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F2 Hybrids (f2 + hybrid)
Selected AbstractsCross-species amplification of microsatellite loci in Aquilegia and Semiaquilegia (Ranunculaceae)MOLECULAR ECOLOGY RESOURCES, Issue 2 2005JI Y. YANG Abstract We developed 16 microsatellite loci from an F2 hybrid between Aquilegia formosa and Aquilegia pubescens. In samples of 28 individuals, we found an average of 14 alleles per locus from each parental species. We tested these loci for cross-amplification in 10 additional species of Aquilegia and found that all 16 loci amplified in other North American species and 12 consistently amplified in European or Asian species. Nine loci amplified in the sister species to Aquilegia, Semiaquilegia adoxoides. The success of cross-species amplification suggests that these microsatellites should prove useful for studies in a broad range of Aquilegia species. [source] Calcium taste preferences: genetic analysis and genome screen of C57BL/6J × PWK/PhJ hybrid miceGENES, BRAIN AND BEHAVIOR, Issue 6 2008M. G. Tordoff To characterize the genetic basis of voluntary calcium consumption, we tested C57BL/6J mice (B6; with low avidity for calcium), PWK/PhJ mice (PWK; with high avidity for calcium) and their F1 and F2 hybrids. All mice received a series of 96-h two-bottle preference tests with a choice between water and the following: 50 mm CaCl2, 50 mm calcium lactate, 50 mm MgCl2, 100 mm KCl, 100 mm NH4Cl, 100 mm NaCl, 5 mm citric acid, 30 ,m quinine hydrochloride and 2 mm saccharin. Most frequency distributions of the parental and F1 but not F2 groups were normally distributed, and there were few sex differences. Reciprocal cross analysis showed that B6 × PWK F1 mice had a non-specific elevation of fluid intake relative to PWK × B6 F1 mice. In the F2 mice, trait correlations were clustered among the divalent salts and the monovalent chlorides. A genome screen involving 116 markers showed 30 quantitative trait loci (QTLs), of which six involved consumption of calcium chloride or lactate. The results show pleiotropic controls of calcium and magnesium consumption that are distinct from those controlling consumption of monovalent chlorides or exemplars of the primary taste qualities. [source] Allochronic differentiation among Daphnia species, hybrids and backcrosses: the importance of sexual reproduction for population dynamics and genetic architectureJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2004T. Jankowski Abstract Seasonal dynamics of the abundance, sexual reproduction and genetic architecture in a Daphnia hyalina-galeata hybrid complex were studied in the large and deep Lake Constance. We found evidence for the occurrence of first and second order hybridization. Our study revealed strong differences between the parental species not only regarding their seasonal dynamics, genetic architecture and diversity, but also their sexual reproductive behaviour. The overwintering D. hyalina showed low genetic diversity, no genetic differentiation during the season, and reproduced sexually in autumn, whereas D. galeata reached higher levels of genetic diversity, reproduced sexually in early summer, and exhibited changes in genetic structure during the season, but was only present from spring to autumn. However, in both species sexual reproduction was a rare event, and daphnids, including hybrids, reproduced predominantly asexually. This allows long-term persistence of hybrids as well without continuing hybridization events. Within all variables studied, F1 and F2 hybrids showed an intermediate pattern, whereas proposed backcross hybrids were more similar to their respective parentals. These differences in phenotype as well as significant differences in pairwise Fst values between parentals suggest that gene flow seems to be relatively low in the Lake Constance hybrid system. We found evidence for unidirectional introgression by backcrossing from D. galeata to D. hyalina and found a decrease in at least one of the proposed introgressed alleles in the hyalina -backcross while the season progressed. Our findings suggest allochronic differentiation within this hybrid population and different microevolutionary trajectories of the parental species, which will be discussed in the light of the ongoing reoligotrophication process of Lake Constance. [source] Reproductive isolation and hybrid pollen disadvantage in IpomopsisJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2003D. R. Campbell Abstract One cause of reproductive isolation is gamete competition, in which conspecific pollen has an advantage over heterospecific pollen in siring seeds, thereby decreasing the formation of F1 hybrids. Analogous pollen interactions between hybrid pollen and conspecific pollen can contribute to post-zygotic isolation. The herbaceous plants Ipomopsis aggregata and I. tenuituba frequently hybridize in nature. Hand-pollination of I. aggregata with pollen from F1 or F2 hybrids produced as many seeds as hand-pollination with conspecific pollen, suggesting equal pollen viability. However, when mixed pollen loads with 50% conspecific pollen and 50% hybrid pollen were applied to I. aggregata stigmas, fewer than half of the seeds had hybrid sires. Such pollen mixtures are frequently received if plants of the two species and F1 and F2 hybrids are intermixed, suggesting that this advantage of conspecific over hybrid pollen reduces backcrossing and contributes to reproductive isolation. [source] A Polymorphism in the ,4 Nicotinic Receptor Gene (Chrna4) Modulates Enhancement of Nicotinic Receptor Function by EthanolALCOHOLISM, Issue 5 2003Christopher M. Butt Background: Several studies indicate that ethanol enhances the activity of ,4,2 nicotinic acetylcholine receptors (nAChR). Our laboratory has identified a polymorphism in the ,4 gene that results in the substitution of an alanine (A) for threonine (T) at amino acid position 529 in the second intracellular loop of the ,4 protein. Mouse strains expressing the A variant have, in general, greater nAChR-mediated 86Rb+ efflux in response to nicotine than strains with the T variant. However, the possibility of the polymorphism modulating the effects of ethanol on the 86Rb+ efflux response has not been investigated. Methods: We have used the 86Rb+ efflux method to study the acute effects of ethanol on the function of the ,4,2 nAChR in the thalamus in six different mouse strains. Experiments were also performed on tissue samples taken from F2 intercross animals. The F2 animals were derived from A/J mice crossed with a substrain of C57BL/6J mice that carried a null mutation for the gene encoding the ,2 nAChR subunit. Results: In strains carrying the A polymorphism (A/J, AKR/J, C3H/Ibg), coapplication of ethanol (10,100 mM) with nicotine (0.03,300 ,M) increased maximal ion flux when compared with nicotine alone with no effect on agonist potency. In contrast, ethanol had little effect on the nicotine concentration-response curve in tissue prepared from strains carrying the T polymorphism (Balb/Ibg, C57BL/6J, C58/J). Experiments with the F2 hybrids demonstrated that one copy of the A polymorphism was sufficient to produce a significant enhancement of nAChR function by ethanol (50 mM) in animals that were also ,2 +/+. Ethanol had no effect on nicotine concentration-response curves in T/T ,2 +/+ animals. Conclusions: The results suggest that the A/T polymorphism influences the initial sensitivity of the ,4,2 nAChR to ethanol. [source] Heterosis performance of yield and fibre quality in F1 and F2 hybrids in upland cottonPLANT BREEDING, Issue 3 2004Y. T. Wu Abstract Because of the difficulty of producing F1 hybrid seeds by hand emasculation and pollination, wide use of heterosis in cotton production has been limited in China. The objective of this study was to evaluate the potential of F2 hybrids for yield and fibre quality. A half diallel involving eight parents and their F1 and F2 hybrids was grown in replicated studies at Linqing and Nanjing in 1999 and Nanjing in 2000. Yield and fibre quality was determined for all 64 entries. Fibre quality was also determined for parents and F1s, but only for Zhongmiansuo 28 (ZMS28), Xiangzamian 2 (XZM2) and Wanmian 13 (WM13) F2s. These three F2 hybrids are extensively planted in China and provide experimental controls with which to compare the performance of new hybrids. Average yield heterosis for F1s and F2s was 15.9 and 9.2%, respectively. Inbreeding depression for yield varied but some F2s greatly out-yielded the best variety. Average F1 heterosis was 6.7, 6.2 and 2.9%, respectively for number of bolls per unit area, boll weight, and lint percentage. The average F2 heterosis for the same traits was 4.4, 3.3 and 1.6%, respectively. F1 heterosis for fibre traits was low. In general, parental average was a good indicator of the yield and fibre quality of F1 hybrids. These encouraging results suggest there is sufficient heterosis for yield to use F2s in China. [source] Heterosis for yield and other agronomic traits of winter triticale F1 and F2 hybridsPLANT BREEDING, Issue 4 2001G. Oettler Abstract Triticale is generally treated as a self-pollinating crop and line breeding is practised. Hybrid breeding has been discussed for some time, but there is little information for winter triticale. This study investigated heterosis for eight agronomic traits in F1 and F2 hybrids grown together with their parents as drilled plots in three environments. On average, grain yield heterosis was 12.5 dt/ha (a relative 10.5%) compared with the mid-parent value for F1 hybrids, and 6.2 dt/ha (5.0%) for F2 hybrids and withawide range of 4.4,17.1 dt/ha for F1 hybrids. A positive contribution to the heterosis of yield was made by kernels/spike and 1000-kernel weight, whereas spikes/m2 showed negative heterosis. Hybrid plants in F1 and F2 were taller than mid-parents (8.3 cm and 5.3 cm, respectively), with a tendency to earlier heading. The negative heterosis for falling number in F1 and F2 hybrids could be a problem for commercial production of triticale hybrids. By selecting parents for combining ability and the identification of heterotic patterns, grain yield heterosis of 20% appears feasible. [source] Detection of arthritis-susceptibility loci, including Ncf1, and variable effects of the major histocompatibility complex region depending on genetic background in ratsARTHRITIS & RHEUMATISM, Issue 2 2009Carola Rintisch Objective To characterize the arthritis-modulating effects of 3 non,major histocompatibility complex (MHC) quantitative trait loci (QTLs) in rat experimental arthritis in the disease-resistant E3 strain, and to investigate the disease-modulating effects of the MHC region (RT1) in various genetic backgrounds. Methods A congenic fragment containing Ncf1 along with congenic fragments containing the strongest remaining loci, Pia5/Cia3 and Pia7/Cia13 on chromosome 4, were transferred from the arthritis-susceptible DA strain into the background of the completely resistant E3 strain. The arthritis-regulatory potential of the transferred alleles was evaluated by comparing the susceptibility to experimental arthritis in congenic rats with that in E3 rats. The RT1u haplotype from the E3 strain was transferred into the susceptible DA strain (RT1av1), and various F1 and F2 hybrids were generated to assess the effects of RT1 on arthritis susceptibility. Results The DA allele of Ncf1 did not break the arthritis resistance of the E3 rats, although it led to enhanced autoimmune B cell responses, as indicated by significantly elevated levels of anticollagen antibodies in congenic rats. Introgressing Pia5 and Pia7 loci on chromosome 4 broke the resistance to arthritis, and the MHC locus on chromosome 20 in DA rats enhanced arthritis when RT1 interacted with E3 genes. Conclusion The findings in these congenic lines confirm the existence of 3 major QTLs that regulate the severity of arthritis and are sufficient to induce the transformation of a completely arthritis-resistant rat strain into an arthritis-susceptible strain. This study also reveals a dramatic difference in the arthritis-regulatory potential of the rat MHC depending on genetic background, suggesting that strong epistatic interactions occur between MHC and non-MHC genes. [source] | |||||||||||||