C1 Generation Research Articles

A novel suspended/supported photoreactor design for photocatalytic decomposition of acetic acid with simultaneous production of useful hydrocarbons

This study reports the generation of combustible C1–C4 hydrocarbons and hydrogen via photocatalytic decomposition of acetic acid in N2 atmosphere. A new photoreactor design based on a hybrid suspended/supported photocatalytic system was proposed. The TiO2 photocatalyst was immobilized on a glass fabric which was mounted in the photoreactor containing additionally TiO2 suspended in the reaction solution. The photodecomposition took place in both liquid and gaseous phases. The configuration allowed for the diffusion of CH3COOH molecules from the reaction solution to the upper part of the fabric where the photoreaction proceeded. Moreover, decomposition of acetic acid molecules which evaporated from the solution took place. An improvement of the effectiveness of methane generation for about 90% compared to the suspended system and for about 50% in comparison with the immobilized system alone was observed. The amounts of the gases evolved after 27 h of the process conducted in the novel photoreactor were equal to 1.95, 1.66, 0.304, 0.059, 0.0014 and 0.007 mmol (5.57, 4.74, 0.87, 0.17, 0.004 and 0.02 mmol/mol CH3COOH) for CH4, CO2, C2H6, C3H8, C4H10 and H2, respectively. The observed improvement of the process efficiency was attributed to: (i) simultaneous CH3COOH decomposition in liquid and gaseous phases and (ii) photoreduction of CO2 to CH4.

An experimental comparison of gas generation from three oil fractions: Implications for the chemical and stable carbon isotopic signatures of oil cracking gas

Although oil cracking has been documented as one of the important sources of gas in many overmature marine sedimentary basins, the chemical and carbon isotopic signatures of gases of this origin are still open to question. In this study a Cambrian crude oil from the central Tarim basin, along with its main separated fractions (saturates, aromatics and asphaltenes), were pyrolyzed in sealed gold tubes to investigate how generated gases vary in chemical and carbon isotopic composition and how this variation would influence the genetic interpretation of oil cracking gas. The results indicate that the gases from cracking of aromatics and asphaltenes are much drier and more enriched in 13C than the gases from the cracking of saturates and crude oil at the same level of thermal maturity. In the experimental run of 20°C/h, the dryness index of the gases (defined as the volume percentage of C1 in C1–5) from the cracking of saturates ranges from 26.2–90.6% with the methane carbon isotope change ranging from −54.8‰ to −35.5‰, whereas the dryness index is never lower than 60.6% for the gases from the cracking of aromatics with methane carbon isotope ranging from −39.9‰ to −32.2‰. Correspondingly, experimental data for the four samples plot in different areas in diagrams designed to distinguish oil cracking gas from kerogen cracking gas, such as ln(C2/C3) vs. δ13C2–δ13C3 and δ13C1 vs. δ13C2–δ13C3, indicating compositional variability of crude oil could assert an important influence in these diagrams. Therefore it is prudent to bring other geological constraints into consideration to avoid misinterpretation.The kinetic parameters for the bulk generation of C1–5 gas and the methane carbon isotope fractionation extrapolated to geological conditions of 2°C/Ma and an initial temperature of 50°C show that the temperatures of C1–5 gas generation from the aromatics and asphaltenes are lower than those from the saturates and crude oil due to their lower activation energies and frequency factors. Generation of C1–5 gases from the aromatics is modeled to be initiated about 122°C whereas the initiation temperature for the saturates sample is 176°C. Below 189°C (EasyRo=1.8%), the yields of C1–5 gases follow the order: aromatics>asphaltenes>crude oil>saturates. At similar thermal maturity levels, the methane carbon isotopic compositions are significantly different for the four samples, with an order of 13C enrichment: aromatics>asphaltenes>crude oil>saturates, however the difference in methane carbon isotopes becomes smaller with increasing temperature. This indicates that methane carbon isotopic values can be significantly different for gases cracked from oils that are compositionally diverse, especially in the early stage of methane generation.

Development of Autotetraploid Perennial Rye (Secale montanum Guss.) and Selection for Seed Set

Different concentrations of colchicine solution (0. 1% and 0.2%) and temperatures (24 and 27 o C) were applied to wild diploid rye and autotetraploid forms were produced. Five hundred seedlings were placed into Petri dis hes for each treatment (total 2000). Cytological research was ca rried out on root tips of plants in C 0 and C 1 generations. Live seedling rate and tetraploid plant rate were change d by 6.4 ‐ 37.4 % and 8.75 ‐ 37.04%, respectively based on treatments. Plants forming the C1 generation were determined as 68.12% tetraploid, 14.71% diploid, 16.89% aneuploid (13.35% hypoploid, 3.57% hyperploid) and 0.27% triploid. Chromosome numbers of aneuploid plants ranged between 2n=19 - 29 and it was determined that plants having a chromosome number of 2n=27 were the most common. Other aneuploid plants (2n=19 - 26) were rare. Prior to chromosome counting in the C 1 generation, the seed lots were divided into five seed size groups (9-11 g, 11-13 g, 13-19 g, 15-17g, 17-19 g). Chromosome numbers were determined by a modification of the conventional root tip squash technique. Chromosome numbers varied with seed size. The rate of tetraploids, diploids and aneuploi ds were varied between 17.86-87.25%, 2.04-42.86%, 10.71- 39.29 %, respectively. As the size of seed was increased, th e rate of diploid and aneuploids decreased. Seed se t rate, spike length and the number of spikelets in plants belonging to different generations (C1, C 2, C 3 and C 4) were investigated. Seed set rate was increased from 30.51% to 61.45% with the selection of plants passing over general average in respect to seed set in each generation, however, it was determined that spike length and number of spikelets decreased. The differences were generally highly significant.

Difference of Growth Traits, Essential Oil Content and Compositions Between Diploid and Iinduced Tetraploid Plants of Basil (Ocimum basilicum L.)

Artificial autotetraploids were done by colchicine treatments in the essential oil bearing basil. A significant increase in the essential oil content was found in C1 generation and tetraploid plants had the potential of productivity 69 %more essential oil than the diploid parents. Twenty- three compounds were identified in the essential oil of diploid basil and twenty-six components in the essential oil of tetraploid basil. The major components that were identified in the essential oil of diploid basil to be linalool (64.9 %), nerol (12.6 %), tau-cadinol (6.5 %), cis-α-bergamotene (5.8 %) and germacrene D (5.7 %). Major components were identified in the essential oil of tetraploid basil were linalool (73.8 %),tau-cadinol (11.2 %), γ-cadinene (5.9%), eugenol (5.6 %) and α-cadinene (4.4 %). Two major constituents of the essential oil such as linalool and 1,8-cineole was increased 13 %and 77 %respectively, in the tetraploids than the diploid plants. This study demonstrated in tetraploid basil revealed significant increases in dry and fresh weight, leaf wide and thickness, stem diameter and number of branches per plant increase in ploidy level causes significant decrease in leaf long, cluster number, seed germination percent and rate as compared with diploid parent.

Haploids and homozygous diploids, triploids and tetraploids in sugar beet

Attempts to induce haploid parthenogenesis in sugar beet by pollination with wild beet pollen and irradiated sugar beet pollen resulted in five haploid plants. Seven additional haploids were found among inbred lines, and still another in the C1 generation after colchicine treatment of an inbred line. The frequency of haploids in different kinds of sugar beet seed, also studied, was higher in offspring from diploids pollinated by tetraploids (about 0.2%) than in diploid crosses. The haploids and homozygous diploid and tetraploid lines synthesized from three of the haploids are briefly described. In a greenhouse experiment with diploids, triploids and tetraploids, which originated from one and the same haploid, the diploids and the euploid triploids did not differ in root weight, while euploid tetraploids weighed on an average 7 per cent less than the diploids. At both the triploid and tetraploid levels, aneuploidy had a much greater negative influence on root development than the physiological imbalance caused by the increase in genome number. Contrary to the root weight, the weight of the leaves increased with the increase in genome number, even when including the aneuploids. These results are discussed in relation to the influence of heterozygosity on the performance of autotetraploids and the present situation in polyploid breeding in sugar beet.

RETRACTED ARTICLE: Dwarf mutations in grass pea (Lathyrus sativus L.): origin, morphology, inheritance and linkage studies

Induction of mutation has been used to create additional genetic variability in grass pea (Lathyrus sativus L.). During the ongoing investigations on different induced-morphological mutants, the author detected three types of dwarf mutants in grass pea. One mutant, designated as dwf1 type was earlier identified in colchicine-induced C2 generation of grass pea variety BioR-231 while the other two, designated as dwf2 and dwf3 were isolated in 250 Gy and 300 Gy gamma ray irradiated M2 progeny of variety 'BioR-231' and 'Hooghly Local', respectively. As compared to their parental varieties (controls), all the three mutants manifested stunted, erect and determinate stem, early maturity and tolerance to pod shattering habit. The mutants differed from each other, as well as with controls, in number of primary branches, nature of stipules and internodes, length of peduncle, leaflet and seed coat colour, seed yield and seed neurotoxin content. The three dwarf mutants were monogenically recessive and bred true in successive generations. F2 segregation pattern obtained from the crosses involving the three mutants indicated that dwarf mutation in grass pea was controlled by two independent non-allelic genes, assigned as df1 (for dwf1 type), df2 (for dwf2 type) and df3 (for dwf3 type), with the df1 locus being multiple allelic. Primary trisomic analyses revealed the presence of df1/df2 locus on the extra chromosome of trisomic type I, whereas df3 was located on the extra chromosome of type III. Linkage studies involving five other phenotypic markers suggested linked association of df1/df2 locus with lfc (leaflet colour) and wgn (winged internode) and df3 locus with cbl (seed coat colour). Both the loci; however, assorted independently with flower colour and stipule character. The dwarf types can be utilized as valuable tools for further cytogenetic research and breeding of grass pea.

α-cleavage of the prion protein occurs in a late compartment of the secretory pathway and is independent of lipid rafts

Endoproteolysis of the cellular prion protein (PrPC) modulates both the normal function of the protein and the pathogenesis of the neurodegenerative prion diseases. PrPC undergoes α-cleavage to generate the N-terminally truncated fragment C1. Utilizing various constructs of PrPC expressed in human neuroblastoma cells we investigated the subcellular compartment where α-cleavage occurs. C1 was detected at the cell surface and the generation of C1 occurred in mutants of PrPC incapable of Cu2+-mediated endocytosis. A transmembrane-anchored form that is not lipid raft-localised, as well as a secreted construct lacking the glycosyl-phosphatidylinositol membrane anchor, were also subject to α-cleavage. However, when this transmembrane-anchored form was modified with an endoplasmic reticulum retention motif, C1 was not formed. Inhibition of protein export from the Golgi by temperature block increased the amount of C1. Our data thus demonstrate that the α-cleavage of PrPC occurs predominantly in a raft-independent manner in a late compartment of the secretory pathway.

Computer Aided Synthesis of Piecewise Rational Motions for Spherical 2R and 3R Robot Arms

This paper deals with the problem of synthesizing smooth piecewise rational spherical motions of an object that satisfies the kinematic constraints imposed by a spherical robot arm with revolute joints. This paper brings together the kinematics of spherical robot arms and recently developed freeform rational motions to study the problem of synthesizing constrained rational motions for Cartesian motion planning. The kinematic constraints under consideration are workspace related constraints that limit the orientation of the end link of robot arms. This paper extends our previous work on synthesis of rational motions under the kinematic constraints of planar robot arms. Using quaternion kinematics of spherical arms, it is shown that the problem of synthesizing the Cartesian rational motion of a 2R arm can be reduced to that of circular interpolation in two separate planes. Furthermore, the problem of synthesizing the Cartesian rational motion of a spherical 3R arm can be reduced to that of constrained spline interpolation in two separate planes. We present algorithms for the generation of C1 and C2 continuous rational motion of spherical 2R and 3R robot arms.

Parvocellular and Magnocellular Contributions to the Initial Generators of the Visual Evoked Potential: High-Density Electrical Mapping of the “C1” Component

The C1 component of the VEP is considered to index initial afference of retinotopic regions of human visual cortex (V1 and V2). C1 onsets over central parieto-occipital scalp between 45 and 60 ms, peaks between 70 and 100 ms, and then resolves into the following P1 component. By exploiting isoluminant and low-contrast luminance stimuli, we assessed the relative contributions of the Magnocellular (M) and Parvocellular (P) pathways to generation of C1. C1 was maximal at 88 ms in a 100% luminance contrast condition (which stimulates both P and M pathways) and at 115 ms in an isoluminant chromatic condition (which isolates contributions of the P pathway). However, in a 4% luminance contrast condition (which isolates the M pathway), where the stimuli were still clearly perceived, C1 was completely absent. Absence of C1 in this low contrast condition is unlikely to be attributable to lack of stimulus energy since a robust P1-N1 complex was evoked. These data therefore imply that C1 may be primarily parvocellular in origin. The data do not, however, rule out some contribution from the M system at higher contrast levels. Nonetheless, that the amplitude of C1 to P-isolating isoluminant chromatic stimuli is equivalent to that evoked by 100% contrast stimuli suggests that even at high contrast levels, the P system is the largest contributor. These data are related to intracranial recordings in macaque monkeys that have also suggested that the initial current sink in layer IV may not propagate effectively to the scalp surface when M-biased stimuli are used. We also discuss how this finding has implications for a long tradition of attention research that has used C1 as a metric of initial V1 afference in humans. C1 has been repeatedly interrogated for potential selective attentional modulations, particularly in spatial attentional designs, under the premise that modulation of this component, or lack thereof, would be evidence for or against selection at the initial inputs to visual cortex. Given the findings here, we would urge that in interpreting C1 effects, a consideration of the dominant cellular contributions will be necessary. For example, it is plausible that spatial attention mechanisms could operate primarily through the M system and that as such C1 may not always represent an adequate dependent measure in such studies.

Efeito da Seleção Recorrente na População UNB-2U de Milho Pipoca por Marcadores RAPD

The aim of this research was to study the effects of recurrent selection on the genetic variability of UNB-2U popcorn population after three cycles of recurrent selection (mass selection, full-sib selection and S1 families) based on RAPD markers in 30 progenies from each selection cycle. There was no significant variation between the C0 and C2 cycles based on RAPD, showing that the use of different recurrent selection strategies in the cycles did not decrease genetic variability, due to the size of the population selected in the different cycles. The significant difference observed between mean values of C1 and C2 cycles was attributed to the smaller population size in C1 generation. Individuals were distributed into three large clusters and 20% of the individuals were placed in a group different from their original cycle. This can be explained by alleles’ transference from one generation to another and by the relationship between cycles

Seed set and some cytological characters in different generations of autotetraploid perennial rye (Secale montanum Guss)

Artificial autotetraploids of diploid perennial rye (Secale montanum Guss) plants were obtained by colchicine treatment. C1 C2 and C3 generations of autotetraploid perennial rye were compared for seed set and cytological characteristics such as irregularities in metaphase I (univalents) and anaphase I and II (lagging chromosomes and/or chromatids and bridge formation) and micronuclei in tetrads. In the three generations (C1 C2 and C3) the percentage of cells with univalents was 18.51, 14.56 and 9.38% respectively. The percentage of cells with irregular anaphase I with univalents was 23.43, 15.93 and 7.85%, and for anaphase II cells it was 20.93, 16.47 and 7.16. The percentage of tetrads with micronuclei was 18.17, 14.07 and 6.17% and seed set was 27.72, 43.51 and 59.59% respectively. A negative correlation was found between seed set and the cytological characteristics investigated. The correlations among the characters investigated during meiosis division were statistically significant. Selection of vigorous plants of autotetraploid perennial rye increased seed setting by increasing the cytological balance. However, abnormalities in the early stage of meiosis division were reflected in the later stages of meiosis.

The effects of sodium azide and colchicine treatments on morphological and yield traits of sesame seed (Sesame indicum L.)

Seeds of Sesame (Sesame indicum L.) were exposed to varying concentrations of sodium azide and colchicine solutions ranging from 0 - 0.250% (w/v). Variations in the percentage germination and survival, number of days to maturity, plant heights, total leaf area/plant, chlorophyll content, pollen sterility, dry matter and fruit size were recorded in the C1 and C2 generations. The frequency of mutation/injury increased with increasing concentrations of the mutagens. The LC50 values based on survival percentages in the M1 generation were fixed at 0.0776 and 0.0473% for sodium azide and colchicine respectively. There were dose related effects of the mutagenic treatments on quantitative traits resulting in reductions in traits such as germination and survival percentages, plant height, number of fruit/plant, but increases in leaf area, maturity time and fruit size. Colchicine treatment produced shortened internodes, deformed leaves, and chlorophyll mutants. Low doses of both mutagens (<0.125%) produced early maturing variants and robust/high yields and can be imposed to obtain beneficial mutants in sesame. Key words: Sodium azide, Colchicine, Sesame, Seeds, Mutagenic effects

The effects of sodium azide and colchicine treatments on morphological and yield traits of sesame seed (Sesame indicum L.)

Seeds of Sesame (Sesame indicum L.) were exposed to varying concentrations of sodium azide and colchicine solutions ranging from 0 - 0.250% (w/v). Variations in the percentage germination and survival, number of days to maturity, plant heights, total leaf area/plant, chlorophyll content, pollen sterility, dry matter and fruit size were recorded in the C1 and C2 generations. The frequency of mutation/injury increased with increasing concentrations of the mutagens. The LC50 values based on survival percentages in the M1 generation were fixed at 0.0776 and 0.0473% for sodium azide and colchicine respectively. There were dose related effects of the mutagenic treatments on quantitative traits resulting in reductions in traits such as germination and survival percentages, plant height, number of fruit/plant, but increases in leaf area, maturity time and fruit size. Colchicine treatment produced shortened internodes, deformed leaves, and chlorophyll mutants. Low doses of both mutagens (<0.125%) produced early maturing variants and robust/high yields and can be imposed to obtain beneficial mutants in sesame.

Asynaptic Variations in Induced Autotetraploid of Soybean

While working on colchiploidy in Glycine max, asynaptic variations was observed in the C2 generation. The cytology and meiotic behaviour of this asynaptic tetraploid was studied. High and variable number of univalents were observed in this plant at diakinesis and metaphase I stage. In some of the PMCs 80 univalents could also be observed at diakinesis stage. The main and distinctive characteristic of the variant was the inability of the univalent chromosomes to congregate at the equatorial plate, so that typical figures of metaphase I were never observed. The stages were hardly distinguishable and these were only identified on the basis of increase in chromosome number due to sister chromatid separation at anaphase II. Because of this abnormal meiotic behaviour aberrated tetrads were formed that gave rise to sterile pollen grains and pods were not formed. Some extrinsic or intrinsic agent might have acted on some genes responsible for synapsis and chiasma formation and resulted in complete disruption of chiasma assembly. Synaptic aberrations are potentially important source of information on the chiasma maintenance mechanism especially in a case when the system under study is an induced autotetraploid.

Oil cracking to gases: Kinetic modeling and geological significance

A Triassic oil sample from LN14 of Tarim Basin was pyrolyzed using the sealed gold tubes at 200―620℃ under a constant pressure of 50 MPa. The gaseous and residual soluble hydrocarbons were analyzed. The results show that the cracking of oil to gas can be divided into two distinct stages: the primary generation of total C1―5 gases from liquid oil characterized by the dominance of C2―5 hydrocar- bons and the secondary or further cracking of C2―5 gases to methane and carbon-rich matters leading to the progressive dryness of gases. Based on the ex- perimental data, the kinetic parameters were deter- mined for the primary generation and secondary cracking of oil cracking gases and extrapolated to geological conditions to predict the thermal stability and cracking extent of crude oil. Finally, an evolution model for the thermal destruction of crude oil was proposed and its implications to the migration and accumulation of oil cracking gases were discussed.

Polyploidy in Gymnosperms: Revisited

AbstractThere are only a few natural polyploids in gymnosperms. These have been reported in Ephera spp. (Gnetales), and Juniperus chinensis ‘Pfitzeriana’ (2n = 4x = 44), Fitzroya cupressoides (2n = 4x = 44), and the only hexaploid conifer Sequoia sempervirens (2n = 6x = 66) (Coniferales). Sporadic polyploids and aneuploids occur at a very low frequency in nurseries in conifers, but most of them show growth abnormalities, remain dwarf, and may not reach maturity. One exception is an autotetraploid tree of Larix decidua (2n = 4x = 48) that has survived in a private estate in Denmark. Colchicine-induced polyploids (colchiploids) have been produced in a several genera of conifers, including, Pinus, Picea, and Larix. These colchiploids (Co) were hybridized to untreated diploids to produce C1 and C2 generations to investigate their chromosome behavior. The colchiploids showed a wide range of chromosome variability, ranging from diploids, triploids, and tetraploids, and many were mixoploids. The colchiploids also show growth retardation, remain dwarf, and their future potential applications in forestry remains uncertain. However, genetic variability in the colchiploids still offers prospects for isolating genetically stable new genotypes. Even though polyploidy is rare in extant conifers, is it possible that ancient polyploidy or paleopolyploidy, that is prevalent in angiosperms, has also played a role in the evolution of conifers. In this paper we shall review the current status of polyploidy in gymnosperms.

Cytology and Fertility of Advanced Populations of Elymus lanceolatus (Scribn. &amp; Smith) Gould × Elymus caninus (L.) L. Hybrids

Within the wheatgrasses and wildryes, amphiploids are frequently made as a means for introgressing desirable traits and restoring fertility in hybrids between diverse species. This study reports the cytology, fertility, and morphological characteristics of Elymus lanceolatus (Scribn. &amp; Smith) Gould, E. caninus (L.) L., their F1 hybrids, advanced generations (F7 and F8), and three generations of advanced amphiploid progenies (C1, C2, and C3). Meiotic chromosome associations of E. lanceolatus and E. caninus are typical of allotetraploids. Chromosome pairing in the F1 hybrids suggests a close relationship between the two parents. Bivalent associations most frequently observed in the F7 and F8 were 14 bivalents. After multiple generations of harvesting available seed each generation from 10 plants, an increase in meiotic regularity was observed in the advanced F generations. Aneuploidy in the amphiploids (C generation) was observed in the C2 and C3 generations with chromosome numbers ranging from 47 to 56. The C1 generation had significantly fewer univalents per cell than the C2 and C3 generations. Combined across chromosome numbers, there was a significant decrease in the number of bivalents from 22.48 to 21.36 to 20.27 in each succeeding C generation, respectively. After seven generations of seed increase, pollen stainability increased from less than 1% in the F1 hybrid to 87 and 85% in the F7 and F8 generations, respectively. Chromosome doubling significantly reduced pollen stainability in the C1, C2, and C3 generations as compared to the parents and advanced F generations. Cluster analysis was able to separate the parents and the different hybrid populations.

GSH Inhibits Trypsinization of the C-terminal Half of Human MRP1

MRP1 is a 190-kDa membrane glycoprotein that confers multidrug resistance to tumor cells. The accumulated evidence has proved that GSH interacts with MRP1 and stimulates drug transport. However, the mechanism of GSH-dependent drug transport by MRP1 remains unclear. In this study, we used limited tryptic digestion of MRP1 in isolated membrane vesicles, in the presence and absence of GSH, to investigate the influence of GSH on MRP1 conformation. We found that GSH inhibited the generation of an approximately 35-kDa C-terminal tryptic fragment (including a C-terminal His tag) termed C2 from MRP1. This effect of GSH was not because of direct inhibition of trypsin activity, and agosterol A enhanced the inhibitory effect of GSH. The main cleavage site in MRP1 for the generation of the C2 fragment by trypsin resided between TMD2 and NBD2 of MRP1. Limited tryptic digestion of membrane vesicles expressing various truncated and co-expressed MRP1 fragments in the presence and absence of GSH revealed that GSH inhibited the production of the C2 fragment only in the presence of the L(0) region of MRP1. Thus the L(0) region is required for the inhibition of trypsinization of the C-terminal half of MRP1 by GSH. These findings, together with previous reports, suggest that GSH induces a conformational change at a site within the MRP1 that is indispensable for the interaction of MRP1 with its substrates.

Genetic changes during mass selection for growth in Nile tilapia, Oreochromis niloticus (L.), assessed by microsatellites

Two control (C1 or first control generation, and C4 or fourth control generation) and three selected (S1 or first selected generation, S2 or second selected generation, S4 or fourth selected generation) stocks of Chitralada Nile tilapia were analysed for microsatellite variation to determine the effect of size-specific mass selection on genetic variability. Genetic variation based on five microsatellite loci (UNH123, UNH147, UNH172, UNH222 and UNH216) showed a slightly higher allelic diversity in the selected stocks (7.4–10 alleles) than in the control stocks (6.8–8.8 alleles). Apparent reductions in the mean number of alleles and He values were noted in successive generations of both control and selected lines. Significant deviations from Hardy–Weinberg equilibrium because of an excess of homozygotes indicated inbreeding in all control and selected stocks. Although estimated inbreeding levels were not significantly different among selected and control lines based on Welch's t-tests, the increase in the degree of inbreeding within the selected line was higher (107.9%) than the control line (64.2%) after four generations. The implications of these results on the management and conservation of genetic diversity in improved breeds are discussed, while the importance of monitoring and minimizing inbreeding are likewise emphasized.

Developing tetraploid perennial ryegrass (Lolium perenne L.) populations

In a breeding programme aimed at developing tetraploids from Australian adapted germplasm, a root‐tip squash technique was initially used for ploidy determination. The highest recovery of tetraploids (39.7%) was obtained by treatment of 1‐week‐old seedlings with 0.1% colchicine concentration. Significant cultivar × colchicine concentration interaction was observed in seedling survival, highlighting the difference in response of the cultivars to colchicine treatment. Subsequently, flow cytometric estimation of the nuclear DNA content in young leaf tissues was used to screen the C1 and C2 generations. The speed and the efficiency of this method make it possible to examine a large number of plants. In the C1 population the percentage of tetraploids, diploids, and aneuploids was 25, 72.7, and 2.3% respectively, while in the C2 generation the percentage of tetraploids, diploids, and aneuploids was 43, 2, and 55% respectively.