排序方式： 共有32条查询结果，搜索用时 15 毫秒
1.
Ocular dimensions,corneal thickness,and corneal curvature in quarter horses with hereditary equine regional dermal asthenia 
下载免费PDF全文
下载免费PDF全文 2.
Solanum lycopersicoides Dun. is a wild nightshade native to Chile and Peru that possesses many traits of potential interest
to tomato breeders, including environmental stress tolerance, resistances to disease and insect pests, and certain fruit quality
characteristics. Sexual and somatic hybrids with the cultivated tomato (Lycopersicon esculentum Mill.) are readily obtained,
yet have a strong tendency towards male-sterility combined with unilateral incompatibility, barriers that have deterred breeding
efforts in the past. We report herein the synthesis of a partially male-fertile F1 hybrid by sexual crosses between tomato and a recently collected population of S. lycopersicoides. Over 280 BC1 plants were obtained by directed backcrossing to tomato at the diploid level, of which 58 were sufficiently fertile to permit
selfing or additional backcrosses. The transmission of S. lycopersicoides genetic markers into a uniform L. esculentum background
was confirmed with 24 isozyme or morphological loci on 11 of the 12 alien chromosomes. Potentially useful tolerance to gray
mold (Botrytis cinerea) was demonstrated by inoculation of stem cuttings with mycelial plugs: at 6 days post-inoculation,
the intergeneric hybrid showed little evidence of disease progression and the length of stem lesions averaged only one third
that of susceptible controls.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Ninety four accessions of the cultivated triploid potatoS. chaucha were analyzed and classified in genotypic groups using 9 isozyme loci and RAPD markers disclosed by 20 arbitrary 10-mer primers.
Eight isozyme loci out of nine were polymorphic. A total of 22 allozymes were analyzed but none of them were specific for
any genotypic group. About half (52%) of the 102 RAPD markers scored, were polymorphic, all of them showing polymorphism among
groups and rarely within groups. Eighteen RAPD markers were specific for certain genotypes. The isozyme markers showed a certain
amount of intra group variation which made classification less reliable than with RAPD markers. A total of 10 triploid genetic
groups were discriminated using both techniques together. A single primer was found to be sufficient to distinguish all 10
groups. All varieties of a single group are considered to have been derived from the same cross and then clonally propagated,
even though there is a high amount of morphological variation within a single genotypic group due probably to somatic mutations.
RAPD markers have been shown to be more reliable in the classification of triploid potato varieties than other genetic markers
like isozymes, proteins and morphological traits. 相似文献
4.
Interest in vine cacti of the genus Hylocereus (Cactaceae) has grown markedly due to their high economic potential as exotic fruit crops. Thus, we investigate the genomic and genetic characteristics of 18 accessions belonging to three Hylocereus species, from which were produced eight progeny from self-pollination and 51 interspecific-homoploid and -interploid hybrids. We reported ploidy estimation, allele frequencies, polymorphic information content (PIC) and genetic relationships observed among the Hylocereus species and their progeny. The progeny were diploid, triploid, tetraploid, pentaploid, or hexaploid. Each primer combination used in this work amplified different sets of restriction fragments ranging from 74 to 102 bands. Among the total number of bands observed for the Hylocereus accessions and their progeny, 97.5 and 98.1 %, respectively, were polymorphic. The variability of PIC between primers, species and hybrids suggested high heterozygosity and gene flow between them. In addition, amplified fragment length polymorphism (AFLP) markers were used to successfully identify one of the H. megalanthus accessions beforehand as the unknown male progenitor of the allotriploid S-75. AFLP markers demonstrate the efficacy for assessing genetic relationships and introgression; and provide strong support for the pursuit of additional breeding programs of these fruit crop. 相似文献
5.
6.
The viscoelastic properties of durum wheat flour doughs were measured using the extensigraph in uniaxial extension and the Rheometrics mechanical spectrometer in oscillatory shear. The research examined the effect of increasing density of cross-links on rubber elasticity in these systems. The stress-strain behavior of durum wheat flour dough was not well simulated by Mooney-Rivlin type nonlinear elasticity. Addition of increasing amounts of iodate made the dough show appreciable strain thickening behavior, approximating the behavior of natural rubbers The estimated apparent molecular weight between cross-links ranged from 10,500 to 16,000, much larger than that of rubbers, for which values are in the range of 500–1,000. When the Mooney-Rivlin equation was tested, it appeared to approximate only moderately well the extensional behavior of iodate-added wheat flour doughs at finite but low extensions, where the finite extensibility of chains is not a factor. It is hypothesized that the cross-linked network is highly diluted with hydrogen and hydrophobic bonds that limit the applicability of rubberlike elasticity theories. Increasing the cross-linked density using iodic acid developed matrices that moved the behavior of durum flour doughs closer to Mooney-Rivlin behavior. 相似文献
7.
8.
9.
We have performed a study on 11 human embryos regarding the development of the tympanic ossicles and their relationship with the first pharyngeal arch. After performing measurements to date the embryos and foetuses chronologically, we performed a meticulous dissection of the temporal bones. Subsequently, they were fixed in 10% formol, decalcified with 2% nitric acid, embedded in Paraplast, sectioned in 7-mm sequences and stained with Martin's trichrome technique. In the 21- and 24-mm cranium-raquis (CR) length human embryos, we have observed the head of the malleus and the body of the incus close to Meckel's cartilage, in addition to the handle of the malleus, the long limb of the incus and the stapes. Between them there was a mesenchymal band inside the primordium of the tympanic cavity. In the 27-mm CR embryo, the various components of the malleus and incus were fusing, and in the 30-mm CR embryo the union was complete. From our observations, we can conclude that the malleus and the incus are derived from the first and second pharyngeal arches. 相似文献
10.
The aim of this study was to develop an efficient methodology to rescue embryos following interspecific crosses in the genus
Hylocereus. Crosses between the diploids Hylocereus polyrhizus and H. undatus in both directions were performed. Fertilized ovules carrying embryos at very early pro-embryonic stages were excised from
ovaries 5 days after pollination (DAP) and placed on half-strength basal MS medium containing 680 μM glutamine, 0.55 μM α-naphthaleneacetic
acid (NAA), 0.45 μM thidiazuron (TDZ) and various concentrations of sucrose. After 30 days in culture, ovules were isolated
from the surrounding tissue and transferred to the same fresh medium. Significant differences were found between the main
effects (cross and sucrose concentration) in ovule response, i.e., increased ovule size and callus formation. The best responses
were obtained in the cross: H. polyrhizus × H. undatus; and sucrose concentration of 0.09 M. In terms of embryo conversion, polyembryony and number of regenerated plants, the highest
responses were observed on the culture medium supplemented with 0.17 M sucrose in both interspecific crosses. All tested plants
were found to be diploid by flow cytometric analyses. Fluorescent amplified—fragment length polymorphism (fAFLP) confirmed
the hybrid origin of the regenerated plants. This study reports on the success of a three-step embryo rescue procedure for
Hylocereus species. The procedure developed here provides the means for producing plants from very-early embryo stage, thus expanding
the prospects for vine-cactus breeding programs. 相似文献