Home About us Contact
|
Home About us Contact | ||
|
|
||
Hybrid Vigour (hybrid + vigour)
Selected AbstractsSynergistic epistasis and alternative hypothesesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2004S. Trouve Abstract Inbreeding generally results in deleterious shifts in mean fitness. If the fitness response to increasing inbreeding coefficient is non-linear, this suggests a contribution of epistasis to inbreeding depression. In a cross-breeding experiment, Salathé & Ebert (2003. J. Evol. Biol. 16: 976,985) tested and found the presence of this non-linearity in Daphnia magna. They argue that epistatic interactions cause this non-linearity. We argue here that their experimental protocol does not allow disentangling the effect of synergistic epistasis from two alternative hypotheses, namely hybrid vigour and statistical non-independence of data. [source] Physiological performance of largemouth bass related to local adaptation and interstock hybridization: implications for conservation and managementJOURNAL OF FISH BIOLOGY, Issue 2001S. J. Cooke Four genetically distinct stocks of age 2+ years largemouth bass Micropterus salmoides were produced using adults collected from two regions in the upper midwest (central Illinois, IL and south-eastern Wisconsin, WI, U.S.A.). Two pure stocks (IL × IL and WI × WI), as well as both of their reciprocal F1 interstock hybrids (IL × WI and WI × IL) were produced in research ponds in Champaign, IL. In general, swimming performance, routine oxygen consumption and activity were highest at 18 × C, intermediate at 12 × C, and lowest at 6. C for all stocks. However, performance indicators varied among stocks at each of the temperatures. The pure Illinois stock (IL × IL) had the lowest activity: cost ratio at 18 × C and the highest at 6_ C (based upon swimming strength, routine activity rates and routine metabolic rates). The opposite pattern was observed for the other pure stock (WI × WI). Although differences were less distinct at lower temperatures, the two pure stocks (IL × IL and WI × WI) outperformed both interstock hybrids. These results indicate that not only do non-native stocks appear to have reduced performance relative to locally adapted stocks, but also that interstock hybrids exhibit performance impairments, not hybrid vigour. [source] Heritability of Phenols in the Resistance of Theobroma cacao against Phytophthora megakarya, the Causal Agent of Black Pod DiseaseJOURNAL OF PHYTOPATHOLOGY, Issue 9 2007P. F. Djocgoue Abstract The black pod disease caused by Phytophthora megakarya is responsible for 80% of the cocoa production loss in Cameroon. To assess the resistance of cocoa plants against this pathogen, necrotic lesions, phenolic content and qualitative alteration of phenolics were conducted in ICS84 and ICS95 clones (two Trinitario introduced from Trinidad) and their hybrids (families F30 and F25) derived from reciprocal cross breeding between these two parental clones after inoculation. The existence of strong hybrid vigour has been shown. Ninety percentage of the hybrid's genotypes manifested a positive heterosis effect for the development of lesion size. This suggests the existence of hybrid vigour with a genetic additive effect. F3086, F2509, F2552 and F2586 hybrids were characterized by localized lesions. Those hybrids genotypes can be considered as elite clones. In relation to analysis of total phenolics and lesion size, no maternal effect was detected in the transmission of these characters. A significant and negative correlation (r = ,0.683) (P < 0.01) has been observed between necrosis evolution and phenolics accumulation. The values of the heritability of lesion size and the total phenolic content in offsprings did not permit to show the maternal effect. Qualitative analyses of phenolics showed high flavonones content in cocoa leaves. Qualitative analyses of phenolics in ICS84, ICS95 clones and their hybrids showed a modification of the phenolics profiles, notably concerning apigenin and luteolin derivatives due to the inoculation. These compounds, along with others that were not identified, could have a role in the reaction and mechanism of defence of cocoa against P. megakarya. [source] Ascorbate-dependent hydrogen peroxide detoxification and ascorbate regeneration during germination of a highly productive maize hybrid: Evidence of an improved detoxification mechanism against reactive oxygen speciesPHYSIOLOGIA PLANTARUM, Issue 1 2000Laura De Gara Ascorbate content and the activities of some key enzymes involved in the detoxification from reactive oxygen species were investigated in germinated embryos of two Zea mays L. inbred lines (B73 and Mo17) and of their heterotic F1 hybrid (B73×Mo17). The F1 hybrid showed a higher ascorbate biosynthetic capability owing to a higher activity of l -galactono- , -lactone dehydrogenase (EC 1.6.5.4), the last enzyme in ascorbate biosynthesis. Ascorbate peroxidase (EC 1.11.1.11), ascorbate free radical reductase (EC 1.6.5.4) and dehydroascorbate reductase (EC 1.8.5.1) activities were much higher in the F1 hybrid than in either inbred line, whereas catalase (EC 1.11.1.6) activity was similar in the three genotypes. Native polyacrylamide gel electrophoresis (PAGE) analysis showed three forms of cytosolic ascorbate peroxidase, both in parental lines and in the F1 hybrid. On the other hand, a complex pattern of proteins with dehydroascorbate reductase activity was observed, with the hybrid combining the different dehydroascorbate-reducing proteins expressed by the inbred lines. The possible involvement of the enzymes of the ascorbate system in the phenomenon of hybrid vigour is discussed. [source] Fertilization, hatching, survival and growth rates in reciprocal crosses of two strains of an African catfish Heterobranchus longifilis Valenciennes 1840 under controlled hatchery conditionsAQUACULTURE RESEARCH, Issue 7 2000D Nguenga A diallelic cross between two strains [Layo strain (LS) and Noun strain (NS)] of the catfish Heterobranchus longifilis Valenciennes was carried out under controlled hatchery conditions to estimate their reproductive performance and aquaculture potential in terms of fertilizability, hatchability, survival, growth and heterosis. The average fertilization rate of all mating groups was as high as 90.4%, the fertilization rate of the purebred NS (95.2%) being significantly higher than that of the purebred LS or the reciprocal crosses (P <,0.05). The average hatching rate of all genetic groups was as high as 84.7%, the hatching rate of NS (89.4%) being significantly higher than that of the purebred LS or the reciprocal crosses (P <,0.05). The mean survival rate of all crosses from hatching up to the onset of exogenous feeding stood at 94.2%, without showing a significant difference (P >,0.05) between the crosses. During the larval rearing period, which extended from the onset of exogenous feeding up to 15 days of age, NS displayed a significantly lower growth rate (P <,0.001) than that of the purebred LS and their reciprocal hybrids. There was no significant difference (P >,0.05) in survival rate (mean 84.7%) between the four crosses at the end of the larval rearing period. During the juvenile rearing phase, the mean growth performance of all crossbreds was similar to that of the purebred LS and significantly different from that of the purebred NS (P <,0.001). The final individual weights attained by LS, NS, LS × NS and NS × LS were 3.31, 0.71, 3.97 and 3.66 g respectively. The increase in weight attained by the fast-growing crossbred LS × NS was 562.2%, 20.4% and 8.7% more than that of NS, LS and NS × LS respectively. The survival rate of NS (57.1%) was significantly lower (P <,0.001) than that of all the rest of the crosses. The crossbreds displayed about 15.1% heterosis in mean body weight relative to the fast-growing purebred LS. It was concluded that cross-breeding of H. longifilis strains could be advantageous because of the hybrid vigour in the progeny. [source] Cross- and self-fertilization of plants , Darwin's experiments and what we know nowBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009SIMON J. OWENS The scientific work recorded by Darwin in his book on the cross- and self-fertilization of plants is an exemplar of interesting choices, careful technique, decades of work and methodical analyses that provided a plethora of robust results. The conclusions Darwin drew from his studies are, for the most part, valid and still relevant today. They focus primarily on providing data to support Darwin's hypothesis about the nature and importance of the benefits derived from cross-fertilization, although he conceded that a few plants seem to be invariably self-fertilized. The work is also a significant forerunner for the concepts of hybrid vigour and inbreeding depression. A wealth of information relating to flowers, flowering time, pollen efficacy, the results of cross- and self-pollination, the behaviour and impact of insects, seed and seed germination and plant breeding systems is scattered throughout the book. Darwin also related this book to several others he wrote in which some of these topics are included. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 357,395. [source] | |||||||||||||