球孢白僵菌营养亲和型多样性与生态背景的关系

本文将来源不同的球孢白僵菌菌株分别按相同地理来源和相同分离奇主进行配对培养,发现相同地理来源菌株的营养亲和型多样性要明显小于相同分离寄主的菌株,前者的P及Shannon-Wiener多样性指数分别为0.4286及0.8708,后者分别为0.7500及1.3321。这说明来源于同一地区的菌株属于同一VCG的概率要大于相同分离寄主的菌株,同时也说明相同地理来源菌株的遗传相似性要高于相同分离寄主菌株的遗传相似性。     

串珠镰孢霉硝酸盐还原途径酶的遗传研究*

通过对菌株突变体有性杂交后代的检测方法,对串珠镰孢霉Fusariummoniliforme氮代谢过程中硝酸盐还原途径相关酶基因间关系进行研究。串珠镰孢霉含钼协同因子突变体缺陷型(nitB)与亚硝酸盐还原酶缺陷型突变体(nitC)间的杂交结果显示,在不同的交配群以及在相同交配群不同寄主上的分离菌株中,控制这两种酶的基因有两种类型,并据此提出细胞核基因和细胞质基因共同调控硝酸盐还原途径酶的假说。当杂交后代出现四种表型(nitD:nitB:nitC:wt=1:1:1:1)时,表明这两种酶的遗传受核基因调控,分离时两种基因自由组合;当杂交后代仅有两种表型时,表现为父本表型隐藏,双基因缺陷型(表型同主氮调节基因缺陷型nitD)表型不出现,即母本表现型:野生型为1:1,表明这种遗传类型除受核基因的控制外,还存在细胞质基因的影响。     

串珠镰孢霉硝酸盐还原途径酶的遗传研究

通过对菌株突变体有性杂交后代的检测方法,对串珠镰孢霉Fusarium moniliforme氮代谢过程中硝酸盐还原途径相关酶基因间关系进行研究。串珠镰孢霉含钼协同因子突变体缺陷型(nitB)与亚硝酸盐还原酶缺陷型突变体(nitC)间的杂交结果显示,在不同的交配群以及在相同交配群不同寄主上的分离菌株中,控制这两种酶的基因有两种类型,并据此提出细胞核基因和细胞质基因共同调控硝酸盐还原途径酶的假说。当杂交后代出现四种表型(nitD：nitB：nitC：wt=1：1：1：1)时,表明这两种酶的遗传受核基因调控,分离时两种基因自由组合：当杂交后代仅有两种表型时,表现为父本表型隐藏,双基因缺陷型(表型同主氮调节基因缺陷型nitD)表型不出现,即母本表现型：野生型为1：1,表明这种遗传类型除受核基因的控制外,还存在细胞质基因的影响。     

新月弯孢菌Curvularia lunata营养体亲和性的进一步研究

来自全国39个地区的70株新月弯孢菌Curvularialunata在WAC培养基上诱导培养后,随机挑取10197个抗KClO3突变体,经CDA鉴定获得2207株nit突变体,nit突变体频率为21.64%。在这些nit突变体中,1397个为nit1,占63.30%;734个为NitM,占33.26%;76个为nit3,占3.44%。70个菌株全部获得了稳定的nit突变体,其中52个菌株获得了NitM突变体。结果表明WAC比先前报道的KPS更适合用于C.lunatanit突变体的筛选。通过不同菌株间互补nit突变体配对测试,将其中的65个C.lunata菌株划分为22个营养体亲和群(VCGS),而另外5个菌株因未获得NitM突变体暂时无法确定其VCG。划分出的22个VCGs中,有11个VCGs是由多菌株组成的,VCG3为优势类群,含18个菌株,其地理来源最复杂,主要为致病性中等以上的菌株;其余11个VCGs内均仅有1个自身亲和的菌株。以上结果初步表明,在C.lunata群体内存在丰富的VCG多样性,VCG3可能是与致病性相关的优势VCG,但营养体亲和性与菌株地理来源没有明显的直接关系。     

新月弯孢菌Curvularia lunata营养体亲和性的进一步研究

来自全国39个地区的70株新月弯孢菌Curvularialunata在WAC培养基上诱导培养后,随机挑取10197个抗KClO3突变体,经CDA鉴定获得2207株nit突变体,nit突变体频率为21.64%。在这些nit突变体中,1397个为nit1,占63.30%;734个为NitM,占33.26%;76个为nit3,占3.44%。70个菌株全部获得了稳定的nit突变体,其中52个菌株获得了NitM突变体。结果表明WAC比先前报道的KPS更适合用于C.lunatanit突变体的筛选。通过不同菌株间互补nit突变体配对测试,将其中的65个C.lunata菌株划分为22个营养体亲和群(VCGS),而另外5个菌株因未获得NitM突变体暂时无法确定其VCG。划分出的22个VCGs中,有11个VCGs是由多菌株组成的,VCG3为优势类群,含18个菌株,其地理来源最复杂,主要为致病性中等以上的菌株;其余11个VCGs内均仅有1个自身亲和的菌株。以上结果初步表明,在C.lunata群体内存在丰富的VCG多样性,VCG3可能是与致病性相关的优势VCG,但营养体亲和性与菌株地理来源没有明显的直接关系。     

不同寄主来源的串珠镰孢生物学性状及其在无性后代的遗传与变异

自安徽、山东、湖北、江苏等地多点采集棉花红腐病、水稻恶苗病、玉米穗腐病的病组织,经分离、鉴定和纯化,获得107个串珠镰孢（Fusarium monilifoFine）菌株。对上述来源于棉花、水稻、玉米的串珠镰孢的菌落形态、生长速率和产孢量等生物学性状及其在无性后代的遗传与变异进行了研究。结果表明,不同寄主来源的串珠镰孢菌株的菌丝生长温度范围和最适温度大致相同,但在菌落形态特别是色素方面存在明显差异,生长速率和产孢量也存在显著差异。棉花菌株的平均生长速率最大,玉米菌株生长速率最小,水稻菌株生长速率居中,相同群体的不同菌株间生长速率有极显著差异;玉米菌株产孢量最大,棉花菌株产孢量最小,水稻菌株产孢量居中。方差分析显示,不同寄主菌株群体间产孢量存在显著差异,而同一寄主群体的不同菌株间产孢量均无显著差异,说明菌株产孢量大小主要与其寄主种类有关,而与地区来源关系不大。遗传测定结果表明,分离自棉花、玉米和水稻的串珠镰孢的菌落形态和生长速率在单分生孢子后代均可稳定遗传;产孢量性状遗传有两种情况：分离自棉花和水稻的串珠镰孢菌株Fm1和Fm31的产孢量性状在单分生孢子后代均可稳定遗传,而分离白玉米的串珠镰孢菌株Fm19的产孢量性状在单分生孢子第一代（CG1）发生变异。     

球孢白僵菌营养亲和型多样性与生态背景的关系

本文将来源不同的球孢白僵菌菌株分别按相同地理来源和相同分离寄主进行配对培养,发现相同地理来源菌株的营养亲和型多样性要明显小于相同分离寄主的菌株前者的Ｐ及Ｓｈａｎｎｏｎ－Ｗｉｅｎｅｒ多样性指数分别为０．４２８６及０．８７０８,后者分别为０．７５００及１．３３２１。这说明来源于同一地区的菌株属于同一ＶＣＧ的概率要大于相同分离寄主的菌株册时也是来源菌株的遗传相似性要高于相同分离寄主菌株的遗传相似性。     

基于SSR标记的琅琊山球孢白僵菌寄主专化性

球孢白僵菌Beauveria bassiana是一类常见的昆虫病原真菌,其自然侵染的寄主昆虫众多,达15目149科750种。为了解球孢白僵菌自然种群的遗传多样性,探讨种群异质性和寄主来源之间的关系,分析其寄主专化性的强弱,本研究利用SSR分子标记技术,比较了安徽琅琊山国家森林公园的85株球孢白僵菌（寄主种类涉及7目24种）群体遗传多样性差异,通过构建聚类树分析菌株基因型和寄主关联性。结果表明琅琊山球孢白僵菌群体Nei’s基因多样性指数h=0.2906,Shannon信息指数I_s=0.4510,多态位点百分率P为100%。不同寄主目球孢白僵菌遗传多样性水平由高至低为鞘翅目>膜翅目>同翅目>双翅目>鳞翅目>直翅目>半翅目,其中菌株数量较多的鞘翅目、膜翅目和同翅目3个亚种群的遗传多样性较高且水平接近。聚类分析发现8对SSR引物将85株球孢白僵菌分成29个基因型,并在遗传相似系数0.70处分别聚为3个分支。分析寄主类型发现相同基因型的株系可侵染不同目的寄主,而同一类型寄主也可被不同基因型的菌株侵染。球孢白僵菌种群的总体遗传多样性较高,遗传谱系与寄主来源无明显相关性,菌株的寄主专化性弱。     

镰孢属几种植物病原真菌分子核型的研究

利用脉冲电场凝胶电泳（ｐｕｌｓｅｄ－ｆｉｅｌｄｇｅｌｅｌｅｃｔｒｏｐｈｏｒｅｓｉｓ,ＰＦＧＥ）,研究了４株串珠镰孢（Ｆｕｓａｒｉｕｍ　ｍｏｎｉｌｉｆｏｒｍｅ）、１株尖镰孢（F．ｏｘｙｓｐｏｒｕｍ）、１株茄镰孢（Ｆ．ｓｏｌａｎｉ）和１株Ｆｕｓａｒｉｕｍｓｐ．的分子核型以及不同地域和寄主来源的串珠镰孢种内菌株间的分子核型差异。以凝胶包埋法（不破除分生孢子细胞壁）制备供试菌株电泳样本,采用３组条件组合进行电泳,分离出供试串珠镰孢完整染色体ＤＮＡ１０～１３条,分子量分布范围０．７Ｍｂ～６．９Ｍｂ,基因组大小为４２．２６Ｍｂ～４７．７５Ｍｂ;尖镰孢８条,分子量分布范围１．２Ｍｂ～６．７Ｍｂ,基因组大小为３２．２５Ｍｂ;茄镰孢６条,分子量分布范围２．４Ｍｂ～６．３Ｍｂ,基因组大小为２５．２Ｍｂ;Ｆｕｓａｒｉｕｍｓｐ．９条,分子量分布范围０．８Ｍｂ～６．８Ｍｂ,基因组大小为３６．４５Ｍｂ。结果表明,供试４种镰孢菌染色体数目、ＤＮＡ分子量及基因组大小都有较大不同,分子核型差异较大。不同来源的串珠镰孢种内菌株间分子核型亦有明显差异。     

不同地域豇豆(Vigna unguiculata)根瘤菌的表型和遗传多样性

豇豆根瘤菌既是豆科植物根际微生物的主要类群,也是重要的根瘤菌资源之一。通过最适碳/氮源、内源抗生素抗性和NaCl耐受性等表型特征和16S-23S Intergenetic Region(IGS)RFLP特征分析对分离自8个不同地域的52株供试豇豆根瘤菌的进行了表型和遗传多样性分析。供试菌株无论是在表型还是遗传型方面均具有丰富的多样性。根据IGS RFLP特征,供试豇豆慢生根瘤菌分为以下4个IGS类群:IGS-Ⅰ为豇豆根瘤菌的优势群体,在系统发育上相对独立;IGS-Ⅱ和IGS-Ⅲ的菌株分别属于Bradyrhizobium japonicum和Bradyrhizobium liaoningense;IGS-Ⅳ属于Bradyrhizobium elkanii。豇豆快生型菌株则分别归为IGS-Ⅴ和IGS-Ⅵ群,在分类地位上分别属于Sinorhizobium fredii和Rhizobium leguminosarum。不同地域的菌株在多样性方面具有明显的差异。分离自湖北红安的菌株仅与黑龙江德都具有一定的相似性,Jaccard系数为0.25,表现出地理隔离作用。来自黑龙江德都和广西武鸣的菌株的多样性最为丰富,其Simpson指数和Shannon-Wiener指数分别为0.667和1.243与0.593和0.961。     

Fumonisin production and other traits of Fusarium moniliforme strains from maize in northeast Mexico.

Strains of Fusarium moniliforme from maize seed collected in four fields in northeast Mexico were tested for fumonisin production in culture, for sexual compatibility, and for vegetative compatibility by using non-nitrate-utilizing mutants. The test results indicate that a diverse population of fumonisin-producing strains of F. moniliforme (Gibberella fujikuroi) mating population A predominates and that a potential exists for production of fumonisins in Mexican maize.     

Screening of microorganisms for biodegradation of poly(lactic-acid) and lactic acid-containing polymers.

The ability of some microorganisms to use lactic acid stereocopolymers and copolymers with glycolic acid as sole carbon and energy sources was studied under controlled or natural conditions. First, 14 filamentous fungal strains were tested in liquid cultures, adopting total lactic acid consumption, nitrogen source exhaustion, and maximal biomass production as selection criteria. Two strains of Fusarium moniliforme and one strain of Penicillium roqueforti were able to totally assimilate DL-lactic acid, partially soluble racemic oligomers (MW = 1,000), and the nitrogen source. Only one strain of F. moniliforme was able to grow on a poly(lactic acid)-glycolic acid copolymer (MW = 150,000) after 2 months of incubation at 28 degrees C on synthetic agar medium. Mycelium development was examined by scanning electron microscopy. F. moniliforme filaments were observed to grow not only at the copolymer surface but also through the bulk of the copolymer. In a second approach, plates made of a racemic poly(lactic acid) were buried in the soil before being incubated in petri dishes containing mineral agar medium under controlled conditions. Five strains of different filamentous fungi were isolated, and their ability to assimilate racemic poly(lactic acid) oligomers was tested in liquid cultures.     

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas.

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.     

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas.

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.     

Dimorphic fungus characteristic of fumonisin-producing strains of Fusarium moniliforme from Zhejiang

Fusarium moniliforme and its fumonisins have been shown to be carcinogenic in lab animals and have been linked to high incidences of human esophageal cancer. In this study we report the dimorphic fungus characteristic of fumonisin-producing strains of F. moniliforme from foodstuffs in Zhejiang, China. All of the twenty strains of F. moniliforme shown produce fumonisin B₁ 475.9–6322.2 μg/g in corn medium. These strains of F. moniliforme form yeast-like colonies in Sabouraud's agar plates contained 9% NaCl at 37 °C incubator and shows mostly budding reproduction. In blood agar plates these strains of F. moniliforme appear grass-green haemolytic reactions. This is the first report that yeast-like growth, dimorphic pathogenic fungus feature is found in F. moniliforme. These results suggest that it is also important to program epidemiological surveys of F. moniliforme as a primary pathogenic fungus, while proceeding to produce mycotoxins of F. moniliforme in food hygiene. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of fumonisins by Fusarium moniliforme strains isolated from corn grain

Fusarium moniliforme is the predominant fusarium species in the grain mycoflora of corn grown in Northern Caucasus, accounting for 95% of fusarium isolates. Eighty-five Fusarium moniliforme strains were grown on grain substrate and checked for the presence of fumonisins (B1 + B2 + B3) by indirect solid-phase enzyme immunoassay (EIA). All strains were capable of producing fumonisins (0.95 to 32,000 mg/kg). Strains sampled in the Krasnodar krai produced the highest fumonisin levels (averaging 5490 mg/kg).     

Isolation, identification and antifungal susceptibility of lemon pathogenic and non pathogenic fungi

Numerous species of filamentous fungi were isolated from lemon on different plantations in the province of Tucuman, Argentina. The techniques suggested by the Subcommittee of Antifungal Susceptibility of the National Committee for Clinical Laboratory Standards, (USA) were adapted. The effect of three different concentrations of the fungicides imazalil, guazatine, SOPP and thiabendazole on the fungi Fusarium oxysporum, Fusarium moniliforme, Aspergillus niger, Aspergillus flavus, Aspergillus clavatus, Geotrichum candidum, Rhizopus sp, Penicillium sp, Penicillium digitatum and Mucor sp were studied. All the tested strains were resistant to thiabendazole. We assayed a mixture of SOPP (5%), guazatine (350 ppm) and imazalil (100 ppm), which showed a synergic effect on Rhizopus sp. Mucor sp was the only fungus resistant to the four fungicides tested as well as to the above mentioned mixture.     

Occurrence and toxigenicity of shape Fusarium moniliforme from freshly harvested maize ears with special references to fumonisin production in Egypt

Using the seed-plate technique, 18 different isolates of Fusarium moniliforme were isolated on pentachloronitrobenzene (PCNB) agar medium from 18 samples of a local variety of corn collected from locations in Minia Governorate. The isolates of F moniliforme were screened for their ability to produce fumonisins on polished rice grains using the solid state fermentation technique. Based on thin layer chromatographic (TLC) analyses using silica gel plates, 14 of the 18 isolates tested produced FB₁ and FB₂ with R _f (0.17) and (0.24), respectively. Concentration of FB₁ was estimated using high performance liquid chromatography (HPLC). Production of FB₁ by the 14 isolates of F. moniliforme tested ranged from 69 to 4495 ppm indicating that mouldy corn may represent a health hazard to consumers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Absence of trichothecenes in toxigenic isolates of Fusarium moniliforme

Thirty-four isolates of Fusarium moniliforme were obtained from cereal grains collected in various parts of the world. The isolates were grown on rice and tested as a diet for toxicity to rats. Of these isolates, 53% caused death, 12% caused congestion and hemorrhage of the stomach and intestine as well as hematuria, 21% caused diarrhea, 38% caused weight loss, and 9% were nontoxic. The cultures were tested to T-2, HT-2, neosolaniol, acetyl-T-2, T-2-tetraol, iso-T-2, diacetoxyscirpenol, monoacetoxyscirpenol, deoxynivalenol, nivalenol, fusarenone-X, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, zearalenone, moniliformin, fusarochromanone, fusarin-C, and wortmannin; all were negative. In addition, F. moniliforme NRRL A25820 was grown on corn and banana fruit as solid substrates as well as on a defined liquid medium; none of the above toxins were found. When F. moniliforme NRRL A25820 was incorporated into a rat diet, no toxicity was noted. Twenty-eight additional isolates of F. moniliforme, isolated from feed associated with equine leukoencephalomalacia, were grown on cracked corn for 2 weeks. The cultures were negative when tested for deoxynivalenol, 15-acetyldeoxynivalenol, diacetoxyscirpenol, monoacetoxyscirpenol, nivalenol, and fusarenone X. Seventy-five percent of the isolates were toxic to ducklings, indicating the presence of a toxin other than trichothecenes. Our results support the conclusion that F. moniliforme does not produce trichothecenes.     

Identity of Fusarium nygamai isolates with long and short microconidial chains from millet,sorghum and soil in Africa

Several Fusarium species have been found associated with millet and sorghum in Nigeria, Lesotho and Zimbabwe. Amongst these, some isolates were originally identified as short- and long-chained types of F. nygamai. However, there was some question as to the correct identification of the long chained types. This study reclassified some of the isolates with long microconidial chains as F. moniliforme. Morphologically, these strains do not produce chlamydospores like F. nygamai, but produce swollen hyphal cells or resistant hyphae. The isolates in this study were crossed with the mating-type tester strains of Gibberella fujikuroi (F. moniliforme and G. nygamai (F. nygamai). Of the isolates with long chains of microconidia and other characteristics of F. moniliforme, 36% crossed with mating population 'A' of G. fujikuroi. Of the isolates with characteristics of F. nygamai, 65% crossed with the testers used to produce the teleomorph of F. nygamai. Mating tests support the separation of the sample population into F. moniliforme and F. nygamai. The results of this study show that genetics can be an aid in resolving some problems in fungal taxonomy. This revised version was published online in August 2006 with corrections to the Cover Date.