accessions was documented by the high WAM value (33.82%). Bayesian clustering algorithms were performed in the STRUCTURE 2.3.4 software. The number of clusters was estimated at K = 2. The accessions were classified according to Q1/Q2 values. The low average values of the parameters Fst_1 (0.3482), Fst_2 (0.1916), and parameter alpha (0.0602) indicated substantial mating barriers between varieties and reproductive isolation due to the limited exchange of genetic resources between breeders. These results demonstrated the importance of extensive collections of genetic resources for the maintenance of genetic diversity and indicated considerable genetic differentiation among accessions. [ABSTRACT FROM AUTHOR]

IntroductionFrench bean (Phaseolus vulgaris L.) holds global significance as one of the most consumed legumes, with commercial value surpassing that of all other legume crops combined. In India, the consumption of French beans has grown steadily, especially in the North Eastern region, driven by heightened consumer interest in its nutritional benefits. Considering these factors, we initiated an induced mutagenesis program to enhance the genetic diversity of locally grown French bean genotypes, traditionally cultivated for their superior adaptability.MethodsTo achieve this, we initiated an induced mutagenesis program. Seeds from the village seed stock were subjected to treatments with varying doses of ethyl methane sulfonate (EMS) ranging from 0.1% to 0.4% and sodium azide (SA) from 0.1% to 0.4%. The objective was to increase yield potential and enhance genetic diversity.ResultsThe treatment with EMS and SA led to a non-specific, dosage-independent reduction in biophysiological characteristics in French bean mutants. Notably, the 0.4% SA treatment significantly inhibited germination and fertility, causing a decrease in chlorophyll (10.02 mg. g-1 FW) and carotenoid (1.57 mg. g-1 FW) levels. This suggests a disruption in genes associated with chlorophyll and carotenoid synthesis. However, in the M2 generation, the mutagenic treatments substantially improved yield and associated traits. The highest pod yield per plant was recorded at 79.50 gm for the 0.2% EMS treatment. A character association study revealed strong correlations (0.217 to 0.995) between pod yield and other agronomic traits.DiscussionThe results indicate that selecting mutants based on these traits in populations treated with EMS and SA can significantly increase crop yield. The 0.2% SA and 0.2% EMS M2 mutant populations exhibited the highest induced variability, making them ideal for selecting higher-yielding mutant lines for further breeding generations. The increased yields in these mutant lines, derived from a local cultivar, show promise for meeting the growing demand for French bean production through their widespread cultivation.

A DNA damage-inducible mutagenic gene cassette has been implicated in the emergence of drug resistance in Mycobacterium tuberculosis during anti-tuberculosis (TB) chemotherapy. However, the molecular composition and operation of the encoded ‘mycobacterial mutasome’ – minimally comprising DnaE2 polymerase and ImuA′ and ImuB accessory proteins – remain elusive. Following exposure of mycobacteria to DNA damaging agents, we observe that DnaE2 and ImuB co-localize with the DNA polymerase III β subunit (β clamp) in distinct intracellular foci. Notably, genetic inactivation of the mutasome in an imuBAAAAGG mutant containing a disrupted β clamp-binding motif abolishes ImuB–β clamp focus formation, a phenotype recapitulated pharmacologically by treating bacilli with griselimycin and in biochemical assays in which this β clamp-binding antibiotic collapses pre-formed ImuB–β clamp complexes. These observations establish the essentiality of the ImuB–β clamp interaction for mutagenic DNA repair in mycobacteria, identifying the mutasome as target for adjunctive therapeutics designed to protect anti-TB drugs against emerging resistance.

Background. The method of induced mutagenesis is used to temporarily increase the frequency of mutations, allowing a higher probability of obtaining plants with new alleles and traits valuable for breeding. The search for new agents with high mutagenic activity is of particular interest for the development of mutational breeding. A new mutagen for barley is phosphemide.Materials and methods. Field and laboratory studies were conducted in 2016–2018. Three barley genotypes were treated with an aqueous solution of phosphemide at two concentrations: 0.002% and 0.01%, exposure: 3 hours. Experimental data were statistically processed by the analysis of variance (ANOVA) using Statistica 7. The error of the mean (Sx) was calculated for the mean values. Significance of differences (P < 0.05) was determined by Student’s t-test. Mutation frequency (Mf), mutagenic effectiveness (ME), and efficiency (Me) were assessed.Results and conclusion. It was found that the greatest contribution to formation of field seed germination of mutant populations in M1 and M2 generations was made by the mutagenic factor (20,36%) and interaction of the genotype × environment (18,55%) and mutagen × environment factors (14,93%). The concentration of 0.01% was recognized as semi-lethal for two accessions. In the M2 generation, the mutagenic effectiveness of the 0.002% phosphemide concentration exceeded that of 0.01% more than 4 times. The low concentration was more effective for cv. ‘Zernogradsky 813’ (17.43%) and accession Dz02- 129 (12.04%). For C.I. 10995, a higher concentration of phosphemide had greater effect (29.66%) providing a high mutation frequency (9.79%) against a relatively low lethality (33.00%). Nine different types were identified in the mutation spectrum. In M3 generation, distinct inheritance of the changes was confirmed in 46.43% of families. The highest number of families with confirmed changes was recorded for C.I. 10995 in the experiment with a higher concentration.

The snowballing growth of scientific data obtained using modern techniques of genome editing (GE) calls for their critical evaluation and comparison against previously applied methods such as induced mutagenesis, which was a leading method of genome modification for many decades of the past century, and its application has resulted in a huge diversity of cultivars. However, this method was relatively long and included a number of stages from inducing multiple mutations using different mutagenic factors to crossing and selecting the most valuable cultivars for several generations. A new technology of genetic engineering and transgenesis enabled us to radically reduce the time required to obtain a new genetically-modified cultivar to one generation and make the modification process more effective and targeted. The main drawback of this approach was that an introduced transgene might uncontrollably affect the other genes of a recipient plant, which led to the limitations imposed on transgenesis application in many countries. These limitations have been effectively surmounted thanks to the development of GE techniques allowing for a precise modification within a single gene that in many characteristics make it similar to a natural allele (especially when it comes to ribonucleoprotein complexes), which has paved the way for wide application of GE in routine breeding. The paper reviews the main stages of GE development in its application in plants. It provides short descriptions of different GE techniques, including those using protein editors such as zinc-finger and transcription activator-like effector nucleases (TALEN), and the CRISPR/Cas9 technology. It lists a number of achievements in using GE to produce new cultivars of higher yield that are resistant to unfavorable factors and have good nutritional properties. The review also considers the de novo domestication approach, which allows for faster obtaining of new cultivars from natural varieties. In the conclusion, the future ways of GE development are discussed.

In order to study the increase in productivity of natural hydrolase producers B. subtilis (producer of amylolytic and proteolytic enzymes) and T. harzianum (producer of xylolytic and cellulolytic enzymes), the efficiency of various approaches to non-directed induced mutagenesis was studied and their comparative characteristics were carried out. Using chemical and physical mutagenesis, new highly active producers of extracellular hydrolytic enzymes B. subtilis strain MB085-1457, B. subtilis strain MB085-2701, B. subtilis strain MB085-3689, T. harzianum strain MF091-962, T. harzianum strain MF091-2093 and T. harzianum strain MF091-3416 were obtained. Comparison of various methods of induced mutagenesis, namely methods of mutagenesis using nitrosoguanidine and nitrosomethylurea, UV and gamma irradiation showed that the greatest efficiency was achieved after mutagenesis using gamma rays. Various methods of induced mutagenesis can be used not only to create effective schemes for increasing the level of accumulation of target enzymes of producers, but also to obtain new drugs based on highly productive strains of microorganisms with hydrolase activity for the purpose of using them in resource-saving technologies for processing agricultural waste (into useful resources) and reducing the negative impact on the environment.

Microsatellite markers were used for the assessment of genetic diversity and genetic structure in a germplasm collection of yellow mustard, Sinapis alba L. The comprehensive collection of genetic resources represented 187 registered varieties, landraces, and breeding materials. Microsatellites generated 44 polymorphic alleles in 15 loci. Eleven of them were medium to highly polymorphic, and the high levels of observed heterozygosity (0.12–0.83) and Nei’s gene diversity index (0.11–0.68) indicated a high level of polymorphism. Based on PCoA and neighbor joining analyses, the genetic resources were divided into two groups. The range of genetic dissimilarity in the analysed collection was in the range of 0.00–1.00. The high level of dissimilarity between the accessions was documented by the high WAM value (33.82%). Bayesian clustering algorithms were performed in the STRUCTURE 2.3.4 software. The number of clusters was estimated at K = 2. The accessions were classified according to Q1/Q2 values. The low average values of the parameters Fst_1 (0.3482), Fst_2 (0.1916), and parameter alpha (0.0602) indicated substantial mating barriers between varieties and reproductive isolation due to the limited exchange of genetic resources between breeders. These results demonstrated the importance of extensive collections of genetic resources for the maintenance of genetic diversity and indicated considerable genetic differentiation among accessions.

The present research work was conducted to improve the phytase production by genetic alteration of Aspergillus niger with induced mutagenesis using solid state fermentation. Strain improvement was carried out in the presence of ultra violet (UV) irradiation and ethylmethane sulphonate (EMS) [0.5% v/v] treatments for various time intervals. We reported an improved strain of Aspergillus niger designated as UV-3 mutant producing a zone of hydrolysis of about 40 mm, in comparison to wild strain (26 mm). The highest enzyme activity was found to be 547.64 IU/g for UV-3 mutant followed by EMS-4 mutant (492.23 IU/g) compared to wild strain which showed 406.45 IU/g of enzyme activity. There was 1.35- fold increase in phytase production after mutation studies of Aspergillus niger. Phytase was applied as poultry feed additive and given to broiler chickens for 5 weeks. The results exhibited that there was increase in body weight gain (BWG) of chicks for experimental group (2028 g) in comparison to control group (1903 g). Thus, physical and chemical mutagenesis was proved as an effective technique for the improvement of strain and ultimately for enhanced and economical phytase production for different industrial applications. [ABSTRACT FROM AUTHOR]

Novel and unique properties of nanomaterials, which are not apparent in larger-size forms of the same material, encourage the undertaking of studies exploring the multifaced effects of nanomaterials on plants. The results of such studies are not only scientifically relevant but, additionally, can be implemented to plant production and/or breeding. This study aimed to verify the applicability of silver nanoparticles (AgNPs) as a mutagen in chrysanthemum breeding. Chrysanthemum × grandiflorum (Ramat.) Kitam. 'Lilac Wonder' and 'Richmond' leaf explants were cultured on the modified MS medium supplemented with 0.6 mg·L−1 6-benzylaminopurine (BAP) and 2 mg·L−1 indole-3-acetic acid (IAA) and treated with AgNPs (spherical; 20 nm in diameter size; 0, 50, and 100 mg·L−1). AgNPs strongly suppressed the capability of leaf explants to form adventitious shoots and the efficiency of shoot regeneration. The content of primary and secondary metabolites (chlorophyll a, chlorophyll b, total chlorophylls, carotenoids, anthocyanins, phenolic compounds) and the activity of enzymatic antioxidants (superoxide dismutase and guaiacol peroxide) in leaf explants varied depending on the AgNPs treatment and age of culture. Phenotype variations of ex vitro cultivated chrysanthemums, covering the color and pigment content in the inflorescence, were detected in one 50 mg·L−1 AgNPs-derived and five 100 mg·L−1 AgNPs-derived 'Lilac Wonder' plants and were manifested as the color change from pink to burgundy-gold. However, no changes in inflorescence color/shape were found among AgNPs-treated 'Richmond' chrysanthemums. On the other hand, the stem height, number of leaves, and chlorophyll content in leaves varied depending on the AgNPs treatment and the cultivar analyzed. A significant effect of AgNPs on the genetic variation occurrence was found. A nearly two-fold higher share of polymorphic products, in both cultivars studied, was generated by RAPD markers than by SCoTs. To conclude, protocols using leaf explant treatment with AgNPs can be used as a novel breeding technique in chrysanthemum. However, the individual cultivars may differ in biochemical response, the efficiency of in vitro regeneration, genetic variation, and frequency of induced mutations in flowering plants. [ABSTRACT FROM AUTHOR]

Induced mutagenesis opens great perspectives for radical genetic improvement of cultivated plants. Scientists seeking new sources and methodological approaches to improve the frequency and extend the range of mutations have drawn attention to the Zone of Alienation around the Chornobyl Nuclear Power Plant, where unique conditions of the influence of mutagenic factors have developed, and therefore needs to be studied for possible use of its territory in propagating parent material for selective breeding of wheat. Plants of winter wheat of Albatros Odesky and Zymoiarka varieties were grown within 10 km of the Chernobyl Plant, inside the Alienation Zone, in Chystohalivka, Kopachi and Yaniv villages of Chornobyl district of Kyiv Oblast. The exposure occurred in the dose of 7.2 ∙ 10–12– 50.0 ∙ 10–12 A/kg. As the control, we used the territory of the Research Institute of Physiology of Plants and Genetics of the Academy of Sciences of Ukraine (Hlevaha urbanized settlement of Vasylkivsky District of Kyiv Oblast), where the power of the exposure dose equaled 0.93 ∙ 10–12 A/kg. Frequency and spectrum of mutant forms were determined in M2–M3 generations according to the ratio of the number of families with mutagenic plants to studied M2 families. Among the observed mutations, we determined the share of the ones important for selective breeding. Chronic ionizing radiation throughout the vegetation period of winter wheat increased the level of noticeable mutations, the frequency of which exceeded the control parameters by 8.0–14.9 times. In the conditions of cultivation of winter wheat in the territory of Kopachi village, where the dose was the lowest, we recorded a high level of mutation variability which exceeded the control parameters by 8.0–9.2 times and was notably different from the frequency of mutations induced by radionuclide contamination of soil in the territories of Chystohalivka and Yaniv villages. The mutation range contained 12–20 types and depended on the density of soil contamination with radio nuclides, magnitude of exposure dose and genotype of plants. The predominant mutations were the ones related to the duration of vegetation period, length of the stem, morphology and awns of the ear. Among the detected mutations, the important selective ones accounted for 24.3–49.3%, predominant being low height, intense growth and long cylindrical ear. Because beneficial agronomic traits are highly likely to be inherited in complex with mutations that reduce the productivity of winter wheat, efficiency of direct selection of mutant forms that are valuable for selective breeding is limited. Enlargement of genetic diversity of the initial selection material using the radionuclide-induced mutagenesis resulting from contamination creates the possibility of using it in cross breeding for the purpose of implementing selective breeding genetic programs of improving wheat varieties.

Lentils (Lens culinaris Medik.) is a protein- and nutrient-rich crop with limited genetic diversity and climate adaptability, making it ideal for mutation breeding research. Hence, in this study, we aimed to select and characterize distinct mutations in the flower and pod traits of lentil crops for enhanced yield and yield stability. In this study, healthy and viable lentil seeds were mutagenized using different concentrations of ethyl methanesulfonate (EMS) (0.10%, 0.25%, 0.50%, 0.75%, and 1.0%). The mutagenized lentil populations were cultivated up to the third generation (M 3) to identify stable mutations in the flower and pod structures with increasing plant height. The notably larger 'bigger pod' (bp) mutant, characterized by its unusually large pods containing 6–7 seeds per pod, was meticulously studied and quantified for its morphological traits in subsequent generations. Morphological observations of the tall bp mutant revealed significant mutations induced by EMS (0.10%) treatment. The quantitative trait means and confidence intervals showed that the mutant and parent cultivar L-4076 exhibited considerable variation. Seed yield (g) and yield-related components, including pods per plant, pod length (cm), and seeds per pod, were significantly higher in the mutant. Seed yield exhibited a significant positive phenotypic correlation with pod length, followed by branches per plant, seeds per pod, plant height, and pods per plant. The novel bp mutant induced in the present study produced increased number of seeds per plant and ensured optimal resource utilization, thus possibly contributing to yield improvement and stability. Further, it also aided in understanding the genetic networks that control legume flower and pod architecture and in genomics-assisted breeding for the development of superior lentil cultivars. • Identification of tall, 'bigger pod' (bp) lentil mutant with 6–7 seeds per pod. • The bp mutant surpasses parent cultivar L-4076 in pod size, seed count, and yield. • Insights into pod architecture genetics aid superior lentil cultivar development through genomic breeding. [ABSTRACT FROM AUTHOR]

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Domesticated crops are characterized by narrow genetic base reflecting one or more bottlenecks during millennia-long selection. As a result, current breeding programs are limited in available germplasm and are forced to deal with incremental improvements of yield, resistance, nutritional value, etc. Since the establishment of modern genetics and biotechnology, several new approaches have emerged to extend the genetic base and germplasm improvement. Among these methods, induced mutagenesis appeared as most useful conventional breeding tool. Although, its successful application currently requires good knowledge of modern molecular tools. In this paper we will make an attempt to overview SSR, ISSR and ISAP techniques as well as to offer examples of their application in tomato breeding programs.

To determine the mutagen agent potency and deduce an optimum dose, cytological analysis for induced chromosomal aberrations is considered as an accurate index in mutation breeding. Therefore, the present investigation was carried out to estimate the relative frequency and spectrum of meiotic abnormalities at various stages of cell division using Gamma rays, EMS and their combination treatments in M1 generation of black gram (Vigna mungo L. Hepper) varieties Pant U-30 and T-9. The analysis of M1 plants revealed a wide range of induced meiotic abnormalities like univalents, multivalents, laggards, chromatin bridges, micronuclei and chromosome stickiness by different mutagen doses. In addition to these, behavioral changes like precocious separation of chromosomes at metaphase, unequal separation of bivalents at anaphase, disturbed polarity and cytomixis at telophase were observed at low frequency. A linear relationship between the frequency of chromosomal aberrations and the strength of mutagen doses was observed in both the varieties and mutagen types. It was found that the combined treatments induced meiotic abnormalities at a higher frequency as compared to individual treatments of Gamma rays and EMS. Comparative estimation of induced cytological abnormalities suggested higher mutagenic sensitivity of var. Pant U-30 than the var. T-9 towards the treatments used. This also confirmed the relatively broader genetic tolerance level of black gram var. T-9 in inducing a significant amount of viable mutations without much lethality at the mutagen doses recommended in this study. Therefore, it can be concluded that the combine treatments of Gamma rays and EMS (300Gy+0.2%, 200Gy+0.3%) are relatively more effective for induction mutations in var. T-9 at the genotypic tolerable level.

Novel and unique properties of nanomaterials, which are not apparent in larger-size forms of the same material, encourage the undertaking of studies exploring the multifaced effects of nanomaterials on plants. The results of such studies are not only scientifically relevant but, additionally, can be implemented to plant production and/or breeding. This study aimed to verify the applicability of silver nanoparticles (AgNPs) as a mutagen in chrysanthemum breeding. Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Lilac Wonder’ and ‘Richmond’ leaf explants were cultured on the modified MS medium supplemented with 0.6 mg·L−1 6-benzylaminopurine (BAP) and 2 mg·L−1 indole-3-acetic acid (IAA) and treated with AgNPs (spherical; 20 nm in diameter size; 0, 50, and 100 mg·L−1). AgNPs strongly suppressed the capability of leaf explants to form adventitious shoots and the efficiency of shoot regeneration. The content of primary and secondary metabolites (chlorophyll a, chlorophyll b, total chlorophylls, carotenoids, anthocyanins, phenolic compounds) and the activity of enzymatic antioxidants (superoxide dismutase and guaiacol peroxide) in leaf explants varied depending on the AgNPs treatment and age of culture. Phenotype variations of ex vitro cultivated chrysanthemums, covering the color and pigment content in the inflorescence, were detected in one 50 mg·L−1 AgNPs-derived and five 100 mg·L−1 AgNPs-derived ‘Lilac Wonder’ plants and were manifested as the color change from pink to burgundy-gold. However, no changes in inflorescence color/shape were found among AgNPs-treated ‘Richmond’ chrysanthemums. On the other hand, the stem height, number of leaves, and chlorophyll content in leaves varied depending on the AgNPs treatment and the cultivar analyzed. A significant effect of AgNPs on the genetic variation occurrence was found. A nearly two-fold higher share of polymorphic products, in both cultivars studied, was generated by RAPD markers than by SCoTs. To conclude, protocols using leaf explant treatment with AgNPs can be used as a novel breeding technique in chrysanthemum. However, the individual cultivars may differ in biochemical response, the efficiency of in vitro regeneration, genetic variation, and frequency of induced mutations in flowering plants.

To cope with stressful conditions, including antibiotic exposure, bacteria activate the SOS response, a pathway that induces error-prone DNA repair and mutagenesis mechanisms. In most bacteria, the SOS response relies on the transcriptional repressor LexA and the co-protease RecA, the latter being also involved in homologous recombination. The role of the SOS response in stress- and antibiotic-induced mutagenesis has been characterized in detail in the model organism Escherichia coli. However, its effect on antibiotic resistance in the human pathogen Pseudomonas aeruginosa is less clear. Here, we analyzed a recA deletion mutant and confirmed, by conjugation and gene expression assays, that RecA is required for homologous recombination and SOS response induction in P. aeruginosa. MIC assays demonstrated that RecA affects P. aeruginosa resistance only towards fluoroquinolones and genotoxic agents. The comparison of antibiotic-resistant mutant frequency between treated and untreated cultures revealed that, among the antibiotics tested, only fluoroquinolones induced mutagenesis in P. aeruginosa. Notably, both RecA and error-prone DNA polymerases were found to be dispensable for this process. These data demonstrate that the SOS response is not required for antibiotic-induced mutagenesis in P. aeruginosa, suggesting that RecA inhibition is not a suitable strategy to target antibiotic-induced emergence of resistance in this pathogen.

Present investigation was carried out using three different categories of chemical mutagens viz., ethylmethane sulphonate (EMS)- an alkylating agent, hydrazine hydrate (HZ)- a base analogue and sodium azide (SA)- a respiratory inhibitor on two varieties viz., Pant L-406 and Type-8 of lentil to study the immediate biological damage induced by the mutagens and to determine the sensitivity of biological material in question. Biological damage induced in M1 generation was estimated in terms of seed germination, seedling height and pollen fertility. A dose dependent reduction with increasing concentrations of the mutagens for all these parameters was observed in both the varieties. The inhibition was more severe at the highest concentration of all the three mutagens under study. Variety Type-8 was found to be more sensitive than the var. Pant L-406 with respect to the mutagens utilized. Reduction in seed germination, seedling growth and pollen fertility in M2 generation was reasonably less as compared to M1 generation. [ABSTRACT FROM AUTHOR]

Bacterial resistance is a severe threat to global public health. Exposure to sub-lethal concentrations has been considered a major driver of mutagenesis leading to antibiotic resistance in clinical settings. Ciprofloxacin is broadly used to treat infections caused by Pseudomonas aeruginosa, whereas increased mutagenesis induced by sub-lethal concentrations of ciprofloxacin has been reported for the reference strain, PAO1, in vitro. In this study we report increased mutagenesis induced by sub-lethal concentrations of ciprofloxacin for another reference strain, PA14-UCBPP, and lower mutagenesis for clinical isolates when compared to the reference strain. This unexpected result may be associated with missense mutations in imuB and recX, involved in adaptive responses, and the presence of Pyocin S2, which were found in all clinical isolates but not in the reference strain genome. The genetic differences between clinical isolates of P. aeruginosa and the reference PA14-UCBPP, often used to study P. aeruginosa phenotypes in vitro, may be involved in reduced mutagenesis under sub-lethal concentrations of CIP, a scenario that should be further explored for the understanding of bacterial fitness in hospital environments. Moreover, we highlight the presence of a complete umuDC operon in a P. aeruginosa clinical isolate. Even though the presence of umuDC did not contribute to a significant increase in mutagenesis, it highlights the dynamic exchange of genetic material between bacterial species in the hospital environment.

X rays and gamma irradiations create genetic variations by widening the gene pool, and induce gene mutation for generating commercially important products through enhancement of superior qualitative trait(s). Gene mutation is of global significance and successful mutagenesis experiment depends on the sensitivity of the genotype (s) to the administered doses of the mutagen (s). Assessment of LD50, lethality, injury, mitotic and meiotic aberration frequency (key components to determine sensitivity of a species) is prerequisite for determining sub-lethal doses and to monitor successful mutation breeding experiments. Mutagens (ionizing radiations: X rays and gamma rays) inducing chromosomal aberrations can be ascertained from mitotic cells following root tip squash preparation (clumping and stickiness, fragments, rings, polyploid cells, pseudochiasma, bridges with or without fragments, paired fragments, micronuclei, giant cell, chromatin disorganization, among others) as well as from meiotic chromosome preparation of M1 plant population (plant carrying reciprocal translocation, inversion, desynapsis, etc.). Mutagens induced chromosomal abnormalities reflect upon sterility (pollen and seed sterilities) which in turn plays key role in screening phenotypic macromutants (as it is visible by naked eye) at M2. Different types of mutagens induced aberrations are discussed. [ABSTRACT FROM AUTHOR]

DNA damage‐induced mutagenesis is a process governed by the SOS system that requires the activity of specialized DNA polymerases. These polymerases, which are devoid of proof‐reading activity, serve to increase the probability of survival under stressful conditions in exchange for an error‐prone DNA synthesis. As an opportunistic pathogen of humans, Pseudomonas aeruginosa employs adaptive responses that originally evolved for survival in many diverse and often stressful environmental conditions, where the action of error‐prone DNA polymerases may be crucial. In this study, we have investigated the role of the polymerases ImuB and ImuC in P. aeruginosa DNA‐damage induced mutagenesis. UV irradiation of imuB‐ and imuC‐deletion mutants showed that both genes contribute to UV‐induced mutagenesis in this bacterium. Furthermore, we confirmed that UV treatment significantly increase the expression levels of the imuB and imuC genes and that they are co‐transcribed as a single transcriptional unit under the control of LexA as part of the SOS regulon in P. aeruginosa. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Bacterial resistance is a severe threat to global public health. Exposure to sub-lethal concentrations has been considered a major driver of mutagenesis leading to antibiotic resistance in clinical settings. Ciprofloxacin is broadly used to treat infections caused by Pseudomonas aeruginosa , whereas increased mutagenesis induced by sub-lethal concentrations of ciprofloxacin has been reported for the reference strain, PAO1, in vitro. In this study we report increased mutagenesis induced by sub-lethal concentrations of ciprofloxacin for another reference strain, PA14-UCBPP, and lower mutagenesis for clinical isolates when compared to the reference strain. This unexpected result may be associated with missense mutations in imuB and recX , involved in adaptive responses, and the presence of Pyocin S2, which were found in all clinical isolates but not in the reference strain genome. The genetic differences between clinical isolates of P. aeruginosa and the reference PA14-UCBPP, often used to study P. aeruginosa phenotypes in vitro , may be involved in reduced mutagenesis under sub-lethal concentrations of CIP, a scenario that should be further explored for the understanding of bacterial fitness in hospital environments. Moreover, we highlight the presence of a complete umuDC operon in a P. aeruginosa clinical isolate. Even though the presence of umuDC did not contribute to a significant increase in mutagenesis, it highlights the dynamic exchange of genetic material between bacterial species in the hospital environment. [ABSTRACT FROM AUTHOR]

To determine the mutagen agent potency and deduce an optimum dose, cytological analysis for induced chromosomal aberrations is considered as an accurate index in mutation breeding. Therefore, the present investigation was carried out to estimate the relative frequency and spectrum of meiotic abnormalities at various stages of cell division using Gamma rays, EMS and their combination treatments in M1 generation of black gram (Vigna mungo L. Hepper) varieties Pant U-30 and T-9. The analysis of M1 plants revealed a wide range of induced meiotic abnormalities like univalents, multivalents, laggards, chromatin bridges, micronuclei and chromosome stickiness by different mutagen doses. In addition to these, behavioral changes like precocious separation of chromosomes at metaphase, unequal separation of bivalents at anaphase, disturbed polarity and cytomixis at telophase were observed at low frequency. A linear relationship between the frequency of chromosomal aberrations and the strength of mutagen doses was observed in both the varieties and mutagen types. It was found that the combined treatments induced meiotic abnormalities at a higher frequency as compared to individual treatments of Gamma rays and EMS. Comparative estimation of induced cytological abnormalities suggested higher mutagenic sensitivity of var. Pant U-30 than the var. T-9 towards the treatments used. This also confirmed the relatively broader genetic tolerance level of black gram var. T-9 in inducing a significant amount of viable mutations without much lethality at the mutagen doses recommended in this study. Therefore, it can be concluded that the combine treatments of Gamma rays and EMS (300Gy+0.2%, 200Gy+0.3%) are relatively more effective for induction mutations in var. T-9 at the genotypic tolerable level. [ABSTRACT FROM AUTHOR]

The present investigation was undertaken to study the frequency and spectrum of Chlorophyll mutations along with the mutagenic effectiveness and efficiency of different doses of EMS, Gamma ray and combination of both, in barnyard millet variety CO(Kv). 2. In M2 generation, no chlorophyll mutations were observed in the control population. The treatments behaved differently in the frequency of occurrence of chlorophyll mutations. The spectrum of chlorophyll mutations (chlorina, xantha, albino, viridis, and striata) were observed and grouped. Except striata, remaining four kinds of mutations viz., xantha, chlorina, viridis and albino were observed more frequently. The overall mutation spectrum showed that chlorina (0.47%) occurred with the highest frequency, followed by albino (0.37%), xantha (0.26%) viridis (0.19%) and Striata (0.08%). The mutagenic effectiveness decreased with the increase in dose of mutagen in both mutagens, indicating that negative relationship between effectiveness and dose of mutagen. Mutagenic efficiency (mutation rate in relation to M1 damage) in both mutagens was highest at the lowest dose and it decreased with the increase in dose. The study concluded that Barnyard millet, Co(Kv).2 millet responds well to EMS, Gamma ray and combination of EMS and Gamma ray treatments. [ABSTRACT FROM AUTHOR]

A study on the sensitivity of two breeding lines of garden pea to mutagenic agents was carried out in the Maritsa Vegetable Crops Research Institute, Plovdiv. The purpose was to evaluate the sensitivity of the Pisum sativum L. genotypes to physical and chemical mutagens. In the experiment, the pea seeds were irradiated single or combined with 60Co gamma rays (40, 80, 100, 200 and 400 Gy) and Ethyl methanesulfonate (EMS) at concentrations of 0.1 and 0.2 %. Visible morphological changes of the stems and leaves were observed in plant of M1 generation, such as shorter stems, double petiole, clover-shaped leaves and a couple of tendrils. Single treatments with 100 Gy 60Co induced the highest mutation frequency M.F. = 7.69 for line 88-7, and М.F. = 2.11 for line 97-3, reported in M2 generation. Higher doses or combined gamma rays and EMS treatments induced more efficiently mutations. Line 88-7 was selected for further mutagenic treatment due to the higher sensitivity assessed.

A study on the sensitivity of watermelon variety Bojura to mutagenic agents was carried out in 2013-2014. The goal was to establish effective doses for mutagenic treatment of dry seeds with 60Co gamma rays (80, 100, 200, 250, 350 and 450 Gy) and swollen seeds with water for 24 hours were treated with ethyl methanesulfonate (EMS) at a concentration of 2%. Dominant mutations were not observed in the M1 generation. Morphological changes in 14 of 1395 M2 plants were observed. Phenotypic variations changes were the colour of the seed coat, chlorophyll disorders of cotyledons, leaves, petals, and alterations of the location of the fruit set in the central stem. Visible changes of the morphological characteristics of the fruit were not observed. The doses induced certain morphological changes, however, higher doses or combined gamma rays 60Co and EMS treatments would induce mutations more efficiently. Subsequent experiments are required to obtain mutants with changes that affect flowers and fruits. The results are important for increasing mutation efficiency in watermelon breeding.

The recent advancements in forward genetics have expanded the applications of mutation techniques in advanced genetics and genomics, ahead of direct use in breeding programs. The advent of next-generation sequencing (NGS) has enabled easy identification and mapping of causal mutations within a short period and at relatively low cost. Identifying the genetic mutations and genes that underlie phenotypic changes is essential for understanding a wide variety of biological functions. To accelerate the mutation mapping for crop improvement, several high-throughput and novel NGS based forward genetic approaches have been developed and applied in various crops. These techniques are highly efficient in crop plants, as it is relatively easy to grow and screen thousands of individuals. These approaches have improved the resolution in quantitative trait loci (QTL) position/point mutations and assisted in determining the functional causative variations in genes. To be successful in the interpretation of NGS data, bioinformatics computational methods are critical elements in delivering accurate assembly, alignment, and variant detection. Numerous bioinformatics tools/pipelines have been developed for such analysis. This article intends to review the recent advances in NGS based forward genetic approaches to identify and map the causal mutations in the crop genomes. The article also highlights the available bioinformatics tools/pipelines for reducing the complexity of NGS data and delivering the concluding outcomes.

A DNA damage-inducible mutagenic gene cassette has been implicated in the emergence of drug resistance in Mycobacterium tuberculosis during anti-tuberculosis (TB) chemotherapy. However, the molecular composition and operation of the encoded 'mycobacterial mutasome' - minimally comprising DnaE2 polymerase and ImuA' and ImuB accessory proteins - remain elusive. Following exposure of mycobacteria to DNA damaging agents, we observe that DnaE2 and ImuB co-localize with the DNA polymerase III β subunit (β clamp) in distinct intracellular foci. Notably, genetic inactivation of the mutasome in an imuB AAAAGG mutant containing a disrupted β clamp-binding motif abolishes ImuB-β clamp focus formation, a phenotype recapitulated pharmacologically by treating bacilli with griselimycin and in biochemical assays in which this β clamp-binding antibiotic collapses pre-formed ImuB-β clamp complexes. These observations establish the essentiality of the ImuB-β clamp interaction for mutagenic DNA repair in mycobacteria, identifying the mutasome as target for adjunctive therapeutics designed to protect anti-TB drugs against emerging resistance., Competing Interests: SG, ZM, MR, JS, RD, AR, ND, Td, SA, DL, JA, TC, JH, RM, JM, RW, VM, ČV, ML, DW No competing interests declared

Highlights • The def1 mutants are prone to self-diploidization. • Diploid def1 mutants look UV-immutable when assayed for canavanine-resistance. • Diploid def1 mutants are UV-mutable when assayed for dominant reversions. • The true haploids with def1 Δ mutation retain substantial UV mutagenesis. Abstract In yeast Saccharomyces cerevisiae, the DEF1 gene is responsible for regulation of many cellular processes including ubiquitin-dependent degradation of DNA metabolism proteins. Recently it has been proposed that Def1 promotes degradation of the catalytic subunit of DNA polymerase δ at sites of DNA damage and regulates a switch to specialized polymerases and, as a consequence, DNA-damage induced mutagenesis. The idea was based substantially on the severe defects in induced mutagenesis observed in the def1 mutants. We describe that UV mutability of def1 Δ strains is actually only moderately affected, while the virtual absence of UV mutagenesis in many def1 Δ clones is caused by a novel phenotype of the def1 mutants, proneness to self-diploidization. Diploids are extremely frequent (90%) after transformation of wild-type haploids with def1::kanMX disruption cassette and are frequent (2.3%) in vegetative haploid def1 cultures. Such diploids look "UV immutable" when assayed for recessive forward mutations but have normal UV mutability when assayed for dominant reverse mutations. The propensity for frequent self-diploidization in def1 Δ mutants should be taken into account in studies of the def1 Δ effect on mutagenesis. The true haploids with def1 Δ mutation are moderately UV sensitive but retain substantial UV mutagenesis for forward mutations: they are fully proficient at lower doses and only partially defective at higher doses of UV. We conclude that Def1 does not play a critical role in damage-induced mutagenesis. [ABSTRACT FROM AUTHOR]

Induced mutagenesis generates macromolecular variations which ultimately alters the bio-physiological and morphological nature of the crop genotypes. In the present study, molecular characterization of six high yielding lentil mutant lines, developed from hydrazine hydrates (HZ) and gamma rays mutagenesis, was carried out with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and random amplified polymorphic DNA (RAPD) markers. Activity of nitrate reductase (NR) and content of chlorophyll and carotenoid were found to be significantly high in the mutant lines. Protein and mineral (Fe, Zn & Cu) contents were also increased considerably in the mutant lines compared to their respective parent genotypes. SDS-PAGE profile of seed storage proteins showed 35 unique bands with 97.14% polymorphism. Genetic divergence analysis generated total 41 reproducible RAPD bands with average calculated polymorphic percentage of 63.06%. Among the primers, OPA-10 showed the highest polymorphism with significant PIC value. Genetic divergent analysis revealed that genome of cultivar DPL 62 mutated relatively more than the cultivar Pant L 406 due to the mutagen treatments, while DPL 62-B and Pant L406-A were the most divergent mutants induced in the present study. Biochemical and molecular profile of the induced mutant lines facilitates a basis for future conservation and utilization strategies to widen the genetic base of the current lentil breeding population. [ABSTRACT FROM AUTHOR]

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Fast neutron (FN) radiation mediated mutagenesis is a unique approach among the several induced mutagenesis methods being used in plant science in terms of impacted mutations. The FN mutagenesis usually creates deletions from few bases to several million bases (Mb). A library of random deletion generated using FN mutagenesis lines can provide indispensable resources for the reverse genetic approaches. In this review, information from several efforts made using FN mutagenesis has been compiled to understand the type of induced mutations, frequency, and genetic stability. Concerns regarding the utilization of FN mutagenesis technique for a plant with different level of ploidy and genome complexity are discussed. We have highlighted the utility of next-generation sequencing techniques that can be efficiently utilized for the characterization of mutant lines as well as for the mapping of causal mutations. Pros and cons of mapping by mutation (MutMap), mutant chromosome sequencing (MutChromSeq), exon capture, whole genome sequencing, MutRen-Seq, and different tilling approaches that can be used for the detection of FN-induced mutation has also been discussed. Genomic resources developed using the FN mutagenesis have been catalogued wooing to meaningful utilization of the available resources. The information provided here will be helpful for the efficient exploration for the crop improvement programs and for better understanding of genetic regulations.