粤、桂、苏、皖四省稻瘟病菌有性态的研究

应用国际稻瘟病菌标准交配型菌株KA3和THl6对2000年从广东、广西、江苏和安徽4省采集的145个稻瘟病菌菌株的育性和交配型测定结果表明,广东、广西和安徽3省稻瘟病菌群体中存在着Matl.1和Matl.2两种交配型,江苏省的23个可交配菌株均为Matl.1。各省间稻瘟病菌群体的可交配率差异不大,总的可交配率为48.3%。有9个菌株与标准菌株交配产生了子囊孢子,可育率为6.2%。检测到2个两性菌株,不同地区稻瘟病菌群体雌雄性别的比例有显著性差异。用不同交配型的可育菌株进行互交,14个组合中只有1个组合产生子囊壳,但没有形成成熟的子囊孢子。     

Pisatin demethylation by fungal pathogens and nonpathogens of pea: association with pisatin tolerance and virulence

Previous studies have indicated that detoxification of their hosts' phytoalexins is a tolerance mechanism for some true fungi, but not the fungus-like Oomycota, and may be involved in determining the virulence of a pathogen. In the present study, the associations between demethylation of the pea phytoalexin pisatin, tolerance to pisatin, and virulence on pea were examined for 50 fungal isolates which represent 17 species of pathogens and nonpathogens of pea. All isolates ofPythium coloratum and P. irregulare failed to metabolize and were sensitive to pisatin, consistent with previous observations that members of the Oomycota generally lack the ability to metabolize and are sensitive to their hosts' phytoalexins. Among true fungi tested, the ability to demethylate pisatin was common, regardless of whether the particular isolate was pathogenic on pea or not. However, when the rate of pisatin demethylation was compared to virulence, all but one of the moderate to highly virulent isolates rapidly demethylated pisatin. In addition, the more rapidly demethylating isolates were generally more tolerant of pisatin. These results suggest that a specialized enzyme system for quickly detoxifying pisatin might be present in most pea pathogens. In previous studies a specific cytochrome P450 enzyme for demethylating pisatin was identified in the pea pathogen Nectria haematococca mating population VI, and genes (PDA genes) encoding that enzyme have been cloned from this fungus. When DNA specific for these genes was used to probe genomic DNA from other fungi that demethylate pisatin, significant hybridization was detected with only one fungus, the pea pathogen Fusarium oxysporum f. sp. pisi. If the other pea pathogens possess a specific cytochrome P450 system for detoxification of pisatin, the genes encoding these enzymes apparently share limited nucleotide similarity with N. haematococca PDA genes.     

稻瘟病菌群体育性分析的主要影响因子研究

 将稻瘟病菌10个两性可育菌株,包括GUY11、KA3、KA9、KA7、6023、2539W、8773R-19、8773R-27、8113R-2和8113R-10相互交配,结果表明,10个菌株育性好,交配型明确;2539W已丧失雌性功能,不再是两性菌株。原先由6023/2539W测为可育的24个福建省田间稻瘟病菌菌株分别与另外8个两性菌株交配,结果得出不同两性菌株测得同一组稻瘟病菌菌株的育性差异很大,这可能是由于两性菌株的交配能力强弱差异以及两性菌株与待测菌株之间的亲和性不同引起的。分析认为,GUY11和KA3最适于测定稻瘟病菌群体的育性和交配型,并用其测定了227个来自福建省田间稻瘟病菌菌株的育性。结果表明,福建省稻瘟病菌群体可育菌株率为81.1%,其中81.0%为交配型MAT1-2,19.0%为MAT1-1。研究结果将有助于进一步认识稻瘟病菌的群体结构特点及其演化规律。     

Variation for virulence among Scandinavian isolates of Peronospora viciae f.sp. pisi (pea downy mildew) and responses of pea genotypes

Variation for virulence among Scandinavian isolates of Peronospora viciae f.sp. pisi (downy mildew) on different pea genotypes was investigated. Variation for virulence was found within and between mass-conidial isolates which were originally obtained from oospore populations. Virulence towards pea cultivars that have not been commerically cultivated in Scandinavia was observed. The specific resistance of the pea cultivars Puget, Cobri, Gastro, Starcovert and Starnain was confirmed. One pea breeding line showed a stable partial resistance to different isolates of the fungus and it was also highly resistant to race 8'from The Netherlands which is considered to be virulent on most pea genotypes carrying known specific resistance factors.     

Specific Behaviour of French Aphanomyces Euteiches Drechs. Populations For Virulence and Aggressiveness on Pea, Related to Isolates from Europe, America and New Zealand

The pathogenic variability of Aphanomyces euteiches on pea was investigated using a collection of 88 pea-infecting isolates from France and 21 isolates from Denmark, Sweden, Norway, USA, Canada and New Zealand. Aggressiveness and virulence were assessed by scoring the root symptoms on a differential set of six pea genotypes. Eleven virulence types were characterised. The virulence type I, previously described as virulent on the whole set, was predominant and included the most aggressive isolates of all geographical origins. The other types were much less prevalent, existing as one to five isolates. Three virulence types (III, IV and V) contained no French isolates. The type III, avirulent on MN313, was composed of American isolates only, and resembled the major group recently described in the USA. A wide range of aggressiveness was found within the virulence type I, and the French isolates appeared globally more aggressive than the foreign isolates. These findings indicate that isolates from the virulence type I should be used as references in breeding programs, and that pea lines PI180693 and 552 may be the most interesting resistance sources to date, despite their only partial resistance.     

云南省稻瘟病菌群体的致病性分析及交配型分布

为明确云南省不同稻区稻瘟病菌Magnaporthe oryzae的毒性频率及交配型分布,利用2007—2013年分离自云南省不同稻区的112株稻瘟病菌单孢菌株,对23个持有不同抗性基因的单基因系和持有Pi57(t)的水稻渗入系IL-E1454进行致病性测定。结果表明,稻瘟病菌对不同抗病基因的毒性频率存在很大差异,分离自粳稻区的稻瘟病菌菌株对持有Piz-t、Pi5、Pi9、Pi20和Pi57(t)这5个水稻品系的毒性频率分别为14.29%、5.36%、5.51%、5.36%和0;分离自籼稻区的稻瘟病菌菌株对持有Pik-h、Piz、Pita、Piz-5、Pita-2、Pi5、Pi7和Pi9这8个水稻品系的毒性频率分别为18.25%、9.13%、9.64%、7.50%、15.72%、0、13.05%和0;分离自陆稻区的稻瘟病菌菌株菌株对持有Pik-h、Pib、Pish、Pi1、Pi5、Pi9、Pi11和Pi57(t)这8个水稻品系的毒性频率分别为6.67%、3.33%、13.79%、13.33%、7.69%、6.67%、0和3.23%;交配型测定结果显示,陆稻区菌株可交配率为100.00%,...     

黑龙江省稻瘟病菌育性及其交配型分析

为明确黑龙江省采集自不同年份、不同地区的稻瘟病菌Magnaporthe oryzae的育性能力和交配型分布,采用2株标准菌株GUY11(MAT1-2)和KA3(MAT1-1)对2016—2017年黑龙江省西部、东部、中部3个地区经单孢分离的241株稻瘟病菌进行育性测定,并利用PCR技术对其交配型进行检测。结果表明,黑龙江省西部、东部、中部的241株稻瘟病菌中可育性菌株比例为11.62%,其中雌性菌株、雄性菌株、两性菌株分别占1.66%、4.56%和1.25%,不能判断其性别的未知菌株占4.15%。采集自不同地区、不同年份的稻瘟病菌可育性差异均较大,西部、东部、中部地区可育性菌株出现频率分别为13.25%、7.27%和12.62%;2016年采集的稻瘟病菌可育性较高,可育性菌株出现频率为25.30%。黑龙江省稻瘟病菌群体中同时存在MAT1-1和MAT1-2两种交配型,主要以交配型MAT1-1占优势,出现频率为58.92%,交配型为MAT1-2的菌株出现频率为8.30%。不同地区稻瘟病菌的交配型亦有差异,交配型为MAT1-1的菌株在黑龙江省东部地区出现频率最高,为72.73%,在中部、西部地区的出现频率次之,分别为61.17%和46.99%。表明黑龙江省水稻种植区的稻瘟病菌同时存在2种交配型菌株,其交配型存在丰富的多态性,但其可育性及交配型分布不均衡。     

Diversity and spatial distribution of vegetative compatibility types and mating types of <Emphasis Type="BoldItalic">Cryphonectria parasitica</Emphasis> in the Aydın Mountains,Turkey

In this study, the population structure of the chestnut blight fungus Cryphonectria parasitica in the Aydın Mountains was investigated to make inferences about fungal reproduction and population diversity. A total of 213 C. parasitica isolates from eight subpopulations were used to determine vegetative compatibility (vc) and mating types of the population. Furthermore geostatistical analysis was performed to define the spatial structure of the population. The results showed that the isolates were vegetatively compatible with the European vc types of either EU-1 or EU-12. Both vc types were found in almost all subpopulations, but their frequencies varied depending on location. The results of a PCR assay showed that both mating types of C. parasitica (MAT-1 and MAT-2) exist in the population. MAT-1 comprised 65% of the total isolates, and the ratio of mating types was significantly skewed from 1:1. Genotyping based on combined vc and mating type data revealed four genotypes: EU-1/MAT-1 (28.6%), EU-1/MAT-2 (34.7%), EU-12/MAT-1 (36.2%) and EU-12/MAT-2 (0.5%). Geostatistatical analysis indicated that vc types, mating types and vc/mating genotypes were spatially autocorrelated and clustered in their distributions. Results suggested that C. parasitica could have a clonal population structure that is generated by asexual reproduction. Low vc-type diversity suggests that the C. parasitica population in the Aydın Mountains may be highly suitable to hypovirus invasion, thereby providing a high potential for successful biological control. However, co-occurrence of sexually compatible strains of EU-1 and EU-12 at the same locations in close proximity creates a high risk of increase in vc-type diversity.     

Variation in growth rates and aggressiveness of naturally occurring self‐fertile and self‐sterile isolates of the wilt pathogen Ceratocystis albifundus

Ceratocystis albifundus is the most important fungal pathogen of black wattle (Acacia mearnsii) grown in plantations in southern and eastern Africa. It is a homothallic fungus but also undergoes unidirectional mating type switching. As a result, the ascospore progeny can be either self‐fertile or self‐sterile. The only apparent difference between these mating types is the deletion of the MAT1‐2‐1 gene in self‐sterile isolates. There is some evidence suggesting that self‐sterile isolates grow more slowly than self‐fertile isolates, but this has not been tested rigorously. The aim of this study was to determine whether self‐sterile isolates are less fit by examining growth rate, relative germination rate and pathogenicity. Five self‐sterile isolates were generated from each of five self‐fertile isolates of C. albifundus and these 30 isolates were compared. The results showed that the self‐sterile isolates grew consistently slower and were less pathogenic than the self‐fertile isolates. The germination ratio of self‐fertile to self‐sterile isolates from single ascospores collected from the ascomata of five self‐fertile isolates was on average 7:3. This could be a consequence of the self‐sterile isolates having a lower germination rate. This observation, and the lower growth and pathogenicity levels, suggests that self‐sterile isolates are not likely to compete effectively in nature, raising intriguing questions regarding their role and value to C. albifundus and other fungi having a similar mating system.     

Characterization of Ascochyta isolates and susceptibility of pea cultivars to the ascochyta disease complex in Alberta

The relative virulence of 109 Ascochyta isolates collected from pea fields in Alberta from 1996 to 1998 were evaluated on 10-day-old seedlings by the excised leaf-assay technique. Twenty-eight isolates were avirulent, while the others produced lesions of various sizes on pea leaves. DNA samples from 86 isolates were amplified by the RAPD technique using PCR with single primers. One dominant genotype of Ascochyta pisi was identified throughout Alberta, but variations in virulence were not clearly differentiated by the RAPD technique. Five Ascochyta isolates, four virulent and one avirulent, were used to assess the susceptibility of 20 field pea cultivars available in Alberta, including 13 yellow types and seven green types. Based on symptom development, the yellow-type cultivars Swing, Eiffel and Delta, and the green-type cultivar Orb, were the most susceptible. Of yellow-type cultivars, Voyageur, Carneval and Montana were most resistant to A scochyta infection.     

Genetic characteristics of Fusarium verticillioides isolates from maize in Costa Rica

Thirty-nine isolates of Fusarium verticillioides from maize seeds from three regions of Costa Rica were classified on fertility, fumonisin production, vegetative compatibility and pathogenicity. The identity of the isolates was verified by sexual crosses with standard tester strains and by isozyme analysis. Twenty-three isolates (59%) were mating type A⁻ and 16 (41%) were A⁺; 29 (74%) were female fertile. The isolates produced high amounts of fumonisin B₁ when grown on sterilized maize grits, 32 isolates producing more than 1000 μg g⁻¹, as determined by TLC, and 7 less than 1000 μg g⁻¹. Vegetative compatibility tests by pairing nit mutants identified 34 vegetative compatibility groups (VCGs), of which 29 had one member and 5 had two members. Isolates belonging to the same VCG were obtained from the same seed sample. Two pathogenicity tests with different inoculation methods were performed: on toothpick inoculation of 7-week-old maize stalks, 71% of the isolates were pathogenic according to the length of the necrosis formed in the stalk, and on sand inoculation of maize seedlings all the isolates were pathogenic, according to shoot length and dry weight production. Differences in aggressiveness between some of the isolates were recorded. It is concluded that natural populations of F. verticillioides in Costa Rica consist of genetically diverse, highly fertile and pathogenic isolates that represent a potential risk for disease development and fumonisin accumulation in maize crops.     

鄂、湘、赣、滇、黔、川六省稻瘟病菌有性态的研究

作者对湖北，湖南、江西、云南、贵州和四川六省水稻栽培区１８４个稻瘟病菌Ｍａｇｎａｐｏｒｔｈｇｒｉｓｅａ Ｂａｒｒ菌株（其中３２个采自马唐草）的能育性和交配型进行了测定。结果表明：不同菌株间能育性差别很大，四川和贵州两省菌株有性态的形成率分别为５３％和５０％，而湖北的菌株全部表现不育，测得的所有可育菌株皆属交配型Ａ，杂草菌株有性态子实体形态结构与水稻菌株的十分相似。     

Virus recognition and pathogenicity: Implications for resistance mechanisms and breeding

The major method of control of virus diseases in crop plants is breeding for resistance. The genetics of resistance, and of matching virulence (the ability of a virus strain to overcome a specific host resistance gene) have been studied less for viruses than for fungal and bacterial pathogens. This paper draws on a survey of the genetics of resistance to a large number of viruses in cultivated crops, and makes some generalisations and predictions about mechanisms. Most resistance to viruses in crops is monogenic. Dominant alleles are associated with virus-localisation mechanisms, which are induced after infection. The nature of the ‘recognition event’ between plant- and virus-coded functions, which triggers resistance plus a cascade of secondary responses, is not yet known. Gene dosage-dependent alleles tend to be associated with non-localising resistance, which allows some virus spread, but inhibits multiplication. Recessive alleles may involve a negative type of resistance mechanism, whereby the resistant plant lacks some function normally required by the virus for pathogenesis. Such resistance tends to be expressed as complete immunity. Many resistance genes have been overcome by virulent isolates of viruses; only 10 % of the sample of resistance genes have proved exceptionally durable. Virulence may involve different viral functions. The production of infectious cDNA clones, and construction of chimaeric recombinants between clones of virulent and avirulent isolates, is now allowing detailed mapping of virulence determinants. Transformation of plants with ‘novel’ genes for virus resistance, based on coat proteins and viral satellites, may allow construction of more robust resistance systems.     

Evidence of Genetic Exchange by Parasexual Recombination and Genetic Analysis of Pathogenicity and Mating Type of Parasexual Recombinants in Rice Blast Fungus, Magnaporthe oryzae

ABSTRACT A selectable marker gene conferring resistance to bialaphos (BI) was introduced into rice blast isolate Y90-71BI and another conferring resistance to blasticidin S (BS) into isolate 3514-R-2BS of Magnaporthe oryzae to demonstrate exchange of DNA. Colonies obtained from co-cultures of these two isolates were resistant to both BI and BS and had both resistance genes as shown by Southern blot analysis of their genomic DNA. Conidia from these BI-BS-resistant isolates had only one nucleus per cell after staining with 4',6-diamidino-2-phenylindole (DAPI). Using flow cytometry, however, these BI-BS-resistant isolates were found to be haploid. Segregation of BI-BS-resistant isolates for pathogenicity (avirulence to virulence) on rice line K59-1 was consistent with a 1:1 ratio, as was segregation for mating type. These BI-BS-resistant isolates were thus apparently derived from parasexual exchange of DNA and the segregation of pathogenicity and of mating type of the parasexual recombinants might correspond to that of the progeny of the offspring of the sexual cross.     

Production of a Mating Inhibitor by Ustilago hordei

ABSTRACT Ustilago hordei, the cause of barley covered smut, was found to produce a factor that inhibited its own mating. The mating inhibition factor (MIF) specifically inhibited mating of U. hordei and other Ustilago spp., but not teliospore germination or sporidial growth. MIF did prevent teliospore germination of Tilletia caries and T. contraversa. MIF was found at low levels in culture supernatants of either mating type of U. hordei grown separately, but at higher levels when both mating types were grown together, in the supernatants of MAT-1 mating type cells transformed with the MAT-1 pheromone gene mfa1 and of MAT-2 cells transformed with either mfa1 or the MAT-1 pheromone receptor gene pra1. Diploid cells produced no detectable inhibitor, nor did MAT-1 cells with a disrupted mating type locus that deleted both mfa1 and pra1. MIF production was restored when mfa1, but not pra1, was added back to the MAT-1Delta cells. MIF activity was altered by protease treatment. Highly purified MIF from MAT-1 cells contained cysteine methyl ester, farnesyl cysteine, farnesyl cysteine methyl ester, and a dodecapeptide with a mass consistent with that of MAT-1 pheromone lacking the terminal cysteine. Since smut fungi must first mate to become pathogenic, mating inhibition has the potential to be an effective method of disease control for these pathogens.     

Comparative Study of Genetic Diversity and Pathogenicity Among Populations of Verticillium Dahliae from Cotton in Spain and Israel

Genetic diversity and phenotypic diversity in Verticillium dahliae populations on cotton were studied among 62 isolates from Spain and 49 isolates from Israel, using vegetative compatibility grouping (VCG), virulence and molecular assays. In Spain, defoliating V. dahliae isolates (D pathotype) belong to VCG1, and non-defoliating isolates (ND) belong to VCG2A (often associated with tomato) and VCG4B (often associated with potato). The D pathotype was not identified in Israel. The ND pathotype in Israel is comprised of VCG2B and VCG4B. Isolates in VCG2B and VCG4B ranged in virulence from weakly virulent to highly virulent. The highly virulent isolates induced either partial defoliation or no defoliation. Virulence characteristics varied with inoculation method and cotton cultivar. Highly virulent isolates from Israel were as virulent as D isolates from Spain under conditions conducive to severe disease. The D pathotype is pathologically and genetically homogeneous, whereas the ND pathotype is heterogeneous with respect to virulence, VCG, and molecular markers based on single-primer RAPD and on PCR primer pairs.     

Measuring Immigration and Sexual Reproduction in Field Populations of Mycosphaerella graminicola

ABSTRACT A field experiment was conducted to determine the relative contributions of immigration and sexual reproduction to the genetic structure of Mycosphaerella graminicola populations during the course of an epidemic. The genetic structure of M. graminicola populations sampled from wheat plots inoculated artificially with 10 isolates was compared with control plots infected naturally by airborne ascospores. Restriction fragment length polymorphisms (RFLPs) were used to test the randomness of associations among loci, and DNA fingerprints were used to identify clones. All isolates in the control plots had unique genotypes and RFLP loci were at gametic equilibrium, findings consistent with random mating. The proportion of isolates in the inoculated plots with DNA fingerprints that differed from the 10 inoculated isolates increased from 3% in the early to 39 and 34% in the mid- and late season, respectively. The degree of gametic disequilibrium was higher in the mid-season than in the late-season population. By the end of the growing season, we estimate that 66% of the isolates in the inoculated plots were asexual progeny of the 10 inoculated isolates, 10% were immigrants, and 24% were sexual recombinants. The proportion of infections caused by ascospores increased over the growing season.     

Pathogenicity and race characterization of Fusarium oxysporum f. sp. phaseoli isolates from Spain and Greece

Virulence (≡ severity of disease) and physiological specialization of nine isolates of Fusarium oxysporum f. sp. phaseoli recovered in El Barco de Avila (Castilla y León, west-central Spain) and of two isolates from Chryssoupolis (Greece) were determined. The susceptibility/resistance response showed by a differential set of common bean cultivars ( Phaseolus vulgaris ) selected at the Centro Internacional de Agricultura Tropical (CIAT) delineated the isolates into two new races: races 6 and 7. The results of pathogenicity tests did not show any significant differences in virulence among the isolates. However, the reactions of several Spanish common bean cultivars indicated the presence of two groups of isolates, highly virulent and weakly virulent, among the Spanish isolates analysed. These results indicate that isolates classified in the same race are not homogeneous with respect to virulence, and suggests that race analysis using the CIAT differential cultivars is insufficient to describe the physiological specialization of F. oxysporum f. sp. phaseoli .     

Production and Germination of Oospores of Phytophthora infestans (Mont.) de Bary in Morocco

One hundred and eight isolates of Phytophthora infestans were collected from infected potato and tomato crops in the middle-north of Morocco during 1997–2000. Pairings of these isolates with tester isolates of mating type A1 and A2 revealed that 60% of the isolates were mating type A2 (65/108) and 40% were mating type A1. After 10 days incubation at 20 °C and a 16-h photoperiod, approximately 25% and 18% of the oospores produced in-vitro germinated in potato soil extract and potato root extract, respectively. Oospores were observed in potato leaf tissues in pairings that were fertile in-vitro. Maximum production of oospores was obtained in potato leaves of cultivars that were moderately susceptible (Desirée, Nicola) after 10 days of incubation at 15 °C and a 16-h photoperiod. These results confirm the presence of P. infestans strains that are sexually compatible under Moroccan climatic conditions. Production of oospores constitutes a threat for these crops because of the occurrence of recombinants with new virulences which may be difficult to control and as a consequence survival of oospores in absence of the host plant in the soil.     

华南瓜类疫霉种群的致病力及其寄主嗜好性

2007—2010年从广西、广东两省(区)9个样区采集冬瓜、黄瓜疫病显症植株,经分离纯化鉴定共获得193株瓜类疫霉。采用菌丝块无伤接种法,将菌株接种冬瓜和黄瓜,测定、比较其对供试寄主植物的致病力及其寄主嗜好性。结果表明,病原群体对寄主植物冬瓜和黄瓜的致病力均存在明显分化现象,可分为强致病力、中等致病力及弱致病力3大类群;来自不同地区的瓜类疫霉对寄主植物冬瓜和黄瓜的致病力明显不同,多数样区以强致病力菌株占优势。瓜类疫霉种群中存在3种寄主嗜好型菌株,A型菌株对冬瓜和黄瓜均表现强致病力,与原始分离寄主无关;B型菌株仅对原始分离寄主冬瓜表现强致病力,而对黄瓜则表现为弱或中等致病力;C型菌株仅对原始分离寄主黄瓜表现强致病力,而对冬瓜则表现为弱或中等致病力。