Frequency Of Chlorophyll Mutations Research Articles

Effects of sodium acetate and sodium chloride on EMS-induced chlorophyll mutations in barley

Sodium acetate solutions to which sodium chloride was added, and acetate or chloride alone have been used as pre-, simultaneous, and post-treatment of dry and pre-soaked seeds of barley to study their effect on the types and frequencies of ethyl methanesulphonate (EMS)-induced chlorophyll mutations in spring barley, variety Elsa, and winter barley, varieties 436 35 and Ager. Application of acetate/chloride on dry seeds before or simultaneously with EMS both resulted in the frequency of chimeral plants with chlorophyll-deficient sectors in M 1 and chlorophyll mutants in M 2 approximately being halved as compared with the controls (EMS treatment alone). An opposite effect was observed after simultaneous treatment with acetate/ chloride and EMS (pH 4.5 and pH 7.0) and application of acetate/chloride after EMS treatment of pre-soaked seeds. In this case the mutagen sensitivity, i.e. the frequency of chimeral plants with induced chlorophyll-deficient sectors in M 1 and of chlorophyll mutants in M 2, was approximately doubled as compared with the control. Separate application of both acetate or chloride as a simultaneous treatment with EMS resulted also in an increase in the chlorophyll mutation frequency as compared with EMS treatment alone. Based on these results some aspects of the acetate/chloride effect are briefly discussed.

Interaction of certain base-specific chemicals and diethylsulphate in the induction of chlorophyll mutations in Oryza sativa L.

The presoaked seeds of a rice cultivar, Tellakattera, were treated with three different concentrations of hydrazine (HZ) or hydroxylamine (HA) in combination with diethylsulphate (dES) (0.05%). In the M 1 generation more than additive effects were observed for increase in chlorophyll chimeras and decrease in seed fertility. A synergistic effect was also observed for both chlorophyll mutation and mutant frequencies, in the M 2 generation, in sequential treatments. However, the degree of synergism, based on M 2 chlorophyll mutant frequency, was greater in dES posttreatment combinations with HA or HZ, compared with dES pretreatments. These differences in reciprocal treatments may be due to more efficient fixation of premutational events by dES than HZ or HA.

Interaction of certain base-specific chemicals and diethylsulphate in the induction of chlorophyll mutations in Oryza sativa L

The presoaked seeds of a rice cultivar, Tellakattera, were treated with three different concentrations of hydrazine (HZ) or hydroxylamine (HA) in combination with diethylsulphate (dES) (0.05%). In the M 1 generation more than additive effects were observed for increase in chlorophyll chimeras and decrease in seed fertility. A synergistic effect was also observed for both chlorophyll mutation and mutant frequencies, in the M 2 generation, in sequential treatments. However, the degree of synergism, based on M 2 chlorophyll mutant frequency, was greater in dES posttreatment combinations with HA or HZ, compared with dES pretreatments. These differences in reciprocal treatments may be due to more efficient fixation of premutational events by dES than HZ or HA.

Differential effect of sodium azide on the frequency of radiation-induced chromosome aberrations vs. the frequency of radiation-induced chlorophyll mutations in Hordeum vulgare

A considerable synergistic increase of the frequency of cells carrying chromosome aberrations was observed in seeds of Hordeum vulgare , variety Himalaya, irradiated dry with gamma rays and hydrated in sodium azide solutions buffered at pH 3, 7 and 11. This effect, which was most evident at pH 3, was detected throughout development up to the formation of the male gametophyte. No synergistic increase of the frequency of radiation-induced chlorophyll-deficient mutants was observed. This differential effect of the sodium azide post-irradiation treatment on the frequency of chromosome aberrations vs. the frequency of mutations is attributed to the formation of two kinds of lesions in the genetic material of barley following exposure to gamma rays. One kind of lesion, similar to those leading to point mutations in procaryotes, is reparable at low energy potentials and, thus, its frequency is not affected by the sodium azide treatment. The other kind of lesion is associated with chromosome breaks and its repair is affected by the presence of the enzymatic inhibitor.

Studies on the mutagenic effects of some monofunctional alkylating agents in rice

The mutagenicity of methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS) and n-butyl methanesulfonate (BMS) was tested on rice seeds using an indica variety, Peta. De-hulled seeds were soaked in 1–9×10 −3 m aqueous solutions of MMS, 1–5×10 −2 m EMS and 1–9×10 −2 m BMS for 10, 16 and 8 hr respectively at 30°C (±1°N). The results showed that low concentrations of MMS and BMS slowly reduced germination, survival, seedling growth and M 1 panicle fertility, while at higher concentrations the damage increased at a more rapid rate. The EMS doses used did not affect germination and survival but seedling growth and M 1 panicle fertility was reduced linearly with the increase in dose. The frequency of chlorophyll mutation was very low at low doses of these agents but increased exponentially with increasing doses.

The influence of pH on damage induced by diethyl sulfate (dES) in barley

The influence of pH of the pretreatment, treatment and posttreatment solutions on damage induced by diethyl sulfate (dES) in hulless barley ( Hordeum vulgare var. Himalaya, 2n=14) was studied using several biological criteria. The dES-induced M 1 seedling injury, M 1 plant lethality, M 1 sterility and M 2 chlorophyll mutation frequency decreased with an increase in the pH of the treatment from 2 or 3 to 11 or 12. The pH of the posttreatment soak solution did not influence the dES-induced seedling injury significantly. Irrespective of the pH of the pretreatment soak, soaked seeds showed higher sensitivity to dES action when seedling injury, plant lethality, spike sterility and chlorophyll mutation frequency per 100 M 2 seedlings were used as the measures of sensitivity. The study led to the following conclusions. ( 1) Low pH inherent in treatments with aqueous solutions of dES plays an important role in the determination of total damage induced by these treatments; ( 2) A significant portion of the seedling injury and plant lethality induced by dES treatments is probably caused by low pH in these treatments and hence could be avoided by maintaining the pH of the dES solutions at a high level (11 or 12) during treatment; ( 3) Low pH, being in itself nnon-utagenic in barley, contributes to the mutagenic effectiveness of dES; ( 4) Soaked seeds are more sensitive to dES action than dry seeds; ( 5) Pretreatment soak appears to have an enhancing effect on the size of the mutated sector induced by dES.

A comparison of mutagenic effectiveness and efficiency of NMU and MNG in Sorghum

A comparative study of the effectiveness and efficiency of NMU and MNG in relation to the effects in M1 plants and induction of mutations in M2 was made in a cultivated variety ofSorghum. There was a decrease in the values obtained in each of the biological criteria in the M1, namely germination, survival, seedling growth and seed fertility, with an increase in the concentration of NMU and MNG. Of the characters, survival following MNG treatments and seed fertility following NMU treatments showed the maximum reduction. NMU was not only effective in decreasing the mean of various characters in the M1, but also efficient in inducing a high frequency and wide spectrum of chlorophyll mutations in the M2 compared with MNG. Low concentrations were found to be more efficient than higher concentrations of NMU. The treated M2 population showed not only a decrease but also an increase in the mean height of plant and length of ear compared with the untreated control population. NMU caused a greater decrease in the mean of both characters and induced greater variability in the length of ear than did MNG treatment.

Chemical mutagenesis inSorghum

The effect of NG, DEB and single and recurrent treatments after NMU on sensitivity in M1 and chlorophyll mutation frequency and spectrum in M2 was studied in the variety Co. 18 ofSorghum subglabrascens. Among the three chemical mutagens DEB was the most effective in delaying the emergence of primary leaf, and reducing the percentage of germination, survival and growth of root, coleoptile and seedlings, whereas NG was the least effective. The effect of mutagens increased with increasing dose. Recurrent treatments with NMU showed more drastic effects with respect to the above criteria than single treatments. The frequency of chimeras for chlorophyll deficiency in the M1 was found to be the maximum in the single treatments as compared to recurrent treatments after NMU. An increase in the reduction of pollen and seed fertility with an increase in dose of NMU and NG was observed. But the treatments with NMU showed more drastic effects on fertility than treatments with NG. The frequency of chlorophyll mutations was found to increase with dose in NMU, whereas such relationship was not observed in teratments with NG. The mutation rate was found to be higher in treatment with NMU than with NG. Whilealbina andxantha only were noticed in treatments with NG, a very wide spectrum of chlorophyll mutations was observed in NMU treatments. Recurrent treatments with NMU induced higher frequency and wider spectrum of chlorophyll mutations than single treatments.

Effectiveness and efficiency of single and combined treatments of radiations and ethyl methane sulphonate inSorghum

The effect of single treatments with X- and gamma rays and EMS and combination treatments of gamma rays sand EMS on survival, seedling growth and seed fertility in M1 and chlorophyll mutation frequency in M2 was studied in the variety Co. 18 ofS. subglabrascens. There was an increase in the reduction of survival and seedling height and seed fertility with an increase in the dose of mutagens. Combined treatments were found to be more effective in reducing the survival and height of seedlings than single treatments, while EMS caused more drastic effect on seed fertility than rest of the mutagens. The frequency of chlorophyll mutations in the M2 increased with dose upto a certain dose level and then levelled off at high doses. EMS induced higher frequency of chlorophyll mutations than treatments with radiations. Combination treatments were found to be the most efficient in inducing the chlorophyll mutations as compared to single treatments. Mutagenic effectiveness was found to be the maximum at high doses of gamma rays and EMS, whereas higher efficiency values were observed at lower concentrations of EMS and middle doses of radiations. EMS was found to be the most effective and efficient mutagen than rest of the mutagens.

Chlorophyll Mutation From Recurrent X‐Irradiation of Flax Seed1

A 1,000‐seed lot from each of seven flax (Linum usitatissimum L.) varieties were allowed to reach moisture equilibrium over NaC1O3 before treatment with 30 kR of high energy x‐rays. Controls were 500 non‐irradlated seeds of each variety. Seeds for subsequent cycles were obtained from random bolls, each taken from a different basal branch of the surviving M1 or control plants. One seed from each selected boll was used to maintain the 1,000‐ or 500‐seed lots for varietal irradiated and control populations, respectively. Seeds were irradiated each generation for four cycles.The chlorophyll mutation frequencies, based on basal branch progenies (primary or secondary stems) were 0.32 ✕ 10‐2, and 0.02 ✕ 10‐2 for irradiated and control populations, respectively. The chlorophyll mutation frequencies, using Frydenberg's seedling method were 4.8 ± 0.5 ✕ 10‐4, and 0.1 ± 0.06 ✕ 10‐4 for irradiated and control populations, respectively.The chlorophyll mutation spectrum consisted of six classes: light‐green 29%, yellow‐green 35%, yellow virescent 12%, yellow 14%, albino virescent 7% and albino 3%. The yellow and albino mutants usually died in the seedling stage.

Sensitivity and induction of mutations in sorghum

The effect of physical (X- and γ-rays) and chemical (EMS, MMS, DES and NEU) mutagens and combination treatments was studied on germination, survival, seedling growth, pollen and seed fertility in M 1 and frequency of chlorophyll mutations in M 2. The percentage of germination, survival and growth of seedlings decreased with an increase in dose of the mutagens. γ-Rays produced greater reduction in germination, survival and seeding growth than the other mutagens. MMS caused more drastic effects than the other chemical mutagens. Combination treatments showed an enhanced effect when compared with single treatments. CO.11 was the most resistant, and Co.12 the least. A linear dependence of pollen and seed fertility on dosage was evident in all three varieties. EMS caused more drastic effects on fertility than did the other mutagens. The mutagens affected fertility on both male and female phases, and the change in fertility status in the male and the female sides was found to be interdependent. Besides a linear relationship of chlorophyll mutation frequency with dose, a saturation effect was observed. EMS was found to be the most potent mutagen in inducing the chlorophyll mutations. The low potency of NEU and MMS was due to their high toxicity. The frequency of chlorophyll mutations was found to depend not only on the type of mutagen and dose but also on the genotype constitution of the material used.

A comparison of mutation induction in diploid and tetraploid rice

A comparative assessment of the frequency and spectrum of chlorophyll mutations in the M 2 and M 3 of three diploids and one tetraploid of rice after X-irradiation was made. As well as a linear relationship of the frequency of mutations with the dose of mutagen, a saturation effect was also evident. Among the three diploids, the maximum frequency of mutations was observed in T. N. 1, followed by G. E. B. 24 and A. S. D. 8. The diploid of G. E. B. 24 showed a higher frequency of mutations than the tetraploid when measured on the M1 plant basis only. The diploids showed a higher rate of mutations in the M 2 than in the M3.There was no relationship between the frequency of different types of chlorophyll mutations and the dose of X-rays. Albina, occurred in greater proportion than the other types of mutations in the diploids as well as in the tetraploid. The diploid showed a wider spectrum in the M 2, whereas the tetraploid recorded the maximum types of mutations in the M 3. Striking differences in the spectrum and the relative frequency of each type were observed among the three diploids and also between the diploid G. E. B. 24 and its tetraploid.The frequency and spectrum of induced mutations in the diploid and autotetraploid provided an insight into the genetic behaviour of the diploid and autotetraploid of G. E. B. 24, indicating that the genetics of diploidisation of the existing diploid rice may give evidence on the nature of the evolutionary pathway.

POST-TREATMENT TEMPERATURE EFFECTS ON MUTATION FREQUENCY IN EMS-TREATED BARLEY

Mutations continued to be induced in barley seeds for some hours after the seeds were transferred from EMS solution to water. Evidence for this was obtained by determining mutation frequencies in plants grown from different batches of seeds that had been treated in identical fashion except that they were subjected to different temperatures during a 12- or 24-hour washing period. Chlorophyll mutation frequencies were lowest after washing at 10 °C. With each 10 °C step up (to a maximum of 40 °C) mutation frequencies increased by 1.4-2.5 × provided that the mutation frequency after 10 °C post-treatment was well below the maximum obtainable with EMS. The effects of temperature during the treatment and post-treatment periods on mutation rate are similar in direction and in amounts. During the post-treatment period mutations probably continue to be induced for more than 12 hours since the frequencies were affected more by a 24-hour than by a 12-hour post-treatment temperature exposure. The effects are probably produced by altered rates of alkylation of DNA by EMS at different temperatures.

The dependence of the frequency of recessive lethal and vital mutations inArabidopsis thaliana (L.)Heynh. on the concentration of N-nitroso-N-methylurea

The dependence of the frequency of recessive lethal (two groups), chlorophyll and morphological mutations on the mutagen concentration was determined in M2 after subjection to N-nitroso-N-methylurea applied to seeds ofArabidopsis in three concentrations (0·05, 0·10 and 0·20mm). The observed frequencies were compared with the theoretically expected ones for the linear and for two exponential types of dependence, by using the t-test, according to the formulas m=k. C, m=k. C3/2, m=k. C2. No satisfactory agreement with any expected type of dependence was found when directly observed frequencies were used. Since a considerable deficit of mutation frequency was observed in high concentrations, the correction of frequency values was done with respect to the probability of occurence of double mutations. After such a correction, a clear exponential relation was found in both types of lethals and a linear one in chlorophyll and morphological mutations. The probable occurence of multiple mutations should be, therefore, taken into account if the dependence of mutation frequency on the concentration of mutagen is discussed.

RADIO-SENSITIVITY IN RAGI (ELEUSINE CORACANA)

Dry seeds of three varieties of ragi (Eleusine coracana) were subjected to gamma irradiation with acute dosage of 20 Kr and 30 Kr. The mutagenic effects of gamma rays in the M1generation and the mutation frequency with regard to chlorophyll and viable mutations in the M2generation were studied.The LD50appears to be around 30 Kr for ragi, although there are enormous varietal differences. Purna is the least and H22the most sensitive to gamma irradiation in the M1generation. There is a direct correlation between the radiation effect produced as measured by seedling growth, pollen fertility and seed fertility with the dosage used. Multivalent formation, lagging chromosomes and stickiness, etc. were observed in meiotic studies in the M1generation.The frequency of chlorophyll mutations was less in populations irradiated with 30 Kr than with 20 Kr. A wide spectrum and a high frequency of viable mutations were produced in Purna. The mutation frequency (viable + chlorophyll) increased with the dosage. The 200 isolated viable mutations included many agronomic types which are useful either directly or in conventional plant breeding.

The Effects of Temperature and Moisture on the Induction of Genetic Changes in Seeds of Barley, Broad Beans, and Peas during Storage

Seeds were ‘aged’ by treatments with various combinations of temperature and moisture content so that viability was reduced to about 50 per cent. It was shown that such treatments induced non-heritable morphological abnormalities in about 10 per cent of the bean plants and 5 per cent of the pea plants; but no non-heritable morphological abnormalities were observed in the barley plants. In all species there was an increased frequency of pollen abortion in the plants produced from ‘aged’ seeds. From the examination of second and third selfed generations it was shown that single-recessive and double-recessive chlorophyll-deficiency mutations of various types were usually induced in sectors of about 1–3 per cent of the plants grown from treated seeds. The evidence from pollen-abortion supports previous cytological evidence that, under most storage conditions, for a given loss of viability, a predictable amount of chromosome damage is found in the surviving seeds, irrespective of how fast viability was lost or which environmental factor was mainly instrumental in the loss of viability. A comparison of the frequency of chlorophyll mutations produced under different storage treatments was not as quantitatively precise, but this evidence also is at least compatible with the thesis that loss of seed viability is associated with chromosome damage which is reflected in gene mutation. It is concluded, therefore, that percentage seed viability is a good index of the loss of genetic purity resulting from mutations which accumulate during storage.

Comparaison de l'action mutagenique d'agents alkylants et des radiations gamma chez Arabidopsis thaliana

Effects on three sulfonate esters, a nitrosamine and γ-radiation have been compared on the basis of mutation rate, sterility and lethality. The most powerful mutagen was ethyl-methane-sulfonate (EMS) inducing up to 16 per cent chlorophyll mutants. After, we have respectively methyl- N-nitro- N′-nitrosoguanidine (MNG) 12 per cent, methyl-methane-sulfonate (MMS) 7·5 per cent, γ-radiation 5·5 per cent and butyl-methane-sulfonate 2·3 per cent. Increase of mutation frequency can arise from decreased lethality in treated plants. Mutagenic efficiencies compared with toxicity correspond fairly well to those obtained for induced sterility. By decreasing power we have EMS > MNG > MMS > γ BMS. Comparison of induced sterility related to chlorophyll mutation frequency showed a maximal efficiency for EMS, meaning that for the same number of induced mutations, this alkane sulfonate induced less sterility. Relations of mutagenic effects with concentration are linear after irradiation, exponential after MNG or EMS and rather sigmoidal after BMS and MMS. Evidence was obtained of preferential induction of some chlorophyllian phenotype with the mutagen utilized. EMS induced relatively few albina as compared with γ-rays. Chlorophyll mutation spectra differed not only with the nature of the mutagen but also with experimental conditions, temperature and pH. Genome itself can interfere to preserve or eliminate some mutations. Mean segregation ratios of M 2 chlorophyll mutations are widely lower than 25 per cent. Their values which is an indication of the mutated sector increases in the direction MMS < γ < MNG < EMS. The analysis of these segregation ratios made us consider the occurence of two or three initials as origin of the generative tissue. Some external conditions can increase the mutation rate. Temperature during the treatment increased the reactivity of MNG. In the case of EMS, seed presoaking has the same action. Increase of pH of the mutagenic solution results in an increase of mutated plants after MMS treatments. Differential sensitivity to EMS appeared in three strains of Arabidopsis from different geographical origins. These differences are concerned as well with the mutability as the biological reactions of the treated generation.

Mutation frequencies in ontogenetically different spikes of hexaploid wheat after ethyl methanesulphonate treatment

Seeds of hexaploid wheat were treated with ethyl methanesulphonate (EMS). The M 1 generation was grown in a greenhouse, and the individual shoots of the plants were classified and marked according to their ontogeny. The sterility in M 1 and the frequencies of chlorophyll and viable mutants segregated in M 2 were estimated. The frequency of chlorophyll mutants was very low and hence not very informative in regard to the mutation frequency in the individual spike categories. On the basis of the viable mutants segregated in M 2, no significant difference in mutation frequency between the different spikes of hexaploid wheat after EMS treatment could be demonstrated.

The influence of post-treatment washing and redrying of barley seeds on the mutagenic activity of N-methyl- N-nitroso-urea and N-ethyl- N-nitroso-urea

Barley seeds were treated with two nitroso-ureas: N-methyl- N-nitroso-urea and N-ethyl- N-nitroso-urea. After the treatment the seeds were washed for up to 24 hr and sown immediately or redried to their original moisture content before planting. With increasing post-washing time, general biological damage and mutation frequency decreased. The criteria used were chromosomal aberrations, seedling height, survival and seed setting in the M 1 generation and the frequency of chlorophyll mutations in the M 2. The rate of the decrease of biological damage and mutation frequency depended on the concentration of nitroso-ureas and on the treatment time. When seeds were redried without a preceding washing, both the M 1 biological damage and the M 2-chlorophyll mutation frequency increased as compared with treatments with no redrying. When the mutagenic treatment was followed by washing, the redrying effect decreased. After a specific washing time, which depended on the concentration of the chemical mutagen and treatment duration, no redrying effect could be observed. The effect of washing found in the present study is explained by a removal of unhydrolyzed nitroso-ureas from the seeds after the termination of the treatment.

The Relationship between Response to Radiations and Nature of Polyploidy in Some Crop Plants

SUMMARYThe use of response to radiations as a tool in assessing the nature of polyploidy is the aim of this study. For this purpose four crop species viz., barley (diploid and autotetraploid), breadwheat (T. aestivum), tobacco (N. rustica) and Upland cotton (G. hirsutum) were chosen. Dry seeds were irradiated with X-rays, gamma rays and fast neutrons. Observations on sterility and incidence of morphological changes in the M1 and frequency of chlorophyll and viable mutations in M2 suggest that the extent of genetic diploidization may increase in the following order:Autotetraploid H. vulgare → T. aestivum → N. rustica → G. hirsutum.The present study would hence suggest that an assessment of radiation response of a polyploid plant would be worthwhile for the purpose of supplementing the available knowledge on the nature of polyploidy in it.