Gender variation in Actinidia deliciosa,the kiwifruit

Summary Flower and fruit characters were measured in ten female, five male and five fruiting male selections of A. deliciosa var deliciosa (A. Chev) Liang and Ferguson. Flowers from female vines had functional pistils, which contained many ovules. Stamens appeared to be fully developed but produced only empty pollen grains. Flowers from male vines had functional stamens that produced high percentages of pollen grains with stainable cytoplasmic contents. Pistils did not contain ovules and were generally small with vestigial styles. Fruiting male vines had both staminate and bisexual flowers. Staminate flowers were similar to those found on strictly male vines. Bisexual flowers produced ovules and stainable pollen. Pistils were smaller than in pistillate flowers. Although the three flower sexes differed in style length, ovary dimensions and ovules per carpel, staminate and bisexual flowers were similar in number of flowers per inflorescence, stamen filament length, pollen stainability, inflorescence rachis length and carpel number, and differed from pistillate flowers in these characters. The three flower sexes had similar sepal and petal numbers. The fruit of fruiting males were considerably smaller than those of females. Low ovule number appears to be the major factor limiting fruit size in the fruiting males studied. Prospects for developing hermaphroditic kiwifruit cultivars through breeding are discussed.     

Sex expression in fruiting male vines of kiwifruit

Summary In three canes on each of five fruiting male kiwifruit vines (A. deliciosa var. deliciosa (A. Chev) Liang and Ferguson), staminate and bisexual flowers were interspersed, so that staminate, bisexual and mixed inflorescences were found. Further variation in inflorescence composition resulted from the abortion of flower buds prior to anthesis. These two sources of variation, in combination, resulted in 19 inflorescence patterns, which varied substantially in frequency among and within vines. Some tendencies were determined. In particular, most of the inflorescences had retained their terminal flower, whereas just over half had retained one or both primary lateral flowers, and in two-thirds of the inflorescences retaining a terminal flower, this was bisexual. The five vines ranged in bisexual flower frequency from 40% to 70%. Phenotypic Gender (P) estimates are given for each vine, based on the frequencies of staminate and bisexual flowers from three canes per vine. Flower development, lability in sex expression and the use of P estimates as part of a selection index in breeding for hermaphrodite kiwifruit cultivars are discussed.     

Males paving the road to polyandry? Parental compensation in a monogamous nesting cuckoo and a classical polyandrous relative

Comparative studies have established the necessity for biparental care as an important factor for monogamy in freshwater fish and birds. However, whether two parents are really needed for offspring care remains an open question in many cases. I experimentally studied female and male contributions to offspring care in the white-browed coucal (Centropus superciliosus), a monogamous and biparental cuckoo with a balanced adult sex ratio, and contrasted it with the sympatric black coucal (C. grillii), a classically polyandrous species with a male-biased adult sex ratio and male-only care. To study the necessity for biparental care, I temporarily removed one partner for 2 days to see whether the remaining parent compensated for the absence of its partner. Both female and male white-browed coucals approximately doubled their feeding rates when their partner was absent, thus fully compensating the number of feeding visits to the nest. However, nestlings maintained their growth only, when males were present and females were removed. When males were removed and only females were present, nestling growth declined. Hence, only male white-browed coucals fully compensated for the temporary loss of the partner, suggesting that females could benefit most from nesting with additional males—if these should become available. Removing female black coucals had no consequence for nestling feeding rates of male black coucals. But male black coucals had to be returned to their territories within a few hours to avoid harming the brood because female black coucals typically would not commence feeding their offspring. In conclusion, the breeding system of white-browed coucals seems quite flexible and the relatively balanced adult sex ratio may stabilize monogamy in this species. Should ecological factors ever favour a stronger bias in the adult sex ratio towards males, female white-browed coucals may easily become polyandrous and relinquish parental care entirely to males.     

Meiotic segregation of five different reciprocal translocations in the onion fly,Hylemya antiqua (Meigen)

For one translocation (T14) with short interstitial segments in Hylemya antiqua significant differences in segregation behaviour between males and females were observed. In males the ratio of alternate:adjacent 1:adjacent 2 was approximately 730 and in females about 813. This difference is attributed to the difference in type of chromosome association. Female meiosis is chiasmate and male meiosis is achiasmate. It is suggested that meiotic pairing in males results in relative short Coorientation Determing Distances (CDDs) between homologous centromeres which favours alternate and adjacent 1 segregation. In females because of non-localized chiasmata on the average no differences in CDD between homologous and nonhomologous centromeres are expected. This might explain the occurrence of coorientation between non-homologous centromeres resulting in adjacent 2 segregations. Four other translocations with longer interstitial segments than T14 showed in males as well as females predominantly an alternate and adjacent 1 segregation, adjacent 2 was hardly found (0–3.6%). The longer distance between non-homologous centromeres is probably the reason.     

Sex determination in Sarotherodon (tilapia)

Summary The simplest possible model of the sex determination process adding autosomal influence to a minimal number of sex chromosomes was developed to explain matings of Tilapia (Sarotherodon) species. Eighteen different genotypes, each having two autosomes (AA, Aa, or aa) and two sex chromosomes (WX, WY, WW, XY, XX or YY) involved in sex determination, are predicted by the theory. Their sex (10 males and 8 females) were determined using a series of directed graphs, showing the relative strength of the chromosome pairs, developed on the basis of Chen's sex ratio results (Chen 1969). This theoretical model predicts eight different sex ratios (01, 13, 35, 11, 97, 53, 31, 10 ); three of them are not predicted by the WXYZ theory. The greatest part of these sex ratios have been obtained experimentally in extensive series of crosses between related species of Tilapia and their hybrids, carried out by several authors. The theory succeeds in explaining all of Chen's results, including those ratios 53 and 01 seen in certain crosses but not predicted by the WXYZ theory. The importance of the autosomes is seen in comparisons of the genotype pairs (AaWY, aaWY), (AaXY, aaXY) and (AAWW, AaWW) in which the first genotype in each case is male while the second is female as proven by the sex ratio results. The members of the pair differ only in the substitution of one autosome for the other. To test the theory, experiments consisting of hormonal sex reversion and a series of crosses are proposed. Finally, theoretical and practical implications of the theory are discussed.     

Onion fly,Delia antiqua,oviposition and mating as influenced by insect age and dosage of male reproductive tract extract (Diptera: Anthomyiidae)

One hundred percent of virgin female onion flies,Delia antiqua, receiving 1/20 of a male equivalent of an aqueous extract of mature male reproductive tract remained unmated in the presence of males and began laying unfertilized eggs at a normally mated rate of about 20 eggs/female/day. The 50% behavioral response (BR₅₀) fell between 1/40 and 1/20 of a male equivalent. Sex peptide responses are not always all-or-none. Some females receiving extract at 1/40 male equivalent oviposited at an intermediate rate. Moreover, at low sex peptide dosages, some females were fully activated ovipositionally but were receiptive to mating. A low level of sex peptide was present in 1-day-old males. Sex peptide titer rose with age until plateauing by 6 days posteclosion. Males began mating at 3 days, when they first had ample mature sperm; 50% of 6-day-old males mated. The mean number of females inseminated per male exposed to an excess of virgin females over 24 h was 4.3±0.6 (±SE). Presence of mature eggs was not always a prerequisite for mating, although probability of insemination was correlated with egg maturation. One-day-old preovipositional females receiving 1/20 of a male equivalent of extract began ovipositing when they had mature eggs at 5–6 days old. Therefore, sex peptide may act early and permanently or have a long half-life and affect behaviors once females reach sexual maturity. Male flies provide females with an excess of sex peptide in many cases.D. antiqua males transferred ca. 5–10 times more sex peptide than necessary to activate females fully. We suggest this excess is related to the speed of female response. It is yet unclear whether sex peptide potency or titer in Diptera has become exaggerated by intra- or intersexual selection.     

Chromosome banding in amphibia

A cytogenetic study performed on a population of the South American leptodactylid frog Eleutherodactylus maussi revealed multiple sex chromosomes of the X₁X₁X₂X₂/X₁X₂Y (=XXAA/XXA^Y) type. The diploid chromosome number is 2n=36 in all females and 2n=35 in most males. The multiple sex chromosomes originated by a centric fusion between the original Y chromosome and a large autosome. In male meiosis the X₁X₂Y (=XXA^Y) multiple sex chromosomes form a classical trivalent configuration. E. maussi is the first species discovered in the class Amphibia that is distinguished by a system of multiple sex chromosomes. Only one single male was found in the population with 2n=36 chromosomes and lacking the Y-autosomal fusion. This karyotype (XYAA) is interpreted as the ancestral condition, preceding the occurrence of the Y-autosome fusion.by H.C. Macgregor     

Effect of the hereditary characteristics of male blue foxes <Emphasis Type="Italic">Alopex lagopus</Emphasis> L. on the sex ratio of their offspring

Family analysis of a commercial population of the blue fox (the Pushkinskoe Breeding Fur Farm, Moscow oblast) with respect to secondary sex ratio has been performed. The offspring of each individual male or female involved in crossing between 1984 and 1988 was analyzed. The study of all families formed by every male and every female has made it possible to determine a group of outstanding fathers (23 out of 287 males), whose offspring was predominantly male (62.1% of the offspring were males, versus 53.9% in the total population). The results of subsequent detailed study on the pedigrees of male blue foxes in whose offspring the sex ratio significantly deviates from 1 : 1 indicate that this character is transmitted from fathers to sons without the deterioration of other commercially valuable characters. It is presumed that the significant deviation of sex ratio from 1 : 1 in the offspring of some male blue foxes is determined by genetic factors.Translated from Genetika, Vol. 41, No. 3, 2005, pp. 422–426.Original Russian Text Copyright © 2005 by Beketov, Kashtanov.     

Irregular segregation at the Pr locus controlling plastid inheritance in Pelargonium: gametophytic lethal or incompatibility system?

Summary Two distinct segregation patterns are recognized after G X W plastid crosses in Pelargonium. Type I parents produce offspring in which maternal zygotes are frequent, biparental intermediate, and paternal zygotes rare (MZ>BPZ>PZ), as defined by the presence or absence of green or white plastids in the young embryos into which the zygotes develop. Type II parents produce offspring in which maternal and paternal zygotes are frequent with biparental zygotes the least frequent class (MZ>BPZPr ₁ Pr ₁. Type II plants, which do not breed true, are regarded as heterozygotes — Pr ₁ Pr ₂. The nuclear gene is symbolized as Pr as it is presumed to control alternative patterns of plastid segregation through an effect on plastid replication.Selfs and intercrosses of heterozygous plants segregate in an unexpected 1:1 ratio and not the expected 3:1 (1:2:1). The alternative homozygote — Pr ₂ Pr ₂ — could not be detected. Reciprocal crosses between heterozygotes (Pr ₁ Pr ₂) and homozygotes (Pr ₁ Pr ₁) give the expected 1:1 ratio when the Pr ₂ allele is derived from the male, whereas there is often, but not always, a highly significant deviation from 1:1 when the Pr ₂ allele is derived from the female.A simple explanation, which is not wholly satisfactory, is to assume that Pr ₂ is a gametophytic lethal on the female side. An alternative, or additional, explanation is that an incompatibility mechanism is involved in which Pr ₁ is a self-compatible allele, Pr ₂ a self-incompatible allele, and Pr ₁-Pr ₂ cross-compatible alleles. Successful fertilization is then determined by sporophytic control on the male side and gametophytic control on the female side.     

Sex ratio among human embryos and newborns in a Russian population

Summary A comparative study was performed on the sex ratio among embryos and newborns in a Russian population (Moscow).The secondary sex ratio was studied in 81 914 babies born in different regions of Moscow during the period 1962–1971. It was 105.8 boys to 100 girls. Neither maternal age nor month of birth was observed to have any effect on the secondary sex ratio.The sex chromatin was studied in 3000 embryos obtained from induced abortions. The ratio of male to female embryos was 103.4:100. It dose not differ from either Mendelian segregation (1:1) or the secondary sex ratio in a population studied. It was calculated that more precise determination of the sex ratio in the embryonal period would require the study of not less than 17 500 embryos.The confidence limits are presented for the significance of possible differences in the sex ratio in samples ranging from 100 to 500000 in size.

---

Zusammenfassung In einer russischen Bevölkerung (Moskau) wurde das Geschlechts-verhältnis unter Embryonen und Neugeborenen verglichen.Das sekundäre Geschlechtsverhältnis (bei Neugeborenen) wurde bei 81 914 in Moskau geborenen Babys für den Zeitraum 1962–1971 untersucht. Ergebnis: 105,8 : 100. Weder das Alter der Mutter noch die Jahreszeit beeinflußte diesen Wert.Bei 3000 Embryonen aus induzierten Aborten wurde das Sex-Chromatin bestimmt. Es ergab sich ein Verhältnis 103,4 : 100 . Es besteht weder ein Unterschied zu dem erwarteten 1:1-Verhältnis noch zu dem sekundären Geschlechtsverhältnis. Für eine genauere Bestimmung wäre eine Stichprobe an mindestens 17 500 Embryonen erforderlich.Es werden die Vertrauensgrenzen für eine mögliche Änderung des Geschlechtsverhältnisses bei Stichprobengrößen von 100 bis 500000 Beobachtungen angegeben.

     

Identification of a polytene chromosome band containing a male sex determiner of Chironomus thummi thummi

Hybrid males of Chironomus thummi piger x Ch. th. thummi crosses were backcrossed with females of both parental stocks. Fourth-instar larvae of these backcrosses showed sex specific differences in the pairing behavior of region D₃d-g in chromosome arm F of salivary gland chromosome III. — Analysis of the banding pattern of region D₃d-g after RB and quinacrine staining demonstrated that in piger x thummi hybrid males a single selectively stained band occurs within this region in the heterozygous condition at map position D₃e₁. This band could only be found in the thummi chromosome partner, it is heterochromatic and contains AT-rich DNA. In female hybrid larvae, however, such a selectively stained band is present in neither the thummi nor the piger chromosome region D₃d-g. From these results it is concluded that the selectively stained band D₃e₁ represents the male sex determiner of our Ch. th. thummi stock and that the male is the heterogametic sex.     

Genetics of the sex ratio anomaly in Drosophila hybrids of the Virilis group

Summary A study was made of the effect of genotype and temperature (25 and 17°C) on sex ratio in the hybrids D. virilis Sturt. X D. littoralis Sokolov. A genetic system has been found controlling sex-differential viability. In the F₁ of the reciprocal hybrids D. virilis X D. littoralis the sex ratio is normal, though at 17°C females are slightly excessive. The abnormal sex ratio is observed only in the progeny of test crosses.The major gene causing the death of female progeny of the cross [ (, D. virilis x , D. littoralis) x D. virilis] x D. littoralis is located on chromosome 2 of D. virilis. It is expressed as a lethal if chromosome 5 is heterogeneous virilis-littoralis. Chromosome 3 of D. virilis bears a modifier-enhancer and chromosome 5, a suppressor, of this lethal found in chromosome 2. This genetic system has a maternal effect and functions at 25°C, interacting with the X-chromosome of D. littoralis. If the maintainance temperature is lowered to 17°C, the progeny of the cross hybrid FB₁ x D. littoralis is predominantly female. Partial death of males is accounted for by a disturbance in the interaction between the genes of X-chromosome in certain combinations with the D. virilis autosomes and the Y-chromosome of the paternal species D. littoralis.Sex-differential mortality in the hybrids D. virilis x D. littoralis is one of the isolating factors between these species which does not appear to act until the second and subsequent F₁ generations due to the formation of the recombination load.     

Lethal genes on the sex chromosomes concealed in a population of the mosquito Aedes aegypti L.

A population has been examined in which an overall parity between the sexes hides considerable between-family variation in sex ratio. A proportion of families show highly distorted sex ratios, with either an excess of females or an excess of males. Distorted sex ratios are invariably associated with mortality in the immature stages at a level appropriate to the action of recessive lethal genes. It has been shown that 26% of M-bearing (Y) chromosomes and at least 24% of m-bearing (X) chromosomes carry a recessive lethal gene.Two such genes have been investigated. l kills males and, in a cross between two heterozygotes, gives rise to a sex ratio close to 2:1 (excess families). k kills females and, in a cross between two heterozygotes, gives rise to a sex ratio close to 1:2 (excess families). Selection for excess or excess did not increase the level of sex ratio distortion.No crossing over occurs between k and the M/m locus whereas l shows 5–10% recombination with M/m. A test for allelism confirmed that l and k are not allelic. The penetrance of k is complete whereas l shows somewhat less than full penetrance. The penetrance of l has been improved by selection.The high frequency of lethals remained in the population during the two year period of study. There was evidence for heterosis preserving this frequency, the heterozygotes living longer and producing more progeny. However lethals were no longer to be found after four further years of laboratory culture.     

The effect of size and sex ratio experiences on reproductive competition in Nicrophorus vespilloides burying beetles in the wild

Male parents face a choice: should they invest more in caring for offspring or in attempting to mate with other females? The most profitable course depends on the intensity of competition for mates, which is likely to vary with the population sex ratio. However, the balance of pay‐offs may vary among individual males depending on their competitive prowess or attractiveness. We tested the prediction that sex ratio and size of the resource holding male provide cues regarding the level of mating competition prior to breeding and therefore influence the duration of a male's biparental caring in association with a female. Male burying beetles, Nicrophorus vespilloides were reared, post‐eclosion, in groups that differed in sex ratio. Experimental males were subsequently translocated to the wild, provided with a breeding resource (carcass) and filmed. We found no evidence that sex ratio cues prior to breeding affected future parental care behaviour but males that experienced male‐biased sex ratios took longer to attract wild mating partners. Smaller males attracted a higher proportion of females than did larger males, securing significantly more monogamous breeding associations as a result. Smaller males thus avoided competitive male–male encounters more often than larger males. This has potential benefits for their female partners who avoid both intrasexual competition and direct costs of higher mating frequency associated with competing males.     

Identification of a RAPD marker linked to sex determination in Pistacia vera using bulked segregant analysis

The Random Amplified Polymorphic DNA (RAPD) technique was used to amplify DNA segments, with the objective of finding markers linked to sex determination in the dioecious species, Pistacia vera. Progenies from two female parents pollinated by a common male parent were studied. Two bulks of DNA were made in each cross, one from males and one from females, by pooling an equal weight of fresh leaves from each individual contributing to the bulk prior to DNA extraction. DNA was extracted from each bulked sample and from each of the contributing individuals. DNA was also extracted from 14 cultivars of P. vera and from 94 open-pollinated, fewweeks-old P. vera seedlings of unknown sex. Seven hundred different decamer oligonucleotide primers were used to perform DNA amplification, with 1 of these (OPO08) producing a 945 bp amplification band that was present only in the bulked female samples and absent in the bulked male samples of the two crosses. The relationship between band presence and female sex expression was conserved in every individual obtained from the two crosses and in the 14 cultivars unrelated to the crosses. We propose that this band is tightly linked to the gene(s) that control sex determination in pistachio. The OPO08₉₄₅ RAPD marker could be used in a breeding program to screen the gender of pistachio plants long before they reach reproductive maturity, resulting in considerable savings of time and economic resources. In order to verify that assumption we screened 94 additional seedlings with the OPO08 primer and obtained results consistent with a 11 male:female ratio.     

Detection of segregation distortions in an indica-japonica rice cross using a high-resolution molecular map

We have constructed a high-resolution rice genetic map containing 1383 DNA markers covering 1575 cM on the 12 linkage groups of rice using 186 F₂ progeny from a cross between a japonica variety, Nipponbare, and an indica variety, Kasalath. Using this high-resolution molecular linkage map, we detected segregation distortion in a single wide cross of rice. The frequencies of genotypes for 1181 markers with more than 176 genotype data were plotted along this map to detect segregation distortion. Several types of distorted segregation were observed on 6 of the chromosomes. We could detect 11 major segregation distortions at ten positions on chromosomes 1, 3, 6, 8, 9, and 10. The strongest segregation distortion was at 107.2 cM on chromosome 3 and may be the gametophyte gene 2 (ga-2). The Kasalath genotype at this position was transmitted to the progeny with about a 95% probability through the pollen gamete. At least 8 out of the 11 segregation distortions detected here are new. The use of the high-resolution molecular linkage map for improving our understanding of the genetic nature and cause of these segregation distortions is discussed.     

Between-family variation in sex ratio in the Trinidad (T-30) strain of Aedes aegypti (L.) indicating differences in sensitivity to the meiotic drive gene M D

Sex ratio in the Trinidad (T-30) strain of Aedes aegypti has remained constant at around 43% during seventeen years of laboratory culture. The divergence from 50% is due to meiotic drive by the M ^D gene on the Y chromosome. The driving Y chromosome gives a much more distorted sex ratio (mean = 5.7%) when coupled with the highly sensitive X chromosomes from strain 64. This was demonstrated in all of 98 families tested, indicating that all or most of the Y chromosomes in T-30 carry the M ^D gene. Consequently the low level of sex ratio distortion in T-30 must be due to resistance to M ^D.Crosses made within T-30 demonstrated wide differences in sex ratio between families, depending on the sensitivity of the male parent's X chromosome to M ^D. However, sex ratios were not continuously variable but fell within fairly discrete categories. Thus, X chromosomes could be classified according to the modal sex ratios associated with them: m ^s3 (12.5%), m ^s2 (32.5%), m ^s1 (40%), m ^r1 (47.5%) m ^r2 (57.5%).The different sex ratio categories were more discrete in the families of sib matings than from random matings, suggesting the possibility of background modification of what is essentially a balanced polymorphism. Evidence is presented suggesting that the polymorphism could be due to interaction at two loci. A further X variant, m ^s4 (<10%) characterised strain 64 but was absent from T-30.A comparison of fertility between the different sex ratio categories in T-30 established that sex ratio distortion was not caused by differential mortality after fertilisation.     

Localization of a male sex determining chromosome region in Chironomus thummi piger

Chironomus th. thummi x Ch. th. piger hybrid males were backcrossed with Ch. th. thummi females. The salivary gland chromosomes of both sexes of the backcross progeny were then studied in respect to their pairing behavior. Region D₃d-g of chromosome III showed sex specific pairing. It is concluded that within this D₃d-g region a male sex determiner of Ch. th. piger is located and that the male is the heterogametic sex.     

Sex specific chromosome polymorphisms in the common Indian Krait,Bungarus caeruleus Schneider (Ophidia,Elapidae)

Chromosome analyses of common Indian Krait, B. caeuleus from three geographical regions of India have revealed variable diploid numbers of 43, 44 and 45 in different female individuals but a constant diploid number of 44 in the males. C-banding and in situ hybridization studies, using radio labelled W sex chromosome specific satellite DNA as a probe, have shown that C-banding and sex chromosome associated satellite DNA's are exclusively localised in the W chromosome. The W chromosome is involved in reciprocal translocations either with a medium sized macroautosome or with a microchromosome resulting in a multiple sex chromosome constitution of Z₁Z₁Z₂Z₂/Z₁Z₂W type. In some female individuals dissociation of the W has resulted in multiple W chromosomes, W₁ and W₂. These polymorphisms are uniquely confined to the female sex only. A predominance of polymorphic females, involving particularly the translocation of a medium sized macrochromosome, in all three geeographical regions and the restriction of the females having the original chromosome constitution (ZW) to one geographical region suggests that polymorphic individuals have adaptive flexibility and higher fecundity.     

Quantitative analysis of estradiol-17β-induced changes in the ultrastructure of the liver of the male zebrafish,Brachydanio rerio

Summary Hepatocytes of male zebrafish, Brachydanio rerio, were studied by means of light- and electron-microscopy, following a period of maximally 16 days of in-vivo treatment with estradiol-17. The responsiveness of the male hepatocytes to this female sex steroid was investigated by use of morphometric methods. The results of this investigation show that the responsiveness was most obvious between 2 and 16 days, as revealed by an increase in cell size, accompanied by a proliferation of the granular endoplasmic reticulum and the Golgi complex. In addition, accumulations of glycogen granules, which are characteristic of hepatocytes in untreated males, had disappeared and lipid droplets had accumulated. These experimentally induced changes in the morphology of the male hepatocyte closely resemble those described for the female hepatocyte during the sexual cycle. It is concluded that the hepatocytes of male zebrafish can be stimulated by estradiol-17 to produce vitellogenin and that in female zebrafish this steroid is a key sex hormone responsible for vitellogenin production by the liver during the natural sexual cycle.