Correlations between chromosome segments and fitness in Drosophila melanogaster. IV. Fecundity, viability and the third chromosome

Unmarked segments within the third chromosome of three different Drosophila melanogaster lines were assessed for their effects on egg production and egg viability. By making a series of crosses among original and derived recombinant lines, it was possible to estimate parameters representing additive, dominance (for egg production), and interaction effects of the segments. Each segment influences both traits, but to extend which are dependent on the genetic background provided by an adjacent segment. There is no clear pattern, however, with respect to the segments' joint effects on the two characters. Unlike in the previous study involving the X chromosome, the majority of the derived recombinant lines were superior in fitness to their original lines. The agricultural implications of this result with respect to the manipulation of chromosomal segments in order to achieve higher yields are discussed.     

Correlations between Chromosome Segments and Fitness in DROSOPHILA MELANOGASTER. II. the X Chromosome and Egg Viability

Unmarked segments within the X chromosomes of four different Drosophila melanogaster isogenic lines were assessed with respect to egg-to-adult viability. The results were compared with those of an earlier study involving egg production. All segments influence both traits, but to extents that are dependent upon the strains being compared. Segmental effects are also a function of the genetical background, which, in this case, constitutes material within the same chromosome. With respect to both traits, the segments are not necessarily parallel in their effects. A segment that increases fecundity, for example, may or may not augment viability. The possibility of manipulating chromosomal segments to improve "yield" in organisms is explored.     

Influence of larvae and workers on egg production of queens of the pharaoh's ant,Monomorium pharaonis (L.)

Summary Social regulation of egg production and weight in queens was studied in relation to presence and absence of larvae and workers in the pharaoh's ant,Monomorium pharaonis (L.).Results were obtained by counting eggs and weighing queens under various conditions.The results confirm the existence of a positive feed-back loop between mated queens and their larvae as evident from a correlation (Y = 4.575 * X + 6.452) between the number of large worker larvae (X) and the egg yield (Y). This correlation seems to relate to the queens preferential feeding on larval secretions. Queens without larvae maintained a low level of egg production of about 6 eggs/day. Queens deprived of larvae as well as workers stopped producing eggs within 24 hours.Repletes, special workers, with greatly distended gasters functioned as a buffer retarding decline of egg production by feeding the queens during short periods without larvae.     

A Female Sterile Screen of the Drosophila Melanogaster X Chromosome Using Hybrid Dysgenesis: Identification and Characterization of Egg Morphology Mutants

We have conducted a hybrid dysgenic screen of the X chromosome for mutations affecting female fertility, with particular attention to those causing abnormal egg and eggshell morphology. In a screen of 4017 dysgenic strains, 398 mutants derived from 168 different germ lines were isolated and assigned to eight classes according to their diverse phenotypes. One interesting class consists of mutants that block oogenesis at specific stages. Our analysis has focused on mutations affecting eggshell formation, including mutants that lay morphologically abnormal sterile eggs as well as those that lay no eggs but exhibit blocks in the late stages of oogenesis. A subset of 48 mutants was assorted into 30 allelic groups by inter se complementation and genetically localized by interval mapping. Two multiallele complementation groups, de1 (7 alleles) and ne1 (8 alleles), were identified as well as five two-allele complementation groups. A search for alleles among mutants generated in other female sterile screens was unsuccessful, pointing to the distinctive nature of the dysgenic mutant collection. The single case of allelism determined in this study was one with a lethal allele of the Broad-Complex, l(1)npr, suggesting a possible involvement of ecdysone in choriogenesis. A subset of 18 dysgenic strains was analyzed for P element hybridization and 16 of these were found to have hybridization signals in the appropriate cytogenetic interval. By examining these signals in two or more alleles of the same complementation group, we have been able to tentatively localize two mutations. Light and electron microscopy of the eggshell in 43 different strains has revealed a variety of effects. The respiratory appendages were defective in 27 of these mutants. Effects on the ultrastructure of the main body of the endochorion were not strongly correlated with the appendage defects, and could be classified as minor (14 mutants) or major (16 mutants). Although 13 mutants showed no ultrastructural chorion defects, six of these had defective respiratory appendages.     

Correlations between chromosome segments and fitness in Drosophila melanogaster III. Differential genetic responses to zinc sulfate and selenocystine.

Genetic X environmental interactions are examined at an intrachromosomal level in Drosophila melanogaster. With respect to two fitness components, egg production and egg-to-adult viability, evidence is provided that different segments of the X chromosome are affected differently by each of the chemical substances, zinc sulfate and selenocystine. The extent of a segment's effect on a trait is not always parallelled by the extent of its association with that trait's sensitivity to chemical treatment. Both attributes are functions of the genetical background. The degree of dominance of each segment is not always greater in the chemical environments, a finding inconsistent with Parson's concept of "extreme-environment heterosis".     

Analysis of genetic control of mating behavior in screwworm (Diptera: Calliphoridae) males through diallel crosses and artificial selection

Summary The mode of genetic control of male screw-worm (Diptera: Calliphoridae) mating behavior was examined using diallel cross and artificial selection. Diallel crosses showed strong dominance effects, with hybrids being uniformly more successful in copulation than their more inbred parental strains. Weaker additive and reciprocal effects were also noted. Environmental (replicate) effects were highly significant. Regression of array variances and covariances indicated that epistatic interactions or unequal allele distribution during gametogenesis may have occurred and that high courtship propensity polygenes show dominance over low propensity genes. Artificial selection on males from outbred strains from Guatemala and Belize resulted in a decreased number of mating attempts for lines selected for reduced activity, but mating attempts in lines selected for high mating activity did not increase. A combination of inbreeding during the selection cycles as well as selection for recessive traits would explain this response. The two types of experiments were in general agreement, indicating significant dominance and environmental influence on male mating behavior with weaker additive and possible maternal effects.     

烤烟主要农艺性状的遗传与相关分析

利用包括基因型与环境互作的加性-显性遗传模型,对14个烤烟品种(系)及其配制的41个杂交组合在4个环境下的7个农艺性状表现进行遗传分析。结果表明,株高、节距、腰叶宽主要受加性效应控制,叶数、腰叶长受显性×环境互作效应影响最大,茎围以加性×环境互作效应、显性×环境互作效应为主,产量以加性效应、显性×环境互作效应为主。适应当地生态条件的品种（系）具有较高的正向加性效应。许多组合的显性主效应及在各试验点的显性×环境互作效应在方向上不尽一致,杂交组合的选配宜针对特定的生态环境进行。性状相关分析表明,大多数成对性状的各项相关系数为正值,且多以加性遗传相关为主,可利用株高对产量进行间接选择。
     

Schistosoma mansoni: mice infected with different worm strains.

Infections with five geographical strains and substrains of Schistosoma mansoni were compared in mice. Two substrains (Lc-1 and Lt-1) were derived from the parent (L-1) St. Lucian strain on the basis of differing infectivity for various snail strains. The Puerto Rican strains (PR-1 and PR-2) were obtained with an interval of 25 years. Consistent differences among the lines were found in egg distribution and numbers of eggs in tissues and feces. One Puerto Rican strain (PR-2) and one St. Lucian substrain (Lc-1) had longer prepatent periods than the other strains. Mice infected with the PR-1 strain consistently had the highest egg accumulation in the tissues per worm pair. Relatively few eggs were passed in the feces of the Lt-1 strain. By Week 9 of infection, eggs were noted in the spleens of mice carrying each of the strains and substrains.     

Quantitative trait loci segregating in crosses between New Hampshire and White Leghorn chicken lines: I. egg production traits

A genome scan was performed to detect chromosomal regions that affect egg production traits in reciprocal crosses between two genetically and phenotypically extreme chicken lines: the partially inbred line New Hampshire (NHI) and the inbred line White Leghorn (WL77). The NHI line had been selected for high growth and WL77 for low egg weight before inbreeding. The result showed a highly significant region on chromosome 4 with multiple QTL for egg production traits between 19.2 and 82.1 Mb. This QTL region explained 4.3 and 16.1% of the phenotypic variance for number of eggs and egg weight in the F₂ population, respectively. The egg weight QTL effects are dependent on the direction of the cross. In addition, genome‐wide suggestive QTL for egg weight were found on chromosomes 1, 5, and 9, and for number of eggs on chromosomes 5 and 7. A genome‐wide significant QTL affecting age at first egg was mapped on chromosome 1. The difference between the parental lines and the highly significant QTL effects on chromosome 4 will further support fine mapping and candidate gene identification for egg production traits in chicken.     

The inheritance of partial self-compatibility inBrassica oleracea L.: results from a half diallel homozygous for a highly recessive S-allele

Summary In a study of partial self-compatbility inBrassica oleracea, flower number, seeded siliqua and seed production were recorded on self- and cross-pollinated inflorescences of the progenies of a half diallel between five unrelated inbred plants homozygous for the same recessiveS-allele.On cross-pollinated inflorescences significant amounts of additively controlled genetic variation were found for seed set per flowering site and its two components, seeded siliquae per flower and seeds per seeded siliquae. Considerable heterosis and gene interaction were also present and a simple additive dominance model did not fully explain the observed variation.On self-pollinated inflorescences, additive gene action was absent for the seed production variates although differences between progenies were highly significant and heterosis was present. Complex gene interactions were considered to be responsible. The characteristics of the method of assessment used and the relationship between self- and outcross seed production are discussed. It appears unlikely that the component lines could be selected for reduced self seed set, but selection for higher outcross seed set may be possible.     

Epistasis in Measured Genotypes: Drosophila P-Element Insertions

Transposon tagging provides an opportunity to construct large numbers of strains of organisms that differ by single insertional mutations. By scoring the phenotypes of these ``measured genotypes,' powerful tests of effects of mutations on phenotypic expression have been performed. Here we extend this approach by constructing with simple crosses all possible two-locus genotypes for each of eight pairs of P-element insertions. Analysis of metabolic phenotypes (fat and glycogen contents, enzyme activities, total protein, and body weight) of the resulting nine genotypes provides direct estimates of additive, dominance, and epistatic effects of the mutations. Nested two-way analysis of variance identified significant epistatic effects in 27% of the tests (35/128 of the trait X P-element combinations). Posterior contrasts were performed to partition the epistatic variance into the four orthogonal components of COCKERHAM, and the data exhibit a tendency toward additive X dominance and dominance X dominance epistasis. Mutations in this study have epistatic effects on metabolic traits that are on the same order of magnitude as main (additive and dominance) effects. Measured genotypes have been used in other contexts to quantify epistatic effects on phenotypic expression, and these results are also briefly reviewed.     

云南香型软米水稻资源农艺性状遗传效应研究

选取5份云南地方香型软米水稻种质资源和6份自育香型软米保持系按5×6不完全双列杂交设计(NCⅡ)配制成30个组合,采用加性-显性-上位性遗传模型,分析云南香型软米11个农艺性状的遗传效应。结果表明,云南香型软米多数农艺性状的遗传主要受加×加上位性效应、加性×环境效应、显性×环境效应的影响,还存在不同程度的加性效应和显性效应,单株产量受基因加性效应、显性效应、加×加上位性效应、加性×环境效应、显性×环境效应的影响;株高、有效穗的遗传率以普通狭义遗传率为主,其他性状的普通狭义遗传率和互作狭义遗传率均达极显著水平;产量构成性状之间存在不同类型和不同程度的遗传相关,多数性状之间以加×加上位性、加性×环境和显性×环境互作效应显著。     

A study of association between genetic markers in candidate genes and reproductive traits in one generation of a commercial broiler breeder hen population

Markers of alleles for three physiological candidate genes for reproductive traits, growth hormone (GHR), gonadotropin-releasing hormone receptor (GNRHR) and neuropeptide Y (NPY) were assessed for the association with the total egg production, number of double-yolked eggs and age at first egg in a single generation of a broiler breeder (Gallus gallus) pedigree dam line. Single-nucleotide polymorphisms and deletions were detected in the GHR, GNRHR and NPY genes. Genotypes were identified using a PCR-RFLP assay. The frequency of restriction enzyme+/-alleles in the population was for GHR 0.68 (NspI-) and 0.32 (NspI+), for NPY 0.78 (DraI+) and 0.22 (DraI-) and for GNRHR 0.54 (Bpu1102I+) and 0.46 (Bpu1102I-). Trait data from a total of 772 hens in 67 sire families from one generation of the pedigree dam line were recorded. However, the analysis used only the offspring of heterozygous sires to reduce the influence of selection and genetic background (n=33 sire families for GHR; n=14 sire families for NPY; n=36 sire families for GNRHR). A dominance effect of NPY on age at first egg and an additive effect of GNRHR on the number of double-yolked eggs were found (P<0.05).     

Among-sibling differences in the phenotypes of juvenile fish depend on their location within the egg mass and maternal dominance rank

We investigated whether among-sibling differences in the phenotypes of juvenile fish were systematically related to the position in the egg mass where each individual developed during oogenesis. We sampled eggs from the front, middle and rear thirds of the egg mass in female brown trout of known dominance rank. In the resulting juveniles, we then measured traits that are related to individual fitness: body size, social status and standard metabolic rate (SMR). When controlling for differences among females in mean egg size, siblings from dominant mothers were initially larger (and had a lower mass-corrected SMR) if they developed from eggs at the rear of the egg mass. However, heterogeneity in the size of siblings from different positions in the egg mass diminished in lower-ranking females. Location of the egg within the egg mass also affected the social dominance of the resulting juvenile fish, although the direction of this effect varied with developmental age. This study provides the first evidence of a systematic basis for among-sibling differences in the phenotypes of offspring in a highly fecund organism.     

Penetration of mouse eggs at various intervals after insemination as influenced by concentration of sperm and strain of male

This study was conducted to determine the extent to which the percentage of mouse eggs that were penetrated by sperm at the end of the period of sperm penetration was due to the proportion of eggs penetrated per unit of time and to the span of time of sperm penetration. Female mice of ICR strain were inseminated 1.5 hr after ovulation with 5 X 10(6) sperm/50 microliter from males of DBA/2N, CF1 or C57BL/6N strains to determine the effect of the male. To determine the effect of concentration of sperm ICR females were inseminated with 2, 4, 6, or 8 X 10(6) sperm/50 microliter from CF1 males. Females were killed at various intervals after insemination and the eggs were recovered and examined for evidence of penetration by a sperm. The time intervals from both insemination to the onset of egg penetration and from insemination to cessation of penetration were similar for the three strains of males. Throughout the period of penetration of eggs a constant percentage of eggs was penetrated per hour for a particular strain of male. The relative percentage penetrated per hour very closely approximated the relative percentage of eggs finally penetrated for each strain of male. The percentage of eggs penetrated per hour was linearly positively related to the concentration of sperm inseminated. The final percentage of eggs penetrated depended primarily on the rate at which the eggs were penetrated during the period of sperm penetration and not on the length of the period of egg penetration which was constant.     

Egg production across a 40-week period in the phasmid Sipyloidea sp. (Diapheromeridae) from a tropical rain forest, north Queensland, Australia

Abstract  In this study we report the results from the first long-term (40 weeks) study of stick-insect fecundity and distribution under natural conditions of which we are aware. We used the number of eggs falling into 72 × 0.5 m² traps to ask: 'Was egg production in Sipyloidea sp. uniform across the sample period'? and 'Was there evidence of host plant species preference or avoidance'? We collected a total of 213 Sipyloidea sp. eggs. The number of eggs caught per week was not uniform and an exponential decay model was the best-fit relationship between egg production and time, indicative of a steep decline from high to low (but continuous) egg production across the study period. Continuous egg production differs from other insect species in tropical areas that often show distinct seasonal differences between wet and dry seasons, timed to leaf production in host plants. The distribution of eggs within traps was aggregated, and more traps than expected from Poisson probabilities received no eggs, or six or more eggs. The concentration of eggs within particular traps was not related to the identity of canopy plant species, however. We suggest that continuous egg production in Sipyloidea sp. may be related to the wider range of plant species available as food resources for the polyphagous Sipyloidea , compared with other tropical insect species.     

Effects of bottlenecks on quantitative genetic variation in the butterfly Bicyclus anynana

The effects of a single population bottleneck of differing severity on heritability and additive genetic variance was investigated experimentally using a butterfly. An outbred laboratory stock was used to found replicate lines with one pair, three pairs and 10 pairs of adults, as well as control lines with approximately 75 effective pairs. Heritability and additive genetic variance of eight wing pattern characters and wing size were estimated using parent-offspring covariances in the base population and in all daughter lines. Individual morphological characters and principal components of the nine characters showed a consistent pattern of treatment effects in which average heritability and additive genetic variance was lower in one pair and three pair lines than in 10 pair and control lines. Observed losses in heritability and additive genetic variance were significantly greater than predicted by the neutral additive model when calculated with coefficients of inbreeding estimated from demographic parameters alone. However, use of molecular markers revealed substantially more inbreeding, generated by increased variance in family size and background selection. Conservative interpretation of a statistical analysis incorporating this previously undetected inbreeding led to the conclusion that the response to inbreeding of the morphological traits studied showed no significant departure from the neutral additive model. This result is consistent with the evidence for minimal directional dominance for these traits. In contrast, egg hatching rate in the same experimental lines showed strong inbreeding depression, increased phenotypic variance and rapid response to selection, highly indicative of an increase in additive genetic variance due to dominance variance conversion.     

Intraspecific and interspecific larval interaction in Drosophila assessed by integrated fitness measure

Intraspecific density effect was investigated for D. simulans , D. suzukii , D. auraria , D. rufa and D. immigrans , and interspecific density effect was examined for combinations of D. simulans , D. rufa and D. immigrans . Different numbers of their eggs were introduced to artificial substrates, and intra- and interspecific interaction were evaluated on the basis of per capita egg production of individuals (eggs) introduced. If individuals died before pupation, their per capita egg production was zero; if individuals survived to pupae, their per capita egg production was estimated from their size based on the relation between the pupal size and lifetime egg production. Per capita egg production thus estimated generally decreased with the increase of the density of conspecific larvae, although a slight increase was detected at high densities in some cases. When two species were introduced, per capita egg production of a species was reduced only when the larval density of co-introduced species was very high, suggesting weak interspecific competition. Interspecific interaction was asymmetric; the effect of D. simulans on D. rufa and D. immigrans was often significantly negative, but the effect of D. rufa or D. immigrans on D. simulans was not significant.