Inbred Groups Research Articles

Differences in memory performance: The effects of sex and reproductive experience on object recognition memory in high- and low-yawning Sprague‒Dawley rats

The novel object recognition (NOR) test is an efficient way to measure nonspatial memory in rodents. The NOR performance of female and male rats is sexually dimorphic because memory performance is better in the former than in the latter. In females, maternal experience enhances spatial memory. We used the NOR test to evaluate short- and long-term recognition memory in both sexes in the high- and low-yawning sublines of rats (HY and LY, respectively), which were generated via a strict inbreeding process from the Sprague‒Dawley (SD) strain for more than ninety generations. Additionally, we evaluated the effect of maternal experience using nulliparous, primiparous, biparous, and multiparous HY, LY and SD dams. Our results revealed that LY rats presented less thigmotaxis, with lower central square crosses and more vertical exploration in the open-field arena, suggesting that they experienced anxiety. Additionally, LY males performed significantly better than LY females in short- and long-term NOR memory, and LY males performed significantly better than SD rats did. Among females, two maternal experiences negatively affected short-term memory in the LY and HY sublines with respect to primiparous dams, and HY dams had better memory performance in the NOR test than did SD dams. Our findings suggest that the yawning sublines are suitable for studying the neurobiological basis of different memory processes under different endocrine conditions in highly inbred groups of rats.

Assessment of inbreeding depression on morphometric traits among North Indian population cohorts

AimInbreeding is thought to affect the morphometric parameters leading to lower health status among the progeny. The present study was aimed to investigate the repercussions of inbreeding on anthropometric traits, namely height, weight and body mass index (BMI).Subjects and methodsThe survey was conducted in two North Indian cities and total 813 individuals were randomly recruited from inbred and outbred families. The morphometric parameters of the subjects were measured using standard methods, BMI was calculated and categorized into underweight, normal weight and overweight. Family pedigrees were drawn and degree of inbreeding in terms of the inbreeding coefficient (F) was calculated.ResultsA significant decline in morphometric measures was observed among inbred individuals as compared to outbred ones. The mean differences (95% CI) were found significant for various inbred and first cousin categories as compared to outbred subjects (p < 0.05). We found the increased frequency of underweight individuals corresponding to the degree of inbreeding for different types of inbred categories (p = 2.086 × 10−9) and also for different subtypes of first cousin unions corresponding to their sex-linked inbreeding coefficients (p = 5.2 × 10−5). The regression slope and correlation coefficient revealed a fitness decline and depression in anthropometric measures (p < 0.05) with the increase in ‘F’ for all inbred groups and first cousin categories.ConclusionsThe present research confirms the adverse effects of inbreeding on morphometric parameters among inbred subjects. It has novelty in shedding light on the hitherto unreported differences in the consequences of inbreeding among different types of first cousin unions.

Genome-wide association and co-expression uncovered ZmMYB71 controls kernel starch content in maize

Starch plays a crucial role as a storage component, greatly affecting the grain yield and quality of maize (Zea mays L.). To meet future demands, it is essential to understand the genetic basis of the natural variation in kernel starch content (SC) for maize breeding. Through a genome-wide association study (GWAS), we identified 84 and 96 loci associated with kernel SC within two years that overlapped with 185 candidate genes. The candidate gene ZmMYB71, which encodes a myeloblastosis (MYB)-related transcription factor, exhibited the highest co-expression frequency with starch synthesis genes. We demonstrated that ZmMYB71 functions as a nuclear located transcription repressor, and the kernel SC of mutants increased by over 2.32%, with a minor effect on amylose content or 100-grain weight. Sh1, Sh2, and GBSSI showed up-regulation in mutants by 1.56-, 1.45- and 1.32-fold, respectively, consistently with the RNA sequencing result; their promoter activities may be directly repressed by ZmMYB71 through the GATATC and TTAGGG motifs. Furthermore, the ZmMYB71 elite haplotype Hap1 was present in over 55% of the high-starch maize sub-populations BSSS and PB but only in 7.14% of the low-starch sub-population PA. Comparing the Hap1 haplotype frequencies in different breeding stages found that its frequency in the inbred group released after 2010 is significantly higher at 40.28%, in contrast to 28.57% and 27.94% in the years 1980 and 1990, and 2000, respectively. The finding provides valuable information on the natural variation in SC of the maize kernel and suggests that ZmMYB71 serves as a negative regulator with the potential to be used to improve SC in the kernels.

FLIGHT ACTIVITY AND POLLEN AND WAX PRODUCTIVITY OF BEES OF DIFFERENT GENEALOGICAL FORMATIONS OF THE CARPATHIAN SUBSPECIES

The research was conducted on bees of different intra-line crosses of the Carpathian subspecies in private apiaries in Navariya village, Lviv region. To conduct experimental studies, 6 groups of 10 bee colonies were formed in each group: I – control group – bees of the Carpathian population of the Vuchkovsky type; II – inbred group ♀ microline "915" x ♂ microline "915"; III – breeding cross ♀ microline "Sto" x ♂ microline "915"; IV – breeding cross ♀ type "Vuchkovsky" x ♂ microline "915"; V – breeding cross ♀ microline "67" x ♂ microline "915"; VI – breeding cross ♀ microline "07" x ♂ microline "915".&#x0D; It was found that bees of different breeding crosses of the Carpathian subspecies differed significantly in flight and pollen collection activity and wax productivity. In terms of flight activity, the bees of the inbred group ♀ microline "915" x ♂ microline "915" significantly differed during observation at 9:00. 12:00 and 15:00 hours. In the morning and at 15:00 hours, the best pollen-collecting activity was characterised by bees of the breeding cross ♀ microline "07" x ♂ microline "915" group. In the afternoon, the bees of the inbred group ♀ microline "915" x ♂ microline "915" collected the most pollen – 312.9, which is 84.1 pieces more than in the control group. In the evening, the best flight activity (392.2 arrivals) and collection of pollen (126.8 pcs.) were observed in insects of the breeding cross ♀ microline "67" x ♂ microline "915". The highest wax yield was characterised by bees of the breeding crosses ♀ microline "07" x ♂ microline "915" and ♀ microline "915" x ♂ microline "915". The strength of the influence of genealogical formation on the flight activity of bees during the day ranged from probable to unreliable values and was in the range of 13.9–28.7%, and on wax productivity in all cases it was reliable P &lt; 0.05, P &lt; 0.001 and ranged, depending on the trait, from 19.2 to 31.3%.

Crossbreeding of two populations of Ruditapes philippenarum reveals high growth and survival heterosis

Hybridization is an important breeding method to improve productive traits in aquaculture. The Manila clam Ruditapes philippenarum, a worldwide cultured bivalve, has achieved the great commercial success owing to a global appreciation of its delicious taste and affordable price. In order to evaluate the aquaculture potential of clam hybridization, a complete diallel cross between two geographical populations (Shandong and Guangdong) was performed in the present study. Two intra-population mating groups LL (L♀ × L♂) and ZZ (Z♀ × Z♂) and two crossbreeding groups ZL (Z♀ × L♂) and LZ (L♀ × Z♂) were established to investigate the potential heterosis of growth and survival in the clams. Three full-sib families were constructed in each mating group to calculate the growth and survival heterosis. During the larval stage (2 ∼ 10d), no significant difference was detected in averaged shell length between reciprocal hybrids and inbred groups. In contrast, hybrid spats after 15d cultivation showed a significantly larger size (shell length and shell height) than that of inbred spats. For the reciprocal hybrids, the greatest growth heterosis of shell length and height (33.42% and 33.13%) was detected from 20 days after fertilization in ZL. After 40d cultivation, ZL displayed the most growth potential in shell length and height, reaching maximum values of 0.900 and 0.858 mm, respectively. The hybrids had 25% ∼ 40% higher survival rates than those of the inbred groups, with the highest survival heterosis in ZL. The positive values for the general combining ability (GCA) were consistently detected in the Zhanjiang population. At day 40, the special combining ability (SCA) in ZL was approximately two-fold higher than that in LZ. These findings indicate that the hybrids produced by Laizhou males and Zhanjiang females have the greater aquaculture potential, providing a useful crossbreeding strategy for clam genetic improvement in aquaculture.

Perg reserve and development of bee colonies of different genealogical formations of the carpathian subspecies

The study of bee colony growth patterns throughout the year makes it possible to substantiate the ways of creating strong families that will ensure high productivity in the collection of bee products. The research was conducted on bees of different genealogical formations of the Carpathian breed in private apiaries in the village of Navariya, Lviv region. To conduct the experimental studies, 6 groups of 10 bee colonies were formed: I – the control group – local bees of the Carpathian population (type “Vuchkovsky”); II – the experimental group – inbred group ♀ UA3-5-9-15.112-2018 x ♂ UA3-5-9-15. 112-2018 (♀ microline “915” x ♂ microline “915”); III – experimental group – breeding cross ♀ UA3-65-2019 x ♂ UA3-5-9-15.112-2018 (♀ microline “Sto” x ♂ microline “915”); IV – experimental group – breeding cross ♀ UA3-5-35-2019 x ♂ UA3-5-9-15. 112-2018 (♀ type “Vuchkovsky” x ♂ microline “915”); V – experimental group – breeding cross ♀ UA3-5-307/67-2018 x ♂ UA3-5-9-15. 112-2018 (♀ microline "67" x ♂ microline “915”); VI – experimental group – breeding cross ♀UA3-5-07-2018 x ♂ UA3-5-9-15.112-2018 (♀ microline “07” x ♂ microline “915”). It was established that bees of different breeding crosses of the Carpathian breed had certain differences in the strength of bee colonies, the number of closed broods, and bee bread productivity. The maximum values of bee colony strength and stocks of perga in all groups were noted during the inspection on 10 June. At the same time, the highest value of bee colony strength was observed in the fifth experimental group (19.7 hives), and the best bee colonies in the second experimental group (6992.0 cells) were found in terms of perg productivity. The highest values of the number of closed brood were recorded during the inspection on 29 May, with the bee colonies of the third experimental group prevailing in this respect (20547.6 cells). Thus, to increase the strength of bee colonies, the number of closed brood, and the bee bread productivity, it is advisable to breed interbreed crosses of the Carpathian subspecies since they are superior to local bees of the Vuchkovsky type in the above characteristics.

Effects of inbreeding and selection on heritability estimates of production traits of Holstein cattle under selection

Inbreeding and selection are forces that affect heritability, important to selection in livestock species. So, this study aims to relate those forces in a Holstein population under selection for superior milk production. Inbreeding coefficients was calculated considering 3 generations, after the individual inbreeding coefficient was calculated, inbred (7.92±2.72) and non-inbred group (0.46±0.38) were formed. The genetic variance was higher for the inbred group and for the residual variance was lower. As result, those variance changes resulted in higher heritability for all traits analyzed for the inbred group. For the levels of inbreeding observed in this study, the selection for higher productions possibly masked the effects of inbreeding.

Analysis of resistance against white spot syndrome virus infection in Fenneropenaeus chinensis considering different inbreeding coefficients

The relationship between inbreeding and traits of disease resistance in shrimp has not been studied comprehensively. To explore the effect of inbreeding on white spot syndrome virus (WSSV) resistance in Fenneropenaeus chinensis, we established F. chinensis “Huanghai No. 5” populations with different inbreeding coefficients. We infected F. chinensis individuals with WSSV to compare WSSV-resistance between five inbred groups and a control group. Survival time, survival rate, distribution of deaths, and cumulative mortality rate were analyzed. A mixed linear model was established based on the acquired data. The viral load in muscle tissue of F. chinensis of 12 families from the five inbred groups and the control group was determined at different time points via real-time PCR. The average survival and longest survival time of the inbred groups were lower than those of the control group, and the coefficient of variation was universally greater than that of the control group. The least squares means of survival time of the five inbred groups (F0.1325, F0.25, F0.3125, F0.375, F0.5) were 118.96 115.14, 124.58, 123.97, and 101.34 h, respectively, which were 10.28%, 13.16%, 6.04%, 6.5%, and 23.57% lower than that of the control group. Further, when the inbreeding coefficient increased by 10%, WSSV infection survival time was changed by − 7.76%, − 5.26%, − 1.93%, − 1.73%, and − 4.71% for the five inbred groups, respectively. Thus, the results indicated that inbreeding enhanced the susceptibility of F. chinensis to WSSV infection, and the resistance of F. chinensis to WSSV declined as the inbreeding coefficient values increased, consequently, resulting in greater population dispersion, intensified differentiation, and instability of resistant phenotypes. In conclusion, we elucidated the effect of inbreeding on F. chinensis resistance to WSSV infection and established a theoretical basis to conduct further research in the future.

Inbreeding affects juvenile shoaling behaviour in sibling groups of a cichlid fish

Whilst the effects of inbreeding on growth and survival have been well studied, knowledge on the impact of inbreeding on the social behaviour is scarce. Animal groups are often composed of relatives, which can facilitate cooperation (due to kin selection) and improve group performance accordingly. Therefore, increased genetic relatedness in inbred kin groups could increase group performance, whilst the reduced genetic diversity could have negative effects (inbreeding depression). We compared the juvenile shoaling behaviour of inbred and outbred sibling groups in Pelvicachromis taeniatus (Boulenger 1901), a West-African cichlid fish with kin mating preferences. Activity (travelled distance), shoal density (inter-individual distance) and recovery from a disturbance (freezing time) in a novel environment were analysed using tracking software. Inbred individuals travelled shorter distances compared to outbred individuals, which may decrease conspicuousness and thus predation risk. Furthermore, inbred sibling groups recovered faster after the disturbance compared to outbred sibling groups suggesting improved coordination. In conclusion, our study revealed differences in shoaling between inbred and outbred sibling groups. The higher relatedness in inbred groups may have positive effects in the form of a reduced conspicuousness. The reduced activity may impair foraging success under natural conditions which might, however, be compensated by faster recovery from disturbances.

Transcriptome analysis of inbreeding depression in the Pacific oyster Crassostrea gigas

The Pacific oyster (Crassostrea gigas) is widely cultured worldwide. Because intercrossing inbred strains improves yield (heterosis), development of inbred lines is needed to implement this breeding strategy. However, inbreeding usually reduces the mean phenotypic value shown by characters connected with physiological efficiency or reproductive capacity. The effects of inbreeding on growth and survival of C. gigas have been reported by numerous studies. However, effects of inbreeding on gene expression still remains to be explored in oysters. In this study, the relationship between gene expression and inbreeding depression was investigated in an inbred line of the Pacific oyster. Two inbred groups, an F1 group containing 15 inbreeding families and an F2 group containing 15 families with a presumed relative higher inbreeding level performing worse in growth and survival rate compared to the F1 group, were constituted by using this inbred line. The shell height and survival rate of two inbred groups were compared with those of the wild group including 15 families (CF). A total of 9 RNA-seq libraries were constructed using oyster gills. Based on differential gene analysis, 2430 differentially expressed genes (DEGs) in the F1 group and 3741 in the F2 group were identified respectively compared to the CF group. A total of 1746 common DEGs were counted shared in two inbred groups, of which 911 were up-regulated and 835 were down-regulated. GO and KEGG analysis showed that common DEGs were significantly enriched in the immune response and actin nucleation pathways. Additionally, 695 DEGs were identified between two inbred groups, and GO analysis revealed that these DEGs were significantly in the pathways related to immune and stress response. Our results show the preliminary exploration of the effect of inbreeding on gene expression of C. gigas, which is helpful for us to better understand and manage inbreeding depression of bivalves, and may potentially benefit the breeding of oyster in aquaculture.

Breeding Strategy Shapes the Composition of Bacterial Communities in Female Nile Tilapia Reared in a Recirculating Aquaculture System.

In industrial animal production, breeding strategies are essential to produce offspring of better quality and vitality. It is also known that host microbiome has a bearing on its health. Here, we report for the first time the influence of crossbreeding strategy, inbreeding or outbreeding, on the buccal and intestinal bacterial communities in female Nile tilapia (Oreochromis niloticus). Crossbreeding was performed within a family and between different fish families to obtain the inbred and outbred study groups, respectively. The genetic relationship and structure analysis revealed significant genetic differentiation between the inbred and outbred groups. We also employed a 16S rRNA gene sequencing technique to understand the significant differences between the diversities of the bacterial communities of the inbred and outbred groups. The core microbiota composition in the mouth and the intestine was not affected by the crossbreeding strategy but their abundance varied between the two groups. Furthermore, opportunistic bacteria were abundant in the buccal cavity and intestine of the outbred group, whereas beneficial bacteria were abundant in the intestine of the inbred group. The present study indicates that crossbreeding can influence the abundance of beneficial bacteria, core microbiome and the inter-individual variation in the microbiome.

Effect of Inbreeding on Preweaning Growth Traits in Egyptian Buffaloes

The aims of the current study were to estimate the effect of inbreeding and genetic parameters of birth weight (BW), preweaning daily gain (PDG) and weaning weight (WW) in buffalo calves. Data were collected from weight records of buffalo calves raised at Mahallet Mousa Farms belonging to the Animal Production Research Institute. It included 2015 progeny of 125 sires, through 17 consecutive years. Effect of inbreeding was highly significant for all studied traits. The overall average of inbreeding coefficient was 0.53% in whole population and 15% in the inbred animals. The means of BW, PDG and WW in non-inbred group were 37.318, 0.490 and 88.86 Kg, respectively. While, the means of the same traits in inbred group were 31.96, 0.446 and 78.82 Kg, respectively. Corresponding the inbreeding depression as overall means of levels for above traits were -0.350, -0.003 and -0.716, respectively. Direct heritability (h2a) in inbred animals for BW, PDG and WW were 0.28, 0.25 and 0.19, respectively. On the other hand, the h2a of studied traits in non-inbred animals were 0.32, 0.30 and 0.23, respectively. The maternal heritability (h2m) for mentioned traits were 0.25, 0.26 and 0.21 within inbred animals and 0.29, 0.28 and 0.22 within non-inbred animals, respectively. Likewise, the genetic correlations (rg) among studied traits were ranged from (0.12 to 0.56) in inbred animals and were ranged from (0.16 to 0.63) in non-bred animals. As well the phenotypic correlation (rp ) among studied traits were ranged from (0.04 to 0.50) for inbreds and were varied between (0.04 and 0.54) for non-inbreds. The inbreeding was pronounced detrimental effects of studied traits in buffalo calves. Therefore, breeding strategies should be develop for reduce the inbreeding effects and inclusion the effects of inbreeding in genetic evaluation programs in Egyptian buffalo calves.

Comparative allometric growth of rare minnow (Gobiocypris rarus) in two culture environments

Allometry, a growth pattern in which different parts of an organism grow at defined rates, is a common feature of fish and can be influenced by environmental factors. The rare minnow Gobiocypris rarus Ye et Fu, 1983 undergoes allometric growth, and this study investigated its allometry patterns and assessed whether the culture environment affects them by comparing growth patterns in conventional (CV) and specific pathogen-free (SPF) stocks using 14 morphological characters. A U-shaped pattern of allometric growth was found in both groups, characterized by higher growth rates of the head and caudal regions than the trunk region. Although the overall allometric growth pattern was similar between these two inbred groups of rare minnows, allometric coefficients for morphometric characters before inflection were higher for SPF fish than CV fish. Growth rates of total length and body mass were also higher for SPF than CV individuals. These results indicate that the environment does play a vital role in rare minnow growth and development, and that a clean culture environment and a U-shaped pattern of allometric growth are highly beneficial for its early growth.

Stuck in fragments: Population genetics of the Endangered collared brown lemur Eulemur collaris in the Malagasy littoral forest.

The Endangered collared brown lemur (Eulemur collaris) is the largest primate living in the littoral forest of southeastern Madagascar, a top priority habitat for biodiversity conservation on the island. Because this lemur is a key seed-disperser, an evaluation of the structure and connectivity of the populations surviving in the forest fragments is urgently needed to guide conservation plans. Genetic variability at autosomal microsatellites and mitochondrial DNA was investigated in a total of 49 collared brown lemurs sampled by non-invasive methods in three littoral forest fragments and in the nearby lowland humid forest. The overall genetic diversity of E. collaris in the southeastern coastal region of Madagascar was lower than in other populations, as well as in other lemur species. The population appears highly structured, with less variable and more inbred groups inhabiting the littoral forest fragments compared to the inland area. Major barriers to gene flow were identified isolating littoral forest fragments from each other and from the inland lowland humid forest. Medium to long-term drift and scarce gene flow is the scenario that best explains the current genetic distribution. Habitat discontinuities such as rivers and grassland between forest fragments played a major role in structuring the population. A common history of size contraction is pointed out by several genetic estimators, indicating a possible ecological crisis triggered around 1,300 years ago. The adoption of strategies aimed at facilitating gene flow and population growth appears crucial to delay further loss of genetic diversity.

Relationship of Rice Grain Amylose, Gelatinization Temperature and Pasting Properties for Breeding Better Eating and Cooking Quality of Rice Varieties.

A total of 787 non-waxy rice lines– 116 hybrids and 671 inbreds–were used to study the apparent amylose content (AAC), gelatinization temperature (GT), and rapid visco analyzer (RVA) pasting viscosity properties of rice starch to understand their importance in breeding better rice varieties. The investigated traits showed a wide range of diversity for both hybrid (HG) and inbred (IG) groups. The combinations of the different categories of AAC and GT were random in HG but were non-random in IG. For inbred lines, the high level of AAC tended to combine with the low level of GT, the intermediate level of AAC tended to have high or intermediate GT, and the low level of AAC tended to have high or low GT. Some stable correlations of the AAC, GT, and RVA properties may be the results derived from the physicochemical relationships among these traits, which rice breeders could utilize for selection in advanced breeding generations. Through cluster analysis, IG and HG were divided into 52 and 31 sub-clusters, respectively. Identifying the cultivars having AAC, GT, and RVA properties similar to that of popular high-quality rice varieties seems to be an interesting strategy and could be directly used for adaptation trials to breed high-quality rice varieties in targeted areas in a more customized manner.

Impact of consanguineous marriages and degrees of inbreeding on fertility, child mortality, secondary sex ratio, selection intensity, and genetic load: a cross-sectional study from Northern India.

The aim of our study was to understand the relationship between consanguineous marriages and reproductive outcomes. A total of 999 families were recruited from five Muslim populations of Jammu region. Family pedigrees were drawn to access the family history and inbreeding status in terms of coefficient of inbreeding (F). Fertility, mortality, secondary sex ratio, selection intensity, and lethal equivalents were measured using standard methods. The significant differences for gross fertility was found to be higher among inbred groups as compared to the unrelated families (P < 0.05) and higher mortality rates were observed among consanguineous families of all populations in comparison with the non-consanguineous family groups. Moreover, the prenatal and postnatal child mortality rates (i.e., U5MR and U18MR) have presented a persuasive increase with an upsurge in the homozygosity level. The mortality rate was found to be maximum among families with the highest value of coefficient of inbreeding (F). The selection intensity (SI) also showed inflations among families with respect to their increasing inbreeding coefficients. The greater values of lethal equivalents per gamete (LEs/gamete) were observed for autosomal inheritance in comparison with sex-linked inheritance. Our conclusive assessment brings out the deleterious consequence of consanguineous marriages on reproductive outcomes.

Adverse effects of inbreeding on colony foundation success in bumblebees, Bombus terrestris (Hymenoptera: Apidae)

The detrimental effects of brother–sister and nephew–aunt matings on the colony foundation success of Bombus terrestris (Linnaeus, 1758) queens were investigated under controlled laboratory conditions. Among 86 hibernated queens, 43 were mated with randomly selected males from the same colony (inbred group), and 43 were mated with unrelated males from other colonies (outbred group). Nests were observed twice a week, and some developmental determinants of colony quality were recorded. The results suggest that inbreeding adversely affects the time taken to initiate a colony, the time taken for the first male to emerge, the number of workers in the first brood, and the total number of workers and young queens. The percentage of the queens that produced at least 50 workers significantly differed between the inbred and outbred groups (13.95 and 62.79 %, respectively). In the inbred group, 48.83 % of the queens produced both workers and males in their first brood, versus 4.65 % in the outbred group. Although the total number of individuals in the first brood was not significantly different for the two groups, the inbred group produced a higher proportion of males in the first brood (43.99 versus 12.74 % in the outbred group). Thus, inbreeding has a substantial deleterious effect on captive B. terrestris populations, so it is necessary to maintain genetic diversity and prevent inbreeding when aiming for the sustainable laboratory rearing of B. terrestris.

Effect of inbreeding on growth and genetic diversity of Portunus trituberculatus based on the full-sibling inbreeding families

This present study aimed to investigate the effects of inbreeding on growth traits and genetic diversity in the swimming crab, Portunus trituberculatus. To this end, full-sibling inbred groups were established at four levels of inbreeding coefficient (F values of 0.25, 0.375, 0.5, and 0.5937). The growth traits of the control group (F ≈ 0) differed significantly from each of the inbred groups at three ages (80, 100 and 120 days old). Significant inbreeding depression was found in all inbred groups (P < 0.05) and this ranged from −2.55 to −21.75 %, and there was a tendency for inbreeding depression to increase with increasing F value and age. At 120 days old, inbreeding depression was 7.6, 15.30, 16.89 and 21.75 % for the F values of 0.25, 0.375, 0.50 and 0.5937, respectively. Moreover, there was a tendency for inbreeding depression of body weight to increase with the increasing age; for example, inbreeding depression was greater at 120 days compared to that of 80 and 100 days old. Inbreeding depression per 10 % increase in the inbreeding coefficient value ranged from −1.02 to −4.08 %. The genetic parameter (e.g., PIC, n a , a e , Ho and He values) decreases with the increasing level of inbreeding. The greatest changes in the various genetic results are between the control group and the group (F = 0.25), thereafter the rate of loss slows. This present study demonstrates that inbreeding has negative effects on growth traits and genetic diversity in P. trituberculatus, thus strengthening the case to maximize genetic diversity in selective breeding programs.

Parental genetic diversity of brown trout (Salmo trutta m. fario) brood stock affects offspring susceptibility to whirling disease.

BackgroundWhirling disease, caused by the myxozoan parasite Myxobolus cerebralis, has high economical and ecological importance worldwide. Susceptibility to the disease varies considerably among salmonid species. In brown trout (Salmo trutta) the infection is usually subclinical with low mortality, which increases the risk of parasite dissemination, especially when farm fish are used for stocking natural habitats. The influence of intraspecific genetic differences (especially the level of homozygosity) on susceptibility is unknown. Therefore, we examined the possible correlations between parental genetic diversity and offspring susceptibility of brown trout stocks to whirling disease.MethodsTwo brown trout brood stocks from a German and a Hungarian fish farm were genetically characterized using microsatellite and lineage-specific genetic markers. The individual inbreeding coefficient f and pairwise relatedness factor r were estimated based on eight microsatellite markers. Brood stock populations were divided into groups according to low and high f and r value estimates and subjected to selective fertilization. The offspring from these separate groups were exposed to M. cerebralis actinospores, and the infection prevalence and intensity was measured and statistically analysed.ResultsThe analysis of phylogeographic lineage heritage revealed high heterogeneity in the Hungarian brood stock since > 50% of individuals were Atlantic-Danubian hybrids, while only pure Atlantic-descending specimens were detected in the German population. Based on fmsat and rmsat estimations, classified non-inbred (NIB), inbred (IB) and a group of closely related fish (REL) were created. The susceptibility of their offspring varied considerably. Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups. In REL and IB groups, a high variability was observed in infection intensity. No external clinical signs were observed in the exposed brown trout groups.ConclusionsOur findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.

Yield trait improvement of bay scallops following complete diallel crosses between different scallop stocks

This study describes the complete diallel hybridization between newly introduced bay scallop stock (W) from Canada and local commercial stock (D) grown under laboratory conditions, in China. Larval survival and growth during all life stages (larvae, spat, and adult) were compared among hybrid (DW, WD) and purebred (DD, WW) populations. Significant heterosis was detected for survival during the larval stage (> 1% of the mid-parent values). The mean heterosis (H (m)) varied in growth throughout the life span. More than 50% of the H (m) values were positive and negative in the DW and WD groups, respectively. The influence of maternal effects and mating types (intrapopulation vs. interpopulation crosses) on growth for all life stages was not consistent. Larval survival did not differ significantly (P > 0.05) with maternal effect or mating type. In the harvest stage, shell length (SL), shell height (SH), shell width (SW), and total weight (TW) were larger in the hybrid compared with the inbred groups. Positive H (m) values were observed in SL (1.5%), SW (5.8%), and TW (12.3%), and were more significant in the DW groups (6.1%, 4.5%, 6.8%, and 27.2%). These results suggest that hybridization between two geographic populations is a good tool for improving bay scallop growth. However, unstable heterosis between the two populations requires further study.