Genetic Diversity of Fusarium oxysporum f.sp. lentis Population Affecting Lentil in Syria

Lentil (Lens culinaris Medik.) is an important food legume crop in Syria. Fusarium wilt (Fusarium oxysporum f.sp. lentis – Fol) is a key yield‐limiting factor in the country. The genetic diversity of Fol population was studied using 96 isolates collected from different parts of the country using molecular markers. A total of 16 markers, random amplified polymorphic DNA, simple sequence repeats and inter‐simple sequence repeats were used and 218 polymorphic markers (scorable bands) were obtained. Cluster and structure analyses grouped the isolates into three major groups and subgroups indicating high genetic diversity in the pathogen populations. The molecular variance within the population accounted 87% of the total variation indicating high diversity within population than among geographic locations. The result of this study showed that no alleles were linked to specific province, and therefore, screening for the Fusarium wilt in one location using virulent isolates could be enough to save time and resources.     

Fusarium spp. are Responsible for Shoot Canker of Kumquat in China

Shoot and branch canker and tree decline of kumquat (Fortunella margarita cv. Guban) were recorded in Yangshuo County, Guilin City, in the Guangxi Zhuang Autonomous Region of China during 2008–2011. Fusarium oxysporum and a new Fusarium species within the Gibberella fujikuroi complex (Fusarium sp. GLB1) were isolated repeatedly from the infected shoots and branches. Species identifications were verified by their high translation elongation factor 1‐alpha (TEF1) sequence similarity with those of the species epitypes. Koch's postulates were fulfilled on kumquat (cv. Guban) and mandarin establishing pathogenicity. To our knowledge, this is the first report of Fusarium shoot canker disease caused by F. oxysporum and Fusarium sp. on kumquat.     

Fusarium cerealis Associated with Barley Seeds in Argentina

Fusarium head blight is a fungal disease caused by a complex of Fusarium species on cereals, such as barley and wheat. It has economic impacts due to yield reductions and mycotoxin contamination. As barley production has increased considerably in the last 5 years in Argentina, a survey was conducted for identifying Fusarium species associated with barley grains. Fusarium cerealis was isolated and identified based on morphological and molecular analysis. The potential production of nivalenol and zearalenone was assessed using specific PCR assays. Koch′s postulates were carried out to confirm the pathogenicity of the fungus.     

Fusarium Species Associated with Mango Malformation in Peninsular Malaysia

Mango malformation has become the most important global disease on mango. Fusarium species previously associated with this disease include F. mangiferae, F. mexicanum, F. sterilihyphosum, F. proliferatum, F. subglutinans and F. tupiense. A few strains of F. proliferatum have been reported from Malaysia, but in this study, we report the results of more extensive sampling. The recovered strains were evaluated with morphology, mating tester strain cross‐fertility, amplified fragment length polymorphisms (AFLPs), and partial DNA sequences of the genes encoding translation elongation factor 1‐α (tef‐1α) and β‐tubulin (tub‐2). Amongst the 43 strains evaluated, three species were identified – F. proliferatum, F. mangiferae and F. subglutinans – with F. proliferatum being the most frequent (69%). None of the Fusarium species that appear to originate in the Americas were recovered in Malaysia, which suggests special measures may be warranted to keep these species from entering the country.     

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.     

First Report of Dieback of Mango Caused by Fusarium decemcellulare in China

During 2009–2011, a dieback disease of mango (Mangifera indica) has recently emerged on mango trees in Panzhihua City, Sichuan province of China. The disease is characterized by large irregular brown‐coloured speckles on the petioles and twigs, vascular necrosis and dry leaves and complete twig mortality. Fusarium species were isolated repeatedly from the infected petioles and twigs. The species was identified as Fusarium decemcellulare Brick based on morphology and sequence analysis of Translation Elongation Factor‐1alpha (TEF‐1α) gene. Koch's postulates were fulfilled by pathogenicity tests on potted mango seedlings. To our knowledge, this is the first record of dieback on mango caused by F. decemcellulare in China.     

Genetic and virulence variation in Fusarium oxysporum f. sp. cepae causing root and basal rot of common onion in Iran

Root and basal rot of common onion (Allium cepae L.) caused by Fusarium oxysporum f. sp. cepae is one of the most important diseases causing tremendous losses in onion‐growing areas worldwide. In this study, random amplified polymorphic DNA (RAPD), intersimple sequence repeats (ISSR) and virulence studies were conducted to analyse 26 F. oxysporum f. sp. cepae isolates obtained from the main onion‐growing regions of Iran, including Fars, Azerbaijan and Isfahan states. Cluster analysis using UPGMA method for both RAPD and ISSR markers revealed no clear grouping of the isolates obtained from different geographical regions, and the isolates were observed to derive probably from the same clonal lineage. Pathogenicity test indicated that all F. oxysporum f. sp. cepae isolates were pathogenic on onion; however, virulence variability was observed among the isolates. The grouping based on virulence variability was not correlated with the results of RAPD and ISSR analyses.     

Development of Pathogenicity and AFLP to Characterize Fusarium oxysporum f.sp. momordicae Isolates from Bitter Gourd in China

Bitter gourd (Momordica charantia L.) cultivated in China is regarded as an important vegetable crop and is of considerable economic importance. However, it is susceptible to fusarium wilt, which causes heavy economic losses. Forty‐eight isolates were isolated from diseased bitter gourd plants that displayed typical fusarium wilt symptoms. Based on the morphological features, the rDNA internal transcribed space (ITS) sequences, pathogenicity and host biotypes, all of the isolates tested were pathogenic to the susceptible bitter gourd plants species (cv. ‘Guinongke No. 2’) and were identified as Fusarium oxysporum f. sp. momordicae (FOM). Our results classified different isolates as slightly, moderately or highly virulent. Among the isolates tested, 43 isolates slightly infected bottle gourd (Lagenaria siceraria var. clavata), whereas they did not infect other species from the family Cucurbitaceae. Genetic diversity among 48 isolates was characterized using amplified fragment length polymorphism (AFLP) analysis. The number of bands amplified by each primer pairs ranged from 41 to 66, with sizes ranging from 200 to 500 bp. A total of 366 bands were observed, out of which 363 were polymorphic (99.14%). The Nei's genetic identity of the six geographical populations varied from 0.7362 to 0.9707. The mean Nei's gene diversity index (H = 0.2644) and the mean Shannon's information index (I = 0.4071) at species level were higher than ones at populations level, indicated that the variation within populations was greater than that among populations. The Nei's GST (0.5103) and gene flow (Nm = 0.4923) revealed that genetic differentiation was mainly among populations and few gene exchanges. The dendrogram obtained from AFLP marker showed that there was a good correlation between isolates from different geographical locations and their pathogenicity. The AFLP marker effectively distinguished the high virulent isolates from the less virulent isolates. The highly virulent isolates were distinctly separated in different clusters, which indicated a significantly high correlation with the geographical origin in the AFLP dendrogram. The pathogenicity and molecular marker analysis confirmed the presence of variation in virulence as well as genetic diversity among the FOM isolates studied.     

Fusarium Species from the Fusarium fujikuroi Species Complex Involved in Mixed Infections of Maize in Northern Sinaloa,Mexico

Fusarium species belonging to the Fusarium fujikuroi species complex (FFSC) are associated with maize in northern Mexico and cause Fusarium ear and root rot. In order to assess the diversity of FFSC fungal species involved in this destructive disease in Sinaloa, Mexico, a collection of 108 fungal isolates was obtained from maize plants in 2007–2011. DNA sequence analysis of the calmodulin and elongation factor 1α genes identified four species: Fusarium verticillioides, F. nygamai, F. andiyazi and F. thapsinum (comprising 79, 23, 4 and 2 isolates, respectively). Differential distribution of Fusarium species in maize organs was observed, that is F. verticillioides was the most frequently isolated species from maize seeds, while F. nygamai predominated on maize roots. Mixed infections with F. verticillioides/F. thapsinum and F. verticillioides/F. nygamai were detected in maize seeds and roots, respectively. Pathogenicity assay demonstrated the ability of the four species to infect maize seedlings and induce different levels of disease severity, reflecting variation in aggressiveness, plant height and root biomass. Isolates of F. verticillioides and F. nygamai were the most aggressive. These species were able to colonize all root tissues, from the epidermis to the vascular vessels, while infection by F. andiyazi and F. thapsinum was restricted to the epidermis and adjacent cortical cells. This is the first report of F. nygamai, F. andiyazi and F. thapsinum infecting maize in Mexico and co‐infecting with F. verticillioides. Mixed infections should be taken into consideration due to the production and/or accumulation of diverse mycotoxins in maize grain.     

Identification and Genetic Division of Fusarium graminearum and Fusarium asiaticum by Species‐Specific SCAR Markers

Fusarium head blight (FHB), also called scab, is a devastating and insidious disease of cereals including wheat (Triticum spp.) and barley (Hordeum vulgare L.) worldwide. Apart from direct yield losses, the most serious concern about FHB is the contamination of the crop with mycotoxins, which pose a health risk to human and livestock. Recent research reported that phylogenetic species F. asiaticum (Fa) and F. graminearum (Fg) were the major causal agents of FHB from infected wheat heads in China. To investigate the population structure of Fusarium species in China by species‐specific as well as the chemotype‐specific markers, sequence‐related amplified polymorphism (SRAP) markers were screened on representative isolates of F. asiaticum‐NIV, F. asiaticum‐ 3ADON and F. graminearum‐15ADON to find amplification products characteristic of either species or chemotypes. Selected amplified fragments were cloned and sequenced so that sequence‐characterized amplified region (SCAR) primer pairs could be developed which permit specific detection of Fusarium species using conventional PCR. Primer pairs SCAR‐Fa1 and SCAR‐Fg1 were confirmed to be able to amplify specific products only in F. asiaticum and F. graminearum isolates, respectively. These species‐specific primers were applied to determine genetic division of F. asiaticum and F. graminearum isolates collected in Yangtze–Huaihe valley. The results indicated that F. asiaticum was the predominant species causing FHB in this wheat production area. It is the first report that SRAP markers were adapted for species characterization in Fusarium isolates.     

Rapid diagnosis of rice bakanae caused by Fusarium fujikuroi and F. proliferatum using loop‐mediated isothermal amplification assays

Rice bakanae is an important disease that causes serious rice production loss worldwide. We describe a new method for rapid diagnosis of rice bakanae caused by Fusarium fujikuroi and F. proliferatum, based on loop‐mediated isothermal amplification (LAMP) assays. After screening, primers were selected to target FusariumDNA sequences, that is, the intergenic spacer (IGS) region of the nuclear ribosomal operon and reductase‐coding region (RED1) in F. fujikuroi and F. proliferatum, respectively. Both LAMP assays efficiently amplified target genes in 70 min at 62°C. A colour change from purple to sky blue (visible to the unaided eye) was observed in the presence of the DNA of the targeted pathogens only, by adding hydroxynaphthol blue to the reaction system prior to amplification. The minimum of genomic DNA needed in the assays was 67 and 346 pg/μl for F. fujikuroi and F. proliferatum, respectively. Using the two assays described here, we successfully and rapidly diagnosed suspected diseased rice plant and seed samples collected from Jiangsu Province.     

Alterations in Root Exudation of Intercropped Tomato Mediated by the Arbuscular Mycorrhizal Fungus Glomus mosseae and the Soilborne Pathogen Fusarium oxysporum f.sp. lycopersici

Arbuscular mycorrhizal fungi (AMF) can control soilborne diseases such as Fusarium oxysporum f.sp. lycopersici (Fol). Root exudates play an important role in plant–microbe interactions in the rhizosphere, especially, in the initial phase of these interactions. In this work, we focus on (i) elucidating dynamics in root exudation of Solanum lycopersicum L. in an intercropping system due to AMF and/or Fol; (ii) its effect on Fol development in vitro; and (iii) the testing of the root exudate compounds identified in the chromatographic analyses in terms of effects on fungal growth in in vitro assays. GC‐MS analyses revealed an AMF‐dependent increase in sugars and decrease in organic acids, mainly glucose and malate. In the HPLC analyses, an increase in chlorogenic acid was evident in the combined treatment of AMF and Fol, which is to our knowledge the first report about an increase in chlorogenic acid in root exudates of AM plants challenged with Fol compared with plants inoculated with AMF only, clearly indicating changes in root exudation due to AMF and Fol. Root exudates of AMF tomato plants stimulate the germination rate of Fol, whereas the co‐inoculation of AMF and Fol leads to a reduction in spore germination. In the in vitro assays, citrate and chlorogenic acid could be identified as possible candidates for the reduction in Fol germination rate in the root exudates of the AMF+Fol treatment because they proved inhibition at concentrations naturally occurring in the rhizosphere.     

Quantification of Alternaria,Cladosporium, Fusarium and Penicillium verrucosum in Conventional and Organic Grains by qPCR

We analysed the levels of Alternaria, Cladosporium, Fusarium and Penicillium verrucosum in grain samples harvested in 2011 and 2012 from conventional and organic farms using qPCR. In general, both Alternaria and Cladosporium occurred in all cereal grains in the highest quantities, followed by P. verrucosum and Fusarium. Alternaria, Cladosporium and P. verrucosum had the highest levels in crop mixtures, barley and rye and lower levels in wheat, while Fusarium levels were the highest in crop mixtures and wheat. The levels of Alternaria and P. verrucosum were higher in organic rye and wheat than conventional grains. Although the level of Fusarium was higher in conventional than organic rye, opposite results were obtained for crop mixtures. A positive correlation was found between Alternaria, Cladosporium and P. verrucosum, indicating that similar factors might affect the distribution of these fungi in grains.     

Identification and antibacterial characteristics of an endophytic fungus Fusarium oxysporum from Lilium lancifolium

Aims: The aim of this study is to isolate and identify an endophytic fungus with antibacterial activity from the Asian medicinal and culinary plant Lilium lancifolium and to study the characteristics of its major antibacterial fractions. Methods and Results: After strict sample sterilization, an endophytic fungus BH‐3 with great antibacterial activity against Leuconostoc mesenteroides was isolated from the bulbs of L. lancifolium and was identified as Fusarium oxysporum on the basis of internal transcribed spacer (ITS) rDNA sequence and morphological traits. After partial purification including superfiltration and gel filtration, the major antibacterial fractions were found to be the substances with the molecular mass ranging from 35 to 60 kDa, mainly 55 kDa. The partially purified antibacterial fractions were stable at thermal processes, with more than 80% of activity left at 60°C for 1 h, and even 70·75% left at 121°C for 15 min. 90·33–98·97% of activity was observed in the pH range of 4·0–7·0. But the fractions were sensitive to different proteases. Conclusions: Endophytic strain F. oxysporum BH‐3 isolated from the bulbs of L. lancifolium produced protein‐like antibacterial metabolites. The antibacterial assay against Leuc. mesenteroides indicated that the fractions were stable at thermal processes and wide pH conditions, but sensitive to proteolyses. Significance and Impact of the Study: This study provides an increasing understanding of endophytic F. oxysporum in L. lancifolium and its metabolites, which have a great potential in food industry as antibacterial agents.     

First Report of Fusarium proliferatum Infecting Carnation (Dianthus caryophyllus L.) in China

In 2011, a wilt disease has been detected on carnation (Dianthus caryophyllus L.) cultivar ‘Light Pink Barbara’ in Kunming, Yunnan, China. A Fusarium sp. was consistently recovered from pieces of symptomatic tissues on Petri dishes containing potato dextrose agar (PDA). On the basis of morphological characteristics and molecular identification by DNA sequencing of ribosomal DNA internal transcribed spacer (rDNA ITS) and partial translation elongation factor‐1α (TEF) gene region, following their phylogenetic trees construction, the putative causal agent was identified as Fusarium proliferatum (Matsushima) Nirenberg, and its pathogenicity was finally confirmed by Koch's postulates. To our knowledge, this is the first report of a wilt disease caused by F. proliferatum on carnation in China.