kR Of Gamma Radiation Research Articles

Improvement of Wax Oil Content of Embryonic Callus of Jojoba Using Gamma Radiation

Embryogenic callus was obtained from the leaf explants of jojoba (Simmondsia chinensis (Link) Schneider cultured on MS containing 0.5 mg/l NAA and 0.5 mg/l Kn. Growth of embryonic callus increased in 0.5 mg/l Kn + 6% sucrose. In order to improve oil content, the embryonic callus was exposed to different doses (5, 10 and 15 Kr) of gamma radiation. It was found that oil content of embryonic callus of jojoba increased 1.41% by exposing to 5 Kr gamma radiation. Also, size of oil bodies in embryonic callus irradiated with 5 Kr increased compared to control. Furthermore, production of the fatty acids was enhanced by gamma irradiation. The highest percentage of total fixed oil (1.41) was recorded in 5 Kr radiation. However, the highest content of total fatty acids (98.612) was obtained when embryonic callus were exposed to 10 Kr of gamma radiation.

Physiological consequences of gamma ray irradiation in tall fescue with elimination potential of Epichloë fungal endophyte

Perennial plants and their associated microorganisms grow in the areas that may be contaminated with long-lived gamma-emitting radionuclides. This will induce gamma stress response in plants and their accompanying microorganisms. The present work investigated the growth and physiological responses of Epichloe endophyte infected tall fescue to gamma radiation, as well as whether the endophyte could persist and infect the host plant once exposed to gamma radiation. Seeds of Iranian native genotype of 75B+ of tall fescue were exposed to different doses, including 5.0, 10.0, 15.0, 20.0, 30.0 and 40.0 krad of gamma ray from a 60Co source. Irradiated and unirradiated seeds were sown in pots and grown under controlled conditions in the greenhouse. The growth and physiological parameters associated with plant tolerance to oxidative stress of host plants, as well as endophytic infection frequency (% of plants infected) and intensity (mean number of endophytic hyphae per the field of view), were examined in 3 months-old seedlings. The results indicated that all gamma radiation doses (except 5.0 kr) significantly reduced the height and survival percentage of the host plant. Days to the emergence of seedling increased gradually as gamma doses rose. A dose-rate dependent induction was seen for photosynthetic pigments and proline content. Malondialdehyde (MDA) content grew with elevation of irradiation doses. Depending on the dose and time, the activities of antioxidant enzymes in the host plant responded differently to gamma radiation. Gamma radiation altered the enzyme activities with sever decline in SOD and CAT activities. However, it had barely any effect on in APX and POD activities. The results also revealed that the persistence and intensity of endophyte were affected after gamma-ray irradiation. The initial percentage of tall fescue seeds infected with the endophyte was 91% in un-irradiated seeds. Presence of the viable endophyte started to decline significantly (23%) at 5.0 kr of gamma radiation. A dramatic reduction in the presence and intensity of endophyte occurred at 10.0 to 40.0 kr intensities. Gamma radiation × trait (GT)-biplot analysis indicated positive correlations between the endophyte symbiosis and antioxidant enzyme activities. Also, negative correlations were observed between the endophyte and MDA content in the host plant. Our results suggest that radiation stress (doses over 5.0 kr) caused reduction in the growth and antioxidant enzyme activities of the host plant that accompanied by a dramatic reduction in the persistence and intensity of endophyte fungi. Our findings have provided the basic information for future studies on the effect of gamma irradiation on the interaction between endophytic fungi and its host plant.

Physical and chemical mutagenesis in Stevia rebaudiana: variant generation with higher UGT expression and glycosidic profile but with low photosynthetic capabilities

The leaf explants of Stevia rebaudiana were exposed to a range of EMS (chemical mutagen) and gamma radiation (physical mutagen) doses. Among all the treatments, doses of 0.4 % v/v EMS and 0.95 KR gamma radiation were found to be most effective treatment for selection of variants via direct shoot bud induction. The field-established plants designated as EMS (E), gamma (G), and control (C) plants were subjected to photosynthetic parameter studies where E and G plants showed lower chlorophyll content, transpiration rate, CO2 exchange rate, and stomatal conductance. The implanted field soil at the time of harvesting of plants showed reduction in organic carbon (OC), electrical conductivity (EC), phosphorus (P)/potassium (K), and total Kjeldahl nitrogen (TKN). The ISSR profiling of E, G, and C scored total of 107 bands out of which 63 % were polymorphic bands, and plant E was found to be more distant from the C plant phylogenetically. On phytochemical analysis, the G plant registered twofold enhanced rebaudioside A with lower stevioside (3.2 ± 0.22 % dry wt.) content, whereas E plant showed more than 1.5- and 2.0-fold increase in stevioside and rebaudioside A as compared to control plants. Both the E (3.1 ± 0.15 % dry wt.) and G (2.3 ± 0.21 % dry wt.) plants registered lower steviol. The enhanced steviol glycoside profile was supported by the RT-PCR analysis of UGT74G1 and UGT76G1 that corresponds to stevioside and rebaudioside A biosynthesis, respectively. While the E plant showed 5–6-fold increase in the UGT74G1 (RQ = 5.51 ± 0.5) and UGT76G1 (RQ = 6.61 ± 0.5) gene expression, the G plant showed 5-fold increase in UGT76G1 (RQ = 5.29 ± 0.2) gene expression.

Mutagenesis and in vitro culture of Tillandsia fasciculata Swartz var. fasciculata (Bromeliaceae)

The genus Tillandsia (Bromeliaceae) has very few variegated species, and cultivars with chlorophyll-deficient variegation are especially rare. With the objective of inducing chlorophyll-deficient leaf variegation, seeds of Tillandsia fasciculata var. fasciculata were treated with gamma radiation, combined gamma and thermal neutron radiation or by chemical mutagenesis with ethyl methanesulfonate (EMS). Wild type, albino, yellow, yellowish-green and variegated phenotypes were obtained in the subsequent M 0 generation. These variegated seedlings were either sectorial or mericlinal chimeras, consequently the variegation of these seedlings was lost as they grew older. Gamma radiation at 21 kR and 27 kR produced the highest percentage of variegated seedlings (4.4%). The highest percentage of seedlings with chlorophyll-deficient leaves was 8.4% with 27 kR gamma radiation, and 15.8% with 1.2% EMS. Radiation and chemical mutagenesis caused chlorophyll-deficiency mutations in one or more of the histogenic layers: LI, LII, LIII. Wild types had greater total chlorophyll a, b and total chlorophyll than mutant phenotypes. Most of the yellow and yellowish-green seedlings multiplied in a solid half-strength MS medium with equimolar 0.3 or 0.5 μM BA and IBA. The yellowish-green seedlings were able to grow photoautotrophically while the yellow ones were not. This is one of the first reports on the mutagenesis of a Tillandsia species. Stable periclinal chlorophyll-deficient chimeras of Tillandsia species can likely be obtained via mutagenesis if large numbers of seeds are treated with a suitable mutagen.

Effect of Gamma Irradiation on Culex Quinquefasciatus (Diptera: Culicidae) Following Exposure to Radioprotectors1

Male pupae of Culex quinquefasciatus were treated with cysteine, tryptophan, ethylenediaminetetraacetic acid (EDTA), mercaptoethylamine (MEA), and 2-aminoethyl isothiuronium bromide (AET) solutions to investigate the genetic and somatic protective efficiency of these compounds against radiation damage. The dose applied was 8 kR of gamma radiation. Pupae were held in solutions with concentrations ranging from 0.05 to 2% for 2–20 h preirradiation plus 0.5 h postirradiation. The variables studied were percentage emergence, incidence of healthy adults, male fertility, and mating competitiveness. When applied for 2 h before irradiation, higher concentrations of cysteine (0.25, 0.5, and 1%) slightly increased the incidence of weak adults that emerged posttreatment; 1% MEA and AET significantly reduced the total emergence when the exposure lasted 18–20 h, while 1 and 2% EDTA slightly reduced both emergence and the incidence of healthy adults. None of the 5 compounds affected the radiation-induced sterility or improved the inadequate mating competitiveness of radiosterilized males.

Survival of Nicotiana tabacum L. Cv. Wisconsin-38 plants regenerated from gamma-irradiated tissue cultures

Explants and callus tissues of haploid and diploid Nicotiana tabacum L. cv. Wisconsin-38 were treated with 2 kR of gamma radiation. The number of calli with buds was determined 42 days after irradiation. From a total of eight different treatment combinations three showed significant increases in number of calli with buds (95% level) and five experiments showed increases which were not significant at the 95% level. Bud regeneration was related to the survival of plants grown from these buds. Plants were considered “survived” when they attained the flowering stage. A decrease in the survival of plants regenerated from irradiated tissues was recorded in seven out of eight different treatment combinations. This effect was ascribed to the high sensitivity of cells with low chromosome number and death of plants during growth due to physiological disturbances.

Irradiated Larval Vaccination of Ponies against Strongylus vulgaris

Nonimmune pony foals 9 to 12 mo of age were vaccinated with third-stage Strongylus vulgaris larvae (L3) irradiated with 70, 100, or 130 Kr of gamma radiation. Ponies receiving per os inoculations of L3 irradiated with 70 or 100 Kr were protected from the clinical disease and lesions associated with challenge infections of 4,300 L3, when compared to nonvaccinated controls. Similarly, the numbers of worms from the challenging population recovered from successfully vaccinated animals were significantly lower than from nonvaccinated controls. The degree of resistance that develops in individuals can be semiquantitated based on clinical and pathological responses.

Sterilization of the Melon fly, Dacus cucurbitae COQUILLETT (Diptera : Tephritidae), with Gamma-Radiation : Mating Behaviour and Fertility of Females Alternately Mated with Normal and Irradiated Males

To evaluate the sexual competitiveness of irradiated male melon fly, Dacus cucurbitae, the effect of alternate mating on mating receptivity and fertility of the melon fly female was examined. Flies were irradiated two days before adult eclosion with 7 kR of gamma radiation. The receptivity to a second mating of females mated first with irradiated males was almost equal to that of females first mated with normal males. The change in fertility of females mated first with irradiated males and then with normal males was larger than that of females mated first with normal males and then with irradiated males. Fertility of above two types of the females was lower than that of females mated once with normal males. The frequency distribution of percent hatch of eggs laid by females mated successively with normal and irradiated males and vice versa are also described. As there is the tendency to monogamy in the melon fly, irradiated males may work satisfactorily in an eradication program, though the competitiveness of sperm from the irradiated males is thought to be less than that from the normal males.

Control of the stable fly, Stomoxys calcitrans (Diptera: Muscidae), on St. Croix, U.S. Virgin Islands, using integrated pest management measures. II. Mass rearing and sterilization.

Stable flies, Stomoxys calcitrans , collected at local dairies on St. Croix, U.S. Virgin Islands, were used to establish a colony for mass production of flies for a sterile male release (SMR) program. Daily adult production ranged from 250,000 to 300,000, with ca. 70,000 pupae/day needed for colony maintenance. When trays were seeded at a rate of ca. 60,000 eggs/tray, average yield was 21,400 pupae/tray, and more than 90% eclosed. Thus rearing efficiency was ca. 30%. The SMRs were most successful when releases consisted of 24- to 48-h-old adults exposed to 2 kR of gamma radiation (cobalt-60). This dosage sterilized 100% of the females and 98 + 2% of the males, and adults were vigorous and highly competitive with the native strain.

Flight Propensity of Anastrepha suspensa13

Anastrepha suspensa (Loew) flies, laboratory reared from bagasse diet and then sterilized with 10 kr of gamma radiation 2 days before eclosion, and unirradiated flies were compared to native flies from guava with a device which measured propensity for flight to an overhead light source. Native males were 27% more responsive (significantly less sedentary) than unirradiated males and 43% more responsive than irradiated males. Unirradiated males were 22% more responsive than irradiated males. Native females were 20% more responsive (significantly less sedentary) than unirradiated females and 29% more responsive than irradiated females. Unirradiated females were 11% more responsive than irradiated females. Since unirradiated laboratory reared flies had a lower flight propensity than unirradiated flies, irradiation could reduce the chances for survival of flies during stressful situations, such as in field release programs.

The optimal radiation dose for competitive males of Culex tarsalis (Diptera: Culicidae).

Five kR of gamma radiation from a 60Co source was the optimal dose to decrease the fertility rate of male Culex tarsalis to 5%. Such males were competitive with unirradiated males from laboratory colony and field populations when tested in small cages indoors or in large outdoor cages.

Radiation-induced changes in the export and distribution of photoassimilated carbon in soybean plants

Soybean plants 18–21 days post initiation of germination received acute doses ranging from 0.25 to 4.9 kR of gamma radiation from a 60Co source. At 15–240 min following irradiation and at light intensities of either 1600 or 2800 ft-c, the plants were allowed to photoassimilate 14CO 2 for 15 min. After an additional 45 min the plants were sectioned and the 14C content assayed in order to determine the magnitude of translocation and distribution pattern of exported 14C-photoassimilate. A 33% reduction was observed in the export of 14C to the region above the node of the source leaf after a radiation dose as low as 1.0 kR. In comparison, a radiation-induced reduction in the extent of photoassimilate export was not observed until an absorbed dose of 3 kR. Despite the difference in radiosensitivity, the distribution pattern 30 min following irradiation and the magnitude of export 2hr after irradiation were observed to return to normal. Furthermore, the recovery of the export process was only observed when the plants were illuminated at 2800 ft-c. The data are interpreted to suggest that the radiosensitive sites affecting changes in export and distribution are different and that these two aspects of translocation can be modified independently of each other. Since no differences were observed between control and irradiated plants in regard to the partitioning of 14C between the 80% ethanol-soluble and insoluble fractions, or in the relative amounts of 14C-compounds present in the ethanol-soluble fraction of the source leaf, it is not likely that the radiation-induced reduction in the magnitude of photoassimilate export was due to a reduced availability of substrate for translocation.

Effects of radiations on Spirogyra azygospora singh. I. Gamma-rays.

The material Spirogyra azygospora (n=12: chromosomes polycentric) beloging to the Order Conjugales, was used as an experimental material to study the morphological and cytological effects of gamma-rays. The doses administered range from 2 kR to 130 kR. Even the dose of 130 kR gamma radiation did not prove to be completely lethal to this alga. Among the various cytological effects chromosome and chromatid breaks, chromatid and isochromatid exchanges and ring, chromosomes are noteworthy. Chromatid and isochromatid exchanges are reported for the first time in polycentric chromosomes. The results were discussed with those of others who studied the effects of ionizing radiations on the karyology of algae.

Enhanced bud formation in gamma-irradiated tissues of Nicotiana tabacum L. cv Wisconsin-38

Pith and callus tissues of Nicotiana tabacum cv W-38, explanted from three different regions of the stem, were irradiated with 2 Kr of gamma-radiation. The observed enhancement of bud regeneration in explants and callus was related to the origin of the explanted tissue and to growth regulators added to the media prior to and after irradiation.

GENETIC INSECT CONTROL: CHROMOSOME REARRANGEMENTS ISOLATED USING A SIMPLE SYSTEM IN THE ONION MAGGOT, HYLEMYA ANTIQUA (DIPTERA: ANTHOMYIIDAE)

AbstractA method for the direct isolation of useful genetic strains was shown effective in the onion maggot. This method circumvents the extensive preliminary investigations called for by current concepts in genetic population control. From genomes treated with 1.5 kr of gamma radiation, the system showed that 17% of those tested carried chromosomal rearrangements potentially useful in genetic population reduction.

Abscission of Phaseolus and Impatiens Explants

Stem-petiole explants from the lower pulvinus of the primary leaves of Phaseolus vulgaris L. cv. Red Kidney and from Impatiens sultani Hook cv. Scarlet Baby were exposed to varying dosages of gamma-radiation. With bean, irradiation of 175 to 525 kiloroentgens (kR) significantly accelerated the onset of abscission with a maximum response at 175 to 280 kR. Higher dosages (beginning at 600-700 kR) usually prevented abscission. With Impatiens, 18 to 35 kR significantly accelerated both the onset of abscission and possibly the initial abscission rate; 350 kR cut the time to 100% abscission in half and substantially accelerated the initial abscission rate. Inhibition of abscission in Impatiens was not possible with the available dose rate (35 kR/hour).The accelerating effect of ionizing radiation was apparently due to primarily a reduction in auxin activity, thus accelerating the shift from the relatively ethylene-insensitive stage I to the ethylene-sensitive stage II. In vitro irradiation of exogenous auxin in agar substantially reduced the abscission-delaying effects of the auxin. The low dosage accelerating effects of the ionizing radiation were negated by exogenous auxin application, either prior to or following irradiation. With prior auxin application, a higher concentration of auxin was required to achieve the same delaying effects as with application following irradiation. Apparently due to this reduction in auxin activity, irradiation hastened sensitivity to exogenous ethylene.The accelerating effects of ionizing radiation may be secondarily due to increased levels of endogenous ethylene. With bean tissues, exposures of 262 through 1500 kR of gamma radiation increased the measurable levels of endogenous ethylene released into the ambient air within 2 or 3 days after irradiation.The results of actinomycin D treatment suggested that required de novo RNA synthesis occurred about 4 hours earlier in those Impatiens explants that had received 105 kR gamma radiation than in the nonirradiated controls.An increased mobilization of Ca from the abscission zone may be a contributing factor in the radiation-induced acceleration of abscission. For both bean and Impatiens, exogenous Ca inhibited abscission of irradiated and nonirradiated explants. In addition, a more concentrated Ca solution was required to inhibit abscission of irradiated bean explants, as compared to the nonirradiated controls.

The effect of pollen irradiation on reproductive capacity, seedling growth, and variation of Betula nigra—II. Seedling growth and induced variation

Betula nigra seedlings were raised from controlled crosses made with pollen exposed to 0, 0·5, 1, 2, 4 and 8 kR of gamma radiation. Plants from the 8 kR treatment had poorer survival than those from all other treatments and were 11·5 per cent shorter than the controls. Their leaves also averaged 11·0 per cent smaller than those of the control plants but leaf length/width was unchanged. Dry weights of leaves, stems and roots after 8 kR were reduced to 79·7, 72·1 and 62·6 per cent, respectively, of those of the controls. Seedlings from this treatment also had the greatest shoot/root ratio. The 1 kR exposure appeared to have a stimulating effect on plant height, leaf size, and dry matter accumulation, but these increases were not statistically significant. Pollen irradiation had a pronounced effect on seedling variation. Plants with abnormal leaves occurred at a frequency of 11·5 per cent in the 8 kR population with asymmetry as the most common type of leaf abnormality. Seedlings with abnormal stems only were rare, whereas plants with various combinations of abnormal leaves and stems increased with the exposure level up to 24·7 per cent after 8 kR. In addition, this treatment level gave rise to 8·2 per cent dwarfs and to 7·7 per cent stunted plants. Thus, the 8 kR exposure resulted in 53·3 per cent aberrant plants, indicating that pollen irradiation should be an effective method of inducing and increasing variation in this species.

Influence of postirradiation washing on the growth and mineral content of Trigonella foenum-graecum L. seedlings

A dose of 30 kR gamma radiation to seeds decreased fenugreek bean seedling height, fresh weight, and dry weight, especially as the seedlings grew older. This radiation dose also increased the observed nitrogen content, possibly due to the reduction in dry weight. Changes in phosphorous uptake were insignificant. A 15 kR dose decreased seedling heights and dry weights but not fresh weights. Intensive washing of nonirradiated seed for 24 hr under running water resulted in reduction of seedling heights, fresh weights and dry weight but not if irradiated. The 15 kR dose, with or without the washing treatment, caused insignificant changes in the nitrogen and phosphorus contents of seedlings. The washing treatment per se decreased seedling dry weight at all age levels, suggesting that some growth-promoting factor (or factors) was removed by the washing process.

The effects of acute gamma irradiation on the brine shrimp, Artemia. I. Life spans and male reproductive performance.

Life span of both sexes Freshly matured male and female specimens of Californian Artemia (stock #3) were irradiated with acute doses of 0, 0.1 , 1, 2, 5, 10, 50, or 100 kR gamma radiation and pair-mated to untreated animals. Significant reductions in life span resulted after 50 or 100 kR to either sex. Reductions in female life span approached significance after 10 kR. This moderate radiosensitivity can be explained if cell proliferation in some adult tissues improves the probability of individual survival. Male reproductive performance Treated males were completely sterile after doses of 50-100 kR. Males which received doses of 5 or 10 kR had an initial fertility period lasting 12 days, followed by permanent sterility. After a dose of 2 kR, 7 out of a sample of 8 males demonstrated the same initial period of fertility, followed by a period of sterility. Two of the 7 subsequently recovered their fertility. No sterile period occurred after 0.1 or 1 kR. These results are interpreted as indicating spermatogonial stem-cell replenishment of the testicular epithelium in some males after 2 kR and in all males irradiated with 1 kR. It is further hypothesized that all spermatocytes were in some way incapacitated or destroyed following doses above 2 kR. Hatchability data failed to detect induced dominant lethality in sperm (and perhaps spermatids) after 2 kR. Induced damage resulted in 73% dominant lethal events at 10 kR. No effect on other stages was observed at less than 2 kR. In the X1 generation, a dose of 10 kR reduced survival to adulthood, fertility, and adult life span. Similar, but less pronounced effects were obtained after 2 and 5 kR. These data indicate induced genetic damage. No significant alterations were observed in sex ratios. X1 sterility appeared to be greater than that observed for irradiated sperm. This point is being reinvestigated, and would be compatible with the reported holokinetic nature of the Artemia chromosome.

Components of the sterility induced in late-stage male pupae of the sugarcane gray borer, Eucosma schistaceana (Lepidoptera: Olethreutidae), with gamma radiation.

Various components of sterility induced in adult male Eucosma schistaccana Snellen with 25 and 35 kR gamma radiation from CO60 can be determined by analyzing the female moths to which they are mated. These analyses are based on the transfer of a spermatophore, the presence of sperm in the spermatheca, sperm motility, and the various stages in which lethals occur in fertilized eggs. Thirteen different responses have been differentiated when adult moths of both sexes were caged together for 2 days, followed by egg deposition of each female moth for 3 days before dissection. It was determined from this analysis of sterility that 10.2% is due to failure of the irradiated males to mate in the 35-kR treatment, 4.8% results from failure of males to transfer sperm, 14.9% is the result of sperm inactivation, 18.9% is from the effect of dominant lethal mutations that cause early embryonic death, and 46.7% of the sterility is from dominant lethal mutations expressed as late embryonic death. Similar results have been found to be true for males receiving 25 kR.