Mutant Progenies Research Articles

Volatile profiling as a potential biochemical marker for validation of gamma irradiation derived putative mutants in polyembryonic genotypes of mango (Mangifera indica L.).

Putative mutants were generated through gamma irradiation in the polyembryonic mango genotype Nekkare. The putative mutant progenies along with control seedlings and mother plants were evaluated by comparing the compositions and relative proportions of their major volatile compounds. Volatile profiling was done using headspace-solid phase micro-extraction (HS SPME) method coupled with gas chromatography-mass spectrometry (GC-MS MS). Furthermore, characterisation of putative mutants and control seedlings was carried out using simple sequence repeat (SSR) markers to ascertain the genetic diversity present in the samples under study. Monoterpenes were the most abundant volatile compound in all the studied samples (ranging from 34.76% to 91.41%) out of which I-Phellandrene and cis-Ocimene formed the major fraction in mother plants (20.45%-21.86% and 16.17%-21.27%, respectively) and control seedlings (23.32%-24.95% and 18.95%-20.81%, respectively), while beta-Phellandrene was dominant in the selected putative mutant samples (2.34%-29.53%). Among sesquiterpenes, trans-Caryophyllene was detected only in the putative mutant samples (0.10%-30.18%). Grouping together of mother plants and control seedlings was seen in the cluster analysis, while the putative mutants grouped apart from them suggesting genetic diversity. Genetic distance between the mother plants and control seedlings ranged from 0.97 to 2.73, while between putative mutants, control seedlings, and mother plants, it ranged from 6.54 to 9.82. SSR-based characterisation of putative mutant seedlings showed that mutation caused variability in the treated population. This was evident from the high allelic richness ranging from 4 to 12 with a mean of 7 and a higher mean Shannon's Information Index (1.50) of the putative mutant population. The study demonstrates that volatile profiling and molecular characterisation using SSR markers could be used as a tool to detect variation in a mutated population. In addition, volatile profiling can be used to validate putative mutants in polyembryonic mango genotypes where the seedlings of nucellar origin are similar to mother plants.

Emergence of Canonical and Noncanonical Genomic Variants following In Vitro Exposure of Clinical Mycobacterium tuberculosis Strains to Bedaquiline or Clofazimine.

In Mycobacterium tuberculosis, bedaquiline and clofazimine resistance occurs primarily through Rv0678 variants, a gene encoding a repressor protein that regulates mmpS5/mmpL5 efflux pump gene expression. Despite the shared effect of both drugs on efflux, little else is known about other pathways affected. We hypothesized that in vitro generation of bedaquiline- or clofazimine-resistant mutants could provide insight into additional mechanisms of action. We performed whole-genome sequencing and determined phenotypic MICs for both drugs on progenitor and mutant progenies. Mutants were induced through serial passage on increasing concentrations of bedaquiline or clofazimine. Rv0678 variants were identified in both clofazimine- and bedaquiline-resistant mutants, with concurrent atpE SNPs occurring in the latter. Of concern was the acquisition of variants in the F420 biosynthesis pathway in clofazimine-resistant mutants obtained from either a fully susceptible (fbiD: del555GCT) or rifampicin mono-resistant (fbiA: 283delTG and T862C) progenitor. The acquisition of these variants possibly implicates a shared pathway between clofazimine and nitroimidazoles. Pathways associated with drug tolerance and persistence, F420 biosynthesis, glycerol uptake and metabolism, efflux, and NADH homeostasis appear to be affected following exposure to these drugs. Shared genes affected by both drugs include Rv0678, glpK, nuoG, and uvrD1. Genes with variants in the bedaquiline resistant mutants included atpE, fadE28, truA, mmpL5, glnH, and pks8, while clofazimine-resistant mutants displayed ppsD, fbiA, fbiD, mutT3, fadE18, Rv0988, and Rv2082 variants. These results show the importance of epistatic mechanisms as a means of responding to drug pressure and highlight the complexity of resistance acquisition in M. tuberculosis.

Characterization and evaluation of putative mutant populations of polyembryonic mango genotype Nekkare for dwarfing rootstock traits

Availability of dwarfing rootstocks is an important pre-requisite for improving productivity of mango orchards in India as it facilitates high density planting as well as impart uniformity within an orchard. An attempt was made to induce variability in polyembryonic mango genotype Nekkare for dwarfness by treating kernels with different doses of gamma radiation ranging from 15 to 35 Gy. Irradiation created significant variation in plant height, stem girth, number of nodes, inter-nodal length, number of leaves, leaf blade length and leaf blade width. The highest reduction in seedling height along with highest variation was observed at 35 Gy where the seedling height ranged from 11.50 to 33 cm with a mean of 23.12 cm as compared to mean plant height of 44.55 cm in control ranging from 33.50 to 56 cm. Further, the effect of irradiation on stomatal parameters was also investigated and the highest stomatal length and width was recorded at 15 Gy (63.39 μm) and 20 Gy (63.12 μm) respectively while 30 Gy treatment produced maximum stomatal density (13.85 per μm2). Furthermore, theconcentration of ABA was found to be highest (429.1 ng/gm) in morphologically dwarf (putative mutant) progenies of Nekkare. The results suggest effectiveness of induced mutation for developing dwarfing rootstocks in mango to be used in high density planting.

Metabolite profiling reveals the metabolic features of the progenies resulting from the low phytic acid rice (Oryza sativa L.) mutant

The low phytic acid (lpa) rice mutant Os-lpa-XS110-2, exhibiting OsMRP5 mutation-induced metabolic features (i.e. decreased levels of phytic acid and raffinose, and increased levels of amino acids and biogenic amine GABA), was crossed with two commercial rice cultivars. The inferior field emergence rate of the lpa mutant was significantly improved upon cross-breeding. The GC/MS-based metabolomics was utilized to investigate the impact of cross-breeding on the metabolite profiles of the resulting progeny rice grains. Multivariate and univariate analyses showed that in spite of the predominant influence of crossing parent on the metabolite profiles of the progenies, the OsMRP5 mutation-induced metabolite signature, was stably expressed in the lpa mutant progenies over generations. The OsMRP5 lpa rice mutant seeds might be considered valuable genetic resources to develop rice grains with favorable metabolic traits.

Induction of genetic variability for quantitative traits in horsegram (Macrotyloma uniflorum) through irradiation mutagenesis

Aim: The study was conducted to explore the magnitude of variability induced by gamma rays, electron beam and its combinations for quantitative traits in horsegram (Macrotyloma uniflorum (Lam) Verdc.). Methodology: The horsegram cultivar PAIYUR 2 was irradiated with twelve combinations involving G, EB and G+EB. Desirable mutagenic doses were identified in M1 based on plant injuries and forwarded to M2. Data on 11 yield component traits were recorded on normal looking M2 plants for identification of micro-mutants. Promising mutants were forwarded to M3 and the induced variability was ascertained using multivariate statistics. Results: Significant transgressive variants were observed in M2. The G+EB combination induced superior variants for yield. A positive shift in mean for yield and its attributing traits was observed in M3. Most of the polygenic traits were governed by additive gene effects. Interpretation: The increased mean for most of the polygenic traits in M3 population proved that selection made on early generation was highly effective. The isolated high yielding mutant progenies of selected families will contribute towards yield improvement in horsegram.

Effect of recurrent mutagenesis on some induced genotypes in safflower (Carthamus tinctorious L.)

Mutation breeding is a tool to induce new genetic variation for improving agronomical important traits. Thus, an investigation was carried out during two successive growing winter seasons 2017/2018 and 2018/2019 on safflower plants, at the Experimental and Research Farm, Faculty of Agriculture, Al-Azhar University, Assiut, Egypt. Three mutagen treatments i.e., dimethyl sulfoxide, electric shock and gamma rays, were used to isolate the desirable mutants in M4 and M5 generations of thirty three safflower genotypes. Three mutagen treatments were used, such as; the chemical mutation mutagen was more effective than the two other mutagens to induce mutant genotypes. On the other hand, some mutant progenies were derived from gamma rays treatment with dose 20 kr which was more effective mutagen for induction of stable promising mutants in safflower, according to final results of M5 generation, particularly high yielding ability trait, softness and earliness as compared to untreated plants. Concerning the important traits, the results showed that the earliest progenies for flowering date were 11 gave 119 days while, 9 gave 120 days with the h1 treatment and rad. in M5 generation. Also, the results showed that two mutated progenies 9 and 12 gave the highest seed yield/plant, 355.64 and 317.67 gm respectively from h3 treatment, one progeny 13 gave 382.90 gm from t1 treatment. The seed oil content trait, showed that the highest progenies no.11 and 12, gave 44.80 and 44.76 % respectively, on using h1 treatment, while, the mutated no. 13 gave 45.32% from t1 treatment. Finally, these results supported that the recurrent mutagenic treatments can be used to induce new mutant safflower genotypes which are characterized by spineless, earliness high seed yield and seed oil content. Thus, they can be involved in breeding programs to get new suitable varieties with high seed and oil yield.

Differences in leaf physiological and morphological traits between Camellia japonica and Camellia reticulata

Plants of the genus Camellia are widely cultivated throughout the world as ornamentals because of their bright and large flowers. The widely cultivated varieties are mainly derived from the mutant lines and hybrid progenies of Camellia japonica Linn. and Camellia reticulata Lindl. While their geographical distributions and environmental adaptabilities are significantly different, no systematic comparison has been conducted between these two species. To investigate differences in how these plants have adapted to their environments, we measured photosynthesis and 20 leaf functional traits of C. japonica and C. reticulata grown under the same conditions. Compared with C. japonica, C. reticulata showed higher values for light saturation point, light-saturated photosynthetic rate, leaf dry mass per unit area and stomatal area, but lower values for apparent quantum efficiency, leaf size, stomatal density and leaf nitrogen content per unit mass. Stomatal area was positively correlated with light-saturated photosynthetic rate and light saturation point, but negatively correlated with stomatal density. The differences between C. reticulata and C. japonica were mainly reflected in their adaptations to light intensity and leaf morphological traits. C. reticulata is better adapted to high light intensity than C. japonica. This difference is related to the two species’ differing life forms. Thus, leaf morphological traits have played an important role in the light adaptation of C. reticulata and C. japonica, and might be first noticed and selected during the breeding process. These findings will contribute to the cultivation of camellia plants.

Evolution of Target-Site Resistance to Glyphosate in an Amaranthus palmeri Population from Argentina and Its Expression at Different Plant Growth Temperatures.

The mechanism and expression of resistance to glyphosate at different plant growing temperatures was investigated in an Amaranthus palmeri population (VM1) from a soybean field in Vicuña Mackenna, Cordoba, Argentina. Resistance was not due to reduced glyphosate translocation to the meristem or to EPSPS duplication, as reported for most US samples. In contrast, a proline 106 to serine target-site mutation acting additively with EPSPS over-expression (1.8-fold increase) was respectively a major and minor contributor to glyphosate resistance in VM1. Resistance indices based on LD50 values generated using progenies from a cross between 52 PS106 VM1 individuals were estimated at 7.1 for homozygous SS106 and 4.3 for heterozygous PS106 compared with homozygous wild PP106 plants grown at a medium temperature of 24 °C day/18 °C night. A larger proportion of wild and mutant progenies survived a single commonly employed glyphosate rate when maintained at 30 °C day/26 °C night compared with 20 °C day/16 night in a subsequent experiment. Interestingly, the P106S mutation was not identified in any of the 920 plants analysed from 115 US populations, thereby potentially reflecting the difference in A. palmeri control practices in Argentina and USA.

Phytic Acid Contents and Metabolite Profiles of Progenies from Crossing Low Phytic Acid OsMIK and OsMRP5 Rice (Oryza sativa L.) Mutants.

The impact of cross-breeding two low phytic acid (lpa) rice mutants on the content of phytic acid and the metabolite profile of the resulting double mutant was investigated. Progenies resulting from the cross of Os-lpa-XS110-1, a rice mutant carrying the myo-inositol kinase (OsMIK) mutated gene, and Os-lpa-XS110-2, with the multidrug resistance-associated protein ABC transporter gene 5 (OsMRP5) as the mutation target, were subjected to high-pressure ion chromatography. The reduction of the phytic acid content in the double mutant (-63%) was much more pronounced than in the single mutants (-26 and -47%). Gas chromatography-based metabolite profiling revealed a superimposition of the metabolite profiles inherited from the lpa progenitors in the double mutant progenies; the resulting metabolite signature was predominated by the OsMIK mutation effect. The study demonstrated that cross-breeding of two single lpa mutants can be employed to generate double lpa rice mutants showing both a significant reduction in the content of phytic acid and the imprinting of a specific mutation-induced metabolite signature.

Selection of mutants with high linolenic acid contents and characterization of fatty acid desaturase 2 and 3 genes during seed development in soybean (Glycine max).

Soybean seeds contain 18-24% lipids, which are made up of 85% polyunsaturated fatty acids. Two of these (linoleic and linolenic acids) comprise essential fatty acids that are not synthesized in humans and animals. Linolenic acid plays a vital role in the maintenance of brain function and is a source of docosahexaenoic acid for retinal and nerve tissue, with its physiological functions being a focus of attention. We developed mutant soybean populations via gamma irradiation of Korean cultivars Danbaek and Daepung and evaluated the linolenic acid content of 78 and 154 M9 mutant progenies. We selected the four mutant lines with the highest linolenic acid contents based on 2 years of investigation of fatty acids. The selected mutant lines had linolenic acid contents that were 33.9% to 67.7% higher than those of the original cultivars and exhibited increased fatty acid desaturase (FAD) gene expression levels during seed development. We also identified nucleotide polymorphisms of FAD genes in the four mutant lines. The present study found that linolenic acid content is related to significantly increased expression levels of the FAD3C and FAD3D genes in the endoplasmic reticulum, which was uncovered by radiation mutation breeding of soybean. © 2019 Society of Chemical Industry.

Impact of Crossing Parent and Environment on the Metabolite Profiles of Progenies Generated from a Low Phytic Acid Rice ( Oryza sativa L.) Mutant.

The low phytic acid ( lpa) rice mutant Os-lpa-MH86-1, exhibiting a mutation-induced metabolite signature (i.e., increased levels of sugars, sugar alcohols, amino acids, phytosterols, and biogenic amines), was crossed with two commercial wild-type cultivars. The resulting progenies of generation F8 harvested at three independent field trials were subjected to a GC/MS-based metabolite profiling approach. Statistical assessments via multivariate and univariate analyses demonstrated that the environment had a strong impact on the metabolite profiles of the resulting progenies. In addition, the metabolites of homozygous lpa progenies were significantly influenced by the lipid profiles of the wild-type cultivars employed as the crossing parents. However, for each individual field trial, both the lpa trait and the mutation-specific metabolite signature were consistently expressed in the homozygous lpa mutant progenies of the two crosses. The data underline that cross-breeding can be employed as a tool to generate lpa progeny rice seeds stably exhibiting the mutation-induced metabolic traits.

Genetic and Leaf Characteristic Diversity on 10 Mutant Progenies of Patchouli (Pogostemon cablin) Provide Insights to Selection Strategies

The importance of patchouli plants to produce essential oil has established this medicinal herb as one of the Indonesia’s main economic contributor. To date, Indonesia can only provide 5 varieties i.e. Sidikalang, Tapak Tuan, Lhokseumawe, Patchoulina 1 and Patchoulina 2. In order to increase national patchouli production, several efforts needs to be done by providing new superior patchouli lines. This experiment was undertaken to reveal diversity of mutant progenies derived from gamma ray irradiation in patchouli. Six SSR primers were used to determine genetic diversity on MV 3 generation of the mutants. Molecular analysis revealed a moderate to high polymorphism based on tested primers, which amplified 73 bands, and resulting of 0.705 PIC value. Dendrogram analysis based on Euclidean dissimilarity showed broad diversity that ranged from 0.23 to 0.82. Phenotypic tree gave clear separation that all mutant clones were clustered into three different group, with Eucledian dissimilarity coefficient ranging from 0.02 to 0.13. This report indicates that Patchouli vegetatively-propagated mutants were able to maintain their variability continuously from their parental lines (M 0 ). Furthermore, our findings offer comprehensive information on breeding strategies of patchouli plants, giving an opportunity to assess important traits at early generation.

Evaluating of Salt Stress Tolerance in Selected Wheat Mutant Progenies with Contributing Expression Analysis of TaWRKY Genes and Antioxidant Defence Parameters

In current work, the seeds from two candidate fifth-generation moderately salt tolerant wheat mutant progenies (Triticum aestivum L. cv. Adana 99) developed with using sodium azide (as a mutagenic agent) and from their parent (commercial cultivar) were sown in the growth chamber to evaluate their performance under control and 150 mM NaCl treatment conditions. Compared with commercial cultivar, mutants demonstrated much higher activities of superoxide dismutase, catalase and guaiacol peroxidase, and chlorophyll contents, and much lower contents of lipid peroxidation and values of electrolyte leakage under control condition. On the other hand, contents of lipid peroxidation and value of electrolyte leakage increased, but chlorophyll content decreased more severely in commercial cultivar than mutants under salt stress condition. In addition to increasing in expression levels of TaWRKY5, TaWRKY10 and TaWRKY44 genes in mutants positively regulated in salt stress responses by either direct or indirect activation of the cellular antioxidant enzyme responses or activation of stress-related gene expression. These candidate salt tolerant wheat mutant progenies will be used to increase the salt tolerance in the wheat-breeding programmers.

Identification of High Herbage and Oil Yielding Variety (Jor Lab P-1) of Pogostemon cablin (Blanco) Benth Through Mutation Breeding

Pogostemon cablin (Blanco) Benth, also known as patchouli is an aromatic herb mainly used for high quality perfumery, aromatherapy and fragrances. The study was conducted to identify high yielding mutant genotype of patchouli through gamma radiation. In this experiment 14 different doses of gamma adiation were given to rooted slips of patchouli variety Johor. All 482 M2 progenies were produced and their morphological, qualitative and quantitative oil data were recorded. Advanced progenies were developed and finally selected a single plant from each M4 progenies on the basis of high essential oil and high herbage yield. These 14 lines were planted in RCBD design along with the check variety with three replications. Significant differences were observed in most of the agronomic characters and oil quality parameters among all mutant progenies. Among all the mutant lines, line no. 9 was found to be superior with plant height, herbage yield per plant, essential oil percent and monopodia length in comparison with the check variety. The multi-location trials revealed that the average fresh herbage yield (960 g/plant), oil content (3.10 %), and patchouli alcohol content (37.94 %) were also found to be significantly higher when compared to the check variety.

Novel Mutations in Oleoyl‐PC Desaturase (ahFAD2B) Identified from New High Oleic Mutants Induced by Gamma Rays in Peanut

To diversify the sources of the high‐oleate trait in peanut (Arachis hypogaea L.), the broad‐based interspecific derivative with inherent resistance to major foliar diseases, GPBD‐4, was subjected to chemical (ethyl methanesulfonate) and physical (γ rays) mutagenesis, resulting in significant variation in fatty acid profile of mutant progenies as tested by gas chromatography in advanced (M4) generations. From these mutant progenies, two stable high‐oleic (>70%) mutant lines, GM 4‐3 and GM 6‐1, were chosen for molecular characterization of ahFAD2B by cloning and sequencing. We report here the identification of two novel mutations (1085A‐G and 1111G‐A) in oleoyl‐PC desaturase (ahFAD2B) of high‐oleic mutant line GM 6‐1 and the latter single transition 1111G‐A in another high‐oleic mutant line GM 4‐3. The deduced amino acid sequence comparison of the parental genotype, GPBD‐4, with normal‐oleic (∼50%) and high‐oleic (>70%) mutant lines indicated the common change from glycine to serine at 372 from start codon due to the common single‐nucleotide polymorphism (SNP, 1111G‐A) observed in both the high‐oleic mutant lines. Another amino acid change from glutamate to glycine was also found in the mutant line GM 6‐1 because of the additional SNP it had at 1085A‐G in the coding region of ahFAD2B. These novel mutations identified in the new high‐oleic mutant lines could be used for marker‐assisted selection for the high‐oleate trait, and these foliar disease‐resistant, high‐oleic mutant lines could serve as additional valuable genetic resources for oil quality improvement in future peanut breeding programs.

Identification of a novel male sterile wheat mutant dms conferring dwarf status and multi-pistils

Plant height and fertility are two important traits of wheat (Triticum aestivum L.), whose mutants are ideal materials for studies on molecular mechanisms of stem and floral organ development. In this study, we identified a dwarf, multi-pistil and male sterile (dms hereafter) wheat mutant from Zhoumai 18. Simple sequence repeat (SSR) marker assay with 181 primer pairs showed that only one locus of GWM148-2B was divergent between Zhoumai 18 and dms. There were three typical phenotypes in the progeny of dms, tall (T; ca. 0.8 m), semi-dwarf (M; ca. 0.6 m) and dwarf (D; under 0.3 m) plants. Morphological investigation indicated that the internode length of M was shortened by about 20–50 mm each; the internode number of D was 2 less than that of T and Zhoumai 18, and its internode length was shorter also. The pollen vigor and hybridization test demonstrated that dms mutant was male sterility. Segregated phenotypes in progeny of M suggested that the multi-pistils and sterility were controlled by one recessive gene locus which was designated as dms temporarily, and the plant height was controlled by a semi-dominant gene locus Dms. Therefore, progeny individuals of the dms had three genotypes, DmsDms for tall plants, Dmsdms for semi-dwarf plants and dmsdms for dwarf plants. The mutant progenies were individually selected and propagated for more than 6 generations, thus a set of near isogenic lines of T, M and D for dms were developed. This study provides a set germplasms for studies on molecular mechanisms of wheat stem and spike development.

Differential Response of Cysteine-deficient Lentil (<i>Lens culinaris</i> Medik.) Mutants Impaired in Foliar O-acetylserine(thiol)-lyase Expression

Lentil is a cool-season pulse crop, rich in protein but deficient in two sulphur-containing amino acids cysteine and methionine. Due to low genetic variability in existing germplasm, induced mutagenic technique has been adopted in lentil, and two mutant lines exhibiting poor growth and low dry weight were isolated in M 2 -mutagenized (0.10% and 0.15% EMS, 6 h) population of variety L 414. Further analysis revealed that plants from both mutant lines were highly deficient in seed cysteine (Cys) content, and thus, were tentatively designated as cysLc1 and cysLc2 mutants. Mutant plants were advanced to M 3 generation. Biochemical analysis through cysteine synthesizing pathway in leaves revealed that activity of serine acetyl transferase (SAT) was normal in both the mutant progenies but both were highly deficient in foliar O -acetylserine(thiol)-lyase (OAS-TL) activity. Transcriptomic analysis by qRT-PCR confirmed normal expression of SAT in both mutants but revealed differential expressions of two OAS-TL isoforms; OAS-TL 1 isoform was not detectable in cysLc1 mutant while expression of OAS-TL 2 isoform was totally repressed in leaves of cysLc2 mutant. Genetic studies and test of allelism pointed out that both the mutants were recessive and were complementing with each other to produce normal in F 1 and normal along with mutant plants in F 2 progeny. The progeny plants exhibiting normal phenotype showed normal mRNA transcripts of both OAS-TL isoforms. Being stable and self-fertile, the mutants will give vital clues in genetic basis of thiol-metabolic network of lentil crops.

Investigation of the Dravet syndrome using a mouse model

ObjectiveTo identify genetic heterogeneity which influence the severity and mortality of the diseaseMethodWe first generated a point mutation allele of Scn1a in the R1 mouse ES cell using a recombineering approach. Germline chimeras were mated with 129/J females to generate mutant mice in a pure 129 stain. Some of the resulting heterozygous mutant males were outcrossed to C57BL/6 females to generate F1 hybrids that mutant progenies in the heterogeneous genetic backgrounds with various degrees of phenotypic presentations can be obtained by F1 intercrosses.ResultIn the pure 129 stain, heterozygous mutant mice were resistant to the disease. However, the homozygous mutant pups became malnourished and showed a significant reduction in their body weight and sizes within 2 weeks. They were also found to have an unstable gait and developed spontaneous seizures. All of them died within the third postnatal week. In contrast, when the mutant allele was brought to a heterogeneous 129 and C57BL/6 mixed stain, sporadic sudden death was observed in some heterozygous animals after the third postnatal week. The survival rate of the adult heterozygotes was reduced to 60% at 7 weeks. These results suggested that some modifier loci in the two different genetic backgrounds have different effects on the mutant phenotypes.ConclusionWe successfully generated a mouse model for Dravet syndrome. The fact that Scn1a mutant seizure severity and gross lethality differ in 129 and C57BL/6 stains indicates an invaluable opportunity to identify modifier genes using these mutant strains.

Chimeras for mutations induced in dormant tomato seeds

Genetic chimeras of the VFNT cherry tomato line (Lycopersicon esculentum) were produced by mutagenizing seeds with ethyl methane sulfonate (EMS). The chimeras thereby produced were evaluated by progeny-testing the fruits of the genetically mosaic tissue. A total of 2011 M1 plants was grown from treated seeds and evaluated by screening their 95175 (M2) progeny for mutations affecting seedling phenotype. Three vigorous and fertile M1 plants bearing mutant progeny with definitive phenotypes were selected for systematic harvesting and analysis. The specific location of each fruit was noted at harvest time, enabling the mutated sporogenous tissue of the mosaic M1 plants to be traced. Sectoring appeared in both branch and floral tissues. In several cases, mutant progenies were restricted to individual branches or parts thereof. True-breeding recessive mutants whose monogenic mode of inheritance was later established occasionally segregated within M1 fruit progenies at frequencies that indicate a non-homogeneous floral meristem origin. The data emphasize the necessity of making a well-distributed harvest of mosaic plants in order to detect as many variants as possible, as mosaic sectors may or may not recur late in ontogeny and may not contribute to sporogenous tissue early in development.

Potential of gamma radiation enhancing the biosynthesis of tropane alkaloids in black henbane (Hyoscyamus niger L.)

A productive yellow flowered mutant with high tropane alkaloid content was isolated in the M2 generation of gamma irradiated (Co60 at 40 kr) progenies ofHyoscyamus niger. Mutant progenies, on an average, were capable of synthetising more than twice crude alkaloid (0.147% to 0.221%) in M3 through M6 generations compared to the parental control (0.065 to 0.106%). In pilot scale trial (M7), two elite lines, Y-15 and Y-17 were found to contain 0.390% and 0.318% crude drug in contrast to 0.211% in an improved inbred used as control. However, owing to conducive plant morphology, Y-17 registered high yield of dry biomass, hence gave more than double yield of crude drug than the improved control (inbred) (23 kg/ha against 11 kg/ha). Also being superior in hyoscyamine and hyoscine yields, it was redesignated as var.Aela, and released for commercial cultivation in India, thus signifying the efficiency of radiation breeding for crop improvement.