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941.
Summary Nobilization in sugarcane is viewed from a genetic angle considering the significance of 2n gametes. The inbreeding coefficients resulting from 2n gametes, for first and second nobilizations are worked out. The implication of 2n gametes to sugarcane breeding are discussed. 相似文献
942.
Summary SI inbreds of P. hybrida and crosses between self-incompatible (SI) petunia plants were brought to flower under winter and summer glasshouse conditions. SI response, as measured by self seed, ranged from zero seed set under both conditions to low or zero seed set during the summer and high seed set during the winter. Some plants produced comparable seed yields during either pollination time. Increased expression of pseudo-self-compatibility (PSC) during the winter months was attributed to a breakdown of the Si system by the low light conditions of Minnesota winters (45°N). Genotypic differences within and between populations in the winter provided differences facilitating selection for increased SI. These differences were masked in some populations by the summer environmental conditions. The use of simulated or natural low light conditions as a technique for selecting for SI should increase selection efficiency.Scientific Journal Series Paper Number 10,499 of the Minnesota Agricultural Experiment Station. 相似文献
943.
Summary The somatic karyotype and meiotic chromosome behavior were studied in an 18-chromosome B1 plant derived from backcrossing a triploid (Brassica napus x B. oleracea ssp. capitata) F1 hybrid to cabbage. It is considered that cabbage chromosomes no. 1 and no. 7 were substituted by two shorter B. napus chromosomes. Meiotic disturbances were more apparent during the late stages of second division. Seed fertility of this plant was largely restored in the second backcrosses with both cabbage and broccoli. 18-chromosome B2 plants resistant to race 2 of Plasmodiophora brassicae were recovered among the progenies.Contribution no. J. 725 from the Research Station, Research Branch, Agriculture Canada, St-Jean, Québec J3B 6Z8. 相似文献
944.
A ten-year study consisting of nine field experiments was conducted to evaluate alfalfa (Medicago sativa L.) for resistance to larval feeding by the alfalfa weevil (Hypera postica
Gyllenhal). The results were consistent over years and experiments. Only one source of alfalfa germplasm, designated Starnes, showed resistance to larval feeding in the field under natural infestations of the weevil. The cultivars Team, Arc, and Liberty have been developed from this germplasm source. The only effective method of selection for field resistance to the weevil was field selection under natural weevil infestations. Selection was based on low larval feeding on spaced plants. After six generations of such selection the Starnes germplasm showed only one-third as much defoliation as did the check cultivars. The heritability of the weevil resistance was moderately high. Field resistance was transferred to other strains through hybridization; hybrids were intermediate to the resistant and susceptible parents. Resistance was stable.Laboratory and greenhouse efforts to breed alfalfa weevil resistant alfalfa-using such techniques as adult cotyledon-nonpreference tests, adult leaf-feeding tests, larval-growth and survival tests, oviposition-stimulus tests, and oviposition-nonpreference tests-have failed to produce field resistance.Paper No. 5308 of the Journal series of North Carolina Agricultural Experiment Station, Raleigh, N. C., in cooperation wich ARS, USDA. Received 15 June 1977. 相似文献
945.
Summary In vitro pollen germination at 10°C, 14°C and 22°C of four groups of two pure line tomato varieties was compared with their plant growth at 19°C D/10°C N under controlled environmental conditions. Generally, pollen germination was slow at 10°C but after 6 h the percentage of germination was similar to that at 22°C. Maximum germination was obtained at 14°C already after 4 h. The longest pollen tubes occurred at 22°C. The two varieties within each group differed significantly from each other for percentage of pollen germination. For one group, this difference was greater at 10°C than at 22°C. The varieties in two groups also differed significantly for pollen tube growth. These differences in pollen tube growth rate were greater at 22°C than at 10°C. There was no clear relationship between pollen germination, pollen tube growth and plant growth in any of the four pairs of varieties. The results are discussed with regard to the possibility of pollen selection at low temperature in order to improve the efficiency of breeding for growth at low temperature. 相似文献
946.
Summary The development and applications of molecular markers to hemp breeding are recent, dating back only to the mid-1990s. The main achievements in this field are reviewed. The analysis of Cannabis germplasm by RAPD, AFLP and microsatellites is discussed, with its consequence for the still debated species concept in Cannabis. DNA-based markers have also been exploited in the field of forensic science, in an attempt to discriminate licit from illicit crop. The main applications of the molecular markers to the breeding, however, have been achieved with the development of markers closely linked to the male sex and to some of the most relevant chemotypes. Active research is carried out by several groups in the field of identification and characterization of the genes involved in fiber quality and quantity, and in the determination of monoecy, another very important target of hemp breeding. Besides, markers associated to new, potentially useful chemotypes are being developed, for the marker-assisted breeding of pharmaceutical Cannabis. 相似文献
947.
The association of culm anatomy with lodging susceptibility in modern spring wheat genotypes 总被引:1,自引:0,他引:1
Selection for lodging resistant cultivars in cereal breeding programs is difficult due to the challenge of screening for this
trait under natural field conditions. The identification of easily measurable culm traits related to lodging resistance would
simplify the selection process. The present study was conducted to determine if differences in culm anatomy exist among modern
wheat genotypes differing in lodging susceptibility, and to determine the association between culm characters and lodging.
From a 2-year field study conducted in Edmonton, Alberta, 13 spring wheat cultivars were chosen based on predetermined susceptibility
to artificially induced lodging. Morphological and anatomical culm measurements were made visually and with an environmental
scanning electron microscope. Genotypes differed (P < 0.05) for plant height, number of internodes per culm, basal internode length and diameter, culm wall thickness and the
number of vascular bundles, but not for adventitious root frequency, lumen diameter or sclerenchyma ring thickness. Mean genotype
field scores for artificially induced lodging were correlated (P < 0.05) with plant height (r= 0.51) and the length of the fourth basal internode (r= 0.51). Short, wide basal internodes and thick culm walls were characteristic of three lodging tolerant genotypes: Kohika,
Sapphire and Olso. Nevertheless, despite such apparent genotype specific association between culm anatomy and field lodging,
general applicable associations were not observed for most traits. The most practical and easily selectable trait for lodging
resistance within a wheat breeding program remains plant height.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
948.
Summary Gene pyramiding in Phaseolus vulgaris is being utilized to develop more effective resistance to the temperature-insensitive-necrosis-inducing (TINI) strains of Bean Common Mosaic Virus (BCMV) present in the USA. Our data indicate that contrary to previous work, the bc-3 gene is effective against these strains in the absence of the strain unspecific bc-u gene in genotypes possessing the I gene. The epistatic bc-3 gene interferes with traditional efforts to pyramid the other recessive resistance genes by masking their activity. Indirect selection based on markers linked to the other recessive resistance genes would likewise be ineffective without the ability to also select for the bc-u gene which is required for expression of the bc-2
2 gene in germplasm carrying the I gene. Because the most resistant genotype (I, bc-u, bc-I
2, bc-22, bc-3) can only be introduced into a wide range of germplasm through the use of molecular markers linked to the different resistance genes, the search for a marker linked to the strain unspecific bc-u gene should also be given priority. 相似文献
949.
Summary Four populations of linseed derived from five parents were advanced from the F2 to the F6 generation by SSD and to the F5 by pedigree selection. These populations were used to compare the efficiency of the two methods in order to provide superior genotypes with respect to grain yield and oil content, i.e. oil yield. The results showed minimum differences between pedigree and SSD lines for grain yield, where in only one cross the SSD lines were significantly superior to the pedigree lines. Since pedigree selection was carried out for both, seed yield and oil content, a positive response to selection was expected. However, early selection for yield, a character with low heritability, was not successful. On the contrary, significant differences for oil content were detected between the two groups of lines in three of the four crosses studied. In these cases the pedigree lines were superior to the SSD lines. These results demonstrate that strict selection in early generations for oil content, a character with comparatively high heritability, is feasible and successful in linseed. However, selection for seed yield should be postponed to later inbred generations. Consequently, in breeding for maximum oil yield of linseed a two-step selection procedure is recommended.Abbreviations PS
pedigree selection
- SSD
single seed descent
- TGW
thousand grain weight 相似文献
950.
Oligonucleotide fingerprinting of tomato DNA 总被引:6,自引:0,他引:6
D. Kaemmer K. Weising B. Beyermann T. Börner J. T. Epplen G. Kahlm 《Plant Breeding》1995,114(1):12-17
Hinfl -digested DNA samples of wild and cultivated species of tomato were hybridized in gel to different oligonucleotide probes complementary to simple-sequence repeats. All motifs tested i.e. (GATA)4, (GGAT)4, (CA)8. (CAG)5, (GTG)5, (GAAGTGGG)2 and (CCTA)4, produced multilocus fingerprints in all tomato species and cultivars. The extent of inter- and intraspecific polymorphism of the banding patterns varied considerably between different probes, with (GGAT)4, (CCTA)4, (GATA)4 and (CA)8 showing a much higher discriminatory potential than the other probes. Cluster analysis of band-sharing data yielded dendrograms which were consistent with the known history of tomato cultivation. (GATA)4 was also successfully used for purity testing of breeding lines, as well as for analysing an F1 progeny of a cross between two lines. 相似文献