Genetic diversity in populations of Cronartium ribicola in plantations and natural stands of Pinus strobus

Genetic diversity was studied in 22 populations of the white pine blister rust fungus Cronartium ribicola from natural stands and plantations of eastern white pine, Pinus strobus. Pseudo-allelic frequencies were estimated at each of 7 putative RAPD loci by scoring for presence or absence of amplified fragments in dikaryotic aecidiospores. Analysis of genetic distance between all pairs of populations did not reveal any trend with regard to geographic origin or type of white pine stand. In addition, when hierarchical population structure was analysed, total genetic diversity (H _s =0.214) was mostly attributable to diversity within populations (H _s =0.199; AMOVA _st =0.121, P<0.01). Genetic diversity of populations relative to region of origin (east, centre, and west) or type of stand (natural stands vs plantations) was not significantly different from zero (P>0.10) Nevertheless, a significant proportion of genetic differentiation was found between populations within region or stand type (F _st =0.114; _sc =0.132, P<0.001). This result indicates that some population structure exists but that it appears to be independent of region of origin or type of stand. At least for 2 populations from white pine plantations, it appears possible that a recent introduction of a limited number of propagules was responsible for low levels of genetic diversity. We interpret these results as meaning that either long-distance dispersal is taking place between populations more than 1000 km apart or that these populations share a common recent ancestor. In addition, we suggest that C. ribicola may still be expanding its distribution by colonizing new plantations.     

Integrating approaches towards the conservation of forest genetic resources: a case study of Araucaria angustifolia

In the past years the conservation of forest genetic resources has been widely recognized because of the risk of adverse effects associated with global changes in the environment. Since little effort has been made towards conservation of these resources, the assessment and the integration of information and knowledge so far generated are valuable tools in order to promote their conservation. In the present work the Brazilian conifer Araucaria angustifolia was used as a case study, integrating information, published between 1980 and 2007, about genetics, biotechnology, palaeobotany, and archeology. These studies were interpreted towards the conservation needs and strategies of the species germplasm. The main conclusions for the conservation of A. angustifolia genetic resources are: (1) despite the reduction of genetic diversity by unsustainable forest exploitation, the genetic system of A. angustifolia seems to be efficient to protect this species against rapid losses of its genetic diversity; (2) conservation measures starting now may be efficient, since the genetic structures of existing populations is more largely influenced by the past evolutionary process than by human disturbance occurred in the last century; (3) there are opportunities to save the genetic resources of the species, if simple measures are taken to safeguard the continued existence of the few remaining araucaria forests. Emerged as a general conclusion that the use of sound scientific arguments supported by different areas of the science could be a very powerful instrument in persuading decision-makers, also by governments, taking into account forest genetic resources as a primary issue for the future.     

油松与赤松疱锈病病原及转主的研究

油松与赤松疱锈病是两针松类枝干上的重要病害,从油松和赤松主干病皮上取锈孢子分别向山芍药、芍药、返顾马先蒿、轮花马先蒿、长白茶藨子、东北茶藨子、香茶藨子和刺李进行室内和室外人工接种试验,终于在山芍药、芍药上接种成功,产生与自然状态下相同的典型症状。同样方法用夏孢子接种也都成功,在两种芍药上所产生的夏孢子堆与冬孢子柱以及夏孢子与冬孢子的形态也基本相同。由此可以肯定,油松疱锈病与赤松疱锈病是同一病原,病原菌为松芍柱锈菌[cronartium flaccidum(Alb·et Schw·)Wint]。取锈孢子用同样方法经多次在返顾马先蒿、轮花马先蒿、长白茶藨子、东北茶藨子、香茶藨子和刺李上接种,均未成功,因此认为这些植物与此两种疱锈病的发生无关,两种疱锈病在辽宁的转主寄主是山芍药(Paeonia obovata Haxim.)和芍药(P.lactiflora Pall.)。     

Genetic identity between populations when mutation rates vary within and across loci

A formula is derived for the probability that two genes taken at random from the same locus in two populations isolated at time t ago are of the same allelic type. The model assumed is a neutral one where there are possibly different mutation rates between different alleles. Inequalities are derived for this probability. A particular result is that for a fixed overall mutation rate, the probability is least for the infinite alleles model. Inequalities and approximations are found for Nei's genetic identity at one locus when mutation rates vary, and also for the identity across loci when the overall mutation rates per locus vary. Genetic identity at the molecular level is considered and a probability generating function found for the number of segregating sites between two randomly chosen gametes from two divergent populations, under various models.     

Genetic structure of introduced European fallow deer (<Emphasis Type="Italic">Dama dama dama</Emphasis>) in Tasmania,Australia

European fallow deer are an introduced species classified as partly protected wildlife in Tasmania, Australia. Current management practices are primarily governed under the Quality Deer Management regime, in which animals are harvested during designated hunting seasons. Among populations, prominent morphological differences have been reported; however, the genetic relationship of these populations has until now been poorly understood. Representative animals were sampled from three key areas across their range and genotyped at ten polymorphic microsatellite loci to investigate genetic diversity, population structure, and genetic bottlenecks. Allelic richness was low in all three populations and ranged between 2.20 and 2.49 alleles/locus. A genetic bottleneck was detected in two of the three populations (P < 0.001). Population differentiation was evident between Lake Echo and Benham (q = 0.122; P < 0.001) and Benham and Connorville (q = 0.110; P < 0.001), but not between Lake Echo and Connorville (q = 0.0235), with individuals being identified as belonging to two genetic clusters. The pattern of population differentiation from the three study populations suggests that deer from the western region of their range are genetically distinct to those from the eastern region. This correlates with morphological variation within Tasmanian fallow deer, in which differences between the regions maybe attributable to geographical barriers.     

Unconstrained gene flow between populations of a widespread epiphytic lichen Usnea subfloridana (Parmeliaceae,Ascomycota) in Estonia

Few studies have investigated the genetic diversity of populations of common and widespread lichenized fungi using microsatellite markers, especially the relationships between different measures of genetic diversity and environmental heterogeneity. The main aim of our study was to investigate the population genetics of a widespread and mainly clonally reproducing Usnea subfloridana at the landscape scale, focusing on the comparison of lichen populations within hemiboreal forest stands. Particular attention has been paid to the genetic differentiation of lichen populations in two geographically distinct regions in Estonia and the relationships between forest characteristics and measures of genetic diversity. We genotyped 578 Usnea thalli from eleven lichen populations using seven specific fungal microsatellite markers. Measures of genetic diversity (allelic richness, Shannon's information index, Nei's unbiased genetic diversity, clonal diversity, the number of multilocus genotypes, the number of private alleles, and the minimum number of colonization events) were calculated and compared between Usnea populations. Shared haplotypes, gene flow and AMOVA analyses suggest that unconstrained gene flow and exchange of multilocus genotypes exist between the two geographically remote regions in Estonia. Stand age, mean circumference of the host tree, size of forest site and tree species composition did not show any significant influence on allelic richness, Shannon's information index, Nei's unbiased genetic diversity, clonal diversity, the number of private alleles, and the minimum number of colonization events of U. subfloridana populations. Therefore it was concluded that other factors of habitat heterogeneity could probably have a more significant effect on population genetics of U. subfloridana populations.     

微卫星遗传标记及其在昆虫种群遗传学中的应用

微卫星是一类短串联重复的寡核苷酸序列,广泛地分散于各类真核生物基因组中,它具有多态性高、检测结果稳定可靠等特点,是目前较为理想的群体遗传研究的分子标记之一。该文阐述了微卫星DNA构成及特点,多态性形成机制、位点获得途径,列举了微卫星遗传标记在昆虫种群遗传学研究中的应用实例,并展望了该技术的应用前景。     

Phytotoxin Production in Bursaphelenchus xylophilus-Infected Pinus sylvestris

Our findings suggest that i) phytotoxic materials can be isolated from Bursaphelenchus xylophilus-infected Scots pine, but not from noninfected pines; ii) the phytotoxins cause wilting of 45-day-old and 2-year-old pine seedlings in a dose and species dependent manner; iii) the phytotoxins are produced early in the infection, accumulate or increase with time, and may function to suppress water transport in the tree; and iv) the phytotoxins are lipid materials of low molecular weight which are not acidic.     

黄颡鱼微卫星标记的筛选及三个野生群体的遗传结构分析

为了探明长江中上游流域黄颡鱼野生群体的遗传多样性状况和遗传结构,本研究采用磁珠富集法筛选出10个黄颡鱼微卫星标记,并利用其对长江中上游流域3个黄颡鱼(Pelteobagrus fulvidrac)野生群体(赤水群体、乐山群体、洞庭群体)的遗传结构进行分析。获得65个阳性克隆并测序,得到36个含有微卫星的序列,设计并合成了22对微卫星引物,经筛选得到10对多态性稳定的引物,其中高多态性位点6个,中多态位点3个。每对引物等位基因数2-9个,平均4.8。3个群体(赤水、乐山和洞庭)的平均多态信息含量(PIC)分别为0.5438、0.4568和0.3965,平均有效等位基因(Ne)分别为2.9928、2.5401和2.1713,平均期望杂合度(He)分别为0.6280、0.5277和0.4757,表明这3个群体遗传多样性水平较高,其中赤水群体遗传多样性最高,洞庭群体最低。种群分化指数(Fst)和遗传距离(Ds)分析表明,洞庭群体和乐山群体之间的亲缘关系最近,而与赤水群体的亲缘关系最远。聚类分析显示,乐山群体和洞庭群体聚为一支,赤水群体单独聚为一支。     

Evaluation of the geographical pattern of genetic diversity of Glycine soja and Glycine max based on four single copy nuclear gene loci: For conservation of soybean germplasm

Genetic diversity and its geographical patterns play a very important role in species conservation and exploitation. Here, nucleotide polymorphism patterns of four single copy nuclear gene loci in wild (Glycine soja) and cultivated soybean (Glycine max) populations from different geographical regions as well as their demographic history were analyzed. The results showed that: (1) Southern subpopulation has the highest, while central subpopulation revealed the lowest genetic diversity among three Chinese G. soja subpopulations. (2) Northern Chinese G. max subpopulation depicted higher genetic diversity than other two Chinese, Korean, Japanese and American G. max subpopulations. (3) Significant genetic differentiation (P < 0.001) was observed among Chinese G. soja subpopulations from three ecological zones. There was also a significant genetic differentiation（P < 0.01）between three Chinese and Japanese subpopulations of G. max. (4) The demographic dynamics revealed that effective population size of G. soja is expanding, while it was constant in G. max. G. soja is a useful germplasm resource to widen the genetic diversity of G. max. This study suggests that native populations of G. soja from different geo-ecological regions should be protected to conserve the genetic diversity.