Changes in soil microbial communities after 10 years of winter wheat cultivation versus fallow in an organic-poor soil in the Loess Plateau of China.

Agricultural management methods, such as cultivation or fallowing, have led to significant changes in soil fertility and hence, crop yield. Such changes may have stemmed from changes in soil microbial communities and associated biogeochemical processes. This phenomenon is particularly true in organic-poor soil in the Loess Plateau of China. In this study, we examined three existing soil management regimes as part of a 10-year field experiment and evaluated their effects on fungal and bacterial community structures by performing high-throughput 454 pyrosequencing. These management regimes were (i) fertilized winter wheat (Triticum aestivum L.) (FW), (ii) continuous natural fallow with weeds but without crop grown (NF), and (iii) continuous bare fallow without weeds or crop grown (BF). After 10 years, soil organic carbon (SOC), microbial biomass carbon (MBC), and available potassium (K) concentrations were highest in NF. Soil N behaved differently, with BF obtaining the highest nitrate nitrogen (N). Meanwhile, slight differences in total N (TN) were observed among FW, NF, and BF. Available phosphorus (P) was highest and available K was lowest in FW. Microbial communities were dominated by Ascomycota (59.1% of fungal sequences), and Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria (75.7% of bacterial sequences) in FW, NF and BF at the phylum level. Soil management regimes did not affect the fungal and bacterial richness and diversity but significantly modified their community compositions. Compared with FW, the abundances of Ascomycota (fungi phylum) and Alternaria, Gibberella, and Emericella (fungi genus) were increased by NF, whereas the values of Chaetomium, Humicola, and Cryptococcus (fungi genus) were decreased by BF. The abundances of Verrucomicrobia (bacteria phylum), and Steroidobacter (bacteria genus) were increased by NF, and Bacteroides (bacteria genus) was increased by BF. Canonical correspondence analysis showed that SOC, available P, and TN might be the key factors in community formation. Therefore, the decadal absence of plants (BF) affected soil fertility by increased available K and nitrate N, whileas natural fallow (NF) affected soil fertility by increased SOC, available K, and MBC, and they all changed fungal and bacterial community compositions.

Giberella fujikuroi species complex isolated from maize and wheat in Iran: distribution, molecular identification and fumonisin B1 in vitro biosynthesis.

BACKGROUND: Contamination of food and agricultural crops by Fusarium species is a major concern of food spoilage and a potential public health hazard. In the present study, natural contamination of maize and wheat samples from main cultivation areas of Iran by Fusarium species belonging to the Giberella fujikuroi species complex was evaluated, with special attention to the ability of the isolates to produce fumonisin B1 (FB1 ). RESULTS: A total of 55 Fusarium isolates were obtained from 27/32 maize samples (84.4%) and 11/15 wheat samples (73.3%). They were identified as F. verticillioides (47.3%), F. proliferatum (47.3%), F. fujikuroi (1.8%), F. nygamai (1.8%) and F. redolens (1.8%) by sequence analysis of translation elongation factor 1-α (TEF1-α). Twenty-two of 55 Fusarium isolates belonging to F. proliferatum (23.6%), F. verticillioides (14.5%) and F. fujikuroi (1.8%) produced FB1 in the concentration range 230.4-9565.0 µg mL(-1) . The dendrogram resulting from the TEF1-α profile showed that the genotypes were divided into clusters I, II and III, of which cluster III contained only F. redolens, its first report from Iran. CONCLUSION: On the basis of in vitro FB1 biosynthesis of the analyzed strains, the high degree of contamination of maize and wheat with Fusarium strains reported here should be considered as a potential public health threat, because a meaningful number of the isolates were found to produce hazardous levels of carcinogenic FB1 .

Gibberella moniliformis AH13 with antitumor activity, an endophytic fungus strain producing triolein isolated from Adlay (Coix lacryma-jobi: poaceae).

In this study, the isolation of an endophytic fungus from the leaves of the medicinal herb adlay (Coix lacryma-jobi L. var. ma-yuen Stapf) is reported for the first time. The fungus produced Triolein (trioleoylglycerol), a major constituent of triacylglycerols (TAGs) of adlay, in rice medium under shake-flask and bench-scale fermentation conditions. The fungus was identified as Gibberella moniliformis (Fusarium verticillioides) by its morphology and authenticated by ITS analysis (ITS1 and ITS2 regions and the intervening 5.8S rDNA region). Triolein was identified by HPLC-ELSD coupled with APCI-MS and confirmed through comparison with authentic standard. The concentration of triolein produced by G. moniliformis AH13 reached 2.536 ± 0.006 mg/g dry weight of mycelium. Moreover, the EtOAc extract of G. moniliformis AH13 showed strong antitumor activity against four types of tumor cells (A549, HCT116, MDA-MB-231, and SW1990). These results suggest that G. moniliformis AH13 in adlay has significant scientific and industrial potential to meet the pharmaceutical demands and sustainable energy requirements for TAGs in a cost-effective, easily accessible, and reproducible way and is also a potential novel source of natural antitumor bioactive agents.

Isolation and characterization of Gibberella intermedia CA3-1, a novel and versatile nitrilase-producing fungus.

Nitrilase-mediated biocatalysis has attracted substantial attention for its application in carboxylic acid production in recent years. In the present study, the fungus CA3-1 was isolated and identified as Gibberella intermedia based on its morphology, its 18S ribosomal DNA (rDNA), and internal transcribed spacer (ITS) sequences. The enzymatic properties of G. intermedia resting cells were determined, and the optimum activity was achieved at 40 °C with pH 7.6. The half-lives of the nitrilase at 30, 40, and 50 °C were 231.1, 72.9, and 6.4 h, respectively. This Gibberella nitrilase showed a wide substrate spectrum with high specificity for heterocyclic and aliphatic nitriles. It remained extremely active in 5% propanol. The presence of Ag(+), Hg(2+), and excess substrate inhibited the nitrilase activity, whereas Fe(2+), Mn(2+), and Li(+) improved enzyme activity. 3-Cyanopyridine (50 mM) was hydrolyzed into nicotinic acid within 30 min, whereas only <5% of nicotinamide was detected. The results show that this fungal nitrilase is a promising candidate for commercial application in nicotinic acid production.

Fusarium tupiense sp. nov., a member of the Gibberella fujikuroi complex that causes mango malformation in Brazil.

Fusarium tupiense, the main causal agent of mango malformation in Brazil, is described through a combination of morphological, biological and molecular markers. This new species belongs to the Gibberella fujikuroi species complex (GFSC) and has an anamorph morphologically similar to Fusarium mangiferae and F. sterilihyphosum. F. tupiense can be differentiated from other species in the G. fujikuroi species complex on the basis of sexual crosses, amplified fragment length polymorphism (AFLP) markers and partial sequences of the tef1 and tub2 genes. Female fertility for field isolates of F. tupiense appears to be low. PCR with primers specific for the mating type (MAT) alleles and sexual crosses identified this species as heterothallic with two idiomorphs. Female-fertile tester strains were developed for the identification of field strains of this species through sexual crosses.

Novel tandem biotransformation process for the biosynthesis of a novel compound, 4-(2,3,5,6-tetramethylpyrazine-1)-4'-demethylepipodophyllotoxin.

According to the structure of podophyllotoxin and its structure-function relationship, a novel tandem biotransformation process was developed for the directional modification of the podophyllotoxin structure to directionally synthesize a novel compound, 4-(2,3,5,6-tetramethylpyrazine-1)-4'-demethylepipodophyllotoxin (4-TMP-DMEP). In this novel tandem biotransformation process, the starting substrate of podophyllotoxin was biotransformed into 4'-demethylepipodophyllotoxin (product 1) with the demethylation of the methoxyl group at the 4' position by Gibberella fujikuroi SH-f13, which was screened out from Shennongjia prime forest humus soil (Hubei, China). 4'-Demethylepipodophyllotoxin (product 1) was then biotransformed into 4'-demethylpodophyllotoxone (product 2) with the oxidation of the hydroxyl group at the 4 position by Alternaria alternata S-f6, which was screened out from the gathered Dysosma versipellis plants in the Wuhan Botanical Garden, Chinese Academy of Sciences. Finally, 4'-demethylpodophyllotoxone (product 2) and ligustrazine were linked with a transamination reaction to synthesize the target product 4-TMP-DMEP (product 3) by Alternaria alternata S-f6. Compared with podophyllotoxin (i.e., a 50% effective concentration [EC(50)] of 529 µM), the EC(50) of 4-TMP-DMEP against the tumor cell line BGC-823 (i.e., 0.11 µM) was significantly reduced by 5,199 times. Simultaneously, the EC(50) of 4-TMP-DMEP against the normal human proximal tubular epithelial cell line HK-2 (i.e., 0.40 µM) was 66 times higher than that of podophyllotoxin (i.e., 0.006 µM). Furthermore, compared with podophyllotoxin (i.e., log P = 0.34), the water solubility of 4-TMP-DMEP (i.e., log P = 0.66) was significantly enhanced by 94%. For the first time, the novel compound 4-TMP-DMEP with superior antitumor activity was directionally synthesized from podophyllotoxin by the novel tandem biotransformation process developed in this work.

Gibberella musae (Fusarium musae) sp. nov., a recently discovered species from banana is sister to F. verticillioides.

Several strains of Fusarium isolated from banana were identified previously as F. verticillioides (Sacc.) Nirenberg but described as unable to produce fumonisin. Here we report biochemical and morphological evidence, as well as multilocus phylogenetic analyses based on elongation factor (EF-1α), calmodulin, ß-tubulin, and the second largest subunit of RNA polymerase II (RPB2) sequences, indicating that these isolates represent a unique lineage in the Gibberella fujikuroi species complex related to but distinct from F. verticillioides. Together with previous results of molecular studies, as well as with results of metabolite analyses, crossing experiments, pathogenicity tests and morphological characterization, these new data indicate that these strains isolated from banana represent a new species, Gibberella musae Van Hove et al. sp. nov. (anamorph: Fusarium musae Van Hove et al. sp. nov.), which is described herein.

Fusarium ananatum sp. nov. in the Gibberella fujikuroi species complex from pineapples with fruit rot in South Africa.

Pineapple (Ananas comosus) is native to South America and widely planted as a fruit crop in the tropics and sub-tropics. This plant is susceptible to a number of fungal diseases of which the most severe is fusariosis. The disease is caused by Fusarium guttiforme and occurs only in South and Central America. The occurrence of a similar disease on pineapples in South Africa has prompted a re-evaluation of the Fusarium sp. associated with pineapple fruit rot. Phylogenetic relationships of isolates from pineapples collected in Brazil and South Africa were assessed based on sequence data for the translation elongation factor-1-α, histone H3 and ß-tubulin gene regions. Analyses showed that the South African isolates represent a species distinct from Brazilian isolates. The South African isolates are characterised by a concentration of aerial mycelium at the centres of the colonies, different to the Brazilian isolates that have an even distribution of aerial mycelium. Both phylogenetic and morphological data show that the disease on pineapple in South Africa is caused by a new Fusarium species described here as F. ananatum sp. nov.

Genetic relationships among populations of Gibberella zeae from barley, wheat, potato, and sugar beet in the upper Midwest of the United States.

Gibberella zeae, a causal agent of Fusarium head blight (FHB) in wheat and barley, is one of the most economically harmful pathogens of cereals in the United States. In recent years, the known host range of G. zeae has also expanded to noncereal crops. However, there is a lack of information on the population genetic structure of G. zeae associated with noncereal crops and across wheat cultivars. To test the hypothesis that G. zeae populations sampled from barley, wheat, potato, and sugar beet in the Upper Midwest of the United States are not mixtures of species or G. zeae clades, we analyzed sequence data of G. zeae, and confirmed that all populations studied were present in the same clade of G. zeae. Ten variable number tandem repeat (VNTR) markers were used to determine the genetic structure of G. zeae from the four crop populations. To examine the effect of wheat cultivars on the pathogen populations, 227 strains were sampled from 10 subpopulations according to wheat cultivar types. The VNTR markers also were used to analyze the genetic structure of these subpopulations. In all populations, gene (H = 0.453 to 0.612) and genotype diversity (GD = or >0.984) were high. There was little or no indication of linkage disequilibrium (LD) in all G. zeae populations and subpopulations. In addition, high gene flow (Nm) values were observed between cereal and noncereal populations (Nm = 10.69) and between FHB resistant and susceptible wheat cultivar subpopulations (Nm = 16.072), suggesting low population differentiation of G. zeae in this region. Analysis of molecular variance also revealed high genetic variation (>80%) among individuals within populations and subpopulations. However, low genetic variation (<5%) was observed between cereal and noncereal populations and between resistant and susceptible wheat subpopulations. Overall, these results suggest that the populations or subpopulations are likely a single large population of G. zeae affecting crops in the upper Midwest of the United States.

Comparative mycotoxin profiles of Gibberella zeae populations from barley, wheat, potatoes, and sugar beets.

Gibberella zeae is one of the most devastating pathogens of barley and wheat in the United States. The fungus also infects noncereal crops, such as potatoes and sugar beets, and the genetic relationships among barley, wheat, potato, and sugar beet isolates indicate high levels of similarity. However, little is known about the toxigenic potential of G. zeae isolates from potatoes and sugar beets. A total of 336 isolates of G. zeae from barley, wheat, potatoes, and sugar beets were collected and analyzed by TRI (trichothecene biosynthesis gene)-based PCR assays. To verify the TRI-based PCR detection of genetic markers by chemical analysis, 45 representative isolates were grown in rice cultures for 28 days and 15 trichothecenes and 2 zearalenone (ZEA) analogs were quantified using gas chromatography-mass spectrometry. TRI-based PCR assays revealed that all isolates had the deoxynivalenol (DON) marker. The frequencies of isolates with the 15-acetyl-deoxynivalenol (15-ADON) marker were higher than those of isolates with the 3-acetyl-deoxynivalenol (3-ADON) marker among isolates from all four crops. Fusarium head blight (FHB)-resistant wheat cultivars had little or no influence on the diversity of isolates associated with the 3-ADON and 15-ADON markers. However, the frequency of isolates with the 3-ADON marker among isolates from the Langdon, ND, sampling site was higher than those among isolates from the Carrington and Minot, ND, sites. In chemical analyses, DON, 3-ADON, 15-ADON, b-ZEA, and ZEA were detected. All isolates produced DON (1 to 782 microg/g) and ZEA (1 to 623 microg/g). These findings may be useful for monitoring mycotoxin contamination and for formulating FHB management strategies for these crops.

Natural occurrence of nivalenol and mycotoxigenic potential of Fusarium graminearum strains in wheat affected by head blight in Argentina

The principal agents of Fusarium head blight in the main cropping area of Argentina were investigated in heavily infected samples. The ability of the isolates to produce trichothecenes was determined by GC and HPLC. Fusarium graminearum was the predominant species and of 33 isolates, 10 produced deoxinivalenol (DON) (0.1- 29 mg kg-1), 13 produced both deoxinivalenol (1.0- 708 mg kg-1) and nivalenol (0.1- 6.2mg kg-1), 12 produced 3-acetyldeoxinivalenol (0.1- 14 mg kg-1), 13 produced 15-acetyldeoxinivalenol (0.1- 1.9 mg kg-1), 10 produced Fusarenone X (0.1- 2.4 mg kg-1) and 7 produced zearalenone (0.1- 0.6 mg kg-1). These results suggest that F. graminearum strains isolated from the wheat growing regions in Argentina belong to DON chemotype. Although some strains produced both deoxinivalenol and nivalenol, nivalenol was produced in lower levels. The natural occurrence of nivalenol in wheat affected by head-blight collected in the main production area during two years (2001-2002) was also determined. From 19 samples 13 were contaminated with deoxinivalenol in a range of 0.3 to 70 mg kg-1and 2 samples with both deoxinivalenol (7.5 and 6.7 mg kg-1) and nivalenol (0.05 and 0.1 mg kg-1), respectively. This is the first report of natural occurrence of nivalenol in wheat cultivate in Argentina.

O principal causador de giberela no trigo na Argentina e sua capacidade de produzir tricotecenos foram estudados por GC e HPLC em amostras altamente infectadas. A espécie predominante foi Fusarium graminearum, sendo que de um total de 33 isolados, 10 produziram deoxinivalenol (0,1-29 mg kg -1), 13 produziram deoxinivalenol (1,0-708 mg kg-1) e nivalenol (0,1-6,2 mg kg-1), 12 produziram 3-acetildeoxinivalenol (0,1-14 mg kg-1), 13 produziram 15-acetildeoxinivalenol (0,1-1,9 mg kg-1), 10 produziram fusarenona X (0,1- 2,4 mg kg-1) e 7 produziram zearalenona (0,1- 0,6 mg kg-1). Esses resultados sugerem que as cepas de F. graminearum isoladas de trigo cultivado na Argentina pertencem ao quimiotipo DON. Embora algumas cepas tenham produzido tanto DON quanto NIV, NIV foi produzido em quantidade inferior ao DON. A ocorrência natural de nivalenol em trigo afetado pela giberela coletado na principal área de produção durante dois anos (2001-2002) foi também determinada. De 19 amostras, 13 estavam contaminadas com deoxinivalenol na faixa de 0,3 a 70 mg kg-1 e 2amostras continham tanto deoxinivalenol (7,5 e 6,7 mg kg-1) quanto nivalenol (0,05 e 0,1 mg kg-1), respectivamente. Esse é o primeiro relato da ocorrência de nivalenol em trigo cultivado na Argentina.

Population genetic structure of Gibberella zeae isolated from wheat in Argentina.

Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight of wheat. The authors used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of two G. zeae populations from commercial wheat fields. The working hypothesis was that sufficient genetic exchange occurs between local populations to prevent significant partitioning of allelic variation. We analysed 216 AFLP loci for 113 isolates collected during the 2002 harvest season. All strains had AFLP profiles typical of G. zeae lineage 7. Both populations were genotypically diverse but genetically similar and potentially part of a larger, randomly mating population, with significant genetic exchange probably occurring between the two subpopulations. Linkage disequilibrium was low, but higher than reported for many other populations of G. zeae, and about 20% of the alleles detected were specific to one of the two subpopulations - results consistent with limited gene exchange between the two subpopulations. This study extends previous work with populations of G. zeae to include those found in Argentina, one of the world's largest wheat growing countries.

Gibberella xylarioides sensu lato from Coffea canephora: a new mating population in the Gibberella fujikuroi species complex.

Gibberella xylarioides Heim & Saccas (presumed anamorph, Fusarium xylarioides Steyaert) is the causal agent of coffee wilt disease, an economically important tracheomycosis in Africa. In vitro crosses carried out with Congolese, Ugandan, and Tanzanian single-ascospore/conidial isolates originating from diseased Coffea canephora/excelsa demonstrated a heterothallic mating system, controlled by a single locus with two alleles, MAT-1 and MAT-2. Compatible isolates produced fertile perithecia within 2 to 8 weeks after mating. Mating type (MAT) was characterized by PCR with primer pairs previously developed for the Gibberella fujikuroi species complex (GFC) and for Fusarium oxysporum. All strains analyzed were morphologically identical and corresponded to Booth's description of the "female" F. xylarioides strain. Based on crossing results and MAT-2/translation elongation 1-alpha (tef) sequence data, G. xylarioides, as currently understood, is demonstrated to encompass at least three "groups": G. xylarioides sensu strictu Ia, defined hitherto by two "historical" West African strains originating from the severe 1930s to 1950s epidemic (CBS 25852 and CBS 74979); G. xylarioides sensu strictu Ib, defined by two "historical" Central African lowland strains (DSMZ 62457 and ATCC 15664); and G. xylarioides sensu lato II, containing Congolese, Ugandan, and Tanzanian C. canephora/excelsa isolates. Infertility of crosses between the coffee wilt pathogen and known GFC mating populations demonstrates that G. xylarioides sensu lato constitutes a new biological species within the G. fujikuroi complex. MUCL 44532/MUCL 43887 and MUCL 35223/MUCL 44549 are proposed as G. xylarioides sensu lato II MAT-1/MAT-2 reference mating type tester strains.

Fusarium species of the Gibberella fujikuroi complex and fumonisin contamination of pearl millet and corn in Georgia, USA.

This study was designed to identify and compare the Fusarium species of the Gibberella fujikuroi complex on pearl millet (Pennisetum glaucum (L.) R. Br) and corn (Zea mays L.) crops grown in southern Georgia, and to determine their influence on potential fumonisin production. Pearl millet and corn samples were collected in Georgia in 1996, 1997 and 1998. Three percent of the pearl millet seeds had fungi similar to the Fusarium species of the G. fujikuroi species complex. One hundred and nineteen representative isolates visually similar to the G. fujikuroi species complex from pearl millet were paired with mating population A (Fusarium verticillioides (Sacc.) Nirenberg), mating population D (F. proliferatum (Matsushima) Nirenberg) and mating population F (F. thapsinum (Klittich, Leslie, Nelson and Marasas) tester strains. Successful crosses were obtained with 50.4%, 10.1% and 0.0% of these isolates with the A, D and F tester strains, while 39.5 of the isolates did not form perithecia with any tester strains. Two of the typical infertile isolates were characterized by DNA sequence comparisons and were identified as Fusarium pseudonygamai (Nirenberg and O'Donnell), which is the first known isolation of this species in the United States. Based on the pattern of cross-compatibility, conidiogenesis, colony characteristics and media pigmentation, a majority of the infertile isolates belong to this species. Fumonisins FB(1) and FB(2) were not detected in any of the 81 pearl millet samples analyzed. The species of the G. fujikuroi species complex were dominant in corn and were isolated from 84%, 74% and 65% of the seed in 1996, 1997 and 1998, respectively. Representative species of the G. fujikuroi species complex were isolated from 1996 to 1998 Georgia corn survey (162, 104 and 111 isolates, respectively) and tested for mating compatibility. The incidence of isolates belonging to mating population A (F. verticillioides) ranged from 70.2% to 89.5%. Corn survey samples were assayed for fumonisins, and 63% to 91% of the 1996, 1997 and 1998 samples were contaminated. The total amount of fumonisins in the corn samples ranged from 0.6 to 33.3 microg/g.

Gibberella xylarioides (anamorph: Fusarium xylarioides), a causative agent of coffee wilt disease in Africa, is a previously unrecognized member of the G. fujikuroi species complex.

Tracheomycosis or coffee wilt has emerged as a major disease of robusta coffee in Uganda in the past 10 years. Coffee wilt historically has been associated with Fusarium xylarioides Steyaert (teleomorph Gibberella xylarioides Heim and Sacc.), a species that has been classified as a member of Fusarium section Lateritium. We investigated the molecular phylogenetics of fusarial coffee wilt isolates by generating partial DNA sequences from two protein coding regions, translation elongation factor 1-alpha and beta-tubulin, in 36 isolates previously identified as F. xylarioides and related fusaria from coffee and other woody hosts, as well as from 12 isolates associated with a current coffee wilt outbreak in Uganda. These isolates fell into two morphologically and phylogenetically distinct groups. The first group was found to represent previously unidentified members of the Gibberella fujikuroi species complex (GFC), a clade that replaces the artificial Fusarium section Liseola. This group of isolates fit the original description of F. xylarioides, thus connecting it to the GFC. The second group, which was diverse in its morphology and DNA sequences, comprised four distinct lineages related to Fusarium lateritium. Our finding of unrelated species associated with coffee wilt disease has important implications regarding its epidemiology, etiology and control.

Utility of the polymerase chain reaction-restriction fragment length polymorphisms of the intergenic spacer region of the rDNA for characterizing Gibberella fujikuroi isolates.

In the present report, a total of thirty-one isolates of Gibberella fujikuroi (Sawada) Wollenw. species complex of Fusarium (section Liseola) morphologically classified as F. moniliforme according to the taxonomy of Nelson, Toussoun and Marasas (1983) were analyzed for their ability to produce fumonisin B1 and fumonisin B2 by an optimized liquid chromatographic method. They were isolated from three hosts (Zea mays, Musa sapientum and Pinus pinea). The results indicate that M. sapientum is a preferential host for G. fujikuroi isolates with low or null capacity for producing fumonisins, while isolates from Z. mays and P. pinea are generally high fumonisin producers. The molecular characterization of isolates was carried out in parallel using an optimized, simple and low-cost method for isolating DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the rDNA intergenic spacer (IGS) region. The haplotypes obtained with Hha I enzyme and combinations of Hha I, EcoR I, Alu I, Pst I and Xho I enzymes provided very characteristic groupings of G. fujikuroi isolates as a function of host type and fumonisin B1 and B2 producing capacity. IGS region restriction patterns showed no relationship to isolate geographical origin. This is the first report on this method's capacity to detect polymorphism permitting discrimination between G. fujikuroi isolates from different hosts and with different toxigenic profiles.

Species diversity of and toxin production by Gibberella fujikuroi species complex strains isolated from native prairie grasses in Kansas.

Fusarium species from agricultural crops have been well studied with respect to toxin production and genetic diversity, while similar studies of communities from nonagricultural plants are much more limited. We examined 72 Fusarium isolates from a native North American tallgrass prairie and found that Gibberella intermedia (Fusarium proliferatum), Gibberella moniliformis (Fusarium verticillioides), and Gibberella konza (Fusarium konzum) dominated. Gibberella thapsina (Fusarium thapsinum) and Gibberella subglutinans (Fusarium subglutinans) also were recovered, as were seven isolates that could not be assigned to any previously described species on the basis of either morphological or molecular characters. In general, isolates from the prairie grasses produced the same toxins in quantities similar to those produced by isolates of the same species recovered from agricultural hosts. The G. konza isolates produce little or no fumonisins (up to 120 micro g/g by one strain), and variable but generally low to moderate amounts of beauvericin (4 to 320 micro g/g) and fusaproliferin (50 to 540 micro g/g). Toxicity to Artemia salina larvae within most species was correlated with the concentration of either beauvericin or fusaproliferin produced. Organic isolates from some cultures of G. moniliformis were highly toxic towards A. salina even though they produced little, if any, beauvericin or fusaproliferin. Thus, additional potentially toxigenic compounds may be synthesized by G. moniliformis strains isolated from prairie grasses. The Fusarium community from these grasses appears to contain some species not found in surrounding agricultural communities, including some that probably are undescribed, and could be capable of serving as a reservoir for strains of potential agricultural importance.

Characterization of Gibberella fujikuroi complex isolates by fumonisin B1 and B2 analysis and by RAPD and restriction analysis of PCR-amplified internal transcribed spacers of ribosomal DNA.

Twenty nine isolates of Fusarium spp. (twenty four of them belonging to the Gibberella fujikuroi complex) isolated from banana and corn from different geographical regions were analyzed for their ability to produce fumonisins B1 and B2 and for genetic relatedness using random amplified polymorphic DNA (RAPD) and restriction analysis of PCR amplification products of the 5.8s ribosomal DNA-intervening internal transcribed spacer regions (ITS I-5.8S-ITS II). For RAPD analysis, six of twenty oligonucleotide primers were selected after testing with five Fusarium spp. isolates and used to characterize 24 additional isolates. DNA fragments from the 29 isolates of Fusarium spp., which were approximately 560 bp, were amplified with the universal primers ITS1 and ITS4. The restriction enzymes HaeIII, MboI, HpaII and MspI were useful for distinguishing the isolates. The RAPD analysis permitted to find interspecific differences among the isolates of Fusarium spp., between isolates with low and high capacity of fumonisin production and among isolates from different hosts. The restriction fragment length polymorphism (RFLP-PCR) analysis permitted to distinguish among different species of Fusarium. In combination with morphological analysis, the results of this research may find an application for the diagnosis of unknown Fusarium spp. and, particularly, for the characterization of fumonisin-producing isolates, which may be very useful in the food technology field.

Occurrence of fusaproliferin and beauvericin in Fusarium-contaminated livestock feed in Iowa.

Fusarium fungal contaminants and related mycotoxins were investigated in eight maize feed samples submitted to the Iowa State University Veterinary Diagnostic Laboratory. Fusarium moniliforme, F. proliferatum, and F. subglutinans were isolated from seven, eight, and five samples, respectively. These strains belonged to mating populations A, D, and E of the teleomorph Gibberella fujikuroi. Fusaproliferin was detected at concentrations of 0.1 to 30 microg/g in four samples, and beauvericin was detected (0.1 to 3.0 microg/g) in five samples. Fumonisins were detected in all eight samples (1.1 to 14 microg/g). Ten of 11 strains of F. proliferatum and all 12 strains of F. subglutinans isolated from the samples produced fusaproliferin in culture on whole maize kernels (4 to 350 and 100 to 1,000 microg/g, respectively). Nine F. proliferatum strains also produced beauvericin in culture (85 to 350 microg/g), but none of the F. subglutinans strains produced beauvericin. Fumonisin B1 was produced by all nine F. moniliforme strains (50 to 2,000 microg/g) and by 10 of the F. proliferatum strains (1,000 to 2,000 microg/g). This is the first report of the natural occurrence of fusaproliferin outside Italy and of the natural occurrence of beauvericin in North America.

Genetic variability in Gibberella fujikuroi and some related species of the genus Fusarium based on random amplification of polymorphic DNA (RAPD).

One of the most important rice pathogens is Fusarium moniliforme (perfect stage: Gibberella fujikuroi), the causal agent of the super-elongation ("bakanae") disease. Thirty-seven strains of this species from different geographical regions were analyzed for their ability to produce gibberellins (GA) and for genetic relatedness by random amplified polymorphic DNA (RAPD). All GA-producing isolates showed nearly identical RAPD patterns using 51 oligonucleotide nona- and deca-mers as arbitrary primers. On the other hand, large differences between GA-nonproducing isolates were obtained. Comparison of the RAPD patterns with those of the tester strains of the six known mating populations (A, B, C, D, E, F) of G. fujikuroi showed that all producer strains belong to mating population C and all nonproducer isolates to other mating populations. Evidence for the usefulness of the RAPD technique to distinguish between mating populations was provided by sexual crossings. Consensus phylogenetic trees based on RAPDs were constructed by the Phylogenetic Analysis Using Parsimony (PAUP) system. In combination with morphological analysis, RAPD can distinguish between different species of the genus Fusarium. These investigations may find an application in the diagnosis of unknown Fusarium spp. and in distinguishing isolates of G. fujikuroi within the section Liseola.