中国作物种质资源安全保存理论与实践

我国是作物种质资源大国,目前已经收集保存了340种作物,保存资源总量达50万份,如何确保安全保存是种质资源管理的首要课题。自"九五"以来,系统地开展了作物种质资源安全保存理论与技术的研究,揭示了种质活力丧失存在关键节点及其生物学机制;明确了发芽率低于关键节点后进行更新,会导致群体遗传完整性降低;提出了种质安全保存寿命的概念,以及延长安全保存寿命的关键因素。研发了种质活力监测预警、繁殖更新与离体保存等关键技术,制定了种质资源入库圃保存、监测预警、繁殖更新、离体保存和设施建设等技术规程,创建了中国作物种质资源安全保存技术体系。该体系应用于全国作物种质资源的保存实践,最大程度延长种质安全保存寿命,并监测预警出需更新的种质,避免因活力和遗传完整性丧失而导致种质资源得而复失,为实现我国作物种质资源长久安全保存提供了有力保障。     

利用SRAP和SSR分子标记检测分析29份棉花种质遗传完整性

利用SRAP和SSR分子标记检测29份棉花种质遗传完整性。结果表明,无论每一份不同更新发芽率水平繁殖后代的种质之间,还是每一份不同繁殖世代数种质之间,其等位基因频率差异不显著,也没有检测到稀有等位基因缺失的情况。本试验表明不同更新发芽率水平和繁殖世代数差异没有对棉花这种常异花授粉作物种质遗传完整性变化产生影响。     

首部作物种质资源安全保存专著《作物种质资源安全保存原理与技术》正式出版

作物种质资源的安全保存是其有效利用的前提,安全保存需要确保维持种质高生活力和遗传完整性。国家农作物种质资源种质库圃已经收集保存超过51万份作物种质资源,此外各省、研究机构、育种单位也保存有大量作物种质资源。然而入库圃保存并不是一劳永逸的,种质库保存的资源会面临因活力下降而丧失的风险,种质圃保存的资源易遭受自然灾害和生境恶化等威胁,也存在丧失的风险。     

繁殖群体量及隔离对蚕豆种质遗传完整性的影响

为研究繁殖群体量和隔离方式对常异花授粉作物蚕豆种质繁殖更新的影响,以9份蚕豆地方种质为对象,以国家库保存的原种为对照群体,采用AFLP分子标记方法,对比了50株和20株群体量及开放无隔离群体和网棚隔离群体更新后代的遗传完整性差异。结果表明:与对照群体相比,50株和20株群体的多态性位点数、多态位点百分率、每位点有效等位基因数、香农指数、遗传多样性指数均出现不同程度下降,但下降幅度20株大于50株群体;遗传相似性和UPGMA聚类分析表明50株群体与对照群体的遗传相似性高于20株群体;网棚隔离可降低群体间串粉与花粉污染,但其遗传完整性却较开放无隔离群体低。     

种子老化对玉米种质资源遗传完整性变化的影响

对经老化处理得到的不同发芽率水平的玉米地方品种条花糯进行农艺性状观察和SSR分子标记分析.结果表明,种子发芽率水平下降影响出苗植株中芽鞘和叶鞘颜色的比率.当发芽率降到32%时,浅紫色芽鞘植株的比率降至0.当发芽率下降时,浅紫色叶鞘植株的比率升高,而白色叶鞘植株的比率则下降.经SSR分析发现,低发芽率群体的多态性条带百分率、等位基因数、有效等位基因数、基因多样性指数、Shannon指数等遗传参数,与对照群体的遗传参数相比都有所下降,表明老化处理后群体内的遗传多样性低于对照群体的遗传多样性,群体内遗传变异出现下降.本试验结果表明,植株形态标记和SSR分子标记可以作为老化种子遗传完整性变化的检测方法,同时认为对于异质种质资源材料,低的发芽率更新标准不利于种质资源遗传完整性的保持.     

作物种质资源的价值及其评估体系的初步构建

通过对作物种质资源的价值评估与核算的维度与要素的分析,提出了作物种质资源价值评估与核算理论的基本框架,初步建立起了包括作物种质资源的实物量核算、价值量核算和质量指数核算、个体核算和总体核算、数量向量核算、质量向量核算在内的多维度作物种质资源价值评估核算体系.作物种质资源的数量向量核算,首先建立种质资源的账户,以反映资源的增减量,通过作物种质资源的现行市场或既往市场价格构成因素,采取对比法、成本法和收益还原法等不同的核算方法进行价值核算;作物种质资源的质量向量的核算评估,包括质量因子核算以及遗传多样性的评估,具体采用DTOPSIS法进行多效应作物种质资源基准价值核算,运用统计学的方差分析方法和分子水平上遗传多样性相关参数的度量,进行遗传多样性评价.     

基于作物种质资源的优异等位基因挖掘：进展与展望

作物种质资源中蕴含着大量优异等位基因,如何鉴定并将这些变异应用于作物遗传改良是种质资源研究的中心任务之一。等位基因挖掘对种质资源遗传多样性分析、作物起源与演化研究、重要性状形成的分子基础阐释、种质创新与作物育种具有重要意义,也是作物分子设计育种的基石。因此,未来需要进一步研发更加高效的等位基因挖掘策略与技术方法,加速优异等位基因的发现及其在作物遗传改良中的应用。本文重点评述了等位基因发掘的主要策略与技术途径,提出了今后的重点任务与发展方向。     

烟草种质繁种更新理论与技术

烟草种质资源的繁种更新是烟草中期库保种的重要任务之一。为保持其在保存过程中的遗传完整性,从烟草的遗传特性出发,对繁育过程中可能产生的遗传漂变、遗传漂移以及混杂等诸多因素进行了讨论;较为系统地总结了烟草种质资源长期研究所形成的繁种更新理论与技术,并就进一步研究提出设想。     

烟草种质繁种更新理论与技术

烟草种质资源的繁种更新是烟草中期库保种的重要任务之一。为保持其在保存过程中的遗传完整性,本文从烟草的遗传特性出发,对繁育过程中可能产生的遗传漂变、遗传漂移以及混杂等诸多因素进行了讨论;较为系统地总结了烟草种质资源长期研究所形成的繁种更新理论与技术,并就进一步研究提出设想。     

基于醇溶蛋白的20份小麦种质遗传完整性分析

采用醇溶蛋白电泳技术对同一品种不同繁殖年份的20份小麦种质进行遗传完整性分析。结果表明：供试种质中有10份具有一种醇溶蛋白谱带带型的同质性种质;另外10份具有2～4种醇溶蛋白谱带带型的异质性种质,其中6份为地方品种。表明地方品种具有较高的遗传多样性。在10份异质性种质中,两个繁殖年份种质之间的醇溶蛋白带型频率变化差异不显著的有5份,其第一繁殖年份的种质发芽率均高于75％,而另外5份存在显著差异的种质,第一年份的发芽率都低于66％。进一步分析表明,这10份异质性种质在两个繁殖年份之间,其发芽率差值与带型频率差值之间呈极显著正相关,相关系数为0．8665。上速结果表明,小麦更新时较高的发芽率是维持异质性种质遗传完整性的关键因素。     

Effect of regeneration procedures on the genetic integrity of Brassica oleracea accessions

A Brassica oleracea collection of landraces collected in the northwest of Spain is kept at the Gene Bank placed at ‘Misión Biológica de Galicia’. Landraces of the collection are regenerated from time to time to restore the viability of the seed and to carry on field trials. The objective of this work is to study the effect of regeneration on the genetic integrity of three accessions of this collection, and to investigate the possible causes of the genetic changes observed. After characterizing the original populations and their following regenerated populations by 25 SSRs we concluded that there were significant changes in the population structure and the allelic frequency of individual loci due to the action of genetic drift, directional selection and probably assortative mating. Protocols to store and regenerate the accessions should be improved in order to avoid the effect of these forces in the genetic integrity of the collection. Research supported by the project PIE20064-01-089 and the Excma. Diputación Provincial de Pontevedra, Spain.     

Genebank biodiversity assessments regarding optimal sample size and seed harvesting techniques for the regeneration of carrot accessions

Small, finite populations are particularly vulnerable to diversity loss during regeneration. The regeneration of a highly outbreeding open-pollinated variety relies on estimated effective population size, via the measurement of temporal change in allele frequencies. Using appropriate estimators for dominant gene markers, effective sizes were calculated for five sizes of a mating population and two seed harvesting procedures. We have shown that, in the case of carrot regeneration, 70 equally harvested plants should provide an effective size (N _e) of at least 50 plants. This value seems sufficient to limit genetic drift and to preserve an efficient level of genetic diversity within the collection. The efficiency of balanced samples (made of an equal number of seeds per plant) is compared to that of bulk samples (seeds randomly chosen among the total seed lot coming from all the plants).     

Effects of native forest regeneration practices on genetic diversity in Eucalyptus consideniana

Impacts of forest harvesting and regeneration practices on genetic diversity in the Australian native forest species Eucalyptus consideniana Maiden (yertchuk) were examined using 29 Mendelian DNA markers (18 RFLPs and 11 microsatellites). Two replicate logging coupes were studied from each of the two most commonly employed silvicultural treatments: clear felling with aerial re-sowing and the seed tree system. For each coupe, genetic diversity measures were compared between a sample of the sapling regeneration and a corresponding control sample from bordering unharvested trees. When calculations were performed over all 29 loci, significant reductions of allelic richness (AR), effective number of alleles (AE) and/or expected heterozygosity (HE) were detected on one or both of seed tree coupes, but on neither of the clear falls. When calculations were performed over the 11 microsatellites alone, all three measures, AR, AE and HE, were significantly reduced on both of the seed replicates but on neither of the two clear falls. In contrast, when the RFLPs were examined separately, there were no significant reductions of diversity on either of the two seed tree coupes or on the two clear falls. These results suggest that genetic erosion is more likely under the seed tree system than under clear-felling with aerial re-sowing and that there is greater statistical power to detect it with microsatellites than with RFLPs. A Monte Carlo simulation to test the statistical significance of the number of apparently lost or gained alleles showed that significant losses of alleles above specified threshold frequencies occurred only in the two seed tree replicates. Three of the four control and regeneration population pairs were significantly differentiated, as indicated by exact tests or by pairwise FST estimates. Comparisons of CONTML dendrograms, constructed for the regeneration populations only versus the control populations only, indicated that genetic drift was significantly promoted under forest management. No significant decreases in observed heterozygosity, or increases in the panmictic index (f), were observed in any of the comparisons suggesting that inbreeding was not promoted by a single rotation of forest management.     

Heterogeneous genetic structure in a Fagus crenata population in an old-growth beech forest revealed by microsatellite markers

The within-population genetic structure of Fagus crenata in a 4-ha plot (200 x 200 m) of an old-growth beech forest was analysed using microsatellite markers. To assess the genetic structure, Moran's I spatial autocorrelation coefficient was calculated. Correlograms of Moran's I showed significant positive values less than 0.100 for short-distance classes, indicating weak genetic structure. The genetic structure within the population is created by limited seed dispersal, and is probably weakened by overlapping seed shadow, secondary seed dispersal, extensive pollen flow and the thinning process. Genetic structure was detected in a western subplot of 50 x 200 m with immature soils and almost no dwarf bamboos (Sasa spp.), where small and intermediate-sized individuals were distributed in aggregations with high density because of successful regeneration. By contrast, genetic structure was not found in an eastern subplot of the same size with mature soils and Sasa cover, where successful regeneration was prevented, and the density of the small and intermediate-sized individuals was low. Moreover, genetic structure of individuals in a small-size class (diameter at breast height < 12 cm) was more obvious than in a large-size class (diameter at breast height >/= 12 cm). The apparent genetic structure detected in the 4-ha plot was therefore probably the result of the structure in the western portion of the plot and in small and intermediate-sized individuals that successfully regenerated under the favourable environment. The heterogeneity in genetic structure presumably reflects variation in the density that should be affected by differences in regeneration dynamics associated with heterogeneity in environmental conditions.     

小麦地方品种繁殖更新过程中的遗传多样性变化分析

采用分别保存于长期库及中期库的3个小麦地方品种的6份材料,进行了9项农艺性状及35个与农艺性状相关的微卫星标记检测,每份材料选取30个单株进行遗传多样性与遗传结构分析。结果表明:(1)更新前,3个小麦地方品种均为遗传异质性群体,在SSR位点上的异质度分别为57.14%、48.57%和5.71%。(2)在农艺性状表现上,只有温泉小麦3在株高和穗粒数上更新后比更新前显著增加,其他材料无显著差异。(3)在SSR位点多态性表现上,3个品种在更新后均发生了遗传多样性变化,8个与粒重、产量、生育期性状相关位点存在等位位点丢失现象,其中2个与粒重、生育期相关位点频率变化显著。(4)综合农艺性状调查与SSR分子标记检测结果发现,3个品种更新前后在多样性指数上无显著差异,遗传分化系数Gst分别为0.0269、0.0324和0.0380,即更新前后遗传差异分别为2.69%、3.24%和3.80%。上述结果建议,经繁殖更新的小麦种质资源能够比较完好地保持其遗传多样性和遗传结构。对于遗传异质性小麦地方品种在繁殖更新后存在遗传多样性丢失的危险,为了保证更新前后的遗传完整性,建议在繁殖更新过程中每个品种至少应保持300个单株的群体。     

Quantitative genetic diversity and conservation strategies for an allogamous annual species,Dasypyrum villosum (L.) Candargy (Poaceae)

Dasypyrum villosum (L.) Candargy is a weedy annual diploid (2n = 14, VV genomes) allogamous grass species (Poaceae, Triticeae). Genetic variation for 12 traits was studied in 43 natural populations (31 from Italy and 12 from Croatia and Montenegro of former Yugoslavia) grown in a common field environment in California. Although 7 of 12 traits followed the theoretical prediction that a larger proportion of genetic variation was distributed within populations than among populations, exceptions were found for spike length, plant height, and days to flag-leaf emergence, heading, and anthesis. Covariate analysis showed that developmentally closely related characters were more likely correlated at both population and family within population levels. Geographically closer populations shared more genetic similarity than distant populations as indicated by mean coefficients of variation and cluster analysis of the Euclidean distances among populations. As few as five populations, each population with five or more half-sib seeds taken randomly from 5 plants, is expected to capture more than 95% of the total genetic variation of this species in the region sampled, but sampling a much larger number of seeds per population (> 1000) for long-term storage would supply research and plant breeding needs for several decades. If seed regeneration is required, populations can be sampled from clusters having similar genetic variation, and grown in reproductive isolation or bulked seed samples from all populations of each cluster group can be grown in isolation. The former is recommended if population integrity is desired while the latter is sufficient to provide genetic resources for plant-breeding purposes.     

潮霉素在大麦遗传转化中的应用研究

以‘B1202’、‘U202’和‘云引1号’3个大麦品种(系)为试材,研究了潮霉素对大麦愈伤组织生长、分化及成熟种子的影响。结果表明:潮霉素对抗性愈伤的适宜筛选浓度为60 mg/L,分化阶段的适宜筛选浓度为40 mg/L,对转基因后代种子筛选以80 mg/L较为适宜,而不同材料对潮霉素的敏感性存在一定程度的差异。通过PCR检测采用农杆菌介导法转化获得的T0和T1代潮霉素抗性苗,结果证实在大麦遗传转化中采用潮霉素进行筛选是可行的。     

Soil seed bank and seed dormancy in wild populations of lima bean (Fabaceae): considerations for in situ and ex situ conservation

Seed dormancy and its impact on the soil seed bank for wild Lima bean (Phaseolus lunatus) populations were studied in the Central Valley of Costa Rica. Five populations were selected in contrasted environments. In all cases, distribution of seeds in the soil was limited to 3 cm depth. No innate dormancy was observed but combination of hard seed coat and hilum opening controlled by environmental conditions were responsible for an induced dormancy and the constitution of a persistent seed bank. Breaking of this dormancy was obtained by a brief elevation of temperature from 25° to 45°C. Impacts of this phenomenon concern both genetic and demographic aspects of in situ conservation of the species. Consequences on ex situ conservation are mainly related with the regeneration of the seed collection.