2007-2008年江苏省稻瘟病菌遗传多样性

利用致病性测定及Pot2-rep-PCR技术对2007、2008年采集自江苏省五大稻区的稻瘟病菌株进行多样性分析,这2年的菌株被划分为10个小种和14个系谱,其中ZG1为优势小种,JSL5为优势系谱,研究结果表明:江苏稻瘟病菌具有丰富的多样性,但与1999 - 2002年的群体结构比较时发现,群体结构趋于简单;对病原菌...     

Combining ability,maternal, and reciprocal effects of elite early-maturing maize population hybrids

Choosing germplasm based on elite and diverse genetic sources is essential for the genetic improvement of maize (Zea mays L.) hybrids. The objectives of this research were to evaluate the agronomic and economic potential of maize population and single-cross hybrids and whether significant maternal (ME) and reciprocal effects (RE) reside in elite population hybrids for seed production purposes. Seven elite maize populations currently under recurrent selection at North Dakota State University (NDSU) [NDSCD(M-S)C11, NDSAB(MER-FS)C14, BS21(R)C7, BS22(R)C7, LEAMING(S)C4, CGL(S₁-S₂)C5 and CGSS(S₁-S₂)C5] were crossed in a diallel mating design to form 42 population hybrids, including their reciprocals. The 42 population hybrids with eight single-cross hybrids were evaluated at six U.S. North Central locations in 2005. Data collected across locations indicated that differences across genotypes were significant (P ≤ 0.05) for all traits observed, except for grain yield ear components. General combining ability (GCA) effects were on average larger than specific combining ability (SCA) effects. ME and RE were not significant for all traits, except for ear height. The large grain yield differences between macro-environments were reflected in the ranking of genotypes, with BS21(R)C7 × BS22(R)C7 being the top performer in eastern environments and CGSS(S1-S2)C5 × NDSAB(MER-FS)C14 being the top one across western environments where drought is the major limitation. The increased ethanol production and demand from maize make test weight (and grain quality), earliness, lodging resistance, and drought tolerance as important as grain yield for maintaining a sustainable maize-ethanol relationship. Part of the thesis submitted by McDonald B. Jumbo in partial fulfillment of the requirements for a MS degree at North Dakota State University.     

长宁竹区竹裂爪螨生物学及楠竹害螨消长动态研究

在21℃、24℃、27℃、30℃、33℃5种不同温度条件下,用新鲜的离体楠竹叶片在室内饲养竹裂爪螨,得出该螨实验种群的主要生物学参数,应用直接最优法计算该螨的世代发育起点温度和有效积温分别为12.53℃、150.25日度,根据气象资料预测竹裂爪螨在长宁竹区年发生13－14代;每年3月下旬－4月上旬出蜇,11月份开始以雌成螨越冬。林间实际调查表明,楠竹害螨在竹区的发生与危害存在明显的春季高峰并与楠竹林的敏感生长期相吻合;降雨与高温严重影响楠竹害螨的生长发育,表现为7、8月份高温多雨季节林间害螨种群数量呈现出急剧下降。     

杀虫剂螨危的亚致死剂量对朱砂叶螨种群参数的影响

朱砂叶螨是桑树的主要害虫之一。从避免过度使用农药造成环境污染和控制害螨的抗性发展的角度,研究了杀虫剂螨危的亚致死剂量对朱砂叶螨敏感种群生存与繁殖能力的影响。分别用质量浓度为1.25、2.5、5、10、40 mg/L的螨危药液处理雌成螨,48 h后的存活率分别为96%、83%、81%、75%、48%;药液对雌成螨和卵的致死中浓度(LC50)分别是35.005 mg/L和0.690 mg/L,卵的敏感性明显高于雌成螨。与对照组相比,随螨危药液处理浓度增高,雌成螨的7 d总产卵量和孵化率呈下降趋势;用10、5、2.5、1.25 mg/L药液处理后朱砂叶螨种群的瞬时增长率(ri)分别是-0.083、0.142、0.214、0.298,而对照组为0.544,有效中浓度(EC50)值为1.627 mg/L。研究结果表明,用低于推荐使用浓度(40 mg/L)的螨危药液就能有效控制朱砂叶螨种群的增长。     

Reduced effective population size in an overexploited population of the Nile crocodile (Crocodylus niloticus)

Unchecked exploitation of wildlife resources is one of the major factors influencing species persistence throughout the world today. A significant consequence of exploitation is the increasing rate at which genetic diversity is lost as populations decline. Recent studies suggest that life history traits affecting population growth, particularly in long-lived species, may act to moderate the impact of population decline on genetic variation and lead to remnant populations that appear genetically diverse despite having passed through substantial demographic bottlenecks. In this study we show that the retention of genetic variation in a partially recovered population of Nile crocodile is deceptive, as it masks the reality of a significant decline in the population’s effective size (N_e). Repeated episodes of unchecked hunting in the mid to late 20th century have today led to a five-fold decrease in the population’s N_e. Using current census data we estimate the contemporary N_e/N ratio as 0.05 and, in light of quotas that permit the ongoing removal of adults, simulated the likely effects of genetic drift on extant levels of variation. Results indicate that even if the current effective size is maintained, both allelic diversity and heterozygosity will decline. Our findings have complex implications for long-lived species; an emphasis on the retention of genetic variation alone, whilst disregarding the effects of population decline on effective size, may ultimately obscure the continued decline and extinction of exploited populations.     

基于气候生产潜力的云南人粮关系及其未来变化

基于云南117个气象站1961?2015年观测实况及全球气候模式模拟的2016?2055年年平均气温、降水量数据,使用Thornthwaite Memorial模型计算并分析云南各地气候生产潜力（Tspv）的时空变化特征,构建并计算Tspv的人口承载力（Tspv-人口承载力）和气候承载力指数。结果表明：（1）云南Tspv呈现明显的纬向分布及垂直分布特征,总体表现为南部高于北部,低海拔地区高于高海拔地区,降水是云南Tspv主要限制因子;（2）1961-2015年全省Tspv仅滇西的部分地区显著增加,滇中局部等地显著减少,其余地区变化不显著,全省平均Tspv年际波动大,在2009年前后发生突变;（3）2006-2015年云南人均粮食供应稳定增长,接近或超过小康型粮食需求,耕地的人口承载力（耕地,人口承载力）逐年增加,但远低于Tspv-人口承载力,即使在极端减产年,Tspv-人口承载力水平仍能满足当前人口、耕地规模下富裕型粮食需求,人粮关系状态为盈余;（4）如果保持现有稳定的人口、耕地及生产力水平增幅,未来不同的排放情景下,云南Tspv及Tspv-人口承载力都将稳定增加,人粮关系状态以粮食盈余为主,且高排放情景下承载力和人粮关系状态水平均优于低排放情景。     

Sclerotium rolfsii dynamics in soil as affected by crop sequences

Crop rotation has been used for the management of soilborne diseases for centuries, but has not often been planned based on scientific knowledge. Our objective was to generate information on Sclerotium rolfsii dynamics under different crop or intercrop activities, and design and test a research approach where simple experiments and the use of models are combined to explore crop sequences that minimize Southern blight incidence.The effect of seventeen green manure (GM) amendments on sclerotia dynamics was analyzed in greenhouse and field plot experiments during two years. The relative densities of viable sclerotia 90 days after winter GM (WGM) incorporation were generally lower than after summer GM (SGM) incorporation, with average recovery values of 60% and 61% for WGM in the field, 66% and 43% for WGM in the greenhouse, and 162% to 91% for SGM in the greenhouse, in 2009 and 2010, respectively. Sclerotia survival on day d after GM amendment was described by the model S_f = S_i × exp(−b × d), relating initial (S_i) and final (S_f) sclerotia densities. Relative decay rates of the sclerotia (b) in SGM amended soil were largest for alfalfa (0.0077 ± 0.0031 day⁻¹) and sudangrass (0.0072 ± 0.0030 day⁻¹). In WGM amended soil, the largest b values were for oat (0.0096 ± 0.0024 day⁻¹), wheat (0.0090 ± 0.0024 day⁻¹) and alfalfa (0.0087 ± 0.0023 day⁻¹).The effect of three cropping sequences (sweet pepper–fallow, sweet pepper–black oat and sweet pepper–onion) on sclerotia dynamics was analyzed in microplot experiments, and the data were used to calibrate the model P_f = P_i/(α + βP_i), relating initial (P_i) and final (P_f) sclerotia densities. Median values for the relative rate of population increase at low P_i (1/α, dimension less) and the asymptote (1/β, number of viable sclerotia in 100 g of dry soil) were 8.22 and 4.17 for black oat (BO), 1.13 and 8.64 for onion (O), and 6.26 and 17.93 for sweet pepper (SwP).By concatenating the two models, sclerotia population dynamics under several crop sequences were simulated. At steady state, the sequence SwP–O–Fallow–BO resulted in the lowest long-term sclerotia density (7.09 sclerotia/100 g soil), and SwP–Fallow in the highest (17.89 sclerotia/100 g soil). The developed methodology facilitates the selection of a limited number of rotation options to be tested in farmers’ fields.     

An evaluation of field and non-invasive genetic methods to estimate brown bear (Ursus arctos) population size

Estimates of population size and density are essential for successful management and conservation of any species. Although there are a variety of methods available for estimating abundance and density of populations, most studies rely on only one estimator and very few studies have compared and critically evaluated the adequacy and the cost of these methods. We used the brown bear (Ursus arctos) in south-central Sweden to compare the performance of three different methods of estimating population size, including methods based on conventional field data as well as on non-invasive genetic data. The method based on observations of females with cubs underestimated the true population size, as the estimates were below the number of unique genotypes determined from faecal data inside the study area. The best traditional method was based on observations of bears from a helicopter. The genetic method using the closed population MARK estimator, as recommended in a previous study, seemed to perform the best. We conclude that approximately 223 (188-282) bears were present in our 7328 km² study area during 2001 and 2002 and suggest that this hunted brown bear population has been relatively stable for about ten years. The non-invasive genetic method was less expensive than the most reliable traditional field method (a CMR method based on observations of bears from a helicopter), and preferable from an ethical point of view. We recommend that future studies using non-invasive genetic methods based on collected faecal samples should aim at collecting 2.5-3 times the number of faecal samples as the “assumed” number of animals.     

The ecology of extinction: population fluctuation and decline in amphibians

Even among widespread species with high reproductive potentials and significant dispersal abilities, the probability of extinctions should be correlated both with population size variance and with the extent of population isolation. To address how variation in demographic characteristics and habitat requirements may reflect on the comparative risk of species decline, I examined 617 time series of population census data derived from 89 amphibian species using the normalized estimate of the realized rate of increase, ΔN, and its variance. Amphibians are demonstrably in general decline and exhibit a great range of dispersal abilities, demographic characteristics, and population sizes. I compared species according to life-history characteristics and habitat use. Among the populations examined, census declines outnumbered increases yet the average magnitudes for both declines and increases were not demonstrably different, substantiating findings of amphibian decline. This gives no support for the idea that amphibian population sizes are dictated by regimes featuring relatively rare years of high recruitment offset by intervening years of gradual decline such that declines may outnumber increases without negative effect. For any given population size, those populations living in large streams or in ponds had significantly higher variance than did populations of completely terrestrial or other stream-dwelling amphibians. This could not be related to life-history complexity as all the stream-breeding species examined have larvae and all of the wholly terrestrial species have direct development without a larval stage. Variance in ΔN was highest amongst the smallest populations in each comparison group. Estimated local extinction rates averaged 3.1% among pond-breeding frogs, 2.2% for pond-breeding salamanders, and negligible for both stream-breeding and terrestrial direct-developing species. Recoveries slightly exceeded extinctions among European pond-breeding frogs but not among North American pond-breeding frogs. Less common species had greater negative disparities between extinctions and recoveries. Species with highly fluctuating populations and high frequencies of local extinctions living in changeable environments, such pond- and torrent-breeding amphibians, may be especially susceptible to curtailment of dispersal and restriction of habitat.     

中亚热带檫树群落种问竞争及其种群密度调节的研究

研究中亚热带檫树群落种间竞争关系结果表明 ,平衡时檫树与其主要伴生树种光皮桦、丝栗栲重要值分别占 80 .6 4 %、12 .4 7%和 6 .89% ,呈共优状态但分布极不均匀。利用自疏模型并经改进单纯形法最优拟合求得檫树种群密度效应模型 ,且拟合结果达显著水平 ,反映出檫树种群自疏过程密度调节规律。