Tunisian Potato virus Y isolates with unnecessary pathogenicity towards pepper: support for the matching allele model in eIF4E resistance–potyvirus interactions

The pathogenic properties of Potato virus Y (PVY; genus Potyvirus, family Potyviridae) isolates collected in naturally infected pepper (Capsicum annuum) fields in Tunisia were evaluated against recessive resistance alleles at the pvr2 locus of pepper. Two pathotypes were observed. Pathotype (0,1,3) isolates were able to infect plants carrying the susceptibility allele pvr2⁺, together with pvr2¹/pvr2¹ and pvr2³/pvr2³ plants, but not pvr2²/pvr2² plants. Pathotype (0) isolates were only able to infect pvr2⁺/pvr2⁺ plants. On the other hand, sequence data and phylogenetic analyses revealed three major groups of isolates, each characterized by particular amino acid residues in the central part of the VPg, the pathogenicity factor towards pvr2. Correspondence between pathogenic properties and phylogeny suggested a single evolutionary step for pathogenicity towards the pvr2¹ and pvr2³ resistances, possibly under the selective pressure of pvr2¹. Indeed, 23% of the pepper plants in this area were shown to carry the pvr2¹ resistance, while pvr2³ was not detected. The data suggested that pathogenicity towards pvr2¹ and pvr2³ were not costly for PVY to infect susceptible pepper genotypes and supported the matching allele model for pepper–PVY interactions.     

Genetic Analysis and QTL Mapping of Mature Seed Culturability in Indica Rice

Genetic segregation analysis for mature seed culturability was conducted using recombinant inbred lines derived from a cross of indica rice, Yangdao 6 and Pei'ai 64s. Three indices of seed culturability, the frequency of callus induction, the frequency of brown callus and the increase of callus weight were investigated. A combined genetic map constructed with simple sequence repeat (SSR), sequence tag site (STS), cleaved amplified polymorphic sequences (CAPS) and single nucleotide polymorphism (SNP) markers covered a total distance of 1 732.5 cM, averaging approximately 12 cM between two neighboring loci. Three QTLs on chromosomes 7, 7 and 10 were detected for the frequency of callus induction; three QTLs on chromosomes 6, 7 and 9 were detected for the frequency of brown callus; and two QTLs on chromosomes 5 and 7 were detected for the increase of callus weight. Common QTLs mapped at the interval flanking RM5481 and RM6835 on chromosome 7 were identified to be involved in the frequency of callus induction and the frequency of brown callus, explaining 7.29% and 12.52% of phenotypic variation, respectively. A total of 14 epistatic effects were detected for the three indices of mature seed culturability.     

大豆光合性状QTL的初步定位

光合速率的提高对大豆产量改良具有重要作用.本研究利用波高和南农94-156杂交所构建的RIL群体对4个光合性状QTL进行了初步定位.结果表明,大豆籽粒与光合速率间存在微弱的正相关,而4个光合性状间除光合速率与胞间CO2浓度外均为极显著的正相关.分别检测到1、2、1和2个QTL位点与光合速率(O连锁群)、气孔导度(A1和D1b W连锁群)、胞间COz浓度(G连锁群)和蒸腾速率(H和M连锁群)有关,相互间均不共位,前3个QTL解释的表型变异略低于10%,而后3个QTL可解释表型变异的10%以上.     

玉米产量因子QTL整合图谱构建与"一致性"QTL确定

应用生物信息学手段,收集和整理了411个玉米产量及构成因子QTL相关信息,借助高密度玉米遗传图谱IBM2 2005 Neighbors,采用BioMercator2.1软件构建出含221个QTL的整合图谱。采用统合分析方法,在LOD值大于4.0时于玉米第6染色体上确定1个与穗数、粒重和单位籽粒产量相关的”一致性“QTL,由标记bnlg1732和bnl8.08c界定,间距14.51cM。从MaizeGDB网站下载”一致性“QTL区间内基因和标记的原始序列,通过NCBI网站在线软件BLASTx同源比对分析,初步获得3个产量位置候选基因。利用比较基因电子定位策略,将53个水稻和玉米产量相关基因定位到玉米IBM2 2005 Neighbors图谱上,在”一致性“QTL区间内发现1个控制水稻分蘖数基因,初步确定为产量位置候选基因。本文结果为确定有关玉米产量因子的QTL及其候选基因提供了信息。     

Estimating allelic richness and its diversity

Assessing allelic richness in a set of populations requires that variations of sample size be taken into account. One way of doing this is to estimate the number of alleles expected in samples of specified size, using the rarefaction method applied in ecology. An alternative method, based on extrapolation, consists of adding to the number of alleles actually seen in a population the expected number of alleles missing, given the number of genes examined in the population and the allelic frequencies observed over the whole set of populations. Heterogeneity of allelic richness across populations and across loci can also be tested in this framework by numerical re-sampling. Both methods provide a measure of “private” allelic richness, a useful criterion in genetic diversity preservation, by allowing evaluation of the uniqueness of each population in terms of allele numbers. The two methods are compared on isozyme loci in the argan tree of Morocco and on microsatellite genotypes in the European pig. In both species, allelic richness and gene diversity behave quasi-independently over the populations compared and a higher differentiation is observed in allelic richness compared to gene diversity. In general, the rarefaction technique is sensitive to the sample size of reference and may lack sensitivity to rare alleles when the sample size of reference is small. Extrapolation may thus be recommended especially when the sample sizes of the populations are either low on average or highly unbalanced among populations.     

乐都本地山羊血清运铁蛋白多态性

采用聚丙烯酰胺凝胶电泳对８０只乐都本地山羊血清运铁蛋白的多态性进行研究。结果：被检山羊中有ＴＦＡＡ和ＴＦＡＢ两种基因型，以ＴＦＡＡ型为优势基因型（８６．３％）；ＴＦＡ和ＴＦＢ等位基因频率分别为０．９３１和０．０６９；基因杂合度和有效等位基因数分别为０．１２８和１．１４７。聚类分析表明，乐都本地山羊与藏山羊、英国阿尔卑山羊有较紧密的遗传联系。     

用(培矮64s/Nipponbare)F2群体对水稻产量构成性状的QTL定位分析

用水稻测序品种培矮64s和Nipponbare为亲本构建的含137个SSRs标记的连锁遗传图谱和（培矮64s/Nipponbare）F₂群体的180个单株，对水稻的单株有效穗数、穗粒数、穗实粒数、结实率、穗着粒密度、千粒重等6个产量构成性状进行了QTL定位分析。共检测到6个性状的22个QTLs，分布在第1、2、4、5、6、9、10、11、12等9条染色体的14个区域,表型贡献率5.0%-19.3%;相关性较强的性状之间具有较多共同或紧密连锁的QTLs;集中分布的QTLs之间既有同向连锁.对不同水稻群体定位的同源QTL进行了比较,对QTL在染色体上的集中分布,以及用QTL定位结果和生物信息学方法相结合预测基因的英勇等进行了探讨。     

两种磷水平下玉米产量性状的变化及其QTL定位

为了解低磷胁迫下玉米产量性状的影响及其遗传基础,以玉米重组自交系为研究材料,分别在低磷处理和正常条件下,比较供试群体的产量及构成性状的变化,并运用复合区间作图法对其进行QTL定位。结果表明,单株产量、穗重和轴重等性状受低磷胁迫影响较大,出籽率、穗行数和粒深等性状受低磷胁迫影响较小;通径分析表明,低磷胁迫主要通过影响行粒数、百粒质量和粒深构成性状导致了单株产量的损失。在2种磷水平下共检测到23个产量及其构成性状QTL;单个QTL可解释的表型变异为4.32%~14.77%;其中,标记区间bnlg666~umc1141和umc1108~bnlg1258分布了不同性状的多个QTL。这些成簇分布QTL的染色体区域和低磷胁迫条件QTL,可为开展玉米耐低磷分子育种提供参考。     

甜高粱茎秆含糖量性状的QTL定位

本研究以低茎秆含糖量的粒用高粱品系LR625(P1)和高茎秆含糖量的甜高粱品系Rio(P2)杂交获得的234个F2:3家系为试验材料,构建了含有92个高粱SSR标记、6个玉米SSR标记和自主开发的28个INDEL标记的遗传连锁图谱,并进行了茎汁混合锤度、茎秆重和出汁率性状的QTL定位。研究结果显示:共检测到7个与茎汁混合锤度有关的QTL,分布在高粱的第LG-3、LG-5、LG-7和LG-9连锁群上,解释的总表型变异为62.45%;4个与茎秆重有关的QTL,分布在高粱的第LG-2、LG-5、LG-6和LG-7连锁群上,解释的总表型变异为60.92%;8个与出汁率有关的QTL,分布在高粱的第LG-1、LG-2、LG-3、LG-6、LG-7和LG-9连锁群上,解释的总表型变异为99.75%。研究结果有助于深入理解茎秆含糖量遗传基础,为茎秆含糖量QTL精细定位和基因挖掘提供依据。     

组织培养、分子标记和QTL技术在青花菜育种中的应用

育种是优异种质资源基因的重组。除传统新种质产生的方法外,通过组织培养、分子标记等技术来扩大物种的遗传基础已成为新种质资源形成的重要手段。青花菜,芸薹属甘蓝中以绿色花球为食用器官的一个变种,近年来在中国的种植面积越来越大,利用现代生物技术手段进行青花菜育种研究工作也越来越受到关注和重视。本文综述了游离小孢子培养、原生质体融合和转基因技术在青花菜种质资源创制中的应用,分析了各种方法存在的问题,并对青花菜遗传图谱构建、花球相关农艺性状及抗病性QTL/基因定位研究进行了探讨,并对其未来研究方向做了展望。