Mating Combinations Research Articles

Two different and sublethal isolates of Nosema lymantriae (Microsporidia) reduce the reproductive success of their host, Lymantria dispar

We examined the effects of two microsporidian isolates of Nosema lymantriae (Germany isolate; Schweinfurt isolate) on the reproductive success of Lymantria dispar L. All possible mating combinations were tested. Both isolates affected the fecundity of infected females and the hatch of neonates. The infection of female L. dispar with either isolate resulted in a higher proportion of non-viable eggs; the survival of neonates during egg stage was not affected. When L. dispar larvae were infected with N. lymantriae [Germany] the number of eggs per egg mass decreased between 24 and 61%. When both adults were infected, the hatch rate decreased to 26%. While the infection of the male or the female host with the Germany isolate affected the number of eggs per egg mass and the hatch of progeny, we did not find a significant effect when male hosts were infected with the Schweinfurt isolate; only infection of the female L. dispar resulted in a reduction of the number of eggs per egg mass between 26 and 37%.

ORIGINAL ARTICLE: Supporting the Hypothesis of Pregnancy As a Tumor: Survivin Is Upregulated in Normal Pregnant Mice and Participates in Human Trophoblast Proliferation

Problem Survivin, a tumor‐promoting antiapoptotic molecule, is expressed in the human placenta. Here, we analyzed its expression during normal and pathological murine pregnancy and investigated its participation in human first trimester trophoblast cell survival and proliferation.Method of study We first analyzed the expression of survivin on the mRNA and protein level at the fetal–maternal interface of normal pregnant (CBA/J × BALB/c) and abortion‐prone (CBA/J × DBA/2J) mice at different pregnancy stages by RT‐PCR and immunohistochemistry. We also evaluated apoptosis in murine trophoblasts in both mating combinations by TUNEL technique. Functional studies were carried out by knockdown survivin by means of siRNA methodology in two human first trimester trophoblast cell lines [Swan.71 (Sw.71) and HTR8 (H8)].Results We observed a peak in mRNA levels on day 5 and a peak of protein levels on day 8 of pregnancy in both combinations. The level of survivin in animals from the abortion‐prone group was decreased compared with normal pregnant mice on day 8, which was accompanied by elevated apoptosis rates. In later pregnancy stages (days 10 and 14), survivin levels decreased to levels comparable to those observed right after fecundation in both groups. Transfection of human first trimester cell lines (H8 and Sw.71) with siRNA targeting the survivin gene led to a 76–82% reduction of its expression leading to reduced trophoblast cell viability and proliferation.Conclusion Our findings suggest an important role of survivin to promote trophoblast cell survival and proliferation during placentation, thus maintaining pregnancy. The pregnancy‐associated expression of a cancer molecule such as survivin supports the ‘pseudo‐malignancy’ hypothesis of pregnancy. Our data may contribute to the better understanding of trophoblast cell development during implantation and placentation.

Effect of mating combination and environmental factors on hatchability of chicken eggs in Tibet

To improve the hatchability of introduced high-yield chickens in Tibet, and ameliorate the egg yield and reproduction traits of the local Tibetan chickens, four mating combinations between the Recessive White and Tibetan chicken were employed to investigate the effect of the mating combination and environmental factors on hatchability in this study. The results showed that the fertility of the eggs with Tibetan chicken as female parent was significantly lower than that with Recessive White as female parent (P < 0.05), while hatchability was the reverse (P < 0.05). The embryonic mortality of Recessive White was significantly higher by 7.95% than the Tibetan chickens, particularly during the last stage of incubation. The hatchability of combination III, whose female parent was Tibetan chicken, was higher by 20.44% than combination II, whose female parent was Recessive White. This provided a theoretical basis for a cross using the Tibetan chicken as female parent. Binary logistic regression analysis results also showed that the mating combination and environmental temperature were of importance to egg hatchability.

Mate compatibility, parental allocation and fitness consequences of mate choice in the sand goby Pomatoschistus minutus

Recent theory and empirical work suggests that there may be variation among females in mate preferences that is adaptive. One of the possible mechanisms maintaining variability in preferences and preferred traits is that the benefits of mate choice may depend on compatibility with potential mating partners. We examined fitness consequences of mate choice in a species of fish, the sand goby, Pomatoschistus minutus with a special focus on mate compatibility. Females were given the opportunity to establish their mate preferences in a dichotomous mate choice experiment. This information was then applied by mating the focal or control female with either the preferred or the non-preferred male. The parental performance of the males of these four mating combinations was then measured. In a separate experiment, we assessed the female differential allocation by determining the residual gonad weight of spawned females as a measure of the proportion of eggs spawned. We also estimated the amount of filial cannibalism separately for both sexes. Our results show that preferred males provided benefits in the form of an increased number of hatching eggs. This benefit was the same when the male was mated with a focal or a control female. Hence, we found no support for benefits that depend on mate compatibility. Neither did we find support for the hypothesis that females would lay a different number of eggs depending on the male status. The results also indicate that male filial cannibalism has a strong role in determining hatching success in this species.

The effect of ionizing irradiation of post-larvae on subsequent survival and reproductive performance in the Kuruma shrimp, Penaeus ( Marsupenaeus) japonicus (Bate)

Considerable genetic advances in the Kuruma shrimp, Penaeus ( Marsupenaeus) japonicus, have been achieved in the last decade, creating the demand for a technique to provide genetic copyright and prevent escapees from farm ponds genetically contributing to natural fishery populations. The induction of sexual sterility is one technique that may provide such protection. This study evaluated the potential of sterilizing reproductive age (10 month old) P. japonicus by ionizing irradiation (IR) treatment at an early life-history stage. To achieve this, a lethal dose curve was established for post-larval stage 15 (PL15) shrimp by treating with different doses of IR. From this curve, six irradiation levels — all below the 100% mortality treatment — were trialed, ranging from 0 to 30 Gray (Gy). Another group of PL15 P. japonicus were subsequently exposed to the six IR treatments and then reared until sexual maturity, at which time their survival and reproductive performance were assessed. At 8 months of age, females and males from each of the 0, 10, 15 and 20 Gy treatment groups were reciprocally crossed to give 16 mating combinations, whilst females and males from each of the 25 and 30 Gy treatment groups were directly crossed with 0 Gy shrimp of the opposite gender to give four direct mating crosses. At 10 months of age, all females had their reproductive performance assessed in a standardized 30 day trial. The percentage of females maturing and spawning in the 0 Gy treatment group (80.97 ± 5.5% and 69.9 ± 5.77%) were significantly higher ( P < 0.05) than for IR treated females in the 10, 15 and 20 Gy treatment groups (63.93 ± 5.34%, 61.68 ± 5.77% and 43.66 ± 6.03% for percentage maturations and 51.44 ± 5.5%, 49.69 ± 6.04% and 38.94 ± 6.31% for percentage spawnings). Similarly, the number of maturations and spawnings per female in the 0 Gy treatment group (1.50 ± 0.13 and 1.24 ± 0.12) were significantly higher ( P < 0.05) than for IR treated females in the 10, 15, and 20 Gy treatment groups (1.13 ± 0.12, 1.04 ± 0.13 and 0.76 ± 0.14 for the number of maturations and 0.88 ± 0.12, 0.84 ± 0.13 and 0.67 ± 0.13 for the number of spawnings). The effects of IR on protozoeal metamorphosis varied. No differences in fecundity, hatch rates, gonadal somatic indices or gonadal histology were found between control and irradiated shrimp. These results indicate that IR of PL15 P. japonicus had some effect on ovarian maturation and spawning, however IR was not able to confer sterility in shrimp. Treatment of PL15s with IR that does not result in death (i.e. between 10 and 30 Gy) is therefore not effective at preventing the production of some viable offspring.

POPULATION DIFFERENTIATION AND GENETIC VARIATION IN HOST CHOICE AMONG PEA APHIDS FROM EIGHT HOST PLANT GENERA

Habitat choice plays a critical role in the processes of host range evolution, specialization, and ecological speciation. Pea aphid, Acyrthosiphon pisum, populations from alfalfa and red clover in eastern North America are known to be genetically differentiated and show genetic preferences for the appropriate host plant. This species feeds on many more hosts, and here we report a study of the genetic variation in host plant preference within and between pea aphid populations collected from eight genera of host plants in southeastern England. Most host-associated populations show a strong, genetically based preference for the host plant from which they were collected. Only in one case (populations from Vicia and Trifolium) was there little difference in the plant preference spectrum between populations. All populations showed a significant secondary preference for the plant on which all the aphid lines were reared: broad bean, Vicia faba, previously suggested to be a "universal host" for pea aphids. Of the total genetic variance in host preference within our sample, 61% could be attributed to preference for the collection host plant and a further 9% to systematic differences in secondary preferences with the residual representing within-population genetic variation between clones. We discuss how a combination of host plant preference and mating on the host plant may promote local adaptation and possibly ecological speciation, and whether a widely accepted host could oppose speciation by mediating gene flow between different populations.

Antibody Response of Chickens to Sheep Red Blood Cells: Crosses Among Divergently Selected Lines and Relaxed Sublines

Crosses were made among lines of chickens that had undergone 30 generations of selection for high or low antibody response 5 d after an intravenous injection with SRBC, and between sublines in which selection was relaxed in generation 24. Antibody responses at 5, 10, and 14 d after injection were measured in the 4 lines and in reciprocal crosses among them. Divergence between the high and low lines selected for SRBC antibody was immediate and increased during selection. Although significant in both cases, separation of the relaxed subline from its respective selected line was greater in the high than the low line. Five-day SRBC titers of the relaxed lines and the crosses were intermediate to the high and low selected lines, with the direction and magnitude of heterosis being line dependent. A high proportion of chickens from low line mating combinations did not have detectable antibody titers at 10 and 14 d postinoculation with SRBC, precluding statistical analysis of these data. Results are discussed in the context of intra- and interlocus effects on the selected trait.

Mating success of two geographically distinct populations of Gulf Coast ticks, Amblyomma maculatum Koch

Gulf Coast ticks collected from Refugio Co., TX and Osage Co., KS are reproductively compatible despite differences in genetic haplotypes, geographic separation and seasonal phenologies. Two heifers per mating combination (TX males × TX females, KS males × KS females, TX males × KS females, KS males × TX females) were each infested with 360 pairs of Gulf Coast ticks. Only mean pre-oviposition and mean egg conversion efficiency index for the Texas male–Kansas female mating were significantly different ( p < 0.05) from other mating treatments. These females began oviposition 1-day later and used 4% less body mass toward egg production when compared to site-specific matings. However, the overall trend in reproductive performance of reciprocal tick matings was slightly lower than that of site-specific matings. There appear to be no pre-zygotic barriers to mating among Gulf Coast ticks from these Texas and Kansas populations.

Failure of decidual arteriolar remodeling in the CBA/J × DBA/2 murine model of recurrent pregnancy loss is linked to increased expression of tissue inhibitor of metalloproteinase 2 (TIMP-2)

Uterine vascular remodeling at mid gestation includes the thinning of the vessel walls and, typically, an increase in lumen diameter. This study aimed to elucidate any differences in structural remodeling in normal murine pregnancies versus those differences that resulted from the crossing of CBA/J female mice by DBA/2 male mice, a combination that is known to exhibit recurrent resorption/pregnancy loss. CBA/J female mice that were pregnant by DBA/2 male mice (abnormals) and DBA/2 female mice that were pregnant by CBA/J male mice (normals) were killed at mid gestation, which is a time when fetal resorption can be identified. Tissues were collected for permanent fixation and gene expression studies with complementary DNA macroarrays that were specific for extracellular matrix proteins. A 2-fold increase in expression or a 50% decline was considered significant. Expression changes were confirmed by real-time reverse transcriptase-polymerase chain reaction. The vessel-to-lumen diameter ratios were found to be significantly greater for the CBA/J implantation sites (1.50 +/- 0.05 vs 1.22 +/- 0.02, respectively; P < .0001), which indicates a lack of vascular remodeling. There was also a trend towards smaller lumen diameters for the CBA/J vessels, but this was not statistically significant (78.2 +/- 4.4 microm vs 93.5 +/- 6.8 microm, respectively; P = .22). The mean coefficient of variation for lumen measurements was 0.8% and for vessel diameter was 0.3%. The ranges were 0 to 3.2% and 0 to 1.4%, respectively. Tissue inhibitor of metalloproteinase 2 expression was up-regulated in the placentas of the group with higher resorption rates when compared with normals. This was confirmed with reverse transcriptase-polymerase chain reaction, where abnormals exhibited 2.6-fold greater tissue inhibitor of metalloproteinase 2 protein quantities when compared with normal controls (P = .03). The expansive vascular remodeling of decidual vessels that is characteristic of normal murine pregnancy is attenuated significantly in the CBA/J x DBA/2 mating combination, which is known for its tendency to recurrent fetal resorption. This has been correlated with a relative overexpression of tissue inhibitor of metalloproteinase 2 protein in placentas of this strain combination and compared with normals.

Lymphocyte phenotyping and NK cell activity analysis in pregnant NOD/SCID mice

The purpose of this study was to outline the fertility features of non-obese diabetic (NOD)/LtSz- scid/ scid (NOD/SCID [severe combined immunodeficiency] for short) mice, and to evaluate the effects of NK cell subsets on the pregnancy outcomes of the syngeneic NOD/SCID × NOD/SCID mating combination. Firstly, lymphocyte phenotyping was performed with flow cytometry to confirm the multiple immunodeficits in NOD/SCID mice. Fertility features were assessed in NOD/SCID × NOD/SCID mice and compared with non-immunodeficiency control BALB/c × BALB/c mice. Although the presence of NK cell deficit is apparent in NOD/SCID mice, a certain level of remnant NK activity could be observed in these mice. The remnant NK cell activity was stimulated with polyinosinic-polycytidylic acid (polyIC), or inhibited with anti-asialo GM1 (ASGM1) anti-serum, respectively. The effects of these factors on pregnancy outcomes were evaluated after administration. Roughly normal fertility could be observed in NOD/SCID × NOD/SCID mice. However, a slightly larger sized litter was observed in polyIC-treated NOD/SCID × NOD/SCID mice compared with control NOD/SCID mice. In contrast, embryo resorption was boosted after ASGM1 injection, and correlated subsequently with a smaller litter size. It indicates that the remnant NK cell activity in NOD/SCID mice may be beneficial to feto-maternal tolerance during pregnancy.

Untersuchungen zur züchterischen Bedeutung der Ellbogendysplasie (ED) beim Berner Sennenhund in Deutschland

Results from the elbow dysplasia screening program in Bernese Mountain Dogs of Germany were analysed in respect to its relevance for genetic evaluation and breeding. In total 2677 gradings were used. The grading was performed radiographically according to the recommendations of the International Elbow Working Group (IEWG). 75.8% of the dogs were free from visible dysplastic signs, 10.8%, 6.8% and 5.5% were classified to be of Grade 1, 2 and 3, respectively. 1.1% were classified as a borderline case between ED-free and Grade 1. A slight reduction of ED could be observed over years. Males had a 3.1 higher rate of dysplasia than females. Treating ED as a numerical trait, coded proportional to the severity of clinical relevant signs, gave a heritability estimation of 0.188 and a maternal effect of 0.07. From different mating combinations it was found, that ED average was higher in the progeny if one mate was affected but there was no increase in the prevalence with increasing grade of ED in the affected mates. About 10% more affected dogs could be observed, if one mate is affected. Heritability for dichotomic coding the trait was found to be 0.20. From these results can be suggested, that the differentiation in various grades of ED to describe the clinical relevance for the specific dog is helpfull, however, from a breeders point of view, dogs with ED should be treated equally for genetic evaluation.

Murine CD200+CK7+ trophoblasts in a poly (I:C)-induced embryo resorption model

Cytokeratin 7 (CK7) is currently regarded as the best marker for trophoblast cells, while CD200 (OX-2), known as 'tolerance signal', plays an important role in normal pregnancy. In this study, the status of CD200 expression was investigated in BALB/c x C57BL/6 and BALB/c x BALB/c mating combinations designed as allogeneic and syngeneic murine models of induced embryo resorption, in which the resorption rate was boosted by an i.p. injection of poly (I:C), a synthetic double-stranded RNA. The percentage of CD200+ cells in the CK7+ cell population (CD200+ CK7+ percentage) and the absolute number of these cells were determined with flow cytometry, using trophoblast cells collected at day 8.5 and day 13.5 of gestation. The potential effect of poly (I:C) on CD200 expression was also evaluated by detecting the CD200+ CK7+ percentage in trophoblast cells incubated in the presence or absence of poly (I:C), in vitro. The distribution pattern of CD200+ cells at the feto-maternal interface was evaluated by immunocytochemical examination. When 10(4) cells were analyzed at day 8.5 of gestation in each case, no significant difference was observed between the poly (I:C)-treated group and the control PBS group either in the CD200+ CK7+ percentage or in the absolute number of these cells. Similar results were observed both in BALB/c x C57BL/6 mice and in BALB/c x BALB/c mice. However, the CD200+ CK7+ percentage was significantly decreased in the poly (I:C)-treated group when evaluated at day 13.5 of gestation. Accordingly, a dramatically elevated rate of embryo resorption was observed at this time point of pregnancy after the administration of poly (I:C). In addition, the CD200+ CK7+ percentage was significantly lower in trophoblast cells incubated with poly (I:C) at a certain concentration, in vitro, while histocytochemical examination showed the CD200+ cells mainly scattered in placental tissue adjacent to the interface of the placenta and uterus. This indicates that sufficient expression of the CD200 molecule on CK7+ cells at the feto-maternal interface may be necessary for the maintenance of embryos during pregnancy in this rodent model, while poly (I:C) administration may increase embryo resorption, at least partially via direct inhibition of CD200 expression on CK7+ cells.

IL-10 prevents naturally occurring fetal loss in the CBA x DBA/2 mating combination, and local defect in IL-10 production in this abortion-prone combination is corrected by in vivo injection of IFN-τ

CBA x DBA/2 placentae are quantitatively or qualitatively deficient in their production of the anti-inflammatory Th2-type cytokines IL-4 and IL-10 compared with the nonresorption-prone CBA x BALB/c mating combination. Wastage in this mating combination is accompanied by increased levels of local inflammatory cytokines. In addition, alloimmunization enhances the placental production of IL-4 and IL-10 in CBA x DBA/2 matings. Furthermore, rIL-10 by itself completely reverses the high incidence of fetal resorption after i.p. injection. Conversely, anti-IL-10 increases the resorption rate, but only in CBA x DBA/2 matings. On the other hand, injecting either anti-IFN-gamma or pentoxifillin (an anti-TNF agent) partially reduces the resorption. When given together, they produce a synergistic remission of fetal loss. Finally, we report that recombinant ovine trophoblast protein, an IFN-tau which is known to influence reproductive outcome in ruminants, can also counteract increased CBA x DBA/2 fetal resorption. It simultaneously induces increased placental IL-4 and IL-10 production in this mating combination. These results indicate that the placentally produced anti-inflammatory cytokines can play a vital role in the survival to term of the fetal allograft, by counteracting deleterious inflammatory cytokines.

Interspecific Hybridization Between &lt;I&gt;Liriomyza trifolii&lt;/I&gt; and &lt;I&gt;Liriomyza sativae&lt;/I&gt;

Abstract Experimental interspecific hybridization between the notorious, worldwide horticultural crop pests Liriomyza trifolii (Burgess) and Liriomyza sativae Blanchard is reported. Premating reproductive isolation was easily disrupted under no-choice crossing conditions; hybrid flies were obtained only in one mating combination (female L. sativae × male L. trifolii). Crosses between them yielded only female progeny, which had some superficial characters identified as L. sativae, but the shape of the genitalia was similar to that of L. trifolii. All of the F1 hybrids were sterile and could not be backcrossed to either parental species. An electrophoretic analysis of internal transcribed spacer region sequences on ribosomal DNA genes and a nucleotide sequence analysis of mitochondrial DNA cytochrome oxidase subunit I DNA sequences confirmed that the progeny were not the result of parthenogenetic reproduction.

The effects of ionizing radiation on the reproductive capacity of adult Penaeus (Marsupenaeus) japonicus (Bate)

The reproductive capacity of adult Penaeus (Marsupenaeus) japonicus (Bate) was assessed after exposure to ionizing gamma radiation from a cobalt-60 source. Males and females were each exposed to 0, 10 and 20 Gray (Gy) of ionizing radiation (IR) and reciprocally crossed to give nine mating combinations. Fecundity and hatch rate of resulting spawnings were used as measures of reproductive capacity. IR significantly ( P < 0.05) reduced the fecundity of females when treated at 20 Gy compared to 0 and 10 Gy. The mean number of eggs per female for the 0 and 10 Gy crosses was 24,280 ± 4680 and 47,000 ± 9670 respectively, compared to 11,600 ± 6840 for the 20 Gy crosses. Hatch rates from spawnings of females crossed with irradiated males were significantly lower ( P < 0.05) than for females crossed with non-irradiated males. The mean hatch rate of spawnings from females crossed with 0 Gy males was 64.02 ± 8.85% compared to 20.77 ± 5.46% for 10 Gy and 11.95 ± 6.13% for 20 Gy male crosses. These results indicate that IR has a negative impact on the reproductive capacity of females at 20 Gy, and males at 10 and 20 Gy. However, IR was not found to be 100% effective at preventing the production of viable offspring using the reported treatment regimes.

Differential Roles of Renin and Angiotensinogen in the Feto-Maternal Interface in the Development of Complications of Pregnancy

We previously identified a transgenic mouse model that developed pregnancy-associated hypertension (PAH) and intrauterine growth restriction (IUGR) by mating females expressing human angiotensinogen (hANG) with males expressing human renin (hRN). These phenotypic defects were not observed in the opposite type of mating combination, despite the feto-placental overexpression of hRN and hANG detected in both types of crossbreeding. Detailed analysis of transgene localization in the labyrinth and its permeability to the maternal circulation revealed that hRN produced in trophoblast giant cells was secreted into the maternal circulation, whereas hANG, produced in chorionic trophoblasts and trophoblastic epithelium, was undetectable in the maternal plasma, probably due to their distinct spatial and temporal expression in labyrinth. These results demonstrated that PAH and IUGR could be mediated by feto-placental hRN through its permeability to the maternal circulation, not by feto-placental hANG production. Furthermore, overexpression of maternally derived hANG in decidua and spiral arteries of pregnant females with PAH and IUGR raises the possibility of local activation of the renin-angiotensin system and its pathophysiological effects on placental hypoperfusion in complications of pregnancy. This study provides in vivo evidence that the cell-specific expression of RN and ANG in the feto-maternal interface impacts their differential roles in pregnancy.

Direct and indirect analysis of the fitness of Chrysochus (Coleoptera: Chrysomelidae) hybrids

The chrysomelid beetles Chrysochus auratus and C. cobaltinus form a narrow hybrid zone in western North America. We used a combination of direct and indirect analyses to examine the fitness of Chrysochus hybrids. For the direct analyses, we compared the mating frequency, longevity, fecundity and fertility of hybrid females and parentals. For the indirect approach, we tested predictions of multilocus genotype frequencies at a focal site in the hybrid zone, based on the frequencies of mating combinations during the previous generation. Hybrid females produced fewer eggs than did parentals and the eggs they produced in the lab failed to hatch, in contrast to those of parental females. In addition, contrary to predictions that 15.8% of the individuals at the focal site would have multilocus genotypes other than those expected of parentals or F1 individuals, we found no such genotypes at this site. This hybrid zone appears to be an example of a classic tension zone, with endogenous selection against hybrid individuals. We discuss the implications of low hybrid fitness for the evolution of premating barriers in this system, and argue that the integration of direct and indirect approaches is a powerful means of assessing the relative fitness of hybrids, particularly for species in which mate choices are easy to observe in the field. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84, 273–286.

The Effect of Mating Different Age Groups of Broodstocks on the Reproductive performance, Sex Ratio, Growth, and Survival bate of Rainbow Trout (Oncorhynchus mykiss)

ABSTRACT Four breeding groups of rainbow trout (Oncorhynchus mykiss), each comprising two males and one female, different from one another based on the age of the breeders. The combinations were: age-3 males x age-3 female (Group A); age-6 males x age-6 female (Group B); age-3 males x age-6 female (Group C); aged males x age-3 female (Group D). Except for Group B, which had a low (63%) rate, fertilization rates of all groups were high and normal. Eyed-egg survival and swim-up rates were both lowest for Group B fish. After nearly one year of monitoring the offspring, the sex ratio of survivors of Groups A and B approached unity, whereas the majority of survivors in Groups C and D were males (76.8 and 89.5%, respectively). The condition factor was similar for fish of all four groups, but the average weight of females was higher than that of males in each group. Although the survival rates of fish in Groups A and B were higher, growth was better demonstrated by fish in Groups C and D. Overall, of all the mating combinations, those of young male x old female appear to be the most productive.

Genetics and morphology in aBorrichia frutescensandB. arborescens(Asteraceae) hybrid zone

Interspecific plant hybridization is a common and evolutionarily important phenomenon. Here, the results of a study of hybridization in the Florida Keys between two species of sea oxeye daisy, Borrichia frutescens and B. arborescens, are reported. Nuclear and chloroplast genetic loci, log-likelihood assignment tests, and maximum likelihood estimates of genealogical class frequencies were used to identify hybrid and parent genotypes, to investigate the utility of leaf and flower morphology for hybrid identification, and to study symmetry and degree of introgression between the species. Genetic analyses confirmed the identity of the hybrid and parent plants that were used for the morphological studies. Together, leaf and flower morphology can be used to identify hybrid and parental types with moderate accuracy (4% error rate). Population genetic analyses indicate that, in spite of a significant level of hybridization, pure B. frutescens and B. arborescens are persisting in the hybrid zone. Of the nonparentals, about 18% appear to be F(1) hybrids, over 50% F(2) hybrids, and the remainder backcrossed individuals but only with the B. frutescens parent. It is postulated that the hybrid zone in the Florida Keys is being maintained by a combination of positive assortative mating and clonal reproduction.

Microconidia act the role as spermatia in the sexual reproduction of Botrytis cinerea

In the sexual reproductive cycle of Botrytis cinerea, large numbers of microconidia were observed in all the crosses that formed sexual bodies. To clarify the role of the microconidia in sexual reproduction, they were separated using a sucrose density gradient and then used in crossing tests with fungal sclerotia. Sexual bodies were formed in all the crosses in the five mating combinations, demonstrating that microconidia are able to function as spermatia during sexual reproduction of B. cinerea.