安徽省小麦白粉菌毒性频率分析

1983及1984年用稍加修改了的Wolfe等提出的毒性频率分析方法,在两套鉴别品种(抗性基因己鉴定及抗性基因未明)上分析了安徽省小麦白粉菌的毒性频率,结果表明该省各地的小麦白粉菌群体基本上相同:毒性基因V_1,V_(3a)、V_(3b)。V_(3c)、V_5较普遍(频率>40%);V_2、V_4、V_2+V_6、V_2+V_(m1d)、V_4+?甚为稀少(频率<6%);洛夫林系统,高加索等黑麦衍生抗源及黔花四号,肯贵阿一号等其它类型的抗源“毒性”频率低。本文结合供试品种成株期表现,讨论了各抗性基因(组合)和抗源在安徽省的应用价值;还讨论了该省小麦白粉菌群体结构形成原因;提出了我省开展抗病育种时应注意的问题和建议。     

Large shifts in pathogen virulence relate to host population structure

Theory on the evolution of virulence generally predicts selection for an optimal level of virulence determined by trade-offs with transmission and/or recovery. Here we consider the evolution of pathogen virulence in hosts who acquire long-lived immunity and live in a spatially structured population. We show theoretically that large shifts in virulence may occur in pathogen populations as a result of a bistability in evolutionary dynamics caused by the local contact or social population structure of the host. This model provides an explanation for the rapid emergence of the highly virulent strains of rabbit hemorrhagic disease virus.     

对洛夫林10小麦品种作为叶锈病抗源的评价

对洛夫林10小麦品种能致病的叶锈菌小种群在不断上升,给抗病育种带来了威胁。本试验选用的小麦品种有目前参加品比、区试和生产上推广的53个优良品种,其中38个其亲本是以洛夫林10为抗源。用对洛夫林10能致病的7个优势小种,和对洛夫林10不能致病的4个优势小种与这些品种进行相互作用研究。结果表明,以洛夫林10为抗源所培育的品种对“洛10”小种不是都感染的,它们与叶锈菌的亲和率为22％,不以洛夫林为抗源的品种与叶锈菌的亲和率则为42％。另外还有4个以洛夫林10为抗源的品种对参试的所有小种都抵抗,说明洛夫林10这个品种作为叶锈病抗源,目前在生产上对叶锈病的防治还有相当的价值。然而,研究也表明,除了“洛10”小种群外,有些非“洛10”小种对以洛夫林10为抗源的品种也能致病,这说明抗性基因在一定的遗传背景中起作用,而在另一些背景中不一定起作用。为此,应避免抗源单一化,并加强遗传学研究,大力筛选新抗源,使抗病性建立在抗源多样化的稳固基础之上。     

Host-parasite coevolutionary conflict between Arabidopsis and downy mildew

Plants are constantly exposed to attack by an array of diverse pathogens but lack a somatically adaptive immune system. In spite of this, natural plant populations do not often suffer destructive disease epidemics. Elucidating how allelic diversity within plant genes that function to detect pathogens (resistance genes) counteracts changing structures of pathogen genes required for host invasion (pathogenicity effectors) is critical to our understanding of the dynamics of natural plant populations. The RPP13 resistance gene is the most polymorphic gene analyzed to date in the model plant Arabidopsis thaliana. Here we report the cloning of the avirulence gene, ATR13, that triggers RPP13-mediated resistance, and we show that it too exhibits extreme levels of amino acid polymorphism. Evidence of diversifying selection visible in both components suggests that the host and pathogen may be locked in a coevolutionary conflict at these loci, where attempts to evade host resistance by the pathogen are matched by the development of new detection capabilities by the host.     

在小麦叶锈病研究中小麦品种和叶锈菌相互作用的辩证分析

本文根据我校在小麦叶锈病研究中的发现,从小麦品种和叶锈菌的相互作用,对小种鉴定和品种抗病性测定,毒性的个性和共性,毒力的强弱与小种消长的关系,毒性的专化性和寄主范围,毒性的地区性和品种的抗病性等方面作了辩证的分析。指出今后研究锈病应有群体观点,因为小麦品种和叶锈菌是以群体对群体起相互作用的。用传统的方法研究锈菌的生理分化,不仅鉴别寄主的有用性是局限的,並且同一小种的不同菌株的毒性不一定相同,任意选一菌株测定品种的抗病性,並且研究的是个体品种与个体菌株的相互作用,这种方法有很大的片面性,把在局限情况下测定的抗病品种推广到自然间锈菌群体中去,就很容易发生抗病性“丧失”问题。今后研究锈病应有生态观点,因为小麦品种锈菌及其相互作用无不受外界条件的影响。在不同生态条件下形成的锈菌群体的毒性不一定相同,培育抗病品种应注意农业生态系的特殊性。今后研究锈病还应有进化观点,因为小麦品种和锈菌是相互联系相互制约地共存和共同进化的,应该从遗传学角度来研究锈菌的适合度和小麦品种抗性的持久性。     

对辣椒抗性基因Me3表现毒性的南方根结线虫 群体的SCAR分子标记

【目的】研究南方根结线虫（Meloidogyne incognita）Me3毒性变异群体的分子标记,用快速有效的分子方法来鉴定毒性变异的发生。【方法】以南方根结线虫的无毒群体以及抗性基因Me3毒性群体为材料,用根据南方根结线虫基因组设计的100对引物和19对来自文献的引物进行扩增,筛选出在3个种群中扩增的差异条带,设计SCAR引物,并建立多重PCR反应体系。【结果】得到了7对能在3个群体稳定扩增出差异条带的多态性引物,把其中的2个位点开发为SCAR标记,能够区分开3个线虫群体。多重PCR反应体系在无毒群体和Me3毒性群体中分别扩增出1条999 bp和1条629 bp的条带,在混合群体扩增出999和629 bp的2条带。【结论】成功开发了对Me3表现毒性的南方根结线虫变异群体的分子标记,可用多重PCR体系一次性鉴定Me3毒性变异的发生。     

几个水稻品种的白叶枯病抗性鉴定

采用4个白叶枯病致病菌系KS-6-6、浙173、JS49-6和PX079,利用人工剪叶接种方法,鉴定了圣稻13、圣稻14、T022、C418、武21621等18个水稻品种的白叶枯病抗性。结果表明,武21621对4个菌系表现高抗甚至免疫,徐稻3号、武优34表现中抗或抗病,圣稻13和圣稻14对浙173表现中感,而对其余3个菌系表现出中抗或高抗,大粮203对4个菌系表现中感,C418对3个菌系表现高感,对PX079表现中感,其余品种对4个菌系表现出不同的抗性。4个白叶枯病致病菌系的致病力存在差异。武21621表现高抗白叶枯病,可以用于抗白叶枯病育种。     

EMS诱导小麦条锈菌毒性突变的研究

以化学诱变剂EM S处理小麦条锈菌CY 17和CY 31的夏孢子诱发其毒性突变,用抗条锈Y r近等基因系筛选毒性突变体,建立了4个CY 17和1个CY 31的突变菌株,各筛选品种上的病菌突变频率明显不同,突变率在2.14×1-0 6~3.68×1-0 5。对突变菌株的毒性测定结果表明,CY 17的所有突变菌株对Y r12发生了毒性突变,且CY 17和CY 31的所有突变菌株对Y r5,Y r10,Y r15和Y r24等4个抗病基因表现无毒性。研究证实毒性突变是小麦条锈病菌毒性变异的重要途径。     

Aerial dispersal of pathogens on the global and continental scales and its impact on plant disease

Some of the most striking and extreme consequences of rapid, long-distance aerial dispersal involve pathogens of crop plants. Long-distance dispersal of fungal spores by the wind can spread plant diseases across and even between continents and reestablish diseases in areas where host plants are seasonally absent. For such epidemics to occur, hosts that are susceptible to the same pathogen genotypes must be grown over wide areas, as is the case with many modern crops. The strongly stochastic nature of long-distance dispersal causes founder effects in pathogen populations, such that the genotypes that cause epidemics in new territories or on cultivars with previously effective resistance genes may be atypical. Similar but less extreme population dynamics may arise from long-distance aerial dispersal of other organisms, including plants, viruses, and fungal pathogens of humans.     

褐稻虱生物型的形成

本文研究褐稻虱连续饲养于具Bph1抗虫基因的IR_(2?)稻种上表现不同致害力群体与生物型形成的关系.试验结果表明,实验室群体的个体间存有不同的致害力.用蜜露分泌量区分不同“致害力”的群体在连续选择压力下,它们间适应IR_(2?)的程度并无明显的差异.三个不同“致害力”的群体应用“苗期群体筛选法”和“群体建立法”测定,表明在IR_(2?)上饲养经过10代,即可使IR_(2?)致死并能适应于该品种;但它们却不能生存于具有BpH_1抗虫基因的Mudgo稻种上.此外,根据蜜露分泌量、飞虱生存率和成虫体重等指标在连续饲养世代的递增,亦证实飞虱群体在IR_(2?)上经过不断的选择,可以演变为一个致害力强的生物型.     

A new pathotype characterization of Daxing and Huangyuan populations of cereal cyst nematode(Heterodera avenae) in China

The cereal cyst nematode(CCN, Heteroder aavenae) causes serious yield loss on cereal crops, especially wheat, worldwide. Daxing population in Beijing City and Huangyuan population in Qinghai Province, China, are two CCN populations. In this study, the CCN pathotypes of Daxing and Huangyuan populations were characterized by tests on 23 standard "International Test Assortment" with the local species Wenmai 19 as the susceptible control. Tested materials were grouped by three nematode populations' virulence on resistant genes(Rha1, Rha2, Rha3, Cre1) and nonresistant genes, varieties and lines. Both Daxing and Huangyuan populations were avirulent to Ortolan(Ha1). Barley cvs. Ortolan, Siri, Morocco, Bajo Aragon 1-1, and Martin 403-2 were all resistant to both populations. Cultivars Herta, Harlan 43 and wheat Iskamish-K-2-light were all susceptible to Huangyuan population, all of them, however, were resistant to Daxing population. The other five oats were all resistant to the two tested CCN populations. Except Iskamisch K-2-light, all the other wheat cultivars(Capa, Loros×Koga, AUS 10894, and Psathias) were susceptible to Daxing population. Because the pathotypes of the two tested CCN populations in Beijing and Qinghai were not identical to any of the 13 pathotypes previously characterized by the test assortment, we classified Daxing and Huangyuan populations as the new pathotypes, named Ha91.     

水稻幼苗感染白叶枯病后若干同工酶的变化

白叶枯病原细菌(Xanthomonas campestris pv.oryzae)感染稻苗后,诱导病株叶片PAL活力的增强,感病品种的酶活力上升更为显著.PAL和酯酶同工酶谱带和各谱带活力在感病后有不同程度的变化:PAL同工酶谱在感病叶片中条数减少。部分酶带活力减弱,抗性强的品种尤为明显;酯酶同工酶谱,在感病后抗性强的品种,慢速区谱带增加1—2条,抗病和感病品种在该区酶活力均增加.相反,高抗品种在中速和高速区均表现酶活力降低.高抗品种只对强毒力菌株反应灵敏,感病品种被中毒力菌株感染后酶谱出现差异,而被高低毒两菌株感染后的酶谱则相似.     

Relation of Antigens of Melampsora lini and Linum usitatissimum to Resistance and Susceptibility

A specific antigen was found in each of four races of Melampsora lini and four rust-differentiating varieties of Linum usitatissimum. Avirulence and virulence were related to resistance and susceptibility through the specific rust antigens. A race was virulent to varieties containing its specific rust antigen as a minor constituent, and avirulent to varieties lacking that antigen. No such correlation was found with flax antigens.     

Success and virulence in Toxoplasma as the result of sexual recombination between two distinct ancestries

Toxoplasma gondii is a common human pathogen causing serious, even fatal, disease in the developing fetus and in immunocompromised patients. Despite its ability to reproduce sexually and its broad geographic and host range, Toxoplasma has a clonal population structure comprised principally of three lines. We have analyzed 15 polymorphic loci in the archetypal type I, II, and III strains and found that polymorphism was limited to, at most, two rather than three allelic classes and no polymorphism was detected between alleles in strains of a given type. Multilocus analysis of 10 nonarchetypal isolates likewise clustered the vast majority of alleles into the same two distinct ancestries. These data strongly suggest that the currently predominant genotypes exist as a pandemic outbreak from a genetic mixing of two discrete ancestral lines. To determine if such mixing could lead to the extreme virulence observed for some strains, we examined the F(1) progeny of a cross between a type II and III strain, both of which are relatively avirulent in mice. Among the progeny were recombinants that were at least 3 logs more virulent than either parent. Thus, sexual recombination, by combining polymorphisms in two distinct and competing clonal lines, can be a powerful force driving the natural evolution of virulence in this highly successful pathogen.     

我国水稻白叶枯病菌致病型划分和水稻抗病育种中应注意的问题

水稻白叶枯病(bacterial blight,BB)是我国水稻上的重要病害之一。本文简要概述了我国水稻白叶枯病发生现状,总结了病菌与水稻互作中亲和与非亲和性的决定因子,归纳了水稻感病性和抗病性基因的类型,并对白叶枯病抗性丧失的原因进行了分析,指出防控我国水稻白叶枯病应针对性加强水稻抗性育种工作,并提出了抗性育种以及生产上抗性品种布局中应该注意的问题。     

小麦叶锈菌生理分化研究中的问题和改进意见

Stakman建立的用鉴别寄主鉴定锈菌生理小种的方法对抗病育种曾起了很大的作用,然而实践证明还存在不少问题。(1)生物间遗传学指出,Stakman建立的方法。其观点偏重于锈菌分类,而忽视寄主和病原物的相互作用。所以所用的鉴别寄主仅注意其鉴别作用,可与生产毫无关系,可以鉴定出许多小种,而不知道它们与生产有关的品种有什么关系。(2)在自然间寄主和病原物是以群体对群体起相互作用的,而传统研究是研究个体与个体的关系。此外,小种内存在变异性,被鉴定为同一小种的不同菌株的毒性不一定相同,任意选择一个菌株来测定品种的抗病性未必有代表性,用这种方法测出的抗病品种推广出去就容易引起抗病性丧失问题。(3)在不同生态条件下形成的锈菌的群体毒性不一定相同,这种毒性不同的类群我们称为生态类群。过去的小麦品种抗病性测定工作多在局限的条件下用人工接种进行。把用这种方法测出的抗病品种推广到广大的锈菌群体中去,也容易引起抗病性丧失问题。我们赞成今后研究小麦锈病应有群体观点,用毒力频率,毒力组合,抗性组合等方法来研究小麦群体和锈病群体的关系。应有生态观点,用异地鉴定来监测锈菌毒性和品种抗性的变异。应有进化观点,以基因鉴定来代替小种鉴定,把寄主的病原物相互作用研究放在遗传学基础上。在利用已知基因作鉴别寄主方面,虽然抗原的抗性基因可与Lr近等基因系的相同,但由于表现型相同基因型不一定相同,所以这两种材料都得同时采用,不能互相代替。抗性基因鉴定是复杂的。一般认为阿芙乐尔会有Lr26基因。Bastos认为除Lr26外,还有Lr3。杨文香认为除Lr26和Lr3外,还有Lrl4a。又Bastos认为洛夫林13含有Lr26和Lr3,相文香认为只含有Lr24,检查不到Lr3。     

小麦品种对条锈病低反应型抗性的组织学和超微结构研究

 采用荧光显微镜、微分干涉显微镜和电子显微镜技术 ,系统研究了非亲和组合中小麦对条锈病低反应型抗性的组织学和超微结构特征。非亲和组合分别由小麦品种牛朱特与条中 2 8号小种、杂种 4 6与条中 2 9号小种、天选 882与条中 2 9号小种组成 ,对照亲和组合由小麦品种辉县红与条中 2 9号小种组成。观察结果表明 ,小麦条锈菌在感病品种和抗病品种上发育的组织学和超微结构特征有明显差异。病菌在抗病品种上表现为菌丝生长受抑 ,菌落形成延迟或败育 ,病菌吸器母细胞和吸器数量明显减少。寄主细胞的坏死与条锈菌的发育受阻密切相关 ,免疫组合中病菌的受抑程度高于近免疫组合的。电镜观察发现 ,在抗病品种上 ,病菌胞间菌丝、吸器母细胞、吸器在细胞和亚细胞水平 ,均发生了一系列异常变化 ,其中包括原生质的电子致密度加深、液泡增多变大、菌丝细胞壁不规则增厚、细胞器排列紊乱及解体、吸器母细胞及吸器丧失其生理功能、病菌最终畸形坏死。同时发现抗病品种受病菌侵染时可迅速产生结构防卫反应 ,新形成胞壁沉积物和吸器鞘等结构 ,以阻碍病菌进一步的扩展与发育。就小麦品种与条锈菌非亲和组合中表现出的组织学和细胞学特征与小麦抗锈性表达的关系进行了讨论。     

Histology and Ultrastructure of Incompatible Combination Between Puccinia striiformis and Wheat Cultivars with Low Reaction Type Resistance

The incompatible combinations between races of Puccinia striiformis and wheat cuitivars withlow reaction type resistance were examined by means of fluorescent microscopy, differential interference con-trast microscopy and electron microscopy. The incompatible combinations consisted of wheat cultivar Niuzhuteplus CY28, Hybrid46 plus CY29 and Tianxuan882 plus CY29, while the compatible combination was wheatcultivar Huixianhong plus CY28. The observation revealed a striking difference in the fungal development andthe host responses between susceptible and resistant wheat cuitivars following infection by the pathogen. Themain histological manifestation of the pathogen development in the resistant wheat cultivars include inhibitionof hyphal growth, delay of hyphal branching and colony formation, decrease of formation of haustorial mothercells and haustoria, and occurrence of host cell necrosis. The observation by electron microscopy demonstratedthat a series of abnormal changes occurred in intercellular hyphae, haustorial mother cells and haustoria dur-ing pathogen development in the resistant wheat cultivars. The cytoplasm became more electron-dense and vac-uoles in the cytoplasm increased in number and size. The cell walls of hyphae, haustorial mother cells werethickened irregularly. The organeiles were disorderly distributed in the cytoplasm and the haustorial mothercells and haustoria lost their physiological function. In the final stage of the pathogen development, the inter-cellular hyphae, haustorial mother cells and haustoria became necrotic and collapsed. The structural defensereactions such as formation of cell wall apposition, collar and encasement of haustorium were essentially morepronounced in the infected wheat leaves of the resistant cultivars than in the susceptible one. In addition, therelationship between the host resistance expression and the histological and cytological features occurred in theincompatible combination was discussed in this paper.     

Enhancement of growth of virulent strains of Escherichia coli by interleukin-1.

Interleukin-1 (IL-1) is a polypeptide cytokine that mediates many physiological responses to infection and inflammation and is a growth factor for certain mammalian cells. Virulent and avirulent clinical isolates of Escherichia coli were grown in culture media in the presence of human IL-1. IL-1 beta, but not tumor necrosis factor or IL-4, enhanced the growth of virulent, but not avirulent, E. coli. This enhancement was blocked by the IL-1 receptor antagonist (IL-1ra). Radiolabeled IL-1 bound to virulent but not avirulent E. coli in a specific and saturable fashion; IL-1ra inhibited this binding. Thus, human IL-1 may recognize a functional IL-1-like receptor structure on virulent E. coli and may be a virulence factor for bacterial pathogenicity.     

苹果实生树枝干对轮纹病菌抗病性反应的差异

为进一步研究苹果枝干对轮纹病的抗病机理,以红玉×金冠杂种后代中表现不同抗病性的杂种实生树为试材,分析了不同抗病性的实生树枝条皮孔密度差异,接种轮纹病菌丝后枝条皮层木质素含量的变化,并采用扫描电镜技术,观察了接种点表面超微结构的变化。对20份不同抗性实生树1年生枝条皮孔密度的调查表明,在本分离群体内,皮孔密度与抗病性未见显著相关性。对苹果枝干轮纹病抗病、感病的杂种实生树进行接种,菌丝均可从皮孔侵入,但抗病的杂种实生树表现为致瘤性弱。接种病原后抗病和感病材料均会导致木质素含量的增加,但抗病材料木质素的增加量显著高于感病材料,表明木质素含量的激增与抗病性相关。金冠×红玉杂种后代中抗病单株的抗病性并非表现为抑制病原菌丝侵入,而表现为侵染后,通过诱导皮层木质素积累,抑制病原菌丝在寄主体内的扩展。