The heterosis estimates for growth and survival traits in sterlet and Siberian sturgeon purebreds and hybrids

The aim of the present study was to estimate and compare the growth and survival traits of the hybrids and purebreds produced by crossing the Siberian sturgeon (Acipenser baerii) (S) and sterlet (Acipenser ruthenus) (St) in order to determine the heterosis effect in the F1 generation. We compared the breeding conditions, mean body weight (BW) and cumulative survival in the artificially produced hybrid crosses of sterlet and Siberian sturgeon with respect to their pure parental species in indoor and outdoor aquaculture systems at different developmental stages. Fertilization and hatching rates were found to be significantly higher in S × S purebred compared to St × S hybrid. The highest values of BW were recorded in St × S hybrid (557.54 ± 179.7 g) on 862 days post-hatch (dph) while the highest cumulative survival was recorded in S × S purebred (14.3%). The recorded cumulative survival and mean BW was significantly lower in St × St purebred. The highest positive heterosis was recorded for mean BW of St × S hybrid (51.3% on 862 dph) throughout the sampling points. The studied sturgeon hybrids had higher mean BW compared to St × St purebred under suboptimal rearing conditions. Although there was no clear demonstration of the superiority in performance of reciprocal hybrids over purebreds, the St × S hybrid can be used for achieving better productivity in aquaculture systems.     

Reproductive isolating mechanisms contributing to asymmetric hybridization in Killifishes (Fundulus spp.)

When species hybridize, one F1 hybrid cross type often predominates. Such asymmetry can arise from differences in a variety of reproductive barriers, but the relative roles and concordance of pre-mating, post-mating prezygotic, and post-zygotic barriers in producing these biases in natural animal populations have not been widely investigated. Here, we study a population of predominantly F1 hybrids between two killifish species (Fundulus heteroclitus and F. diaphanus) in which >95% of F1 hybrids have F. diaphanus mothers and F. heteroclitus fathers (D♀ × H♂). To determine why F. heteroclitus × F. diaphanus F1 hybrids (H♀ × D♂) are so rare, we tested for asymmetry in pre-mating reproductive barriers (female preference and male aggression) at a common salinity (10 ppt) and post-mating, pre-zygotic (fertilization success) and post-zygotic (embryonic development time and hatching success) reproductive barriers at a range of ecologically relevant salinities (0, 5, 10, and 15 ppt). We found that F. heteroclitus females preferred conspecific males, whereas F. diaphanus females did not, matching the observed cross bias in the wild. Naturally rare H♀ × D♂ crosses also had lower fertilization success than all other cross types, and a lower hatching success than the prevalent D♀ × H♂ crosses at the salinity found in the hybrid zone centre (10 ppt). Furthermore, the naturally predominant D♀ × H♂ crosses had a higher hatching success than F. diaphanus crosses at 10 ppt, which may further increase their relative abundance. The present study suggests that a combination of incomplete mating, post-mating pre-zygotic and post-zygotic reproductive isolating mechanisms act in concert to produce hybrid asymmetry in this system.     

Hybridization and F1 backcrosses between two closely related tropical species of sea urchins (genus Echinometra) in Okinawa

Summary

Four species of sea urchins of the genus Echinometra, designated species A, B, C, and D, occur along the coast of Okinawa; they are distinguished by color pattern and other characteristics. The two most distinct species, Echinometra sp. A (Ea) with white-tipped spines and Echinometra sp. D (Ed) with nearly black spines (possibly E. oblonga), were examined for potential hybridization through a series of fertilization experiments and rearing of the resulting hybrids. Fertilization was reciprocally asymmetrical; Ed ova were readily fertilized by sperm of Ea, but less than 20% of the ova of Ea were fertilized by sperm of Ed. Nevertheless, hybrids resulting from crosses in both directions developed normally through larval and juvenile stages to produce sexually mature adults. Larvae of Ed♀×Ea♂ and Ed♂×Ed♀ were larger than those of Ea♂ × Ed♀ and Ea♂ × Ea♀, reflecting the larger eggs of Ed. However, Ea♂×Ea♀ juveniles and later stages, up to maturity, were consistently larger than those of equivalent ages of the other crosses; largest to smallest were Ea♂×Ea♀, Ed♂×Ea♀, Ea♂ × Ed♀, and Ed♂×Ed♀, respectively. Ova and sperm of the hybrids were viable and fertilizable in all combination of crosses, although fertilization of those of Ed♂×Ea♀ hybrids was consistently higher than those of Ea♂ × Ed♀ hybrids. These experiments represent the first reported successful production of hybrid sea urchins with viable gametes. They indicate that reproductive isolation is achieved by prezygotic isolating mechanisms in these two species. Of these mechanisms, gametic incompatibility is probably only partly involved, if at all, and differences in spawning times, habitat segregation, or other factors appear to be important for maintaining reproductive isolation in these closely related species.     

Proteomic profiling of eggs from a hybrid abalone and its parental lines: Haliotis discus hannai Ino and Haliotis gigantea

Proteomic analysis was performed on the eggs of hybrid abalone and their corresponding parental lines. A total of 915 ± 19 stained protein spots were detected from Haliotis discus hannai♀ × H. discus hannai♂ (DD), 935 ± 16 from H. gigantea♀ × H. gigantea♂ (GG) and 923 ± 13 from H. gigantea♀ × H. discus hannai♂ (GD). The spots from DD and GD were clustered together. The distance between DD and GG was maximal by hierarchical cluster analysis. A total of 112 protein gel spots were identified; of these, 59 were abalone proteins. The proteins were involved in major biological processes including energy metabolism, proliferation, apoptosis, signal transduction, immunity, lipid metabolism, electron carrier proteins, protein biosynthesis and decomposition, and cytoskeletal structure. Three of 20 differential expression protein spots involved in energy metabolism exhibited as upregulated in GD, 13 spots exhibited additivity, and four spots exhibited as downregulated in the offspring. Eleven protein spots were expressed at the highest level in DD. The proteins involved in stress responses included superoxide dismutase, peroxiredoxin 6, thioredoxin peroxidase and glutathione‐S‐transferase. Two of seven differential expression protein spots involved in response to stress exhibited as upregulated in GD, three exhibited additivity, and two exhibited as downregulated. These results might suggest that proteomic approaches are suitable for the analysis of hybrids and the functional prediction of abalone hybridization.     

SEX DETERMINATION IN DIPLOID-TRIPLOID CROSSES OF SPINACIA OLERACEA

Mahoney , D. L. Jules Janick , and E. C. Stevenson . (Purdue U., Lafayette, Ind.) Sex determination in diploid-triploid crosses of Spinacia oleracea. Amer. Jour. Bot. 46(5): 372–375. 1959.—Segregation for sex in spinach was studied in a series of diploid pistillate × triploid staminate crosses. The genetic data indicated that the functional gametes from staminate triploids were not confined to n and n + 1 types. Cytological analyses of progenies from a number of 2n ♀ × 3n (XYY and XYY) ♂ crosses revealed similar but non-homogeneous types of chromosome segregation. These crosses produced 49.3% diploids, 17.9% trisomies, 0.5% with 14 chromosomes, 1.2% with 16 chromosomes, 11.4% with 17 chromosomes, 18.9% triploids, and 0.8% with 19 chromosomes. The reciprocal crosses produced a higher percentage of aneuploid types including 1.7% with 15 chromosomes. Segregation for sex in each of the various chromosome numbered progeny of diploid-triploid crosses was presented and analyzed.     

Effect of feeding frequency as a rearing system on biological performance,survival, body chemical composition and economic efficiency of Asian seabass Lates calcarifer (Bloch, 1790) reared under controlled environmental conditions

A 70-day rearing trial was done to determine the optimal frequency of feeding on growth performance (GP), feed conversion rate (FCR), cannibalism, survival rate (SR), body chemical composition and economic efficiency of the Asian sea bass. This study tested four different treatments of feeding frequencies (FF), once (T1), twice (T2), three times (T3), and four times (T4) per day. An average initial weight of Asian sea bass fry was 0.2 g (SD = ±0.12) were stocked 10 individuals per m³ (9.14 m × 1.82 m × 1.22 m, L × W × H; water depth 0.61 m) with two replicates per treatment (4 × 2 = 8). Fry were fed a mixture of larval commercial feed and shrimp with a pellet diet containing (46% CP). Initially, the feeding rate of 8% biomass per day was further adjusted according to fish biomass on a weekly basis. Results showed that, the FF significantly affected (p < 0.05) on growth indictors and survival rate (SR). Specifically fry fed three times a day (T3) had the best FBW, FL, SGR, ADWG and FCR followed by T4 and T2 while fry fed one time a day was the lowest in these parameters. Also, VSI, HSI and CF (k) significantly differed among the treatments. The fish whole body content of protein, moisture and ash did not significantly (p < 0.05) be affected by feeding frequency, but lipid content differed and both T3, T4 were the highest. It could be concluded that, increasing FF up to three times a day had a positive effect on weight gain, survival rate and feed utilization of Lates calcarifer. The second degree polynomial regression indicates that fed three times a day is optimum for best growth performance and survival for Asian sea bass.     

Development of a spermatogonia cryopreservation protocol for blue catfish,Ictalurus furcatus

Sustainability of channel catfish, Ictalurus punctatus ♀ × blue catfish, Ictalurus furcatus ♂ hybrid aquaculture relies on new innovative technologies to maximize fry output. Transplanting spermatogonial stem cells (SSCs) from blue catfish into channel catfish hosts has the potential to greatly increase gamete availability and improve hybrid catfish fry outputs. Cryopreservation would make these cells readily accessible for xenogenesis, but a freezing protocol for blue catfish testicular tissues has not yet been fully developed. Therefore, the objectives of this experiment were to identify the best permeating [dimethyl sulfoxide (DMSO), ethylene glycol (EG), glycerol, methanol] and non-permeating (lactose or trehalose with egg yolk or BSA) cryoprotectants, their optimal concentrations, and the best freezing rates (−0.5, −1.0, −5.0, −10 °C/min until −80 °C) that yield the highest number of viable type A spermatogonia cells. Results showed that all of these factors had significant impacts on post-thaw cell production and viability. DMSO was the most efficient permeating cryoprotectant at a concentration of 1.0 M. The optimal concentration of each cryoprotectant depended on the specific cryoprotectant due to interactions between the two factors. Of the non-permeating cryoprotectants, 0.2 M lactose with egg yolk consistently improved type A spermatogonia production and viability beyond that of the 1.0 M DMSO control. The overall best freezing rate was consistent at −1 °C/min, but similar results were obtained using −0.5 °C/min. Overall, we recommend cryopreserving blue catfish testicular tissues in 1.0 M DMSO with 0.2 M lactose and egg yolk at a rate of either -0.5 or −1 °C/min to achieve the best cryopreservation outcomes. Continued development of cryopreservation protocols for blue catfish and other species will make spermatogonia available for xenogenic applications and genetic improvement programs.     

Postprandial changes in pH and enzyme activity from the stomach and intestines of Tilapia rendalli (Boulenger, 1897), Oreochromis mossambicus (Peters, 1852) and Clarias gariepinus (Burchell, 1822)

The ability to utilise dietary components differs among fish species. Digestive enzymes may be used to determine the efficiency of the digestive process. In this study, the activities of the digestive enzymes in Tilapia rendalli, Oreochromis mossambicus and Clarias gariepinus were explored. Protease, amylase, lipase and cellulase activities were measured in different parts of the digestive tract of the three fish species. The pH dynamics along the digestive tract were monitored. In all fish species, the presence of food led to a reduction in stomach pH, whereby pH values of 1.54, 1.58 and 2.01 were recorded 12 h after feeding in O. mossambicus, T. rendalli and C. gariepinus, respectively. Protease and amylase activities were significantly higher (P < 0.05, anova ) in the tilapias than in C. gariepinus. The tilapias may be pre‐adapted to produce more protease and amylase to digest plant material, which is more difficult to digest than animal matter. In all species amylase activity was significantly higher in the proximal intestine than in the other parts of the digestive tract (P < 0.05, anova ). The highest protease activity was recorded in the distal intestines. This is because of the alkaline pH recorded in the proximal and distal intestines, which favours amylase and protease activity, respectively. Lipase activities were significantly higher (P > 0.05) in C. gariepinus than in both tilapias. Marginal cellulase activities were recorded in all species. It is inferred here that phylogeny and not diet may be the main factor influencing enzyme activities, as all fish were fed a similar diet.     

Nutritional profile of soaked Cajanus cajan (L.) Millsp. and its utilization as partial replacement for soybean meal in the diet of Clarias gariepinus (Burchell, 1822) fingerlings

This study aimed to investigate the efficacy of soaking as a cheap processing method in improving the nutritional utilization of Cajanus cajan for partial replacement of soybean meal in formulated diets of the African catfish Clarias gariepinus (Burchell, 1822). The nutrient profile of soaked C. cajan revealed a significant reduction (≤50%) in all anti‐nutritional factors. Proximate and amino acids were also affected by this processing method. Six practical diets (35 g/kg crude protein, 19.1 KJ/g diet) containing substitution levels of 0, 10, 20, 30, 40 and 50% C. cajan for soybean protein (included at 578 g/kg) were then formulated and fed to triplicate groups (n = 50 in each group) of C. gariepinus fingerlings (1.41 ± 0.06 g) in a hapa pond system (1 × 1 × 1 m³) for 56 days (mean temperature 25.3 ± 0.6). The results revealed that fish survival was not significantly affected until a 40% substitution of soybean was reached. However, beyond 20% soybean substitution, growth was significantly reduced (≥7%; p ≤ .05). Fish fed the highest substitution of soaked C. cajan meal (50% soybean replacement) had the poorest performance. The cost of the compound diets was substantially reduced with the inclusion of soaked C. cajan. Production costs of 1 kg fish using the diet with an inclusion of up to 20% soaked C. cajan meal replacement were comparable to using the control diet. It was concluded that soaking C. cajan seed for 24 hr improved the nutritional profile of the ingredients to replace 20% of the soybean (included at 57.8%) protein in the diet of C. gariepinus with no negative effect on growth and nutrient utilization.     

The roles of age,parentage and environment on bacterial and algal endosymbiont communities in Acropora corals

The bacterial and microalgal endosymbiont (Symbiodiniaceae spp.) communities associated with corals have important roles in their health and resilience, yet little is known about the factors driving their succession during early coral life stages. Using 16S rRNA gene and ITS2 metabarcoding, we compared these communities in four Acropora coral species and their hybrids obtained from two laboratory crosses (Acropora tenuis × Acropora loripes and Acropora sarmentosa × Acropora florida) across the parental, recruit (7 months old) and juvenile (2 years old) life stages. We tested whether microbiomes differed between (a) life stages, (b) hybrids and purebreds, and (c) treatment conditions (ambient/elevated temperature and pCO₂). Microbial communities of early life stage corals were highly diverse, lacked host specificity and were primarily determined by treatment conditions. Over time, a winnowing process occurred, and distinct microbial communities developed between the two species pair crosses by 2 years of age, irrespective of hybrid or purebred status. These findings suggest that the microbial communities of corals have a period of flexibility prior to adulthood, which can be valuable to future research aimed at the manipulation of coral microbial communities.     

Larval rearing of fringe-lipped carp,Labeo fimbriatus (Bloch) with low cost diets including green bottle fly Lucilia sericata (Meigen) larvae meal incorporated diet

A study was conducted with non-conventional ingredients to test their efficacy as fishmeal (FM) replacers in the diet of fringe- lipped carp. Labeo fimbriatus first feeding larvae and fry were reared for 30 and 60 days in indoor, 50 L, aerated, circular plastic tanks at 100 and 30 numbers tank⁻¹, respectively. In the first feeding larvae to fry rearing experiment (Exp. 1), the fish were fed with either of the following isonitrogenous and isocaloric diets – live plankton, FM diet, green bottle fly (Lucilia sericata) larvae meal (GBFLM) diet and silkworm pupa (SWP) diet. The fry to fingerling rearing (Exp. 2), was also conducted using the same diets described above except live plankton. All compounded diets were formulated to contain 40% crude protein for the experiment 1 and 35% for experiment 2 and were fed ad libitum. Triplicate tanks were maintained for each treatment in both the experiments. In Exp. 1, the mean final weight of fry was higher with plankton and FM diets, while no difference (p > .05) was observed between FM and GBFLM diets. Weight of fish fed SWP diets was not statistically different from those fed GBFLM diet. No difference (p > .05) in final length, survival and condition factor was recorded. Analysis of digestive enzyme activity of whole fish revealed lower (p < .05) activity of amylase in fish fed plankton. In Exp. 2, no difference (p > .05) was observed between the different diet groups in terms of mean final weight, length, survival and condition factor. Analysis of digestive enzyme activity of whole fish revealed no difference (p > .05) in the activity of digestive enzymes between the treatments except a lower (p < .05) activity of trypsin in FM diet and lipase in FM and GBFLM diets. Since the survival and condition factors of animals is the most important aspect during nursery rearing, similar (p > .05) values recorded in different treatments indicate the possibility of incorporation of these non-conventional protein sources in the diet of L. fimbriatus during first feeding larvae to fry and fry to fingerling rearing.     

Studies on the fungal infestation of five traditionally smoke-dried freshwater fish in Ago-Iwoye,Nigeria

Samples of traditionally smoke-dried Clarias gariepinus (Burchell), Chrysichthys nigrodigitatus (Lacepede), Sarotherodon galilaeus (Trewavas), Heterotis niloticus (Cuvier) and Heterobranchus bidorsalis (Geoffroy) were obtained from Oja Oba Market, Ago-Iwoye, Nigeria and examined for fungal infestation. The fish samples incubated on potato dextrose agar (PDA) for 7 days showed fungal infestation. Fungi isolated and identified included Mucor sp., Aspergillus sp., Rhizopus sp. and Fusarium sp. Six fungal species were isolated from C. nigrodigitatus, five each on C. gariepinus and H. niloticus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of production,early growth and survival ofClarias gariepinus (Burchell),Heterobranchus longifilis (Val.) (Pisces: Clariidae) and their F1 hybrids in ponds

Clarias gariepinus andHeterobranchus longifilis were successfully hybridized to produce reciprocal F₁ progeny during a two-year study.C. gariepinus produced significantly heavier spawn thanH. longifilis during the same period. Fertilized eggs were incubated in aerated static-water in fibre-glass troughs, and hatching rates were not found to be significantly different (P<0.05) between any two of the four catfish groups produced. Eight-day old fry of each group were reared in fertilized nursery ponds, and F₁ hybrids fromH. longifilis maternal parent had the best growth and survival rates at the end of 18 days. The reciprocal cross showed intermediate growth rate between both parents. At harvest, differential growth was less pronounced among both hybrids than among the parents.     

Reproductive performance of partial gonadectomized male African catfish, Clarias gariepinus broodstocks

This study was conducted to evaluate the effect of partial gonadectomy on reproductive performance of male Clarias gariepinus broodstock. Testes from C. gariepinus broodstock were surgically removed; 25% of the testes (Treatment 1), 50% of the testes (Treatment 2), 75% of the testes (Treatment 3), and removal of the sperm from the testes sac using syringe after the abdominal cavity had been cut open (Treatment 4) {control}. The incisions were sutured and the fish kept inside separate concrete tanks for 4 mo. The incisions closed up within 8 to 9 wk of surgery. The postsurgical survival of C. gariepinus was 100%, indicating the efficiency of the surgical procedure. There was no significant difference (P > 0.05) in sperm production, percentage fertilization, hatchability and survival of the larvae using sperm derived from regenerated testes of the partially gonadectomized C. gariepinus and nongonadectomized C. gariepinus. It also reveals that partial gonadectomy could not alter the quality of sperm production of C. gariepinus. Sperm derived from regenerated testes performed effectively for fertilization of eggs. Based on the results of this study, the removal of 75% of testes during partial gonadectomy proved to be the best as the total number of spermatozoa was more than that of other methods and the sperm was able to fertilize more eggs. Hence the removal of 75% of testis during partial gonadectomy of C. gariepinus is recommended based on the results of this study.     

Impact of pre‐ and post‐pollination barriers on pollen transfer and reproductive isolation among three sympatric Pedicularis (Orobanchaceae) species

• Pedicularis is the largest genus in the Orobanchaceae (>300) with many species co‐occurring and co‐blooming in subalpine to alpine meadows in the Himalayas. Although it is well known that different Pedicularis species place pollen on different parts of the same bumblebee's body, thus reducing interspecific pollen transfer, it is not known whether post‐pollination components also contribute to reproductive isolation (RI).
• In this study, we quantified the individual strengths and absolute contributions of six pre‐ and post‐pollination components of RI between three sympatric species in two pairs; Pedicularis gruina × Pedicularis tenuisecta (gru × ten) and Pedicularis comptoniifolia × Pedicularis tenuisecta (com × ten).
• All three Pedicularis species shared the same Bombus species. Individual foragers showed a high, but incomplete, floral constancy for each species. Therefore, pre‐pollination barriers were potentially ‘leaky’ as Bombus species showed a low but consistent frequency of interspecific visitation. The RI strength of pre‐pollination was lower in com × ten than in gru × ten. In contrast, post‐pollination barriers completely blocked gene flow between both sets of species pairs. Two post‐pollination recognition sites were identified. Late acting rejection of interspecific pollen tube growth occurred in com♀ × ten♂, while seeds produced in bi‐directional crosses of gru × ten failed to germinate.
• We propose that, although floral isolation based on pollen placement on pollinators in the genus Pedicularis is crucial to avoid interspecific pollen transfer, the importance of this mode of interspecific isolation may be exaggerated. Post‐pollination barriers may play even larger roles for currently established populations of co‐blooming and sympatric species in this huge genus in the Himalayas.

     

Critical swimming speed of sterlet (Acipenser ruthenus): Does intraspecific hybridization affect swimming performance?

We studied the effect of intraspecific hybridization on swimming performance in sterlet, hypothesizing that such hybridization increases the performance by inducing the hybrid vigor. A total of 12 purebred and hybrid crosses were reproduced from Danube (D) and Volga (V) populations of Acipenser ruthenus. Within each cross, one group of fish was exposed to temperature challenges mimicking the temperature variation in the natural environment during summer. Temperature challenges comprised a constant increase from 19°C to 24°C and then return to 19°C within 12 hr (dT<1°C/hr), and were carried out every third day over the experimental period of 20 days. As a control, fish from each cross were kept at a constant temperature of 19°C. Critical swimming speed (U_crit) was assessed on day 0 (29 days post hatch, dph), 10 (39 dph) and 20 (49 dph). The critical swimming speeds ranged from 5.12 cm/s (1.63 TL/s) to 16.44 cm/s (2.4 TL/s) during the experimental period (29–49 dph). There were no significant differences observed in U_crit between repeatedly temperature challenged and control groups, indicating that the temperature challenge did not alter the swimming performance. The critical swimming speed showed positive relationship with total body length. Comparing intraspecific hybrid crosses with purebred crosses, no significant difference in swimming performance was observed. It is thus concluded that swimming performance is a family specific trait. There is no indication that intraspecific hybridization affects swimming performance nor that close‐to‐natural temperature regimes increase swimming performance.     

Effect of stocking density on growth and survival of Clarias batrachus (Linn.) larvae and fry during hatchery rearing

Experiments were conducted to determine optimum stocking density for Clarias batrachus larvae and fry during hatchery rearing. The increase in stocking density decreased the total weight, specific growth rate (SGR) and percent weight gain of Clarias larvae during a 13‐day experiment. Survival rate was highest at a stocking density of 1000 m^?2 and lowest at 5000 m^?2. Stocking density did not influence the total biomass production of larvae. Clarias batrachus fry performance was studied during a 28‐day hatchery rearing experiment whereby fry stocked at a density of 100 m^?2 attained the highest total body weight (P < 0.05). The survival rate greatly declined to 59–61% by a density increase to 300 m^?2 and above. Stocking density influenced growth and survival of C. batrachus larvae and fry during hatchery rearing. The best performance was obtained when larvae were stocked at 2000 m^?2; survival was highest with C. batrachus fry stocked at 200 m^?2.     

Three representative inter and intra‐subspecific crosses reveal the genetic architecture of reproductive isolation in rice

Systematic characterization of genetic and molecular mechanisms in the formation of hybrid sterility is of fundamental importance in understanding reproductive isolation and speciation. Using ultra‐high‐density genetic maps, 43 single‐locus quantitative trait loci (QTLs) and 223 digenic interactions for embryo‐sac, pollen, and spikelet fertility are depicted from three crosses between representative varieties of japonica and two varietal groups of indica, which provide an extensive archive for investigating the genetic basis of reproductive isolation in rice. Ten newly detected single‐locus QTLs for inter‐ and intra‐subspecific fertility are identified. Three loci for embryo‐sac fertility are detected in both Nip × ZS97 and Nip × MH63 crosses, whereas QTLs for pollen fertility are not in common between the two crosses thus leading to fertility variation. Five loci responsible for fertility and segregation distortion are observed in the ZS97 × MH63 cross. The importance of two‐locus interactions on fertility are quantified in the whole genome, which identify that three types of interaction contribute to fertility reduction in the hybrid. These results construct the genetic architecture with respect to various forms of reproductive barriers in rice, which have significant implications in utilization of inter‐subspecific heterosis along with improvement in the fertility of indica–indica hybrids at single‐ and multi‐locus level.     

Genetic variations in the SPP1 promoter affect gene expression and the level of osteopontin secretion into bovine milk

Osteopontin (OPN) is now recognized as an important cytokine and extracellular integrin‐binding protein at the crossroads of inflammation and homeostasis. In a previous study, we found that OPN gene (SPP1) polymorphisms are associated with milk performance traits and somatic cell score (SCS), a parameter used to estimate the genetic value of udder health in dairy cattle. In this study, we assessed whether the genetic variations had an impact on SPP1 promoter activity, immune response and the level of OPN secreted into milk. The influence of DNA polymorphisms on the promoter activity of SPP1 was confirmed in vitro. To measure the impact of the genetic variations on OPN secretion into milk, we measured OPN levels in both plasma and milk throughout lactation. Cows were grouped by the OPN haplotypes associated with a high (H2 × H3) or low (H1 × H4) SCS. For both H2 × H3 and H1 × H4, the OPN level in plasma remained low throughout lactation, although the concentration in the milk of H1 × H4 cows increased more in late lactation. Moreover, the macrophages of H1 × H4 cows expressed a lower SPP1 and proinflammatory IL6 in response to infection. Regarding the immune cell response, cows with the genetic potential to secrete higher OPN levels during late lactation had macrophages expressing fewer proinflammatory cytokines, a situation that might explain the genetic association with low somatic cells. Although OPN's favorable roles during late lactation remain to be elucidated, the tissue remodeling properties associated with OPN may be beneficial for reducing the incidence of infection during the transition period in lactating cows.