河北省西瓜枯萎病菌致病性分化及其RAMS分析

本文对50个西瓜枯萎病菌株,(其中46个来自河北省石家庄、保定、唐山等12个西瓜种植区的代表菌株)进行了致病性测定、RAMS(Random amplified microsatellites)扩增和致病类型与RAMS类群的相关性分析。根据鉴别寄主对不同菌株的抗感反应,将50个菌株划分为3个不同的生理小种,即0号、1号和2号生理小种,分别占供试菌株的18%、64%和18%;21个RAMS引物对供试菌株扩增出188条带,其中多态性带134条,占总带数的71%。基于RAMS标记聚类分析,50个菌株被划分为3个类群(RAMSGroups,RGs)。RGI包含来自不同地区的41个菌株,以1号生理小种为主(32个),占该类群的78.1%;RGII包括来自保定、唐山和新疆的3个菌株,均为0号生理小种;RGIII包括张家口、石家庄、保定等地的6个2号生理小种菌株。RAMS类群与生理小种之间存在一定相关性,与菌株的地理来源关系不明显。     

Pathogenic Variability in Colletotrichum lindemuthianum and Evaluation of Resistance in Phaseolus vulgaris in the North-Western Himalayan Region of India

Eightyfive isolates of Colletotrichum lindemuthianum (bean anthracnose) collected from different kidney bean growing areas of a hilly state (Himachal Pradesh) of India, were characterized on the basis of their reaction types on International and CIAT differentials. On international differentials, 12 races viz., Alpha-Brazil, Beta, Gamma and Ind I to Ind IX were characterized. The races designated as Ind I to Ind IX were different from those identified in Europe and USA, thus forming a new race group from the Indian subcontinent. On the CIAT differential set the 85 isolates have been grouped into 19 races. Of these, only races 65 and 73 resembled the North American races. Exotic accessions AB 136 and G 2333 were resistant to all the Indian races. However, race specific resistance has been found in a number of indigenous and exotic genotypes of Phaseolus vulgaris.     

New Races of Sunflower Downy Mildew (Plasmopara Halstedii) in Germany

Plasmopara halstedii, the causal agent of downy mildew of cultivated sunflower (Helianthus annuus), was documented in Germany for the first time in commercial fields. The pathogen was first observed in the Württemberg area, where races 1 and 4 were identified using a set of differential lines. Later, commercial fields near Baden were found to be infected by race 5, which is the first occurrence of that race outside of North America. With the discovery of race 5, there are now eight races of the sunflower downy mildew fungus that have been found in Europe. The sunflower cultivars most frequently grown in Germany were investigated for resistance to race 1, 4 and 5; while all were resistant to race 1, none were resistant to either race 4 or 5.     

Genetic Diversity and Pathogenicity of Fusarium oxysporum f.sp. melonis Races from Different Areas of Italy

Fusarium wilt caused by Fusarium oxysporum f.sp. melonis (FOM) is a devastating disease of melon worldwide. Pathogenicity tests performed with F. oxysporum isolates obtained from Italian melon‐growing areas allowed to identify thirty‐four FOM isolates and the presence of all four races. The aims of this work were to examine genetic relatedness among FOM isolates by race determination and to perform phylogenetic analyses of identified FOM races including also other formae speciales of F. oxysporum of cucurbits. Results showed that FOM race 1,2 was the most numerous with a total of eighteen isolates, while six and nine isolates were identified as race 0 and 1, respectively, and just one isolate was assigned to race 2. Phylogenetic analysis was performed by random amplified polymorphic DNA (RAPD) profiling and by translation elongation factor‐1α (TEF‐1α) sequencing. The analysis of RAPD profiles separated FOM races into two distinct clades. Clade 1, which included races 0, 1 and 1,2, was further divided into ‘subclade a’ which grouped almost all race 1,2 isolates, and into ‘subclade b’ which included race 0 and 1 isolates. Clade 2 comprised only race 2 isolates. The phylogenetic analysis based on TEF‐1α separated FOM from the other formae speciales of F. oxysporum. Also with TEF‐1α analysis, FOM races 0, 1 and 1,2 isolates grouped in one single clade clearly separated from FOM race 2 isolates which grouped closer to F. oxysporum f.sp. cucumerinum. RAPD technique was more effective than TEF‐1α in differentiating FOM race 1,2 isolates from those belonging to the closely related races 0 and 1. Both phylogenetic analyses supported the close relationship between the three different FOM races which might imply the derivation from one another and the different origin of FOM race 2.     

New Races of Sunflower Downy Mildew (Plasmopara Halstedii) in Germany

Plasmopara halstedii, the causal agent of downy mildew of cultivated sunflower (Helianthus annuus), was documented in Germany for the first time in commercial fields. The pathogen was first observed in the Württemberg area, where races 1 and 4 were identified using a set of differential lines. Later, commericial fields near Baden were found to be infected by race 5, which is the first occurrence of that race outside of North America. Withthe discovery of race 5, there are now eight races of the sunflower downy mildew fungus that have been found in Europe. The sunflower cultivars most frequently grown in Germany were investigated for resistance to race 1, 4 and 5; while all were resistant to race 1, none were resistant to either race, 4 or 5.     

海南省香蕉枯萎菌生理小种的RAPD分析

利用随机扩增多态性DNA(RAPD)分子标记方法对海南省香蕉枯萎病菌2个生理小种(小种1和小种4)进行遗传多样性分析,以筛选出的15个随机引物对采自海南省各市县发病蕉区的分别属于1号生理小种和4号生理小种的16个代表菌株及广东省2个1号和4号生理小种对照菌株进行RAPD-PCR扩增,结果产生97个RAPD分子标记,其中多态性的条带有76条,通过聚类分析探讨了供试小种间的亲缘关系,并寻找到了1、4号生理小种的特异性条带,为在分子水平上进行香蕉枯萎病菌生理小种鉴定提供更为便利的手段。     

Genetic Analysis of Resistance to Meloidogyne chitwoodi Introgressed from Solanum hougasii into Cultivated Potato

An accession of Solanum hougasii, a wild tuber-bearing potato species native to Mexico, was found to be resistant to races 1 and 2 of Meloidogyne chitwoodi. A resistant selection was selfed and its progeny possessed the same combined resistance uniformly. A selected resistant seedling from the selfed progeny was crossed to cultivated tetraploid potato (S. tuberosum) to form an F₁ hybrid, and was backcrossed to cultivated tetraploid potato to form a BC₁ population in which resistance to the two races segregated. Progeny of the BC₁ were tested in inoculation experiments with four replicates for each progeny genotype for each race of nematode. Resistance was evaluated on the basis of extracted egg counts from the entire root system of pot-grown plants. Considering resistance to each race separately, for race 1, non-host (Rf ≤ 0.1) status was exhibited by approximately half of the BC₁. About one-third of the progeny showed non-host status to race 2. Egg production among progeny that showed non-host status for both races was higher with race 2 than with race 1. Analysis of co-segregation established that genetic control for the two races appears to be independently segregating. Although genes for resistance to race 1 derived from S. bulbocastanum and S. fendleri were previously described, this report is the first analysis showing independent genetic control in Solanum spp. for resistance to race 2 of M. chitwoodi only.     

Determination of Races of Pseudomonas syringae pv. glycinea Occurring in Europe

Fifty-eight strains of Pseudomonas syringae pv. glycinea were collected from France, Germany, Hungary, Italy, Poland, The Ukraine and the former Yugoslavia. The bacterial cultures were fluorescent on King's medium B, oxidase negative, produced levan, and induced a hypersensitive reaction (HR) on tobacco leaves within 24h. The race of each strain was determined by inoculating a set of seven differential soybean cultivars: Acme, Chippewa, Flambeau, Harosoy, Lindarin, Merit and Norchief.Conditions of plant cultivation, bacterial inoculation and plant incubation had to be standardized scrupulously to obtain reproducible results. Authentic strains belonging to races 1, 4, 5, and 6 produced the expected reactions on the differentials. However, strains of race 2 and race 4 induced identical responses on the differential cultivars. The differentiating critierion between these two races was the ability of race 2 to produce a brown diffusable pigment on King's medium B. The most prevalent race, occurring in every European country studied, was race 4. This is the most aggressive race of P. glycinea, since it infects all the cultivars of the set of differentials. From 58 strains tested, 42 belonged to race 4, 4 to race 6, and 6 to race 9. For two strains race identification was impossible. The remaining 4 isolates did not fit into the pattern of known races. It is proposed that these strains belong to a new race (no. 10) which is similar to race 5, but can inf, ect the soybean cultivar ‘Lindarin’. On the other hand, race 10 can not infect cv. ‘Chippewa’, in contrast to race 9.     

Race Distribution, Vegetative Compatibility and Pathogenicity of Fusarium oxysporum f. sp. melonis Isolates in Greece

Races and vegetative compatibility groups (VCGs) in Greek isolates of Fusarium oxysporum f. sp. melonis(Fom) were characterized. Three races (0, 2 and 1–2) among 12 isolates tested and two VCGs among 19 isolates tested, were identified. Race 1–2 was the most common and race 1 was not detected. One widespread VCG corresponded to a VCG previously reported from Israel (coded 0138), and included seven isolates of races 0 and 1–2. The other VCG, which was unclassified, included four isolates of races 0, 2 and 1–2. The latter VCG was detected only in a specific melon‐growing location of Evros. The remaining eight isolates tested for VCG did not show positive reactions with other isolates, with each other or with the testers of VCGs 0135 or 0138, although they produced complementary mutants. Using two inoculation methods, the local cv. ‘Golden Head’ was found susceptible to all known Fom races, and especially to race 1–2. These results show the presence of more than one VCG and the widespread distribution of the race 1–2, in Greece.     

WRR4 encodes a TIR-NB-LRR protein that confers broad-spectrum white rust resistance in Arabidopsis thaliana to four physiological races of Albugo candida

White blister rust in the Brassicaceae is emerging as a superb model for exploring how plant biodiversity has channeled speciation of biotrophic parasites. The causal agents of white rust across a wide breadth of cruciferous hosts currently are named as variants of a single oomycete species, Albugo candida. The most notable examples include a major group of physiological races that each are economically destructive in a different vegetable or oilseed crop of Brassica juncea (A. candida race 2), B. rapa (race 7), or B. oleracea (race 9); or parasitic on wild crucifers such as Capsella bursa-pastoris (race 4). Arabidopsis thaliana is innately immune to these races of A. candida under natural conditions; however, it commonly hosts its own molecularly distinct subspecies of A. candida (A. candida subsp. arabidopsis). In the laboratory, we have identified several accessions of Arabidopsis thaliana (e.g.,. Ws-3) that can permit varying degrees of rust development following inoculation with A. candida races 2, 4, and 7, whereas race 9 is universally incompatible in Arabidopsis thaliana and nonrusting resistance is the most prevalent outcome of interactions with the other races. Subtle variation in resistance phenotypes is evident, observed initially with an isolate of A. candida race 4, indicating additional genetic variation. Therefore, we used the race 4 isolate for map-based cloning of the first of many expected white rust resistance (WRR) genes. This gene was designated WRR4 and encodes a cytoplasmic toll-interleukin receptor-like nucleotide-binding leucine-rich repeat receptor-like protein that confers a dominant, broad-spectrum white rust resistance in the Arabidopsis thaliana accession Columbia to representative isolates of A. candida races 2, 4, 7, and 9, as verified by transgenic expression of the Columbia allele in Ws-3. The WRR4 protein requires functional expression of the lipase-like protein EDS1 but not the paralogous protein PAD4, and confers full immunity that masks an underlying nonhypersensitive incompatibility in Columbia to A. candida race 4. This residual incompatibility is independent of functional EDS1.     

I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: Variation in Pseudomonas morsprunorum and the selection of cherry cultivars resistant to bacterial canker

During 1971 and 1972 leaf spot infection caused by Pseudomonas morsprunorum was far more severe on the cv. Roundel than on the normally more susceptible cv. Napoleon, and Roundel supported higher leaf surface populations of the pathogen. This unprecedented reversal in the established field performance of the two cultivars was associated with the presence on the trees of a colony variant (race 2) of P. morsprunorum that differed from the forms of the organism previously described (race 1) in physiological, pathological and phage sensitivity characteristics. In inoculation experiments race 2 isolates showed some specificity for Roundel and race 1 isolates for Napoleon. This difference was reflected in the distribution of the races on trees of the two cultivars growing in experimental plots and commercial orchards. Similar interactions between race and host genotype were observed amongst progeny from breeding programmes and material originally selected for resistance to bacterial canker after inoculation with race 1 proved susceptible to race 2. Three distinct groups of isolates with the colony characteristics of race 2 have been identified and one of these has affinities with Pseudomonas syringae. Group 1 isolates, corresponding to P. morsprunorum and comprising non-fluorescent forms, were the most virulent in pathogenicity tests and accounted for the majority of race 2 infections in the field.     

黑龙江省葫芦科白粉病菌RAPD分析

2010年采集黑龙江省不同生态区不同设施内的甜瓜、黄瓜、南瓜、西瓜等瓜类白粉病菌菌株17份,采用国际通用的瓜类白粉病菌生理小种鉴别寄主对17份白粉病菌进行了生理小种鉴定。根据13个鉴别寄主的抗感反应,初步确定黑龙江省葫芦科作物白粉病菌存在3个生理小种,即单囊壳白粉菌Podosphaera xanthii的生理小种1和生理小种N1号及一个新生理小种,其中生理小种1为优势小种。通过对13份白粉病菌的RAPD分析,从119个随机引物中筛选出10个条带清晰而且重复性好的引物,扩增得到157个位点,其中多态性位点为138个,多态性位点频率为97.89%,表明黑龙江省葫芦科作物白粉菌具有丰富的遗传多样性。利用NTSYS-PC软件进行数据分析,结果表明13个菌株之间遗传相似系数的变化幅度为0.52－0.75。根据遗传相似系数用类平均法（UPGMA）对其聚类,以遗传相似系数0.60为阈值,供试菌株可区分为4个类群。同是生理小种1的菌株部分聚到了同一类,新生理小种与部分生理小种1菌株聚到同一类,同是生理小种N1的两个菌株未聚到同一类;相同地理来源或相同寄主来源的白粉菌也未聚到一类。初步确定葫芦科白粉病菌致病性与DNA多态性不形成对应关系,菌株的遗传多样性与菌株地理来源、寄主来源及设施类型亦无明显的直接关系。     

Restriction Digest Patterns of Total DNA from Different Races of Fusarium oxysporum f. sp. pisi– an Improved Method for Race Classification

Seven isolates of Fusarium oxysporum f. sp. pisi were allocated to either race 2 or race 6 by their ability or inability to cause disease on the six host differentials New Season, New Era, Dark Skin Perfection, WSU 28, WSU 23 and Little Marvel. The isolates showed similar colony morphology on various solid media and their growth rates were inhibited to a similar extent by nystatin, cycloheximide and trichodermin when these compounds were included in potato dextrose agar. Total DNA waspurified from each isolate, digested separately with the restriction endonucleases EcoRI, EcoRV, Pstl, BamHl, SmaI and PvuII and the resulting DNA fragments separated by agarose gel electrophoresis. The patterns obtained were indicative of the presenceof repetitive DNA sequences. Moreover, the patterns obtained for the five race 2 isolates were identical for a given enzyme as were the patterns for the two race 6 isolates. Hence classification of isolates into races by their restrictive enzyme digestion, patterns coincided with that according to pathotypes and could be an improved, more reliable and reproducible method of race classification. An eighth isolate, originally classified as race 1, had lost its ability to cause disease on all six host differentials. The restriction digest patterns of its DNA were different from those of the DNA from both the race 2 and the race 6 isolates.     

THE SUSCEPTIBILITY OF POTATO VARIETIES TO INFESTATION BY THE EELWORMS DITYLENCHUS DESTRUCTOR AND D. DIPSACI

Twenty-five varieties of potato in common commercial cultivation were found to be susceptible to tuber attack by potato-derived populations of Ditylenchus destructor under field and pot experimental conditions. Stunting and leaf deformation may also be caused by the eelworms but appear less consistently. A race of D. destructor from mushroom spawn had almost no effect on potatoes. Various races of D. dipsaci can reproduce in the shoot tissue of potato, sometimes causing damage. One population of this stem eelworm produced lesions on the tubers.     

Molecular characterisation of resistance against potato wart races 1, 2, 6 and 18 in a tetraploid population of potato (Solanum tuberosum subsp. tuberosum)

Potato wart is caused by the obligate biotrophic fungus Synchytrium endobioticum, which is subject to quarantine regulations due to the production of long persisting spores in the soil and the lack of effective fungicides. The objective of this study was to identify quantitative trait loci (QTL) for resistance against potato wart races (R) 1, 2, 6 and 18 in a tetraploid potato population developed by crossing cv. Saturna (resistant to R1) with cv. Panda (resistant to R1, R2, R6, R18). A total of 92 progenies were used for phenotyping and genotyping. Resistance tests were performed for races 1 and 18 in 2 years and for races 2 and 6 in 1 year on 10 to 20 eyepieces per genotype. Based on amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers, linkage maps were established for the female and male parent, respectively. Single marker analysis followed by a multiple regression analysis revealed initial marker–trait associations. The interval mapping routine of TetraploidMap was applied for QTL analysis. A major QTL for resistance against race 1 explaining between 46 % and 56 % of the phenotypic variation was identified near Sen1, a known resistance locus for potato wart race 1 on chromosome XI. Other resistance QTL were detected on chromosomes I (to R2), II (to R6, 18), VI (to R1, 2, 6, 18), VII (to R2, 6, 18), VIII (to R1, 2, 6, 18), X (to R2, 6, 18), XI (to R2, 6, 18) and on an unknown linkage group (to R18) explaining minor to moderate effects of the phenotypic variation. Resistance QTL against different potato wart races often overlapped, particularly concerning races 2, 6 and 18. Overall, this study gives a valuable insight into the complex inheritance of resistance against potato wart.     

Increasing the effectiveness of spring trap crops for Leptinotarsa decemlineata

Insecticide resistance problems have increased interest in trap crops as a cultural control strategy for overwintered Colorado potato beetle adults, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae). Growers in the north central United States have noticed and treated concentrations of adults at the edge of some of their potato fields each spring. Based on sampling in commercial potato fields over a 2-year period, early planted fields that are adjacent to the previous year's potato crop are most likely to have concentrations of adults at the field edge. Frequency of fields with significantly more adults at the edges than in the center sections as well as adult population density in the center sections of fields declined with both distance from the previous potato field and later planting date. The effects of both physical and chemical barriers to movement into potato fields from the field edges were studied in small plot trials and at the edges of commercial potato fields. In small plot trials, physical barriers had a greater impact than chemical barriers on adult beetle movement from a potato trap crop to the protected potatoes beyond the barrier. Barrier treatments reduced beetle numbers in and just beyond the barrier in commercial fields, but the effects were localized and no significant reduction of beetles was observed further into the field. Beetle flight was hypothesized to be responsible for the localized effects of barrier treatments and the lack of edge concentrations in later planted and more distantly rotated fields. In field studies, larger potato plants attracted more colonizing potato beetles than smaller plants. Attracting Colorado potato beetles to trap crops containing potato plants that were larger than those in the remainder of the field, however, provided no significant reduction of beetles in the remainder of the field. We found little opportunity to reduce beetle populations with trap crops at the edges of potato fields without controlling the adults in the trap crop itself. Growers can exploit naturally occurring concentrations of adults at the edges of early and adjacent potato plantings if they are prepared to monitor and regularly treat the field edges.     

New Races of the Sunflower Downy Mildew Pathogen (Plasmopara halstedii) in Europe and North and South America

Collections of the causal agent of sunflower downy mildew (Plasmopara balstedii) (PH) from several European and North and South American countries were used to inoculate a series of sunflower inbred lines to differentiate races. Race 3 was identified from Argentina; race 4 from France, Hungary, and Bulgaria; race 6 from Canada and France; and race 7 from Argentina. This is the first report of race 3 in South America and of race 4 in Europe, and is the first identification of races 6 and 7. Reactions of USDA lines RHA-274, RHA-325, and DM-2 differentiate races 2, 6, and 7, with RHA-274 resistant to all three. Thirty-three commercial hybrids from 11 countries were tested; 70 % were resistant to race 2, only 27 % had resistance to race 6, and none were resistant to race 4. Surveys to determine the relative proportions of the various races within each country are needed to assess their potential impact. The USDA lines HA-335, HA-336, HA-337, HA-338, HA-339, RHA-340, HA-R4, and HA-R5 are resistant to all seven mildew races and could be utilized for the production of PH resistant hybrids. For the short term, it appears that seed treatment with metalaxyl may be the most effective control.     

Solanum Tuber-bearing Species Resistance Behavior Against Nacobbus aberrans

Naccobus aberrans is a major pest of the potato crop in the Andean regions of Argentina, Bolivia, and Perú. It is endemic in northwest Argentina and is also found in lowlands. The resistance of eleven Andean potato landraces and three accessions of the wild tuber-bearing species Solanum acaule, S. infundibuliforme, and S. megistacrolobum were evaluated against a population of N. aberrans from Coctaca, Jujuy province, while Solanum tuberosum ssp. tuberosum 'Spunta', 'Kennebec', and 'Frital INTA' were evaluated against a population from the southeast of Buenos Aires province. The presence, the number of galls, and the number of individuals were recorded. In addition, a reproduction factor was calculated and races were determined. Results showed that the N. aberrans population from Coctaca corresponded to race 2 and the population from the lowlands belonged to the sugar beet group. Landrace Azul, one genotype of S. megistacrolobum, and two genotypes of S. acaule showed resistance towards the race from Coctaca while no infection was recorded in potato cultivars with the Naccobus race from the lowland area.     

Detection of Cochliobolus heterostrophus races in South China

Cochliobolus heterostrophus is the causal pathogen of the southern corn leaf blight (SCLB). There are three known races: race O, race C and race T. To determine which C. heterostrophus races comprise the field population in southern China and to assess diversity of these strains in terms of virulence, 200 isolates from diseased plants were collected in nine provinces/municipalities. All were race O, that is, no race T or race C isolates were found. Sixty race O isolates that sporulated well were chosen for further analysis. Virulence was measured using the integral optical density (IOD) of leaf lesions on four maize inbred lines. UPGMA cluster analysis of AFLP markers was applied to the 60 race O isolates plus control race O, T and C strains. Phylogenetic distribution, geographic location and virulence were not correlated. These results can provide valuable information for guidance in early warning and disease control.     

Gene-for-gene interactions between Pseudomonas syringae pv. phaseolicola and Phaseolus.

The gene for cultivar-specific avirulence to Phaseolus vulgaris cv. Tendergreen in races 3 and 4 of Pseudomonas syringae pv. phaseolicola was isolated and sequenced. Genomic clones from libraries of race 3 in pLAFR1 and race 4 in pLAFR3, which altered the phenotype of race 5 from virulent to avirulent in Tendergreen, were found to possess a common approximately 15-kb region of DNA that contained the determinant of avirulence. Subcloning and insertion mutagenesis with Tn1000 located an avirulence gene within a 1.4-kb BglII/HindIII DNA fragment in races 3 and 4. Comparison of the nucleotide sequences of regions of DNA that confer avirulence confirmed that both races have an identical gene for avirulence (designated avrPph3) comprising 801 base pairs (bp) and predicted to encode a cytoplasmic protein of 28,703 Da. A sequence, TGCAACCGAAT, 91% homologous to the motif found in promoter regions of avrB and avrD from P. s. pv. glycinea was located 89-99 bp upstream of the start of the open-reading frame 1. Hybridization experiments showed that avrPph3 was not plasmid-borne and was absent from isolates of P. s. pv. phaseolicola races 1, 2, 5, 6, 7, and 8, P. cichorii, P. s. pvs. coronafaciens, glycinea, maculicola, pisi, syringae, and tabaci. Cosegregation studies of crosses between cultivars resistant (Tendergreen) and susceptible (Canadian Wonder) to races 3 and 4 and transconjugants of race 5 confirmed that a gene-for-gene relationship controls specificity in the interaction between Tendergreen and races 3 and 4 of P. s. pv. phaseolicola.