粳型三系不育系混杂退化原因及对策的探讨

从理论与实践分析BT型、滇型粳稻不育系具有高度的遗传稳定性,发生混杂退化的主要原因在于:①繁殖过程中保持系的机械混杂;②杂交稻或恢复基因的迁移、扩散;③一般常规品种不育基因迁移及其连锁反应.针对BT型不育系混杂退化原因,提出“人工回交株系循环法“不育系原种繁种程序.     

The Agersoe cattle: the last remnants of the Danish island cattle (Bos taurus)?

A phenotypically interesting strain of cattle existed on the small island of Agersoe, on the west coast of Zealand, Denmark, in the beginning of the last decade. The cattle share a great resemblance to the extinct Danish breed, the Island cattle. The objective of this study was to genetically characterize the Agersoe cattle, using microsatellites, amplified fragment length polymorphism (AFLP) and mtDNA markers, and analyse the genetic variability within the breed and the genetic relationship to 14 European breeds with focus on the Red Danish and Jutland breed. The results show diversity in nuclear markers comparable to that of modern breeds and that the Agersoe cattle are separable from the two native breeds. The absence of inbreeding and the degree of genetic diversity are taken as a sign of recent admixture. The Agersoe cattle did not exhibit a consistent association with any of the European breeds. Several arguments based on this survey have been put forward in favour of characterizing the Agersoe cattle as being the last remnants of the Danish Island Cattle.     

混凝土外加剂技术应用中存在的问题及建议

随着混凝土外加剂应用量的不断增加 ,与外加剂应用有关的一些问题逐渐暴露出来。本文就外加剂含碱量的合理取值及混凝土外加剂发展方向等提出讨论。     

Inference of admixture in the endangered Blanca Cacereña bovine breed by microsatellite analyses

Blanca Cacereña cattle is the most threatened Spanish bovine breed. Although a Conservation Plan, exists, the little reproductive success and some chromosome abnormality were observed in the breed making it advisable to extend the genetic basis of the animals opening up the recorded herd book to new animals from local farms. However, the crossing with meat breeds like Charolais cattle is used to improve the commercial product. We used 30 microsatellites to determine the Charolais genetic influence in the current herds by the identification of the hybrids and to recognize new “purebred” animals in the “Blanca Cacereña” population. Blood samples were taken from animals of Blanca Cacereña bovine breed (112 animals with pedigree and 68 without pedigree), Charolais breed (60 animals) as a breed used commercially in crosses with Blanca Cacereña, and Retinta breed (60 animals) as a reference population. STRUCTURE analyses were performed with or without prior population information to assign individuals to breed, identifying admixed individuals, and inferring their ancestry. We have found that 37/68 animals without pedigree were purebred. Our results will be useful to manage a conservation plan of the breed, preserving the characteristic genetic pool and avoiding its extinction.     

Hybridisation with introduced chukars (Alectoris chukar) threatens the gene pool integrity of native rock (A. graeca) and red-legged (A. rufa) partridge populations

The decline of over-hunted red-legged (Alectoris rufa) and rock (A. graeca) partridge populations has been contrasted with massive releases of captive-reared birds, often hybrids with non-indigenous A. chukar. Released interspecific hybrids raise the risks of introgressive hybridisation, and can contribute to further depress the fitness of native populations. Aiming to assess the extent of hybridisation, we genotyped the mtDNA control-region and eight nuclear microsatellites in 671 red-legged, rock and chukar partridges and hybrids, identified by phenotypic traits. Results reveal a diffuse occurrence of hybridisation: (1) 39 samples (6.2%) show mtDNA haplotypes discordant with their phenotypes, indicating red-legged and chukar mtDNA introgression in native rock partridges; (2) admixture analyses of the microsatellite genotypes identified 32 additional rock partridges (5.1%) hybridised mainly with chukars. We analysed also 39 samples collected from a presumed natural red-legged x rock partridge hybrid zone in the French Alps. Surprisingly, 28% birds showed typical chukar mtDNAs, indicating hybridisation with introduced chukars or hybrids. This hybrid zone led to an introgression cline of chukar alleles into neighbouring Alpine rock partridges detectable up to 100 km, which was shorter than expected by neutral genetic theory, and that suggested natural selection against hybrids. These findings indicate that introgressive hybridisation may disrupt local adaptations in natural red-legged partridge and rock partridge populations, and call for strict control of farming and restocking operations.     

Productivity and economics of mixed two-storied spruce and birch stands in Southern Finland simulated with empirical models

The profitability of growing a naturally emerged birch (Betula pendula Roth or Betula pubescens Ehrh.) overstory in a young Norway spruce (Picea abies (L.) Karst.) plantation was examined with empirical stand structure, growth and yield, logging cost, and logging damage models. In the projected alternatives, an overstory of either birch species was thinned to 200–1000 stems per ha at the age of 15 years and retained for another 15 years. Development of the remaining spruce stand was simulated up to rotation age (70–85 years). Alternative treatments included removing the overstory completely at 15 years, and managing a pure spruce stand that was kept free of birch throughout.

Growing a birch overstory of 200–1000 stems per ha up to age 30 years resulted in a 61–93 m³ ha⁻¹ or 9.1–16.8% yield loss for the spruce stand due to growth retardation, and a mortality of 382–498 out of 1900 stems per ha through logging damage. This was compensated for or exceeded by the additional yield of the birch (54–173 m³ ha⁻¹) except for the lowest stocking (200–400 stems per ha) alternatives with B. pubescens. Treatment regimes with a birch overstory were clearly the most profitable alternatives, yielding up to 151% (B. pendula) and 113% (B. pubescens) of the net present value of the pure spruce alternative, at 4% interest rate. Removing the birch overstory already at 15 years was the least profitable alternative with 79 and 83% net present values, respectively. The most profitable treatment with current technology, price, and cost structure appears to be to grow 500–800 birch per ha up to about age 40 years for B. pendula and 45–50 years for B. pubescens.     

Genetic diversity,structure and individual assignment of Casta Navarra cattle: a well‐differentiated fighting bull population

The Casta Navarra lineage was one of the populations used to establish the fighting bull (FB) breed, and it has also been reproductively isolated from the others FBs. A total of 1284 individuals from two generations of 16 Casta Navarra herds were sampled to analyse their diversity, their genetic structure and the ability of 28 microsatellite markers to assign individuals to closely related populations. These animals were compared with closely related phylogenetic (FB) or geographical (Pirenaica and Monchina) populations. Hardy–Weinberg equilibrium analysis showed that 82% of the loci had a significant heterozygote deficit as a consequence of the Wahlund effect. The average proportion of genetic variation explained by farm differences was 9% by Wright's F_ST index. A phylogenetic tree constructed with a neighbour‐joining method based on Reynolds genetic distances and a Bayesian Markov chain Monte Carlo clustering approach revealed clear differences between farm groups that generally corresponded to historical information and could unambiguously differentiate Casta Navarra cattle from the other populations. The percentage of animals correctly assigned to the Casta Navarra population was 91.78% for a q threshold of >0.9. Admixture was only detected in 4.45% (q < 0.8) of the cattle. These results are relevant for the maintenance and development of diversity and conservation in the Casta Navarra population.     

菌渣混合发酵技术及产品应用效果调查

[目的]研究菌渣混合发酵技术,并对发酵产品的应用效果进行调查。[方法]研究菌渣发酵过程中的温度、水分和pH值变化情况,对产生的一种用于渔用水质改良剂的发酵物进行HA、微生物及N、P、K和重金属含量的测定,并对其应用效果进行调查。[结果]该发酵产品能持续地稳定水体pH值,有效地提高水中溶解氧的含量,显著地降低水中COD和NH4＋-N的含量。[结论]该研究可为我国菌渣的有效利用和水产养殖的进一步发展提供科学依据。     

Predicting seed admixture in maize combining flowering characteristics and a Lagrangian stochastic dispersion model

The seed purity problem has received very low attention in maize coexistence studies, and has not been considered in prediction tools that simulate pollen flow and out-crossing between maize fields. To fill this gap we developed the Seed Admixture Model (SAMETH) able to predict seed admixture dispersion combining flowering characteristics (pollen shed, silks exertion) with a Lagrangian stochastic dispersion model. The model was tested with a dataset obtained from 20 fields in 2007 and in 2008, whose seeds were mixed with 1% of a homozygous blue-kernelled hybrid. The model was first calibrated with data from 6 fields and then validated with the data from the remaining 14 fields. Moreover, a sensitivity analysis was performed to test the consequences of different pollen quantities released by the admixture and the commercial hybrids. The measured seed admixture ranged from 0.7% to 6% and the model was able to simulate the seed admixture with r² = 0.83. The sensitivity analysis showed that the model was sensitive to the absolute released pollen quantities but it was still able to predict seed admixture rather accurately. Because of its reliability, the model could become a useful tool for case study scenarios that involve seed admixture and for which field implementations would be too complex and time-consuming.