Effect of nitrosourea in small doses on the frequency of mutation in Salmonella typhimurium

The effect of N-nitroso-N-methylurea (NMU), N-nitroso-N,N'-dimethylurea (NDMU) and N-nitroso-N-ethylurea (NEU) at doses less than 100 mkg/ml on mutability of Salmonella typhimurium strains of Ames' system (G-46, TA-1950, TA-1535, TA-100, TA-1538) has been studied. NMU and NEU at doses of 5-10 mkg/ml have been found to increase the survival and decrease the number of reversions from auxotrophity in histidine to prototrophity. The effect of given doses of NMU and NEU on bacteria repair activity has been shown. The role of pk M101 plasmide in this process is being discussed. NDMU in contrast to NMU and NEU induces read frome shift mutations and exhibits high mutagenous activity at all doses examined.     

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 M₁ 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 M₂ generation, in sequential treatments. However, the degree of synergism, based on M₂ 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.     

Increasing the toxic effect of pulmonary carcinogens by destruction of epithelial-mesenchymal interaction in explants of embryonic respiratory tract of mice

The explants from 17-day old embryos of A and C57BL mice were used for long-term organ cultures. The following series of explants were studied: 1) the intact control explants; 2) the explants treated by NMU; 3) the explants treated by BP; 4) the explants isolated from mesenchyma (M); 5) the explants isolated from M and treated by NMU; 6) the explants isolated from M and treated by BP. The survival of explants treated by NMU or BP did not differ from the intact control explants (p less than 0.1). The removal of M decreased the survival only in the explants from the distal RT of A mice (p 0.01). The survival of explants isolated from M and treated by NMU or BP was significantly lower than it was in intact explants (p less than 0.01-0.001). Thus, the destruction of epithelial-mesenchymal interaction induced by removal of M can modulate the toxic effect of pulmonotropic carcinogens.     

Developing stable progenies of ×Brassicoraphanus, an intergeneric allopolyploid between Brassica rapa and Raphanus sativus, through induced mutation using microspore culture

Induced mutations were used to improve the low seed fertility of an intergeneric allopolyploid, ‘Baemoochae,’ ×Brassicoraphanus, synthesized following hybridization between Brassica rapa and Raphanus sativus. The mutagen N-methyl-N-nitroso-urethane (NMU) was added to microspore cultures. Four lines of nine in the Mi₂ generation showed very high fertility under controlled pollination. The progeny lines (Mi₃) confirmed this result under open pollination, and excellent uniformity was observed in plants grown in the field, as well as in their AFLP profile. On attaining high fertility and uniformity, one of the lines was released to farmers as a new leafy vegetable crop. The original nine lines shared very similar AFLP banding patterns, without any large differences between the high and low seed fertility lines. Thus, mutation induction accelerated genetic stabilization of a newly synthesized allopolyploid, ×Brassicoraphanus.     

Field performance of maize grown from <Emphasis Type="Italic">Fusarium verticillioides</Emphasis>-inoculated seed

Fusarium verticillioides is an important fungus occupying dual roles in the maize plant. The fungus functions as an endophyte, a fungal/host interaction beneficial to the growth of some plants. At other times, the fungus may function as a mycotoxin producing pathogen. The advantages and/or disadvantages of the endophytic relationship must be established in order to target appropriate sites for controlling diseases and mycotoxins in maize. One possibility could be to ensure seed maize is fungal free prior to planting. Reciprocal inoculations were made with two fungal isolates on seed of two maize genotypes. Yield was measured at harvest by ear and seed characters and vegetative growth at one-month intervals for plant survival, height, weight and stem diameter. Yield and vegetative growth differed among mature plants only once based on seed inoculation status. In 1998, plant weight was reduced and seed weight per ear was increased for the dent maize, GT-MAS: gk, grown from F. verticillioides RRC 374- inoculated seed compared to other seed treatments. Most vegetative characters were reduced at the first collection for Silver Queen plants grown from F. verticillioides-inoculated seed in 1997 and 1999, but not in 1998. However, no significant differences occurred among mature Silver Queen plants during any of the three growing seasons. In conclusion, yield and vegetative growth of mature maize plants grown from F. verticillioides-inoculated seed were equal to or greater than plants grown from non-inoculated seed under south Georgia field conditions during 1997, 1998, and 1999.     

外来杂草薇甘菊在不同群落中的种子生产特征

对3个群落花甘菊种群种子生产的3个特征即花序特征、种子产量和种子干粒重进行了分析。结果表明：不同种群中小花数、结实率、种子产量和种子干粒重存在显著差异,小花数变异范围为93281．6-154698．0朵／0．25m^2;平均结实率为25．75％一34．58％;平均种子产量的变异范围为23673．40—52616．71粒／0．25m^2;干粒重为0．0880—0．10208。在以有性生殖为主的种群和以无性生殖为主的种群中,前者的种子较大。结合薇甘菊种群对环境的适应对结果进行了讨论。     

EFFECTS OF CROSS AND SELF-FERTILIZATION ON PROGENY FITNESS IN LOBELIA CARDINALIS AND L. SIPHILITICA

Inbreeding depression, or the decreased fitness of progeny derived from self-fertilization as compared to outcrossing, is thought to be the most general factor affecting the evolution of self-fertilization in plants. Nevertheless, data on inbreeding depression in fitness characters are almost nonexistent for perennials observed in their natural environments. In this study I measured inbreeding depression in both survival and fertility in two sympatric, short-lived, perennial herbs: hummingbird-pollinated Lobelia cardinalis (two populations) and bumblebee-pollinated L. siphilitica (one population). Crosses were performed by hand in the field, and seedlings germinated in the greenhouse. Levels of inbreeding depression were determined for one year in the greenhouse and for two to three years for seedlings transplanted back to the natural environment. Fertility was measured as flower number, which is highly correlated with seed production under natural conditions in these populations. Inbreeding depression was assessed in three ways: 1) survival and fertility within the different age intervals; 2) cumulative survival from the seed stage through each age interval; and 3) net fertility, or the expected fertility of a seed at different ages. Net fertility is a comprehensive measure of fitness combining survival and flower number. In all three populations, selfing had nonsignificant effects on the number and size of seeds. Lobelia siphilitica and one population of L. cardinalis exhibited significant levels of inbreeding depression between seed maturation and germination, excluding the consideration of possible differences in dormancy or longterm viability in the soil. There was no inbreeding depression in subsequent survival in the greenhouse in any population. In the field, significant survival differences between selfed and outcrossed progeny occurred only in two years and in only one population of L. cardinalis. For both survival and fertility there was little evidence for the expected differences among families in inbreeding depression. Compared to survival, inbreeding depression in fertility (flower number) tended to be much higher. By first-year flower production, the combined effects on survival and flower number caused inbreeding depression in net fertility to reach 54%, 34% and 71% for L. siphilitica and the two populations of L. cardinalis. By the end of the second year of flowering in the field, inbreeding depression in net fertility was 53% for L. siphilitica and 54% for one population of L. cardinalis. For the other population of L. cardinalis, these values were 76% through the second year of flowering and 83% through the third year. Such high levels of inbreeding depression should strongly influence selection on those characters affecting self-fertilization rates in these two species.     

Estimation of efficiency of seed irradiation by thermal neutrons for inducing chromosomal aberration in M2 of cotton Gossipium hirsutum L

Cytogenetic analysis of M2 plants after irradiation of cotton by thermal neutrons was performed in 56 families. In 40 plants of 27 M2 families, different abnormalities of chromosome pairing were found. These abnormalities were caused by primary monosomy, chromosomal interchange, and desynapsis. The presence of chromosome aberrations in some cases decreased meiotic index and pollen fertility. Comparison of the results of cytogenetics analysis, performed in M1 and M2 after irradiation, showed a nearly two-fold decrease in the number of plants with chromosomal aberrations in M2, as well as narrowing of the spectrum of these aberrations. The latter result is explained by the fact that some mutations are impossible to detect in subsequent generations because of complete or partial sterility of aberrant M1 plants. It was established that the most efficient radiation doses for inducing chromosomal aberrations in the present study were 15 and 25 Gy, since they affected survival and fertility of altered plant to a lesser extent.     

土壤肥力对绞股蓝种群行为的影响

利用半控制实验生态学方法探讨土壤肥力对绞股蓝种群行为的影响。结果表明：土壤肥力的提高可显著提高繁殖器官生物量分配比,显著降低非繁殖器官生物量分配比,叶片、支持结构生物量分配随土壤肥力的提高略有降低;提高土壤肥力对绞股蓝种群形态特征和平均相对生长速率的影响不明显;多数繁殖特征对土壤肥力的提高有显著响应。总之,绞股蓝种群的不同行为对土壤肥力变化的敏感性各异。     

土壤肥力对绞股蓝种群行为的影响

利用半控制实验生态学方法探讨土壤肥力对绞股蓝种群行为的影响。结果表明：土壤肥力的提高可显著提高繁殖器官生物量分配比,显著降低非繁殖器官生物量分配比,叶片、支持结构生物量分配随土壤肥力的提高略有降低;提高土壤肥力对绞股蓝种群形态特征和平均相对生长速率的影响不明显;多数繁殖特征对土壤肥力的提高有显著响应。总之,绞股蓝种群的不同行为对土壤肥力变化的敏感性各异     

Effect of N-nitroso-N-methylurea on viability and mutagenic response of repair-deficient strains of Escherichia coli

Various E. coli mutants, deficient in DNA repair, differed in their response to increasing concentrations of N-nitroso-N-methylurea (NMU).Loss of viability due to exposure to NMU was greatest in those strains with a reduced capacity for repair of single-strand breaks. Viability of wild-type and uvrA^? strains was not affected by NMU concentrations up to 3.0 mM. Some loss of viability occurred, at the higher NMU concentrations, in both strains carrying exrA^? while strains carrying uvrA^?polA^? or recA^? were the most sensitive. The results support the hypothesis that the lethal effect of NMU on repair-deficient E. coli was due to its ability to induce single-strand breaks.Induction of mutations by NMU was observed in all the strains used and the results suggested that NMU damage per se was the major mutational event. The dose response curve for induction of revertants by NMU was, however, influenced by the repair system(s) present. The number of revertants scored at the higher NMU concentrations was greater in those strains lacking the recA and polA dependent repair functions than in the wild-type strain. However, at NMU concentrations below 2.0 mM the numbers of revertants induced in exrA^? carrying strains, prossessing accurate rec-dependent repair, were lower than the comparable wild-type values. The evidence suggests that the uvrA gene product also acts on some, possibly non-mutagenic, types of NMU damage and that error-prone repair of these lesions increases the number of potential revertants.     

Plant tissue culture as a model system for mutagenicity testing of chemicals

Two karyotypically stabilized callus strains of Crepis capillaris (2n = 7 and 2n greater than or equal to 12, respectively) were employed to illustrate the utility of plant tissue culture method for screening and analysis of cytogenetic effects of chemicals following long-term treatment. The cytogenetic analysis of callus cells revealed significant differences in the toxic and mutagenic effects of chemicals under study (2,4-D, MH, NMU and kinetin). A certain dose-response relationship (though not necessarily linear) was observed. The maximum cytogenetic activity of chemicals was associated with certain intermediate concentrations (4.5 X 10(-5) M-9 X 10(-5) M), whereas a further increase in the dose either gave rise to the opposite effects (i.e. decrease in the ana- and telo-phase aberration rates and increase in the modal karyotype frequency) or the aberration rate remained unchanged.     

Mutagenic action of alkylating agents on prophage lambda

The lethal and mutagenic effects of 7 alkylating agents: N-nitroso-N-methylurea (NMU), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), nitrogen mustard (HN2), mitomycin C (MC), bifunctional acridine mustard (AM)--and of cyanate (KNCO) on heat inducible lambda cI857 prophage were studied. After treatment of lysogenic cells with mutagens, prophage was heat-induced either immediately or after 90 min incubation in nutrient broth and c mutants forming clear plaques at 32 degrees C were scored. NMU (0.02 M) when immediately induced with heat, induces c mutants very efficiently (maximal yield 10%) not only in the wild-type cells but also in repair-deficient mutants recA13, lexA102, uvrA6 umuC36, recF143, xthA9, polA1, uvrD3 and uvrD502. These data show that NMU-induced mutations are fixed as replication errors due to mispairing modified bases. After delayed heat induction, the prophage survival enhances and the frequency of c mutations declines considerably in host cells of all repair genotypes tested. Carbamoylation is not involved in the mutagenic action of NMU, because KNCO (0.02 M) has a very slight lethal effect and does not induce mutations. MNNG (100 micrograms/ml) and EMS (0.1 M) also induce mutations by replicative mechanism, because maximal yield of c mutations does not depend on RecA+ and is about 15 and 2%, respectively. MMS is a mutagen of the repair type, since its mutagenic action is suppressed by recA mutation of the host. NH2 only inactivates prophage, but does not induce mutations. MC (50 micrograms/ml) and AM (150 micrograms/ml) induce mutations rather inefficiently (the maximal yield 0.1 and 0.3%, respectively) both in recA+ and recA- hosts. The mutagenic action of these agents is probably due to intercalation.     

Genetic effects of N-nitroso-N-methylurea on Saccharomyces cerevisiae yeasts. I. The influence of radiosensitivity mutations on lethal and recombinogenic effects]

Effect of mutations rad2 and rad54 in homozygous state on survival, mitotic segregation and crossing-over induced by NMU in yeast was studied. Mutation rad2 did not influence on these effects of NMU. The mutation rad54 increased sensitivity to the lethal effect, the frequencies of NMU-induced segregation and crossing-over were decreased in the strain rad54 rad54. The recombinogenic effect of NMU on yeast was lower than under the action of UV and gamma rays.     

Plasma progesterone profiles,ovulation rate,donor embryo yield and recipient embryo survival in native Saloia sheep in the fall and spring breeding seasons

The response to superovulatory (SOV) and estrus synchronization (ES) treatments and the fertility of donor (n=68) and recipient (n=118) Saloia ewes was evaluated in the fall and spring breeding seasons. The proportion of acyclic ewes at treatment time was significantly higher in the spring than in the fall (42.6% versus 4.0%, P<0.00001). Donors treated with eCG had a significantly higher mean number of follicles over 5mm in diameter in the ovaries at embryo recovery and a significantly lower mean efficiency of recovery than FSH-treated ewes. These negative effects were more pronounced in the fall than in the spring, which resulted in a significantly lower mean number of total and fertilized ova recovered from eCG-treated ewes, compared to FSH donors in the fall, but not in the spring. Season had no significant effect on the ovulation rate and plasma P4 concentrations of recipients treated with a progestagen plus eCG combination. Although the recipient lambing and embryo survival rates were higher in the fall than in the spring the differences were not significant. No significant differences were observed in the ovulation rate or P4 concentrations of recipients that lambed compared to those that did not lamb. These preliminary results show that, in Portugal, response of Saloia ewes to SOV or ES treatments and donor fertility following the SOV treatment were similar in the spring and the fall, which suggests that in the spring acyclic ewes are in moderate anestrus. The effect of season on fertility following embryo transfer should be confirmed in further studies involving a larger number of animals. The semilaparoscopic transfer method reported here allowed lambing and embryo survival rates higher (although not significantly) than a standard surgical approach.     

Enhanced shoot organogenesis in Bixa orellana L. in the presence of putrescine and silver nitrate

An efficient protocol for direct shoot organogenesis in Bixa orellana, known as achiote or annatto or Latkhan (India), has been developed. Using nodal shoot-tip explants, significant organogenetic responses, mean shoot number and shoot elongation were observed when these were incubated on Murashige and Skoog (MS) medium containing 6.66 ??M 6-benzyladenine (BA) and 4.9 ??M indole-3-butyric acid (IBA), and supplemented with either 200?C1,500 ??M putrescine or 40 ??M silver nitrate (AgNO₃). Putrescine at 800 and 1,000 ??M promoted the highest mean shoot length and mean shoot number per explant, respectively. Moreover, various concentrations of putrescine induced callus development. Incorporation of a polyamine biosynthesis inhibitor Difluro-Methyl Ornithine (DFMO) inhibited in vitro shoot multiplication and also altered the endogenous polyamine pool of B. orellana shoots. The field survival of in vitro-derived plants of putrescine and AgNO₃ treatments was 70%. This protocol can be used for improving the in vitro regeneration of B. orellana for transformation studies.     

薇苷菊乙醇提取物对桔全爪螨种群的控制作用

研究薇苷菊(Mikaniamicrantha)乙醇提取物对桔全爪螨(Panonychuscitri)种群的控制作用,并比较其与常用杀螨剂哒螨灵的效果.在实验室用0.1、0.2、0.4g·L^-13个浓度提取物分别喷布桔全爪螨卵、幼螨和若螨,除了01g·L^-1浓度处理对卵没有效果外,该处理幼螨、若螨存活率以及另2个浓度处理3个螨态的存活率都显著下降.在非选择性试验条件下,用这3个浓度的提取物处理叶片饲养的桔全爪螨雌螨繁殖量显著减少,寿命也显著缩短.在田间用这3个浓度的提取物在20d内连喷2次,桔全爪螨卵、幼螨和若螨的存活率都低于对照,干扰作用控制指数分别为0518、0.292、0.277,即对种群增长控制的效果分别为4.82%、70.8%、72.3%,比15%哒螨灵乳油2000倍处理更有效控制桔全爪螨的田间种群.田间试验结果还表明,提取物处理的叶片比对照和哒螨灵处理的浓绿,而且对桔全爪螨的天敌较安全     

Modifying effect of dioxane on the cytogenetic activity of N-nitroso-N-methylurea

Dry seeds of Crepis capillaris L. were treated with N-nitroso-N-methyl urea (NMU) and with dioxane (DO) an organic solvent, at pH 7.0 and pH 5.7. The treatment with NMU only was used as a positive control. Three concentrations of NMU were applied. The cytogenetic activity of NMU was found to considerably decrease at two values of pH, while NMU was solved in DO. The relationship between different types of chromosome aberrations remained unchanged in this case.     

Evaluation of the effect of pollen irradiation on karyotype variability in M2 cotton plants

The karyotypes of biomorphologically abnormal cotton (Gossypium hirsutum L.) plants obtained in M2 after pollination with pollen irradiated at dose rates 10, 15, 20, and 25 Gy were studied. Various genomic and chromosomal mutations were detected in 57 M2 families. The primary monosomics isolated in M2 were found to be cytologically more stable and more viable, since they had higher meiotic indices, pollen fertility, and seed formation. In M2, a decrease in the number of plants with multiple karyotype aberrations and interchromosomal exchanges with high frequency of multivalent formation was observed. The multivalents had diverse patterns and types of chromosome segregation and translocation complexes. Their pollen fertility was higher than in translocants found in M1. Desynapsis often occurred in M2, including plants with chromosome deficiency or rearrangements. The variation in the number of univalents in various cells was found to result from different expression of synaptic genes. The results indicate stabilization of karyotypes, increase in cytologic stability and viability, and the absence of sterility in aberrant plants.     

Comparative demographic analysis in contrasting environments of Magnolia dealbata: an endangered species from Mexico

The study of population regulation and demography in natural habitats is critical for the conservation of rare and endangered species. We address the impact of cattle exclusion on the demographics of Magnolia dealbata (Magnoliaceae), an endangered species according to IUCN and Federal Mexican laws. Sixteen permanent plots were established, eight of which were enclosed to livestock, in the mountain cloud forest in Coyopolan, Mexico, which has the largest population of M. deadlbata. Censuses of the plots were undertaken annually during three annual cycles to record seed number, recruitment, mortality, and growth (defined as length and diameter at breast height). The effects of two treatments (with and without livestock exclusion) on the dynamics of M. dealbata were investigated using transition matrix models and life table response experiment (LTRE) analysis. Contrary to expectations, there was no significant effect of cattle exclusion on population growth rates (λ). Furthermore, the λ, estimated from the mean transition matrix for both treatments was greater than one. The transitions with the highest elasticity values were similar between the two treatments, while reproductive stage contributed more to differences in population growth rate and were less variable than the non-reproductive stage. LTRE analysis showed that treatment differences had little effect on λ. Livestock exclusion appears to lead more to differences in the arrangement of the values of the transition matrix than to the rate of population growth for M. dealbata.