Assignment of RFLP linkage groups to chromosomes using monosomic F1 analysis in hexaploid oat

The availability of molecular genetic maps in oat (Avena spp.) and improved identification of chromosomes by C-banding are two recent developments that have made locating linkage groups to chromosomes possible in cultivated hexaploid oat, 2n=6x=42. Monosomic series derived from Avena byzantina C. Koch cv Kanota and from Avena sativa L. cv Sun II were used as maternal plants in crosses with the parents, Kanota-1 and Ogle-C, of the oat RFLP mapping population. Monosomic F₁ plants were identified by root-tip cell chromosome counts. For marker analysis, DNAs of eight F₂ plants from a monosomic F₁ were combined to provide a larger source of DNA that mimicked that of the monosomic F₁ plant. Absence of maternal alleles in monosomic F₁s served to associate linkage groups with individual chromosomes. Twenty two linkage groups were associated with 16 chromosomes. In seven instances, linkage groups that were independent of each other in recombination analyses were associated with the same chromosome. Five linkage groups were shown to be associated with translocation differences among oat lines. Additionally, the results better-characterized the oat monosomic series through the detection of duplicates and translocation differences among the various monosomic lines. The F₁ monosomic series represents a powerful cytogenetic tool with the potential to greatly improve understanding of the oat genome. Received: 24 April 2000 / Accepted: 10 May 2000     

Genetic analysis of artificial pigmentation mutants in Porphyra yezoensis Ueda (Bangiales, Rhodophyta)

Porphyra yezoensis Ueda artificial pigmentation mutants, yel (green), fre (red‐orange) and bop (pink), obtained by treatment with /V‐methyl‐/V′‐nitro‐N‐nitrosoguanidine, were genetically analysed. The mutations associated with color phenotypes are recessive because all of the heterozygous conchocelis resembled the wild type color when they were crossed with the wild type (wt). In the reciprocal crosses of yel × wt, both parental colors and eight types of blades appeared in the F₁ gametophytic blades from the heterozygous conchocelis. Both colors segregated in the sectored F₁ blades in a 1:1 ratio, indicating that the color pheno‐type of yel resulted from a single mutation in the nuclear gene. In the reciprocal crosses of fre × wt, however, four colors and more than 40 types of blades appeared in the F₁ blades from the heterozygous conchocelis, indicating that the color phenotype of fre resulted from two mutations in different genes. In the reciprocal crosses of bop×wt, three colors and 12 types of blades were observed in the F₁ blades from the heterozygous conchocelis. Both parental colors appeared far more frequently than the third new color. These results indicated that the color phenotype of bop resulted from two closely linked mutations in different genes, and the epistasis occurred in the F₁ blades. The mutants, yel, fre and bop, differ from the spontaneous green (C‐O), the red (H‐25) and the violet (V‐O) mutants of P. yezoensis, respectively.     

Prospects for interspecific hybridization of Lupinus atlanticus Gladst. with L. cosentinii Guss.

Summary Successful crossing is reported between L. atlanticus Gladst. (2n = 38) and L. cosentinii Guss. (2n = 32), using lines of both species selected for crossability followed by selection of relatively fertile progenies. In one cross, 82E75, from a single F₂ segregating plant, 22 F₃ seeds were obtained. Some other less crossable combinations were completely sterile in the f₁ or F₂. Backcrossing to both parent species was successful, but some crosses gave relatively more seed by using F₂ plants for backcrossing rather than F₂'s. It is concluded that potential exists for introgression of useful genes in both directions.     

KARYOTYPE POLYMORPHISM IN DIFFERENT GEOGRAPHIC POPULATIONS OF GREEN PEACH APHID MYZUS PERSICAE (SULZER) IN CHINA*

Abstract This paper deals with the karyotype of green peach aphid, Myzus persicae (Sulzer), with three different life cycles in different regions of China. The results showed that four types of karyotype were found in the natural populations of red form and brown form aphids. Four types of karyotype are as follows: 2n = 12 with autosomes 1, 3 translocated (T_1–3); 3n = 18 normal triploid; 3n = 18 with T_1–3 translocation; and 2n = 11. However, in the yellowish‐green aphids there were only two types of karyotype, normal karyotype 2n= 12 (NK) and 2n = 12 with T_1–3 translocation. There was no significant difference in the relative lengths of chromosomes in 2n = 12 karyotype among different color forms and groups from different regions.     

Thinopyrum distichum addition lines: production,morphological and cytological characterisation of 11 disomic addition lines and stable addition-substitution line

Plants of the partial amphiploid Inia 66/Thinopyrum distichum (2n = 70)//Inia 66 (2n = 56) were used as male parents in crosses with the monosomic series in the common wheat cultivar Inia 66. The genome and homoeologous group of the monosomic used in the cross affected the distribution of chromosome number of the progeny plants in the F₂ and F₄. Meiosis in the pollen mother cells of the B₁F₇ partial amphiploids was not stable, and not different from that of the B₁F₁ in which univalents and multivalents were observed. Disomic addition lines were selected on the basis of morphology and meiotic stability in the F₂, F₄ and F₅. Eleven of the fourteen possible wheat-Th. distichum disomic addition lines were identified using chromosome C-band pattern, as well as size and arm ratio, as genetic markers. Addition of T. distichum chromosome J ^dll produced a phenotype indicating homoeology with wheat group-2 chromosomes. Clear indications of homoeology based on morphological characteristics were not obtained in any of the other addition lines, probably due to the mixed homoeology of the Th. distichum chromosomes relative to wheat. The addition lines were all susceptible to leaf rust, unlike the germplasm-line Indis which carries a leaf rust resistance gene on a translocation segment derived from Th. distichum. Instability of meiotic pairing was observed in all addition lines. The stability, or not, of progeny chromosome counts did not reflect the level of chromosome pairing instability in the parental plants. SDS-PAGE for gliadin-type seed proteins revealed two addition lines which expressed seed storage proteins uncommon to Inia 66 but typical of Th. distichum.     

The Effect of Lr19-Translocation on in Vitro Androgenesis and Inheritance of Leaf-Rust Resistance in DH3 Lines and F2 Hybrids of Common Wheat

Leaf-rust resistance and androgenesis were studied in the anther cultures of Triticum aestivum L., which included Saratovskaya 29 cultivar, the isogenic line Ps29, and three F₁ hybrids (L503/S55, L504/S58, ATS7/L1063) with 7DS-7DL-7Ae#1L translocation of Lr19 gene (Lr19 translocation) from Agropyron elongatum (Host.) P.B. The Lr19 translocation was shown to affect the induction of embryogenesis and green plant regeneration. The frequencies of Lr19 translocation differed in F₂ hybrids obtained by traditional hybridization and in sets of DH₃ lines obtained in F₁ anther cultures derived from the same combinations of T. aestivum parental forms. The number of leaf-rust resistant genotypes tended to decrease. The frequency of Lr19 translocation in the set of DH₃ lines derived from F₁ L504/S58 was significantly lower than in other sets of DH₃ lines and F₂ hybrid populations.     

Interspecific hybridization of perennial Medicago species using ovule-embryo culture

Summary New interspecific hybrids between alfalfa (Medicago sativa L.) and several perennial Medicago species were obtained by embryo rescue techniques. The methodology, designated ovule-embryo culture, involved preculturing the fertilized ovule (10 to 20 days post-pollination) for a period of six to 12 days followed by excision and direct culture of the embryo. Placement of the hybrid embryo directly onto culture medium without the interim ovule culture was unsuccessful. Ovule culture to germination without removing the embryo also was unsuccessful. Ovule-embryo culture was essential for recovering interspecific hybrids between diploid alfalfa (2n=2x=16) and the following diploid (2n=2x=16) species: M. hybrida Traut., M. marina L., M. papillosa Boiss., M. rhodopea Velen. and M. rupestris M.B. In addition, trispecies hybrids between M. sativa x M. dzhawakhetica Bordz. F₁ hybrids (2n=3x=24) and either M. cancellata M.B. (2n=6x=48) or M. saxatilis M.B. (2n=6x=48) were obtained from ovuleembryo culture. Media manipulations using M. sativa x M. rupestris F₁ and first backcross generation embryos demonstrated the optimum concentration of 12.5 mM NH₄ ⁺ for successful embryo rescue; ammonium salt formulation (whether chloride, nitrate or sulfate) was not critical. From a few thousand crosses, hybrids between M. sativa and either M. rhodopea or M. rupestris were recovered relatively efficiently with 157 and 66 hybrids, respectively. However, only 13 hybrids between M. sativa and M. papillosa were obtained from more than 2,000 crosses, and just two hybrids each have been recovered from the combinations M. sativa x M. hybrida and M. sativa x M. marina from 2,000 to 3,000 crosses. The predominant chromosome number between diploid alfalfa and the other diploid perennial species was 2n=2x=16. Morphology of the hybrids was generally intermediate. Electrophoretic analysis of the F₁ hybrids and parental clones on uniform or gradient polyacrylamide gels demonstrated that peroxidase phenotypes could be used to confirm hybridity. For all interspecific combinations there was at least one peroxidase isozyme unique to the wild species that was present in the F₁ interspecific hybrid.     

Gamete composition and chromosome variation in pollen-derived plants from octoploid triticale x common wheat hybrids

Summary Anther culture of secondary octoploid triticale (AABBDDRR) and F₁ hybrids (AABBDDR) of octoploid triticale x common wheat crosses was carried out, and 96 pollen-derived plants were developed and studied cytologically. In addition to the 8 types of pollen-derived plants with the theoretically predicted chromosome number, plants with the chromosome constitutions of 2n = 38, 43, 45, 47, 74, and mixoploids were obtained. The haploids and the diploids had different distributions. The frequencies of plants with one and two (pairs of) rye chromosomes were extremely high, and anther culture may be an expeditious route for creating alien addition lines of distant hybrid F₁s. Chromosome aberrations, including deletions, inversions, translocations, as well as isochromosomes and ring chromosomes, were observed in some plants. Abnormal meioses, such as chromosome non-disjunction, were also found. The reasons for the chromosome aberrations are discussed.     

Reproductive compatibility between populations of the citrus red mite,Panonychus citri (McGregor) (Acarina: Tetranychidae)

Reproductive compatibility was studied among populations of different types of the citrus red mite, Panonychus citri (McGregor ), i.e., the diapausing type from pear (DP), the non-diapausing type from citrus (C) and that from pear (NP). Copulation was also observed between mates of different types (DP and C). Only in crosses between C ♀ and DP ♂, was copulation occasionally broken off prematurely; duration of copulation varied considerably between pairs and the average duration was much shorter than that between DP ♀ and C ♂ and than that in crosses between mates of the same types. No F₁ adult females were produced at all from crosses between DP and C, showing that there was a complete reproductive isolation between the two types. There was a significant reciprocal difference in the egg hatchability and survival rate of immatures in the F₁ progeny; mortality in the eggs and that in the immature stage were significantly higher in crosses between DP ♀ and C ♂, as compared to those in the reciprocal cross. This suggested that fertilization may have occurred in the former cross, whereas it seemed that eggs were not fertilized in crosses between the C ♀ and DP ♂. The NP was compatible with the C, whereas it was completely incompatible with the DP. Thus, there was a complete reproductive incompatibility between the diapausing and non-diapausing type of P. citri.     

Chemical races in the red alga Laurencia nipponica (Rhodomelaceae, Ceramiales)

Genetic variation in the synthesis of halogenated secondary metabolites in the Japanese marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) has been investigated in laboratory crossing experiments and chemical analyses, F₁ tetrasporophytes and F₁ gametophytes resulting from crosses within chemical races produced major metabolites characteristic of these races. F₁ tetrasporophytes derived from reciprocal interracial crosses produced: (i) both parental types of secondary metabolites; (ii) either of the parental types; or (iii) a further major compound in addition to both parental types or in addition to either of the parental types. The latter cases suggest that hybrid-specific products were formed by the combined enzymatic complements of the parents, as F₁ gametophytes derived from these interracial F₁ tetrasporophytes yielded one or other of their parental products in an approximate 1:1 ratio. The population structure was analyzed at localities in Hokkaido, where two of the chemical races occur sympatrically. At Usujiri (Minami-kayabe), where the prepacifenol race and the laureatin race were sym-patric, hybrid gametophytes (recombination type) were found in high frequency in addition to hybrid tetra sporophytes, which strongly suggests that a new, pre-pacifenol/laureatm race is beginning to be produced by natural hybridization and recombination. By contrast, at Oshoro Bay, where the laurencin race and the epi-lauraliene race grew together, the interracial hybrids were rare: only a few tetrasporophytes (probably F₁ generation) were found, suggesting that racial integrity may be retained by habitat segregation and/or the absence of recombination-type gametophytes.     

The segregation pattern of a translocation quadrivalent

The segregation pattern of a translocation quadrivalent was studied in three hybrid families of the tetraploid (2n=28) oat, of the Avena strigosa polyploid complex. The rate of IV formation in F₁ was high and the fertility was normal. The adjacent-alternate orientation of this quadrivalent was very variable. Conspicuous variation in this frequency was found between anthers of the same floret and between florets. The alternate type was usually more common toward the end of MI. The adjacent-alternate ratio was found to be an unreliable measure for calculating the type of gametes produced by the F₁ and the F₂ plants derived from them. An attempt was made to determine the type of viable gametes produced on the F₁ and their frequency by examining the cytology of F₂ plants. The various combinations of the chromosomes of the translocation complex expected in the F₂ plants were derived and their expected frequencies calculated by taking into account chiasma formation at the chromosome ends and various restrictions of gamete viability. In none of the three hybrid families F₂ individuals were found to produce trivalents as the most complex chromosome configuration, indicating that one type of gamete derived from adjacent separation was not formed. The 11 ratio between F₂ plants having only bivalents (2II) and those with F ₁-like quadrivalent configuration R(c), expected when gametes resulting from alternate separation are fully functional, with the exclusion of other types, was not found. That ratio 2II/R(c), was 2-1/3 in the various families. The cytology of selected F₃ individuals basically followed the predictions based on chromosome association in the F₂.     

Maternal Inheritance of Chloroplast DNA in Interspecific Crosses of Bromus

Inheritance of chloroplast DNA (cpDNA) was examined in 41 F₁ progeny obtained from the following interspecific Bromus crosses: Bromus arvensis (2n = 14) × B. inermis (2n = 4x = 28); B. arvensis × B. inermis (2n = 8x = 56); B. arvensis × B. erectus (2n = 6x = 42); B. arvensis × B. erectus (2n = 8x = 56); B. arvensis × B. erectus (2n = 10x = 70). Chloroplast DNA of the parental species was digested with BamHI, EcoRI and HindIII and species-specific restriction fragment length polymorphisms were identified by observation of ethidium bromide stained agarose gels as well as by filter hybridization experiments involving heterologous cloned barley cpDNA probes. The stability of these point mutations was verified by examining the cpDNA restriction patterns of at least 28 individual plants raised from seed of each of the parental species. No intraspecific cpDNA variability was detected. All the F₁ progeny examined exhibited the cpDNA restriction fragment patterns of the female parent. There was no evidence of any paternal or biparental cpDNA inheritance. The results provided evidence for the uniparental-maternal inheritance of cpDNA in the Bromus crosses examined.     

New hybrids between Agropyron and wheat

Summary Intergeneric hybrids of Triticum aestivum (2n=42,AABBDD) with Agropyron ciliare (2n= 28,SSYY), A. trachycaulum (2n=28,SSHH), A. yezoense (2n=28,SSYY) and A. scirpeum (2n=28) are reported for the first time. F₁ hybrids of T. aestivum were also produced with A. intermedium (2n=42,E₁E₁E₂E₂Z₁Z₁) and A. junceum (2n=14,JuJu). All wheat-Agropyron hybrids were obtained by embryo rescue technique. Cultivars and reciprocal crosses differed for seed set, seed development and F₁ plant production. The F₁ hybrids were sterile. Attempts to obtain amphiploids were unsuccessful. However, backcross derivatives were obtained with wheat as the recurrent parent.The level of chromosome pairing in A. trachycaulum x wheat, A. yezoense x wheat and wheat x A. junceum hybrids provided no evidence of homologous or homoeologous pairing. Mean pairing frequencies in A. ciliare x wheat, wheat x A. scirpeum and wheat x A. intermedium hybrids indicated homoeologous or autosyndetic pairing. Ph gene was more effective in regulating homoeologous pairing in A. yezoense x wheat hybrids than in A. ciliare x wheat hybrid. Chromosome pairing data of BC₁ derivatives indicated that either some of the wheat chromosomes were eliminated or Agropyron chromosomes caused reduced pairing of wheat homologues.Contribution No. 82-653-J, Department of Plant Pathology, Kansas State Agricultural Experiment Station, Manhattan, Kan, USA     

Reproductive relationships between annual species ofCalendula (Compositae)

Breeding experiments were carried out inCalendula species. In the annuals, which are selfers, rarely some outcrossing was observed only in the most peripheral flowers. In experimental crosses fruit was produced in all combinations. Fertile F₁ and F₂ hybrids could be grown from crosses between parents with similar chromosome numbers:C. palaestina ×C. pachysperma and crosses of different morphological forms ofC. arvensis. In crosses of species with different chromosome numbers at least partly fertile F₁ hybrids were obtained fromC. tripterocarpa ×C. stellata andC. tripterocarpa ×C. arvensis and crosses of the latter withC. palaestina. Fertile F₂ plants were grown from the combination ofC. arvensis ×C. tripterocarpa. Considering this information and previously obtained data, a scheme is proposed for explaining speciation in the genusCalendula.     

Nature and type of gene action governing resistance to Helminthosporium turcicum leaf blight in maize (Zea mays L.)

Six generations, consisting of three resistant parents, three susceptible parents, their 15 possible F₁ crosses, 15 F₂'s, 15 BC₁'s (F₁ x resistant female parent) and 15 BC₂'s (F₁ x susceptible male parent) were analysed following Hayman (Heredity 12: 371–390, 1958) to evaluate the nature and type of gene action governing resistance to H. turcicum. The results showed that all types of gene effects, viz., additive, dominance and epistasis (i.e., additive x additive, additive x dominance and dominance x dominance) were operating in one cross or the other in controlling resistance. However, it was additive gene action and dominance x dominance type of epistasis with duplicate nature that were important in controlling resistance in most crosses. Depending upon the final objectives, one of the breeding methods, viz., recurrent selection, heterosis breeding, back-cross method or full-sib selection (bi-parental mating) may be followed.     

DIVERSITY OF HALOGENATED SECONDARY METABOLITES IN THE RED ALGA LAURENCIA NIPPONICA (RHODOMELACEAE,CERAMIALES)1,2

Many morphologically similar, but chemically distinct, populations have been found in the marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) growing in Japan. Each chemical type is characterized by a specific end-product of halogenated secondaly metabolite synthesis: chamigrane-type sesquiterpenoids such as prepacifenol and halochamigrene epoxide and C₁₅ bromoethers such as laurencin, laureatin, isoprelaurefucin, epilaurallene, and kumausallene. These seven types of secondary metabolite syntheses remained the same in the wild and under various culture conditions. Because bromoethers and terpenoids are probably synthesized by different metabolic pathways, it is virtually certain that different sets of enzymes participate in their synthesis. Prepacifenol- and laureatin-producing populations were selected as representatives of terpenoid and bromoether groups, respectively. F₁ tetrasporophytes derived from crosses between reciprocal, female and male gametophytes of prepacifenol- and laureatin-producing strains bore both types of metabolites, suggesting that the genes Producing these enzyme systems are encoded by nuclear genomes. The F₁ gametophytes resulting from the reciprocal crosses produced either prepacifenol or laureatin, and the four individuals derived from spore tetrads (a set of tetraspores derived from a single tetrasporangium) produced either prepacifenol or laureatin in a 1:1 ratio, indicating that genes participating in terpenoid synthsis and those participating in bromoether synthesis are on different loci of homologous chromosomes and are segregated at meiosis (tetrasporogenesis). One individual of this interpopulational F₁ gamtophyte produced both parental types of metabolite, perhaps indicating the occurrence of a recombination type. Natural hybrid individuals, including such recombination-type gametophytes, were found in a sympatric locality at which these two chemical types occur. F₁ tetrasporophytes derived from crosses between respective prepacifenol- and laureatin-producing strains and their F₁ gametohytes produced only parental-type metabolite-producing plants. These results indicate that the diverse chemical types can be referred to as races (chemical races).     

Chloroplast DNA inheritance in theStellaria longipes complex (Caryophyllaceae)

Inheritance of chloroplast DNA (cpDNA) was examined in F₁ progenies derived from three crosses and three corresponding reciprocal crosses betweenStellaria porsildii andS. longifolia. Chloroplast DNA restriction fragments were analyzed using methods of nonradioactive digoxigenin-11-dUTP labeling and chemiluminescent detection with Lumi-Phos 530. Distinct interspecific restriction fragment polymorphisms were identified and used to demonstrate the mode of cpDNA inheritance. Mode of cpDNA inheritance differed among crosses. Two crosses in whichS. porsildii, SP2920-21, was the maternal parent exhibited three different types of plastids, maternal, paternal and biparental, among the F₁ hybrids, suggesting a biparental cpDNA inheritance and plastid sorting-out inStellaria.     

High transmission of paternal plastid DNA in alfalfa plants demonstrated by restriction fragment polymorphic analysis

Summary A high frequency of paternal plastid transmission occurred in progeny from crosses among normal green alfalfa plants. Plastid transmission was analyzed by hybridization of radiolabeled alfalfa plastid DNA (cpDNA) probes to Southern blots of restriction digests of the progeny DNA. Each probe revealed a specific polymorphism differentiating the parental plastid genomes. Of 212 progeny, 34 were heteroplastidic, with their cpDNAs ranging from predominantly paternal to predominantly maternal. Regrowth of shoots from heteroplasmic plants following removal of top growth revealed the persistence of mixed plastids in a given plant. However, different shoots within a green heteroplasmic plant exhibited paternal, maternal, or mixed cpDNAs. Evidence of maternal nuclear genomic influence on the frequency of paternal plastid transmission was observed in some reciprocal crosses. A few tetraploid F₁ progeny were obtained from tetraploid (2n=4x=32) Medicago sativa ssp. sativa x diploid (2n=2x=16) M. sativa ssp. falcata crosses, and resulted from unreduced gametes. Here more than the maternal genome alone apparently functioned in controlling plastid transmission. Considering all crosses, only 5 of 212 progeny cpDNAs lacked evidence of a definitive paternal plastid fragment.Contribution No. 89-524-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan     

Genetic studies of self-fertility in rye (Secale cereale L.). 1. The identification of genotypes of self-fertile lines for the Sf alleles of self-incompatibility genes

Segregation for self-fertility has been studied in progenies from the crosses of self-sterile (SS) plants with interline hybrids obtained by a diallel scheme of pollinations between seven self-fertile (SF) lines (nos. 2–8) and with F₁ (SS plant x SF line) hybrids. All the offspring families from the SS plant x F₁ (SS plant x SF line) crosses demonstrated a 1SF1SS segregation. The crosses of SS plants with some interline hybrids gave only self-fertile plants, whereas the crosses with other interline hybrids gave a segregation of 3SF:1SS expected in the case of digenic segregation. The data obtained permitted us to identify three different S loci (S1, S2, S5) and to estimate the genotypes of self-fertile lines for their Sf alleles: lines 5, 6, 7 and 8 are S1f/S1f S2n/S2n S5m/S5m, line 4 is S1n/S1n S2f/S2f S5m/S5m, and lines 2 and 3 are S1n/S1n S2m/S2m S5f/S5f(Sn, Sm designate active alleles of the incompatibility genes). The identification of the particular S gene which is presented by the Sf allele in each line has been made on the basis of our data concerning the linkage of the Sf mutation with isozyme markers of particular rye chromosomes, which is reported in an accompanying paper.     

Elimination of Wolbachia from Urolepis rufipes (Hymenoptera: Pteromalidae) with Heat and Antibiotic Treatments: Implications for Host Reproduction

Molecular analyses using ftsZ and wsp primers identified infections of type-A Wolbachia bacteria in populations of Urolepis rufipes (Ashmead) (Hymenoptera: Pteromalidae), a potential biocontrol agent for pest flies (Diptera: Muscidae) in livestock confinements. Incidence of infections ranged from 10 to 45% for three field populations and 100% in a laboratory colony. Provision of adult wasps with sugar water containing 50 μg mL^–1 tetracycline hydrochloride, or continuous rearing at 34±0.5°C eliminated Wolbachia from experimental populations after four and six generations, respectively. Results were similar for experimental crosses between infected parents, between uninfected parents, and between infected female and uninfected male parents. Embryonic mortality was less than 5% for the F₁ generation, which had an adult sex ratio of 2♀:1♂. In contrast, experimental crosses between uninfected female and infected male parents were associated with an embryonic mortality of about 20% and produced 37% fewer F₁ adults. However, because of an F₁ sex ratio of almost 0♀:1♂,?this latter cross produced an overall higher number of F₁ males. These combined results reflect elements of both male development (MD) type cytoplasmic incompatibility (CI) and female mortality (FM) type CI Wolbachia. MD type CI Wolbachia in incompatible crosses causes haploidization of fertilized (i.e., female) eggs. The resultant haploid eggs develop into males so that more males are produced in incompatible versus compatible crosses. FM type CI produces fewer offspring and a male-biased F₁ generation caused by enhanced mortality of female embryos. We speculate that the fate of fertilized eggs - haploidization versus mortality - may reflect differences in bacterial densities.