We used amplified-fragment-length polymorphism (AFLP) markers to evaluate genetic variation in a set of bread wheat (Triticum aestivum L.) landraces and improved materials. Landraces collected from different geographic and agro-ecological zones in Pakistan
in 1987, 1989 and 1991 were separated into two groups based on their geographic origins: northern (Himalaya) and south-western
(Balochistan) Pakistan. Six AFLP primer combinations detected 453 AFLP markers in the 43 landrace accessions and four high-yield
varieties (HYVs). Of these, 225 (49.67%) were rare (shared with < 5% of all accessions). Among these rare alleles, 23 (10.22%)
were common in the Himalaya (shared with > 10% of accessions collected there) but were not found in Balochistan. We conclude
that there is a higher probability of collecting rare alleles at overall, but which are in contrast locally common ones in
the Himalayan region. Gene diversity was 0.17 in the Himalayan group and 0.15 in the Balochistan group. Considerable genetic
variability was found in both groups. Accessions from different agro-ecological zones were indistinguishable by cluster analysis,
indicating intensive seed trading within the country. Cluster analysis indicated that the landraces and the HYVs are genetically
distinct; suggesting that genetic erosion of wheat landraces has been unlikely taken in place. This study provides an example
of how analysis of existing materials and data, can serve as a basis for future collection planning and conservation policies. 相似文献
Variability in catch-per-unit-effort (CPUE) was examined for the autumn cohort of Ommastrephes bartramii collected with research driftnets during 1979–1998 along five longitudinal transects passing through the Subarctic, Transitional and Subtropical Domains in the North Pacific. CPUE was generally low during the period of intensive commercial driftnet fishing (1980–1992) and increased following the 1992 moratorium on the use of large-scale driftnets. However, CPUE levels were low for the cohorts hatched in 1992 and 1996 (captured in subsequent years owing to a one-year life of O. bartramii ) that experienced low sea surface temperatures from hatching to recruitment. Among similar-aged squid collected from 180° and 179°30'W in June, mantle lengths were significantly greater in 1997 than during 1995–96. These findings suggest that the driftnet fishery and sea surface temperatures from hatching to recruitment strongly affected stock abundance and possibly growth. 相似文献
A 2 × 4 factorial experiment was conducted to determine the bioavailability of zinc (Zn) from amino acids chelated (Zn–Am) and glass embedded Zn (Zn–Gl) as sources for rainbow trout, Oncorhynchus mykiss , fed practical type diets. Two levels of Zn (20 and 40 mg kg−1) were supplemented to the diets using either zinc sulphate (Zn–Sf), zinc methionine (Zn–Mt), Zn–Am or Zn–Gl. Rainbow trout with an average weight of 2 g were fed the experimental diets for 15 weeks. Growth and feed gain ratio (FGR) were not significantly influenced by the dietary Zn content and forms. Alkaline phosphatase (ALP) activity for both levels of Zn–Am was significantly higher than that of Zn–Sf and Zn–Gl at 20 mg supplementation. In another experiment, fish of about 95 g were fed the same experimental diets to determine the absorption of Zn and it was found to be significantly higher from Zn–Am compared with the rest. Retention from Zn–Am at 20 mg was significantly higher than the rest, excluding Zn–Sf. The results suggest that the availability of Zn from Zn–Am might be superior among the sources compared. 相似文献
Summary A combination of compatible second pollinations and embryo rescue was applied for systematic production of true tetraploid hybrids from crosses between disomic tetraploid Solanum acaule and tetrasomic tetraploid potato, S. tuberosum. Several genotypes of tetraploid potatoes were pollinated with S. acaule, and the compatible second pollinations were made on the following day, with a genotype of S. phureja, IvP 35 to promote fruit development. Embryo rescue was carried out in 21 families, 14 to 27 days after the first pollination. A total of eight plants were obtained from the embryo rescue and their chromosome numbers were counted in the root tips. Three of the eight plants were identified as tetraploid, and five others as diploid. Morphology, isozyme banding patterns, and pollen stainability, as well as potato spindle tuber viroid (PSTVd) resistance, indicated the hybrid nature of the three plants. This is the first report of successful tetraploid hybrid production between disomic tetraploid S. acaule (4x) and tetrasomic tetraploid potatoes. Seed set from the crosses between one of hybrids and diploid potatoes indicated workable levels of both male and female fertility for introgression of valuable genes from S. acaule into the cultivated potato gene pool. The methodology used may be applied to other disomic tetraploid tuber-bearing Solanum species and with some modifications also to distantly related solanaceous species and genera. 相似文献
Although fish roes (or the egg-laden ovary) are seafood products with high nutritional value and are considered abundant in vitamins including vitamin B12, nevertheless, the detailed properties of vitamin B12 have not been fully elucidated in fish roe products. Vitamin B12 content was determined using C18-reversed-phase high-performance liquid chromatography after purification of samples from immunoaffinity columns. Salmon egg-laden ovary products (sujiko), salmon roe products (ikura), dried mullet roe products (bottarga), and white sturgeon roe products (caviar) were found to contain substantial levels of vitamin B12 (more than approximately 15 µg/100 g wet weight). Interestingly, high levels of vitamin B12 per 100 g wet weight have been measured in pollack roe products (tarako) and flying fish roe products (tobiko). Liquid chromatography–electrospray-ionization/tandem mass spectrometry analysis revealed that vitamin B12 was the predominant corrinoid in the evaluated fish roe products examined, while no inactive corrinoid compounds were identified. These results suggest that commercially available fish roe products could be an important source of vitamin B12 for use as a dietary product for humans.