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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Rapid Diagnosis of Soya Bean Root Rot Caused by Fusarium culmorum Using a Loop‐Mediated Isothermal Amplification Assay

We report a rapid diagnosis of soya bean (Glycine max L.) root rot caused by Fusarium culmorum, using a loop‐mediated isothermal amplification (LAMP) assay. We used the CYP51C gene sequence to design LAMP assay primers specific for F. culmorum. The LAMP assay amplified the target gene efficiently in 60 min at 63°C. The sensitivity of the assay was 100 pg/μl of genomic DNA. Among the tested soya bean pathogens, a positive colour (sky blue) was only observed in the presence of F. culmorum with the addition of hydroxynaphthol blue (HNB) dye prior to amplification, whereas other species isolates showed no colour change. Suspected diseased soya bean samples collected in the field from Jiangsu, Shandong and Anhui provinces and Beijing were diagnosed successfully using the LAMP assay reported here. This study provides a new and readily available method for rapid diagnosis of soya bean root rot caused by F. culmorum.     

Survival of Phytophthora cinnamomi and Fusarium verticillioides in commercial potting substrates for ornamental plants

Live plants, particularly when accompanied by soil or potting substrates, are considered the main pathway for international spread of plant pathogens. Modern, rapid shipping technologies for international plant trade increase the probability of plant pathogen survival during transport and the subsequent chances of disease outbreaks in new locations. The survival of two model pathogens, an Oomycete, Phytophthora cinnamomi, and a filamentous fungus, Fusarium verticillioides, was studied in two different commercial potting substrates (peat and peat‐free) under glasshouse conditions in the absence of a plant host. Survival rates were analysed at 2, 7, 12 and 17 months after substrate inoculation. Fusarium verticillioides had the longest survival rate, and was still present at 17 months. In contrast, P. cinnamomi survived up to 7 months but was not recovered after 12 or 17 months. There was no significant difference in the number of colony‐forming units (CFUs) of either pathogen in the two substrates, except at 2 months, when higher numbers were recovered from peat substrates.     

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.     

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.     

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.     

Morphological and Molecular Characterization of Fusarium Isolated From Maize in Syria

Maize is the third most important cereal after wheat and barley in Syria. Maize plants are attacked by several Fusarium species causing mainly stalk and ear rot of maize which poses a major impact worldwide. Identification of Fusarium species is important for disease control and for assessment of exposure risk to mycotoxines. To identify Fusarium species attacking maize in Syria, a total of 32 Fusarium isolates were recovered from maize ears collected from four different geographical regions, mainly from Ghouta surrounding Damascus. Fusarium isolates were identified based on morphology and on partial DNA sequencing of the TEF1‐α and rDNA/ITS genes. The majority (26 of 32) of these isolates was identified as F. verticillioides (subdivided into four groups), whereas three isolates turned out to be F. thapsinum, F. equiseti and F. andiyazi. The remaining three isolates were close to F. andiyazi, although further investigation is needed to confirm whether they represent a yet undescribed species. Furthermore, our results showed that sequencing the TEF1‐α gene is much more informative than sequencing of the rDNA/ITS region for Fusarium identification at the species level. PCR analysis showed that only F. verticillioides isolates were potentially fumonisin producers and that only the F. equiseti isolate was potentially trichotecene producer. This is the first report on Fusarium thapsinum, F. equiseti and F. andiyazi attacking maize in Syria.     

Minor Differences in Anther Extrusion Affect Resistance to Fusarium Head Blight in Wheat

Fusarium head blight (FHB) remains a serious problem due to yield loss and mycotoxin accumulation in wheat production worldwide. We previously reported that the closed‐flowering (no anther extrusion) characteristic was effective for increasing resistance to FHB infection. In this study, we investigated the relationships between the degree of anther extrusion (AE) and FHB damage using double haploid lines (DHLs), derived from F₁ plants from crosses between closed‐flowering and opened‐flowering varieties. These DHLs exhibited various degrees of AE, and the degree of AE was significantly different among DHLs, regardless of the year and environment (pot‐ or field‐grown). FHB severity was the lowest in closed‐flowering DHLs, and DHLs with partially extruded anthers showed significantly higher FHB symptoms than those with closed‐flowering phenotypes. In general, DHLs with partially extruded anthers also had relatively severe FHB symptoms compared with those exhibiting full anther extrusion. FHB severity was significantly correlated with Fusarium‐damaged kernels and deoxynivalenol concentration. The results of this study showed that partially extruded anthers were considered to be a source of FHB infection. The closed‐flowering phenotype improved resistance to FHB infection. Meanwhile, phenotypes with rapid anther extrusion and ejection also could contribute to the avoidance of FHB infection.     

Host‐induced gene silencing of an essential chitin synthase gene confers durable resistance to Fusarium head blight and seedling blight in wheat

Fusarium head blight (FHB) and Fusarium seedling blight (FSB) of wheat, caused by Fusarium pathogens, are devastating diseases worldwide. We report the expression of RNA interference (RNAi) sequences derived from an essential Fusarium graminearum (Fg) virulence gene, chitin synthase (Chs) 3b, as a method to enhance resistance of wheat plants to fungal pathogens. Deletion of Chs3b was lethal to Fg; disruption of the other Chs gene family members generated knockout mutants with diverse impacts on Fg. Comparative expression analyses revealed that among the Chs gene family members, Chs3b had the highest expression levels during Fg colonization of wheat. Three hairpin RNAi constructs corresponding to the different regions of Chs3b were found to silence Chs3b in transgenic Fg strains. Co‐expression of these three RNAi constructs in two independent elite wheat cultivar transgenic lines conferred high levels of stable, consistent resistance (combined type I and II resistance) to both FHB and FSB throughout the T₃ to T₅ generations. Confocal microscopy revealed profoundly restricted mycelia in Fg‐infected transgenic wheat plants. Presence of the three specific short interfering RNAs in transgenic wheat plants was confirmed by Northern blotting, and these RNAs efficiently down‐regulated Chs3b in the colonizing Fusarium pathogens on wheat seedlings and spikes. Our results demonstrate that host‐induced gene silencing of an essential fungal chitin synthase gene is an effective strategy for enhancing resistance in crop plants under field test conditions.