大白菜骨干自交系的苗期抗病性评价

为明确大白菜骨干自交系的抗病性,本研究于2012-2014年,对课题组保存和创制的203个大白菜自交系进行了霜霉病、病毒病、黑腐病、黄萎病和根肿病的苗期抗性评价。结果显示,高抗上述病害的自交系分别有7、9、0、31和12个;只抗其中一种病害的自交系82个;兼抗两种病害的有61个,兼抗三种病害的自交系有28个,兼抗四种病害的自交系有4个。自交系11-234、04-622、12-85、13-108和09-894综合抗病性最优。此外,春大白菜、夏大白菜和秋大白菜三种生态类群间,以及四种叶球抱合类群间的抗病性表现出明显差异。     

Internal transcribed spacer 2 amplicon as a molecular marker for identification of Peronospora parasitica (crucifer downy mildew)

AIMS: The purpose of the study was to characterize the internal transcribed spacer (ITS) regions of Peronospora parasitica (crucifer downy mildew) in order to evaluate their potential as molecular markers for pathogen identification. METHODS AND RESULTS: PCR amplification of ribosomal RNA gene block (rDNA) spacers (ITS1 and ITS2) performed in 44 P. parasitica isolates from different Brassica oleracea cultivars and distinct geographic origins, revealed no length polymorphisms. ITS restriction analysis with three endonucleases, confirmed by sequencing, showed no fragment length polymorphisms among isolates. Furthermore, ITS amplification with DNA isolated from infected host tissues also allowed the detection of the fungus in incompatible interactions. The combination of the universal ITS4 and ITS5 primers, for amplification of full ITS, with a new specific forward internal primer for ITS2 (PpITS2F), originates a P. parasitica specific amplicon, suitable for diagnosis. CONCLUSIONS: As ITS2 regions of P. parasitica, B. oleracea, other B. oleracea fungal pathogens and other Peronospora species are clearly distinct, a fast and reliable molecular identification method based on multiplex PCR amplification of full ITS and P. parasitica ITS2 is proposed for the diagnosis of crucifer downy mildew. SIGNIFICANCE AND IMPACT OF THE STUDY: The method can be applied to diagnose the disease in the absence of fungal reproductive structures, thus being useful to detect nonsporulating interactions, early stages of infection on seedlings, and infected young leaves packed in sealed plastic bags. Screening of seed stocks in sanitary control is also a major application of this diagnostic method.     

Basic compatibility of Albugo candida in Arabidopsis thaliana and Brassica juncea causes broad-spectrum suppression of innate immunity

A biotrophic parasite often depends on an intrinsic ability to suppress host defenses in a manner that will enable it to infect and successfully colonize a susceptible host. If the suppressed defenses otherwise would have been effective against alternative pathogens, it follows that primary infection by the "suppressive" biotroph potentially could enhance susceptibility of the host to secondary infection by avirulent pathogens. This phenomenon previously has been attributed to true fungi such as rust (basidiomycete) and powdery mildew (ascomycete) pathogens. In our study, we observed broad-spectrum suppression of host defense by the oomycete Albugo candida (white blister rust) in the wild crucifer Arabidopsis thaliana and a domesticated relative, Brassica juncea. A. candida subsp. arabidopsis suppressed the "runaway cell death" phenotype of the lesion mimic mutant lsd1 in Arabidopsis thaliana in a sustained manner even after subsequent inoculation with avirulent Hyaloperonospora arabidopsis (Arabidopsis thaliana downy mildew). In sequential inoculation experiments, we show that preinfection by virulent Albugo candida can suppress disease resistance in cotyledons to several downy mildew pathogens, including contrasting examples of genotype resistance to H. arabidopsis in Arabidopsis thaliana that differ in the R protein and modes of defense signaling used to confer the resistance; genotype specific resistance in B. juncea to H. parasitica (Brassica downy mildew; isolates derived from B. juncea); species level (nonhost) resistance in both crucifers to Bremia lactucae (lettuce downy mildew) and an isolate of the H. parasitica race derived from Brassica oleracea; and nonhost resistance in B. juncea to H. arabidopsis. Broad-spectrum powdery mildew resistance conferred by RPW8 also was suppressed in Arabidopsis thaliana to two morphotypes of Erysiphe spp. following pre-infection with A. candida subsp. arabidopsis.     

Identification of the BrRHP1 locus that confers resistance to downy mildew in Chinese cabbage (Brassica rapa ssp. pekinensis) and development of linked molecular markers

Inheritance of resistance to downy mildew (Hyaloperonospora parasitica) in Chinese cabbage (Brassica rapa ssp. pekinensis) was studied using inbred parental lines RS1 and SS1 that display strong resistance and severe susceptibility, respectively. F(1), F(2), and BC(1)F(1) populations were evaluated for their responses to downy mildew infection. Resistance to downy mildew was conditioned by a single dominant locus designated BrRHP1. A random amplified polymorphic DNA (RAPD) marker linked to BrRHP1 was identified using bulked segregant analysis and two molecular markers designated BrPERK15A and BrPERK15B were developed. BrPERK15B was polymorphic between the parental lines used to construct the reference linkage map of B. rapa, allowing the mapping of the BrRHP1 locus to the A1 linkage group. Using bacterial artificial chromosome clone sequences anchored to the A1 linkage group, six simple polymerase chain reaction (PCR) markers were developed for use in marker-assisted breeding of downy mildew resistance in Chinese cabbage. Four simple PCR markers flanking the BrRHP1 locus were shown to be collinear with the long-arm region of Arabidopsis chromosome 3. The two closely linked flanking markers delimit the BrRHP1 locus within a 2.2-Mb interval of this Arabidopsis syntenic region.     

Sources of resistance to downy mildew (<Emphasis Type="Italic">Peronospora parasitica</Emphasis> (Pers. (ex Fr.) Fr.) in Sicilian germplasm of cauliflower and broccoli

Downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) is a serious disease of brassicas in several countries. Seedlings are very susceptible to this pathogen and crops require frequent fungicide treatments to reach a good marketable yield. The use of resistant cultivars can be the most economical, reliable and environmental friendly method for managing this disease. In this work 32 Sicilian landraces and 16 commercial cultivars of cauliflower and broccoli (B. oleracea) were screened for downy mildew resistance at the cotyledon stage using one P. parasitica strain from Portugal and one from Sicily (Italy). Seven-day old seedlings were inoculated by deposing a droplet of a spore suspension on the cotyledons, incubated under controlled environment and scored 7 days later using a seven-class scale of interaction phenotype (IP), which took into consideration host response and pathogen sporulation. There were no differences in virulence between the two P. parasitica isolates. Accessions ranged from very susceptible to highly resistant to downy mildew showing a variable number of resistant individuals per accession. Forty accessions were very susceptible to downy mildew and are of no interest as sources of resistance, since most of the seedlings were scored in the most susceptible IP classes. Seven accessions had intermediate resistance and included individuals that expressed some degree of resistance. Accession Cv 90 (Cavolfiore Torino) and Br 63 (Sparaceddu) showed the majority of seedlings in the resistant IP classes and may constitute valuable sources of resistance to downy mildew to be used in breeding programs.     

Characterization of eds1, a mutation in Arabidopsis suppressing resistance to Peronospora parasitica specified by several different RPP genes.

The interaction between Arabidopsis and the biotrophic oomycete Peronospora parasitica (downy mildew) provides an attractive model pathosystem to identify molecular components of the host that are required for genotype-specific recognition of the parasite. These components are the so-called RPP genes (for resistance to P. parasitica). Mutational analysis of the ecotype Wassilewskija (Ws-0) revealed an RPP-nonspecific locus called EDS1 (for enhanced disease susceptibility) that is required for the function of RPP genes on chromosomes 3 (RPP1/RPP14 and RPP10) and 4 (RPP12). Genetic analyses demonstrated that the eds1 mutation is recessive and is not a defective allele of any known RPP gene, mapping to the bottom arm of chromosome 3 (approximately 13 centimorgans below RPP1/RPP14). Phenotypically, the Ws-eds1 mutant seedlings supported heavy sporulation by P. parasitica isolates that are each diagnostic for one of the RPP genes in wild-type Ws-0; none of the isolates is capable of sporulating on wild-type Ws-0. Ws-eds1 seedlings exhibited enhanced susceptibility to some P. parasitica isolates when compared with a compatible wild-type ecotype, Columbia, and the eds1 parental ecotype, Ws-0. This was observed as earlier initiation of sporulation and elevated production of conidiosporangia. Surprisingly, cotyledons of Ws-eds1 also supported low sporulation by five isolates of P. parasitica from Brassica oleracea. These isolates were unable to sporulate on > 100 ecotypes of Arabidopsis, including wild-type Ws-0. An isolate of Albugo candida (white blister) from B. oleracea also sporulated on Ws-eds1, but the mutant exhibited no alteration in phenotype when inoculated with several oomycete isolates from other host species. The bacterial resistance gene RPM1, conferring specific recognition of the avirulence gene avrB from Pseudomonas syringae pv glycinea, was not compromised in Ws-eds1 plants. The mutant also retained full responsiveness to the chemical inducer of systemic acquired resistance, 2,6-dichloroisonicotinic acid; Ws-eds1 seedlings treated with 2,6-dichloroisonicotinic acid became resistant to the Ws-0-compatible and Ws-0-incompatible P. parasitica isolates Emwa1 and Noco2, respectively. In summary, the EDS1 gene appears to be a necessary component of the resistance response specified by several RPP genes and is likely to function upstream from the convergence of disease resistance pathways in Arabidopsis.     

Evidence for Differential Resistance to Peronospora parasitica (downy mildew) in Accessions of Brassica juncea (mustard) at the Cotyledon Stage

Thirty-one Brassica juncea accessions were screened at the cotyledon stage for resistance to four isolates of Peronospora parasitica. Isolates R1 and P003 were derived from crops of oilseed rape (B. napus ssp. oleifera) in the UK and isolates IP01 and IP02 were derived from crops of mustard (B. juncea) in India. B. napus cv. Ariana, which was used as a susceptible control for isolates from B. napus, was resistant to isolates from B. juncea. All, B. juncea accessions were resistant to isolates from B. napus except one accession which expressed moderate resistance to isolate P003. Five groups of B. juncea accessions with differential resistance were identified. Lines homogeneous for resistance were selected from seedling populations of accessions that exhibited a heterogeneous reaction to isolates from B. juncea. The differential resistance identified in the B. juncea-P. parasitica combination can be used as a foundation for future studies of the genetics of the host-pathogen interaction and for breeding for disease resistance.     

Inheritance of resistance to Bt toxin crylac in a field-derived strain of pink bollworm (Lepidoptera: Gelechiidae)

Laboratory selection with Cry1Ac, the Bacillus thuringiensis (Bt) toxin in transgenic cotton, initially produced 300-fold resistance in a field-derived strain of pink bollworm, Pectinophora gossypiella (Saunders), a major cotton pest. After additional selection increased resistance to 3,100-fold, we tested the offspring of various crosses to determine the mode of inheritance of resistance to Cry1Ac. The progeny of reciprocal F1 crosses (resistant male x susceptible female and vice versa) responded alike in bioassays, indicating autosomal inheritance. Consistent with earlier findings, resistance was recessive at a high concentration of Cry1Ac. However, the dominance of resistance increased as the concentration of Cry1Ac decreased. Analysis of survival and growth of progeny from backcrosses (F1 x resistant strain) suggest that resistance was controlled primarily by one or a few major loci. The progression of resistance from 300- to 3,100-fold rules out the simplest model with one locus and two alleles. Overall the patterns observed can be explained by either a single resistance gene with three or more alleles or by more than one resistance gene. The pink bollworm resistance to Cry1Ac described here fits "mode 1" resistance, the most common type of resistance to Cry1A toxins in Lepidoptera.     

Lactuca saligna,a non-host for lettuce downy mildew ( Bremia lactucae), harbors a new race-specific Dm gene and three QTLs for resistance

Lactuca sativa (lettuce) is susceptible to Bremia lactucae (downy mildew). In cultivated and wild Lactuca species, Dm genes have been identified that confer race-specific resistance. However, these genes were soon rendered ineffective by adaptation of the pathogen. Lactuca saligna (wild lettuce) is resistant to all downy mildew races and can be considered as a non-host. Therefore, L. saligna might be an alternative source for a more-durable resistance to downy mildew in lettuce. In order to analyze this resistance, we have developed an F(2) population based on a resistant L. saligna x susceptible L. sativa cross. This F(2) population was fingerprinted with AFLP markers and tested for resistance to two Bremia races NL14 and NL16. The F(2) population showed a wide and continuous range of resistance levels from completely resistant to completely susceptible. By comparison of disease tests, we observed a quantitative resistance against both Bremia races as well as a race-specific resistance to Bremia race NL16 and not to NL14. QTL mapping revealed a qualitative gene ( R39) involved in the race-specific resistance and three QTLs ( RBQ1, RBQ2 and RBQ3) involved in the quantitative resistance. The qualitative gene R39 is a dominant gene that gives nearly complete resistance to race NL16 in L. saligna CGN 5271 and therefore it showed features similar to Dm genes. The three QTLs explained 51% of the quantitative resistance against NL14, which indicated that probably only the major QTLs have been detected in this F(2) population. The perspectives for breeding for durable resistance are discussed.     

烟草白粉病抗性基因的遗传分析

以烟草抗白粉病品种台烟7号为母本,感病品种NC89为父本,构建6个世代的群体,利用主基因 多基因混合遗传模型的分离分析方法,研究烟草白粉病的抗性遗传规律。结果表明,烟草白粉病抗性的遗传是由两对加性-显性-上位性主基因 加性-显性-上位性多基因（E-0模型）控制的。B1、B2和F2世代主基因的遗传率分别为88.05%、32.62%、84.43%,主基因遗传率很大,说明可以在抗病育种早期进行选择;B1、F2世代多基因遗传率均为0.00%,说明烟草白粉病的发生受一定环境影响。     

部分小麦近缘物种材料的白粉病抗性鉴定

鉴定了170份小麦近缘物种材料苗期对北京地区流行的小麦白粉菌小种的抗性表现,包括引自美国和欧洲的斯卑尔脱小麦81份,密穗小麦27份,中国的西藏半野生小麦4份,和引自 CIMMYT 的人工合成六倍体小麦58份。结果表明,3份斯卑尔脱小麦表现抗病,它们是瑞士品种 Hubel 和 Lueg 以及德国的原始品种69Z6.245(编号 PI348085)。人工合成六倍体小麦中有19份材料表现高抗至免疫。密穗小麦材料中有2份(即美国材料 DN-2263和 Coda)表现抗病。4份西藏半野生小麦苗期都不抗小麦白粉病。     

Inheritance of resistance to clopyralid and picloram in yellow starthistle (Centaurea solstitialis L.) is controlled by a single nuclear recessive gene

The noxious weed yellow starthistle (Centaurea solstitialis L.) can be controlled effectively at the seedling stage with foliar application of the auxinic herbicides picloram or clopyralid. Although resistance to these herbicides is rare, a yellow starthistle biotype resistant to picloram and cross-resistant to clopyralid was observed in 1989 near Dayton, WA, in a pasture that had been subjected to intensive picloram selective pressure. Our objective was to determine the mode of inheritance for this resistance trait. Transmission of the resistant phenotype was monitored in reciprocal F(1) crosses between susceptible (SCI) and resistant (RDW) plants, their testcross and pseudo-F(2) progeny. Progeny from all crosses, as well as RDW and SCI seedlings of original populations, were sprayed with picloram or clopyralid to distinguish between susceptible and resistant individuals. All F(1) progeny were susceptible to both herbicides, indicating that the resistance trait was of nuclear origin and recessive in nature. Segregation of the resistant phenotype among pseudo-F(2) and testcross progeny of F(1) genotypes demonstrated monofactorial inheritance (P >.25) for resistance to both herbicides. The conclusion that resistance is conferred by a single recessive allele is consistent with the observation that no other picloram-resistant yellow starthistle populations have been identified in the area since picloram selection pressure was abated.     

White rust (Albugo candida) resistance loci on three Arabidopsis chromosomes are closely linked to downy mildew (Peronospora parasitica) resistance loci

Two accessions of Arabidopsis thaliana (Ksk-1 and Ksk-2) were used to identify and map three loci ( RAC1 , RAC2 and RAC3 ) of genes that confer R esistance to A lbugo c andida (white rust). The phenotypes associated with these genes were classified as either FN (necrotic f lecks on upper surface of cotyledons and n o blisters) for RAC2 and RAC3, or FYN ( f lecks surrounded by y ellowing and n o blisters) for RAC1 . Both phenotypes exhibited rapid death of host cells penetrated by the parasite (hypersensitive response), with callose deposition commonly encasing the haustorium. F₆ recombinant inbred lines were produced specifically for the purpose of mapping each RAC locus relative to molecular markers. Dominant resistance at the locus RAC1 in Ksk-1 was previously mapped to chromosome 1 between RFLP markers m253 and m254, and co-segregating with a downy mildew resistance specificity RPP9 in the accession Wei-0. We report here a fine-scale map interval and co-segregating markers for this locus, which in turn enabled mapping of a previously unnoticed source of resistance in Ksk-1 designated RAC3 that exhibits an FN phenotype hyperstatic to the FYN phenotype of RAC1. RAC3 is closely linked to the RPP8/HRT on chromosome 5, a locus which contains specificities for resistance to downy mildew and turnip crinkle virus. Recombinant inbreds also enabled mapping of recessive resistance at RAC2 in Ksk-2 to the bottom arm of chromosome 3, in the 6 cM interval between two downy mildew resistance loci ( RPP1 and RPP13 ) .     

Inheritance of resistance to flumethrin in the Mexican Aldama strain of the cattle tick Boophilus microplus (Acari: Ixodidae)

The objective of this study was to evaluate the inheritance mode of resistance to flumethrin in the Mexican Aldama Boophilus microplus strain. Two Mexican strains were used, the Chiapas susceptible (SS), and the Aldama flumethrin-resistant from Tamaulipas. Six steers weighing ca. 250 kg were randomly assigned for each of six crosses: the susceptible (SS), resistant (RR), and the F1 (RS, SR) reciprocal crosses and F2 (RS x RS and SR x SR). The reciprocal crosses were made to evaluate maternal and sex linkage effects. Bioassays tested resistant and susceptible larvae along with their hybrid F1 and F2 progeny against a series of concentrations of flumethrin (0, 0.0075, 0.00150, 0.00300, 0.00600 and 0.01200 microg/g). To test the single-gene hypothesis of resistance, a nonparametric line-cross test proposed by Collins was used. The bioassay data were subjected to probit analysis and the resistance factor and effective dominance obtained. Results of this study indicated that inheritance for flumethrin resistance in the Aldama strain was autosomal and controlled for more than one gene. The F1 and F2 larvae had similar lower resistant factor (RF 2.8-4.5) while the resistant Aldama strain was 21-fold higher (RF 81.8) than the mean of the F1 and F2. The extent of flumethrin resistance in the Aldama B. microplus strain depended upon the concentration of the pesticide used. Resistance was almost dominant at the lowest dose while almost completely recessive at the highest dose. Maternal effects were shown for egg-mass. These results shown here indicate more than one gene basis of flumethrin resistance in B. microplus ticks are present. Therefore it is necessary to locate and understand the major loci for elucidate the mechanism of resistance and improve the ability to track and delay the evolution of resistance.     

甘蓝种质资源根肿病抗性鉴定及CRa、Crr1a同源基因分析

利用来源于湖北长阳、陕西太白、河南新野3个地方的根肿病菌对22份不同甘蓝材料进行抗病性鉴定。采用同源比对的方法,对甘蓝基因组中的大白菜抗根肿病同源基因CRa和Crr1a进行分析;同时对不同抗、感根肿病甘蓝材料中的CRa和Crr1a同源基因序列进行了扩增、测序和比对分析。结果表明:供试22份甘蓝材料对3份根肿病菌存在较大的抗感差异,推测来源于3个地区的菌种可能不是同一个生理小种;筛选出的抗性品种BDH3、Chou hybride Tekila、SW-110、CGL-8、先正达品种、SW-109将来可用作根肿病抗源和抗性基因挖掘;在甘蓝7号染色体上存在3个预测基因为CRa的同源基因,分别是Bo7g107710、Bo7g107730和Bo7g107740,其中,Bo7g107730基因在抗病材料SW-110存在较大的序列变异,推测可能与根肿病抗性相关;在甘蓝3号染色体上存在1个预测基因Bo3g164040为Crr1a的同源基因,所分析的抗、感病材料中Bo3g164040基因序列一致性极高,没有发现与抗根肿病有关的位点,说明甘蓝中Bo3g164040基因可能没有根肿病抗性功能。     

Identification of a second linkage group carrying genes controlling resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.)

A sunflower line, XRQ, carrying the gene Pl5, which gives resistance to all French downy mildew races shows cotyledon-limited sporulation in seedling immersion tests; consequently, segregations in crosses with other downy mildew resistance sources were tested both by this method and by a secondary infection on leaves. Pl5 was found to segregate independently of Pl7 (HA338) but to be closely linked, or allelic, with Pl8 (RHA340). F₃ and F₄ progenies from a cross with a line containing Pl2 showed that Pl5 carries resistance to race 100 which segregates independently of Pl2. The Pl5 gene was mapped on linkage group 6 of the Cartisol RFLP map, linked to two RFLP markers, ten AFLP markers and the restorer gene Rf1. Tests with downy mildew race 330 distinguished Pl5 and Pl8, the first being susceptible, the second resistant, whereas both these genes were active against race 304 to which Pl6 (HA335) and Pl7 gave susceptibility. It is concluded that Pl5 and Pl8 are closely linked on linkage group 6 and form a separate resistance gene group from Pl6/Pl7 on linkage group 1. The origins of these groups of downy mildew resistance genes and their use in breeding are discussed. Received: 10 November 2000 / Accepted: 8 February 2001     

黄瓜霜霉病抗性相关基因的AFLP标记

运用AFLP技术,采用集群分析法研究与黄瓜霜霉病抗性基因相关的分子标记.结果表明,在F2群体中E25M63-103标记与霜霉病病情指数的相关系数(0.337)和回归分析的F值(20.98)都达到了极显著水平.用E25M63-103标记对国内外的其它27份黄瓜材料进行检测,该标记与霜霉病病情指数的相关系数为0.555,也达到极显著相关水平,进一步证明该标记与控制黄瓜霜霉病感病的相关基因是连锁的.E25M63-103片段长度为103 bp,通过BLAST查询,该片段的同源性较小,表明E25M63-103标记可能是黄瓜基因组特有的一段DNA序列.     

棉花种质资源光子性状的遗传分析

文章利用来源于不同国家和地区的102份陆地棉材料和85份海岛棉材料分别与陆地棉遗传标准系TM-1和海岛棉毛子品种新海13号杂交,得到陆地棉和海岛棉两种F₁群体,同时从陆地棉F₁群体中随机选取呈隐性性状的材料"库光子"、"SA65"和"陆无絮"后代,配制3个F₂分离群体,用于进一步研究陆地棉和海岛棉光子性状遗传特征。结果表明:（1）同一材料种植于不同生态区,其种子短绒多少存在变化,新疆和海南要少于安阳,说明棉花短绒多少和生态环境有关系;（2）陆地棉光子材料中26份（25.49%）呈显性遗传,8份（7.84%）呈不完全显性遗传,22（21.57%）份呈隐性遗传;海岛棉光子材料中5份（5.88%）呈显性遗传,16份（18.82%）呈部分显性遗传,9份（10.59%）呈隐性遗传。其余为隐性性状或显性性状不明显材料和毛子材料;（3）库光子的光子性状由两对隐性等位基因控制,并且有互补效应;陆无絮的光子性状由两对隐性等位基因控制,基因间呈积加作用;SA65的光子性状由单隐性基因控制。大量光子材料的初步鉴定为深入研究棉花纤维发育和育种利用提供了基础材料和理论依据。