Significant Dominance Effects Research Articles

Inheritance of Resistance to Alternaria Leaf Blight in Muskmelons

Muskmelon (Cucumis melo L.) breeding line AC-82-37-2 was identified as having resistance to alternaria leaf blight caused by Alternaria cucumerina (Ell. and Ev.) Elliot. An analysis of this resistance with a three-factor scaling test indicated that both additive and dominance effects were highly significant. The x2 value indicated that there were epistatic effects as well. The six-factor scaling test revealed no significant dominance effect, but the additive and homozygote × heterozygote epistatic interaction effects were highly significant.

Motor activity and the mesotelencephalic dopamine function. II. Multivariate analysis of genetically segregating generations

Previous experiments on genetically different inbred strains of mice demonstrated parallel variations between the activity of regional brain tyrosine hydroxylase (TH) and locomotor behavior. Based on these associations, it was hypothesized that genetic variations in mesotelencephalic TH activity, an index of dopamine neurotransmitter function, would correlate positively with exploratory and locomotor behavior. In order to test this hypothesis, open-field motor behaviors and mesencephalic and striatal TH activities were analyzed by multivariate statistical methods in genetically segregating (C57BL/6ByJ X BALB/cJ)F2 and (C57BL/6ByJ X CXBI/ByJ)F2 generations. Factor analysis, based on correlation matrices of variables with significant genetic dominance or additive effects, demonstrated that locomotor activity and frequency of occurrence of various motor patterns were not correlated with mesencephalic and striatal TH activity. These results indicate that the assumption of a positive phenotypic correlation between spontaneous motor activity and mesotelencephalic TH activity does not hold in genetically segregating populations. Strategies and problems in revealing the behavioral consequences of genetically based variations in the mesotelencephalic DA system are briefly discussed.

Maternal effects and generation mean analysis of seed-oil content in cotton (Gossypium hirsutum L.)

The nature of gene action and of maternal influence governing cottonseed oil attributes were determined with four lines, two each with high and low seed-oil percentage. For this purpose, P1, P2, F0, F1, F2 and alternative sets of BC1 and BC2 generations were analysed in six cross-combinations and their reciprocals. Marginal extents of heterosis for seed-oil percentage were noticeable in F1, with inbreeding depression in F2. Data from reciprocal backcrosses provided evidence in favour of maternal rather than cytoplasmic effects of seed-oil development. Relatively higher extents of heterosis, sizeable inbreeding depression and reciprocally unequal F2 averages were characteristic of the seed index trait, which often showed a reversal of effects from F1 to F2. Reverse reciprocal backcrosses exhibited some differences, including greater resemblance between the types, (A/B)A and (B/A)A, in addition to variable dose effects in seed index. Thus, the differences between F1 seed index values were not due to cytoplasmic influence. Positive heterotic effects for seed-oil index, especially among the backcrosses, ranged between 16.08% and 47.29% over midparent averages. Genetic component estimates from analysis of similar sets of crosses differing only in reciprocal backcrosses, and also from sets of reciprocal crosses between any two parental combinations, were inconsistent. Scaling tests detected presence of epistasis within and between a majority of cross-combinations. Despite reciprocal differences, additive gene effects for seed-oil percentage were significant in 7 out of 24 crosses, representing high x low, low x high and low x low seed-oil parents. Those were, however, accompanied by significant dominance effects of higher order. In crosses involving low seed-oil percentage parents SA1060 and SA229, all six components were detected significant, with opposite effects of dominance and dominance x dominance epistatic components. Significant additive components were also detected for seed index and seed-oil index in 7 and 5 out of 24 crosses, respectively. In the inheritance of seed index and seed-oil index, dominance effects were more important. Epistatic components of additive x additive, and to a lesser extent, those of dominant x dominant were found significant.

Inheritance of Potassium Efficiency, Sodium Substitution Capacity, and Sodium Accumulation in Tomatoes Grown Under Low-potassium Stress

Abstract One hundred tomato (Lycopersicon esculentum Mill.) strains were grown under low-K stress (0.071 mm K) in the absence and presence of added Na to identify strain differences in efficient K use, efficient substitution of Na for K, and upper leaf Na accumulation. Five strains, selected as representing extreme differences for K efficiency and Na substitution capacity, were used as parents to create a series of F1, F2, and backcross generations to study the inheritance of K efficiency, Na substitution, and upper leaf Na accumulation of tomatoes grown under low-K stress. Reciprocal differences in the F1 generation were relatively unimportant in the inheritance of K efficiency, Na substitution capacity, and Na accumulation. K efficiency in the absence of Na was a trait of low heritability, with highly significant additive, dominance, and additive × additive epistatic effects. Na substitution capacity was highly heritable, with highly significant additive and dominance effects. Na accumulation also was highly heritable, with highly significant additive effects. Moderately high correlations were observed between Na accumulation and Na substitution capacity within genetically segregating generations.

Tests for mutagenic effects of ammoniated glycyrrhizin, butylated hydroxytoluene, and gum Arabic in rodent germ cells.

Ammoniated glycyrrhizin, butylated hydroxytoluene, and gum Arabic are "generally recognized as safe" (GRAS) substances that are used primarily as additives in foods. These substances were incorporated into rodent diets and fed to male rats and mice for 10 and 8 wk, respectively. The treated male mice and rats were then tested for dominant lethal effects. The mice were also tested for induced heritable translocation. Results of the rat studies indicated a statistically significant dominant lethal effect of each of the compounds tested; however, the biological significance of this response is not known. Results of the mouse dominant lethal and heritable translocation studies, on the other hand, indicated no adverse effects of the compounds tested.

Assessment of mutagenic damage following ethyl methanesulfonate mutagenesis in the axolotl (Ambystoma mexicanum).

When male axolots (Ambystoma mexicanus) were treated with 100 mg/liter of ethyl methanesulfonate (EMS), a dominant lethal effect was obtained. Embryonic survival of F1 progeny was most severely reduced between about 50 and 150 days after treatment. Dominant lethal lesions probably consist of chromosome breaks that lead to loss of parts of chromosomes or entire chromosomes. The appearance of embryos with a single nucleolus was used to assess this type of damage. The peak incidence of such embryos coincided with the peak of dominant lethality. At 25 mg/liter EMS, there was no significant dominant lethal effect, but as many as one-fourth of the embryos appeared morphologically abnormal during the period between 50 and 120 days after treatment. A small but significant number of embryos with a single nucleolus were also obtained. To assess possible recessive lethal damage, androgenetic haploids were produced from some of the mutagenized males. A broad trough of reduced haploid survival was obtained at 100 mg/liter, suggesting that damage is produced in most or all spermatogenic stages. At 10 mg/liter, where there was no dominant lethal effect or significant incidence of embryos with a single nucleolus, a broad period of reduced haploid survival was also obtained. Though we cannot exclude the possibility that chromosome abnormalities contribute to the reduced haploid survival, even at this low dose, the type of damage being assessed is almost certainly less severe than that leading to dominant lethality.

Human neurologic function and the aging process.

Sixty-one normal men whose ages ranged from 20 to 80 years were evaluated on two occasions by means of a comprehensive series of 128 instrumented tests of neurologic function. The tests measured cognition, vision, strength, steadiness, reactions, speed, coordination, fatigue, gait, station, sensations, and tasks of daily living. The reliability of each test measured was determined, and any measure found unreliable (r less than or equal to 0.41) was not further analyzed. Significant age-related linear decreases were found for almost all neurologic functions. The declines over the age span varied from less than 10 percent to more than 90 percent for different functions. For the upper extremities, the largest declines (greater than 50 percent) were in hand-force steadiness, speed of hand-arm movements, and vibration sense; for the lower extremities, the largest declines were in one-legged balance with eyes closed and in vibration sense. For 13 of 14 tests in which significant dominant body-side effects were found, larger re-testing 7-10 days later, the subjects improved their scores by more than 5 percent on only 17 tests, 9 of which concerned the activities of daily living. No significant differential learning effects were found across age groups. The results point to the importance of developing a data bank on age-based neurologic function so that therapeutic effects can be evaluated in terms of age- and sex-matched normal functioning.

Analysis of Generation Means for Yield in Six Crosses of Cucumber1

Abstract Six crosses were produced from 8 breeding lines and cultivars of cucumber (Cucumis sativus L.). Within each cross, 11 generations (P1, P2, F1, F2, F3, BC1 5 BC2, BC1×1, BC1×2, BC2×1, BC2×2) were studied. Data were collected on fruit weight/plot, fruit number/plot, average fruit weight and fruit bearing index at 2 locations. Preliminary analyses indicated the adequacy of an additive-dominance model for all characters in most crosses. The model was extended to include environment and genotype × environment interactions. The model was either significant or highly significant for all characters in all crosses. Dominance was a major contributing factor in the inheritance of all 4 characters. This was evidenced by significant dominance effects and substantial amounts of heterosis for all characters in most crosses. Such heterotic effects were large enough to justify the cost of hybrid seed production. Low incidences of dominance × environment interactions provided evidence for the stability of hybrids under different environments. Additive effects were significant for certain characters in some crosses. Significant additive effects suggested the effectiveness of selection for development of superior parental genotypes. Various degrees of additive × environment interactions were obtained. The interactions suggested that effective selection for yield should be carried out under more than one environment.

Inheritance of Some Agronomic Characters in a Cross of Safflower1

Parents, F1, F2, and backcross generations (BC1 and BC2) of a cross of safflower, Carthamus tinctorius L., were planted at two locations in Iran (Safiabad and Ahvaz). Data were collected on yield/plant, heads/plant, seeds/head, seed weight, flowering time, and height. Location effects were either significant or highly significant for all traits except for heads/plant. Generation differences were either significant or highly significant for all traits except for heads/plant and seeds/head. Location ✕ generation interaction was significant only for seed weight. Genetic analysis of the generation means were carried out at each of the two locations for those traits that showed significant differences among generaions. Dominance played a major role in the variation of yield/plant and seeds/head at Safiabad. For the remaining traits at either location, in addition to different degrees of additive and dominance effects, significant interallelic interactions were obtained. The full model analysis for seed weight showed, in addition to highly significant additive and dominance effects, a highly significant additive ✕ location interaction. Dominance ✕ location was not significant for seed weight

Agronomic Performance and Nature of Gene Effects in Progenitor Species‐Derived Genotypes of Tobacco1

An investigation was conducted to determine the nature of genetic effects in segregating populations produced by crossing selected progenitor species‐derived tobacco (Nicotiana tabacum L.) lines to the tobacco cultivar used in the original interspecific hybridization.Two genetically stable tobacco lines developed from interspecific crosses of N. tabacum ✕ N. sylvestris Speg. and Comes and N. tabacum ✕ N. otophora Griesbach, respectively, were crossed with the flue‐cured tobacco cultivar, ‘SC 58’, and F2 and backcross generations were produced. Data on agronomic characters and chemical constituents of cured leaf were collected and subjected to generation means analyses.The tobacco parent exhibited poorer performance than other generations for all agronomic characters, except grade index and chemical attributes of cured leaves. Conversely, species‐derived lines were frequently higher performing for yielding ability, days to flower, plant height, and number of leaves per plant, but cured leaf quality was inferior to other genetic entries. Significant positive heterosis for yield was found in three of the four families, and inbreeding depression was usually low.Additive genetic effects were significant for all characters in all families. Yield had significant dominance effects for every family while other chacacters varied from family to family. Frgm an evolutionary aspect of gene action, species germplasm tended to exhibit dominance in a positive direction for yield, days to flower, plant height, and number of leaves per plant, and in a negative direction for leaf quality. Deviations from the additive and dominance model were not observed.

A new approach to dominant lethal testing

Male weanling rats were given triethylenemelamine (TEM) at 0.025, 0.050, or 0.075 mg/kg and male adult rats were given TEM at 0.050 mg/kg, all by gavage 5 days/week for 10 weeks. At the end of the treatment period, the animals were immediately cohoused with two females each during Week 1 and with two other females during Week 2. The females were sacrificed 14 days from the midweek of cohousing, and the numbers of corpora lutea and live and dead implantations were counted. Statistical analyses of the number of dead implantations per pregnant female and of the number of females with one or more dead implantations or with two or more dead implantations indicated significant increases in all indexes for the adults and a more variable response on the part of the weanlings. The results from this study indicate that there is no loss of pertinent information by employing this approach except that of stage sensitivity. It reduces the amount of data usually required and assesses the more significant dominant lethal effect, that of postimplantation loss.

Breeding Potentials of Noncultivated Cottons. III. Inheritance of Date of First Flower1

Date of first flower was analyzed in parental, F1 F2, and backcross generations of two cultivars and three Texas race stocks of cotton (Gossypium hirsutum L.). The cultivar ‘Deltapine 16’ (DPL) differed from Texas 203 (T‐203) by an additive component and from Texas 40Y (T‐40Y) by an additive and an epistatic component. T‐203 and T‐40Y were similar phenotypically but showed slight genetic differences from one another in flowering response. Both differed from the third race stock, Texas 711 (T‐711), by at least two genetic factors. DPL‐16 differed from T‐711 by more factors for flowering response than T‐203 or T‐40Y. The other cultivar, ‘Stoneville 7A’ (St 7A), seemed closely related phenotypically to DPL‐16. However, the hybrid combination between the two revealed significant additive, dominance, and epistatic effects. St 7A differed genetically from T‐40Y but not from T‐203 for date of first flower. St 7A, like DPL‐16, was quite different from T‐711. Favorable F1‐midparent heterosis was exhibited by two of the 10 hybrid combinations, DPL‐16 ✕ T‐711 and St 7A ✕ T‐711.

Visual observing by rhesus monkeys: Some relationships with social dominance rank

Five rhesus monkeys were tested in a visual exploration situation to determine whether the mean frequency or mean duration of visual observing were systematically related to the dominance status of the observing animal. A dominance hierarchy among the five subjects was first determined by means of a competitive food-getting task. Following dominance testing, visual exploration testing was begun. All subjects were permitted to observe all other subjects in a round-robin pairing system involving two animals at a time. In each pairing, one animal served as the experimental subject (observer); the other as the stimulus (visual incentive). A highly significant linear effect of dominance was found in regard to duration of observing. Subjects high in the dominance hierarchy observed for significantly shorter durations than low-dominant subjects. Significant effects of dominance on the frequency of observing were also found, with animals intermediate in the hierarchy viewing more frequently than animals at either extreme. The data were interpreted in terms of the arousal and reduction of fear as a function of dominance and also through the notion of dominance distance.

Analysis of the dominance effect of a spontaneous recessive lethal in the mouse on homozygous and heterozygous genetic background

A spontaneous lethal (l15) without detectable dominant phenotypical effect has been studied in F4 offspring on a homozygous (CBA/CBA) or a heterozygous (CBA/AJax) genetic background. No significant dominance effect resulting in increased intra-uterine death or decreased mating ability was found irrespective of the genetic background.

Analysis of the dominance effect of a spontaneous recessive lethal in the mouse on homozygous and heterozygous genetic background

A spontaneous lethal ( l 15) without detectable dominant phenotypical effect has been studied in F 4 offspring on a homozygous (CBA/CBA) or a heterozygous (CBA/A Jax) genetic background. No significant dominance effect resulting in increased intra-uterine death or decreased mating ability was found irrespective of the genetic background.

Brain weight changes resulting from enriched rearing conditions: a diallel analysis.

AbstractHousemice from 6 inbred lines and their F1 crosses were reared in standard or enriched laboratory cages. A genetic analysis of brain and body weights indicated a significant directional dominance effect toward larger brain in F1 crosses among enriched animals only, even when adjustments for body weight were made. The proportion of additive genetic variance was greater in standard caged animals than in enriched animals. Maternal effects played a small but significant role in influencing brain weights apart from those indirectly caused by body weight effects. The use of laboratory reared animals for genetic studies is questioned when environmental influences are known to have a strong effect on the character being studied, and the results are to be used to make inferences concerning the adaptive significance of the character.

A study of the genetic basis of the sexual dimorphism for wing length in Drosophila melanogaster.

The genetic basis of a sexually dimorphic quantitative character in Drosophila melanogaster was investigated by means of two-way directional selection for increased and decreased differences between male and female wing length. The sex dimorphism (SD), defined as the mean wing length difference between the sexes, within families, provided the criterion for selection.-The two lines (High SD, Low SD) diverged rapidly during the 15 generations of selection, indicating the presence of extensive genetic variability for the genotype-sex interaction underlying the observed sexual dimorphism. There was evidence that genetic variability persisted in both lines when selection was relaxed. Most of the divergence between the two lines remained after 10 generations of relaxed selection.-The change in the level of sex dimorphism in the High line was due primarily to a decrease in male wing length; in the Low line most of the change in SD was the result of a decrease in female wing length. An overall reduction in wing length in both sexes in both lines is interpreted as an effect of inbreeding.-The distribution and nature of the genetic control underlying the SD characteristic of the two selection lines was investigated by chromosome substitution between selection lines using a marked inversion technique. The two lines differed by factors located on each of the three major chromosome pairs. Chromosome III had the greatest effect on the difference in SD level between lines, and showed an overall additive effect when present in homozygous versus heterozygous combination. Chromosome II had the least effect, with a significant dominance effect of the High II being evident when heterozygotes were compared with homozygotes. The effect of the X chromosome was intermediate. There was some evidence of interaction between non-homologous chromosomes.

Genetic analysis of salinity tolerance in rice

The genetics of salinity tolerance in rice was studied by visual scoring in parents F1 F2 and backcross generations of six crosses. Segregation analysis indicated partial dominance for salinity tolerance. Estimation of genetic parameters under epistatic model indicated the importance of additive effects in the inheritance of salinity tolerance. Highly significant additive type of gene action in Pokkali/BR29 and both additive and dominance type of gene action in Nonabokra/BR29 without interaction were observed suggesting absence of epistasis and validity of additive dominance model. Significant dominance effect of genes in Nonabokra/BR29 suggests the use of hybrid rice where production of hybrid rice seed is feasible. The non-interactions with duplicate type of epistasis were observed in the crosses with moderately tolerant and susceptible parents. As heritability of the trait was low to moderate, the breeding population must he large and selection for tolerance must be exercised in later generations under controlled conditions. Key words: Genetic analysis, salinity, rice.doi: 10.3329/bjar.v33i4.2284 Bangladesh J. Agril. Res. 33(4) : 519-529, December 2008

A Study of Three Tests of Central Function with Normal Hearing Subjects

The purpose of the study was to investigate the cerebral dominance effect as reported by several investigators. A group of subjects with normal hearing were administered three tests purported to give some evidence of higher level auditory function. The tests were the Kimura digits, the Katz SSW and the Dirks filtered PB's tests. The results indicated a significant right ear dominance effect for the Kimura and Katz tests. No difference between ears was found for the Dirks test. The findings could suggest that demonstration of ear dominance is test dependent. However, additional research is needed to resolve the issue.