甘蓝型油菜(Brassica napus)无花瓣突变体“ Ap-Tengbe ”花瓣性状的遗传规律

本项研究旨在探明甘蓝型油菜突变体Ａｐ－Ｔｅｎｇｂｅ无花瓣性状的遗传规律,‘Ａｐ－Ｔｅｎｇｂｅ’和德国栽培品种‘Ｆａｌｃｏｎ’之间通过正反交产生两个方向的Ｆ１,ＢＣ１－１（Ｆ１和‘Ａｐ－Ｔｅｎｇｅｂｅ’之间）,ＢＣ１－２（Ｆ１和‘Ｆａｌｃｏｎ’之间）以及Ｆ２各遗传群体,根据田间各遗传群体ＰＤｇｒ（花瓣度）的观察和统计,作者提出‘Ａｐ－Ｔｅｎｇｅ’突变体无花瓣性状的遗传由细胞质和两对核隐性基因共同控制     

The influence of the system of silage harvesting and feeding and the use of protected protein on milk production

The study compared two systems of silage harvesting, direct-cutting flail harvesting (flail-direct) or pre-cutting, followed by wilting and collection by a meter-chop harvester (precision-wilted). Each silage was self or easy fed to dairy cows. In addition, the response to protected soya bean meal included in the supplementary concentrate was also examined. Approximately 400 t of each of the two silages were produced from the same swards under good weather conditions with formic acid applied as an additive. The resulting silages were well preserved and had mean particle lengths of 43 and 29-mm, and D-values of 0-74 and 0-71 for the flail-direct and precision-wilted silages, respectively. During a 159-d feeding period commencing on 5 November, the silages were offered to 88 British Friesian cows in a 2³ factorial design, continuous feeding experiment. The cows calved during the experiment and had a mean calving date of 18 January. The feeding treatments involved both silage types, two systems of silage feeding (self and easy) and two sources of protein in the supplementary concentrate given after calving (soya bean or 100 g kg^-1 protected soya bean). No concentrates were offered pre-calving and all animals were given 7.6 kg d^-1 concentrates post-calving. There were no significant interactions between the system of silage harvesting and feeding. Animals on the precision-wilted silage consumed 14% more silage dry matter (10.9 vs. 9.6 kg DM d^-1) over the total period and by the end of the experiment were producing 7% less milk per day (25.4 vs. 27.2 kg). However, the responses in the output of total milk constituents (fat and protein) were lower than those obtained in milk yield. Animals offered silage by self feeding had similar dry matter intakes, but produced marginally less milk than those easy-fed. Ration digestibility and nitrogen utilization data, obtained from a concurrent change-over design experiment, suggested that the energy from the precision-wilted silage was less efficiently utilized for milk production. There was no significant response in either milk yield or composition to the inclusion of protected soya bean in the supplement.     

An evaluation of a high-quality grass silage for milk production

Forty British Friesian cows with a mean calving date of 28 January were used in a randomized block design experiment to evaluate a high-quality grass silage for milk production. The high-quality silage was made from two consecutive cuts of a perennial ryegrass sward after regrowth intervals of 37 days, wilted to 51% dry matter, finely chopped and ensiled using 2.2 1 t^-1 (0.5 gallons per ton) of formic acid. The resulting silage had a dry matter digestibility of 72.9% and was fed ad libitum with 3.8 kg (8.4 lb) concentrates as a supplement. A medium-quality grass silage, of lower digestibility and dry matter content (70.0 and 25.4% respectively), was also fed ad libitum in addition to either 3.8, 5.7 or 7.6 kg (8.4, 12.5 or 16.7 lb) concentrates. The feeding treatments were commenced immediately after calving and were terminated on 9 April giving a mean period of 72 d on the treatments. Over the experimental period the animals on the high-quality silage consumed 15% more silage dry matter and produced 8% more milk that those on the medium-quality silage with the same level of concentrate supplementation. From the results it was estimated that 1.9 kg (4.3 lb) of additional concentrates would be required with the medium-quality silage to give an equivalent milk output to that achieved with the high-quality silage. Milk composition, liveweight change, ration digestibility and nitrogen balance data are also presented.     

Mode of action of thiocyanate and iodide in relation to IAA metabolism

Whole plant studies have reaffirmed that of the halides and pseudohalide thiocyanate, only iodide and thiocyanate possess defoliant properties. Established work has indicated their possible involvement with IAA (indole-3-acetic acid). In vitro studies have suggested that IAA destruction is not through a direct interaction between IAA and the halides and pseudohalide but depends on their conversion to the halogen or pseudohalogen which can then destroy IAA. This may be accomplished by the peroxidase enzyme system for iodide only and docs not provide a mechanism for thiocyanate activity. However, both iodide and thiocyanate have chemical oxidation potentials suitable for their conversion to the halogen or pseudohalogen respectively via the photosynthetic apparatus. Hence, this would provide an explanation for then activity and the apparent inactivity of bromide, chloride and Buoride which would be oxidized very slowly or not at all.     

Genotypic diversity in a South African population of the pitch canker fungus Fusarium subglutinans f.sp. pini

The genotypic diversity in a South African population of Fusarium subglutinans f.sp. pini ( F.s. pini ) was determined, based on the number of vegetative compatibility groups (VCGs). Isolates of F.s. pini from South Africa (69), California (five) and Florida (19) were included in the study. The nit1 (or nit3 ) and NitM mutants were selected as chlorate resistant sectors and paired on minimal medium. The South African isolates of F.s. pini were assigned to 23 different VCGs. No heterokaryons formed between isolates from South Africa, California and Florida. The high degree of genotypic diversity in the South African population of F.s. pini is probably due to some level of sexual reproduction in the population.     

The identification of a gene for race-specific resistance to Peronospora parasitica (downy mildew) in Brassica napus var. oleifera (oilseed rape)

The oilseed rape cultivar Cresor was resistant to 14 isolates of Peronospora parasitica derived from crops of Brassica napus in the UK. Segregation for resistance to one isolate among F₂ plants and F₃ progeny of crosses between Cresor and the susceptible cultivars Victor and Jet Neuf indicated that resistance was controlled by a single gene. There was evidence that genetic background and environment could influence the phenotypic expression of this resistance. Two sexual progeny isolates derived from a homothallic isolate of P. parasitica avirulent on Cresor were completely virulent on this cultivar. This suggested that the parental isolate was heterozygous at a matching locus or loci for avirulence and demonstrated the race-specific nature of the resistance.     

Changes in the long‐term distribution of zooplankton in the Humboldt Current Ecosystem off Peru, 1961–2005, and its relationship to regime shifts and environmental factors

We used a dataset assembled by the Peruvian Marine Research Institute (IMARPE) from 1961 to 2005, to examine the influence of seasonal, environmental (temperature and salinity), temporal (day–night and year) and location (north‐south and on‐off shelf) variables on the distribution and biovolume of zooplankton. Classification and regression trees (CART) showed that the zooplankton distribution can be divided into four time regimes: prior to 1974.5, 1974.5–1989.5, 1989.5–1997.5 and 1997.5–2005. These periods differ in overall biovolume but, more importantly, in having different spatial distributions of variables. Offshore‐onshore, seasonal, diel and north‐south patterns are all apparent in the temporal changes observed in zooplankton distribution. In the early period zooplankton biovolume was high throughout the Peruvian Humboldt Current Ecosystem, with enhanced biovolume in all seasons but winter. After 1974.5, biovolume was considerably lower. There was an increased difference between the shelf (lower biovolume) and offshore (higher biovolume), with a significant day–night effect offshore, due to diel migration and possibly diel catchability changes. After 1989.5, seasonal effects were more marked and biovolume appeared to be higher in the winter in the northern region. In other seasons, during the daytime, biovolume was highest farther offshore (greater than 65 km offshore of the 200‐m isobath) and, during the night, higher after 1997.5 than before. We relate these changes in distribution and biovolume to changes in large‐scale current patterns in different regimes and to the possible effect of the fishery in removing nutrients from the system.     

Potentiation by adrenaline of a proteolytic activity associated with purified myosin

Proteolytic activity accompanies myosin through three reprecipitations. The fact that this activity can be potentiated by very small doses of 1-adrenaline supports the view that adrenaline receptors are protein in nature and that adrenaline-like compounds exert their action through modification of the activity of enzymes.