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排序方式: 共有41条查询结果,搜索用时 15 毫秒
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Kerr RJ Graser HU Kinghorn BP Johnston DJ 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》1994,111(1-6):110-120
SUMMARY: Ambiguous paternity can be incorporated into the mixed model equations (MME) by including the average numerator relatinship matrix (average A), which averages the true sire-offspring relationship over the putative sires. A previous study has shown that some overestimation of genetic trend results from this substitution. A population of 40 breeding females and 2 breeding males was simulated 1,000 times with either random mating or sequential selection continuing for 8 breeding cycles. In the selection case candidates were ranked on estimated breeding values (EBVs) calculated from the MME with an animal model and the average A. Variances of the EBVs and prediction errors were computed. The results showed the average A incorrectly perceives both the variance of family sizes among males and the variance loss due to selection to be smaller. This will lead to an overestimation of genetic trend. ZUSAMMENFASSUNG: Folgerungen aus der Anwendung einer durchschnittlichen Verwandtschaftsmatrix bei der Zuchtwertsch?tzung für eine Population mit mehreren V?tern in einer Paarungsgruppe In den Mischmodellgleichungen kann eine unklare v?terliche Abstammung durch die Verwendung einer durchschnittlichen Verwandtschaftsmatrix, die die Abstammung zu gleichen Teilen über die m?glichen V?ter aufteilt, berücksichtigt werden. Eine frühere Arbeit hat gezeigt, da? diese Ma?nahme zu einer gewissen übersch?tzung des genetischen Fortschritts führt. Eine Population mit 40 weiblichen und 2 m?nnlichen Tieren wurde 1000mal über 8 Paarungsperioden simuliert und zwar mit und ohne gerichteter Selektion. Im Falle der Selektion wurden die Tiere aufgrund der mit einem Tiermodell und der durchschnittlichen Verwandtschaftsmatrix gesch?tzten Zuchtwerte geordnet. Die Varianzen der Zuchtwerte und der Sch?tzfehler wurden berechnet. Die Ergebnisse zeigen, da? durch eine durch-schnittliche Verwandtschaftsmatrix die Varianz der Gr??e der Nachkommensgruppen der V?ter und der Verlust an genetischer Varianz aufgrund der Selektion untersch?tzt wird. Dies führt zu einer übersch?tzung des genetischen Fortschritts. 相似文献
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Uri Gerson 《Soil biology & biochemistry》1983,15(1):105-110
Twenty six species of pteridophytes (ferns and fern allies) were offered to the soil mite Rhizoglyphus robini Claparède (Acari: Astigmata: Acaridae) in Petri dishes. All plants provided nutrients and promoted growth of mite populations. Leaves of sixteen (61.5%) species were totally consumed or skeletonized while green, another seven only upon browning. The remaining three were left intact even after 3 months, although sori and their leachates provided food for the mites. Paper impregnated with pteridophyte leachates was consumed and encouraged mite reproduction. These findings neither support nor oppose the view that pteridophytes are under-utilized by arthropods but the adaptability of the specific experimental organism might have affected the results. Invertebrates feeding on dead, decomposing pteridophytes possibly reduce the latters' allelopathy to other plants. The ability of Rhizoglyphus to subsist on plant leachates, as well as bacteria or fungi developing thereon, could explain the mode of survival of this and other soil arthropods in deep, mineral soil strata. 相似文献
5.
Utilization of the genetic resources of wild species to create a nontransgenic high flavonoid tomato
Willits MG Kramer CM Prata RT De Luca V Potter BG Steffens JC Graser G 《Journal of agricultural and food chemistry》2005,53(4):1231-1236
Flavonoids represent a large and important group of plant natural products that are ubiquitous in the plant kingdom. Epidemiological studies have shown the health benefits of a diet high in flavonoids. However, the dietary intake of flavonoids in most western populations is limited, creating a need to find alternative food sources for these polyphenolic secondary metabolites. The domestication of many of our cultivated food crops has resulted in alterations in the biosynthetic pathways of many essential micronutrients and vitamins through inadvertent counterselection against nutritional traits in favor of agronomic ones. Flavonoids are nearly absent from fruits of cultivated tomato (Lycopersicon esculentum Mill.), a major vegetable in human diets. Previous attempts to restore the flavonoid pathway in tomato fruits have been limited to transgenic strategies, suggesting that the problem was intractable through traditional methods. Here, we describe for the first time a nontransgenic metabolic engineering approach to developing a high flavonoid tomato using a wild tomato species (Lycopersicon pennelliiv. puberulum) and demonstrate the opportunities for restoring functional pathways using the genetic resources of wild species, resulting in production of healthier foods. 相似文献
6.
Cyhexatin, dienochlor and four experimental acaricides, U-25322 (1-benzoyl-3-phenylhydrazine), U-27415 1-benzoyl-3-(2, 4, 6-trichlorophenyl)hydrazine, U-42558 [N1(4-chloro-o-tolyl) N2-methyl-N1-(phenylthio)formamidine], and U-42564 [N2-methyl-N1-(phenylthio)- N1-(2, 4-xylyl)formamidine], at 125 mg litre-1, induced spindown by the carmine spider mite, Tetranychus cinnabarinus (Boisduval). Cyhexatin caused the largest number of mites to spin-down, dienochlor the least. Spinning occurred only during the first 6 h after treatment. Mites spun the same average length of threads in response to all compounds. The pattern of spin-down was even and similar for all the compounds except dienochlor for which it was sporadic. Acaricide-induced spin-down is postulated to be an ‘all-or-nothing’ reaction. 相似文献
7.
Daniela Basso FACCO Edicarla TRENTIN Gerson Laerson DRESCHER Rodrigo Knevitz HAMMERSCHMITT Carlos Alberto CERETTA Leandro Souza DA SILVA Gustavo BRUNETTO Paulo Ademar Avelar FERREIRA 《土壤圈》2023,33(3):496-507
Copper(Cu)-based fungicide application to control foliar diseases in grapevine(Vitis vinifera L.) can increase soil Cu availability. Brazilian soils have high natural Cu and manganese(Mn) concentrations, increasing the potential for toxicity to grapevine plants. Application of amendment substances can reduce the concentrations of toxic chemical species of Cu and Mn in soil solution, especially for the soils grown with young plants. We evaluated the chemical speciation of Cu and Mn in soil soluti... 相似文献
8.
Bruno C. Perez Julio C. C. Balieiro Roberto Carvalheiro Fabio Tirelo Gerson A. Oliveira Junior Juliana M. Dementshuk Joanir P. Eler Jos B. S. Ferraz Ricardo V. Ventura 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2019,136(1):23-39
The objective of the present study was to investigate the impact of considering population structure in cow genotyping strategies over the accuracy and bias of genomic predictions. A small dairy cattle population was simulated to address these objectives. Based on four main traditional designs (random, top‐yield, extreme‐yield and top‐accuracy cows), different numbers (1,000; 2,000 and 5,000) of cows were sampled and included in the reference population. Traditional designs were replicated considering or not population structure and compared among and with a reference population containing only bulls. The inclusion of cows increased accuracy in all scenarios compared with using only bulls. Scenarios accounting for population structure when choosing cows to the reference population slightly outperformed their traditional versions by yielding higher accuracy and lower bias in genomic predictions. Building a cow‐based reference population from groups of related individuals considering the frequency of individuals from those same groups in the validation population yielded promising results with applications on selection for expensive‐ or difficult‐to‐measure traits. Methods here presented may be easily implemented in both new or already established breeding programs, as they improved prediction and reduced bias in genomic evaluations while demanding no additional costs. 相似文献
9.
Robert G. S. Prado Chris H. Gardiner Mrcio A. O. Moura Gerson B. E. Gonzalez Marcos D. Duarte Tiago F. S. Santos Pedro S. Bezerra Valíria D. Cerqueira Alessandra S. Amaral Gabriela Riet-Correa 《Journal of veterinary diagnostic investigation》2021,33(5):949
A pig was in left lateral recumbency with limb spasticity, accentuated prostration, and strabismus, and was euthanized. During autopsy, yellowing of the leptomeninges at the ventral pons to medulla oblongata was noted. In the cerebellar peduncles, there was a focally extensive black-to-yellow area at the level of the vestibular nuclei. Histologic examination revealed a cross-section of a nematode larva, consistent with Stephanurus dentatus, bordered by edema and marked infiltration of mononuclear cells, plasma cells, and a few eosinophils. Vacuolation of the neuropil, with rare gitter cells and axonal spheroids, was also observed. We diagnosed parasitic encephalitis caused by S. dentatus migration based on the pathology findings and characterization of the parasite. 相似文献
10.
In a study of date fruit damage caused byOligonychus spp., we investigated whether the cultivar affects phenology, and on what hosts the mites over-winter. Samples were taken
from ‘Deglet Noor’, ‘Barhi’ and ‘Medjool’ trees from mid-April through mid-September during the years 1999–2002. In the ground-cover
mites were monitored by collecting Bermuda grass (Cynodon dactylon) under each sampling tree. Over 99% of the mites collected on Deglet Noor and Barhi fruit were identified asO. afrasiaticus. Mean population levels ofO. afrasiaticus reached ten mites or more (initiation of infestation) on Medjool in the second half of May, whereas on Deglet Noor this did
not occur before the first week of July. On Barhi the initiation of infestation varied between plots and years, ranging from
the second half of May to the beginning of July, but always occurred earlier than Deglet Noor. Mite populations on the pinnae
remained low from June through October, not exceeding seven mites per pinna, whereas on fruit strands they reached peak populations
of approximately 4000 mites per strand. The sex ratio (proportion of females) ofO. afrasiaticus on fruit of all three cultivars was highly female-biased, usually above 0.85. During winter,O. afrasiaticus was found on Bermuda grass in the orchard ground-cover as well as on fronds of all three cultivars.
http://www.phytoparasitica.org posting Jan. 30, 2003. 相似文献