Identification,virulence factors characterization,pathogenicity and aggressiveness analysis of <Emphasis Type="Italic">Fusarium</Emphasis> spp., causing wheat head blight in Iran

Fusarium head blight (FHB), mainly caused by Fusarium graminearum species complex (FGSC) and also by other species of this genus, is one of the most destructive cereal diseases with high yield losses and mycotoxin contamination worldwide. The aim of this study was to identify Fusarium species, characterize their virulence factors such as trichothecene genotypes and cell wall degrading enzymes (CWDEs), and also investigate virulence of the isolates obtained from wheat plants with FHB symptoms in Golestan province of Iran. Among 41 isolates tested, 24 were F. graminearum sensu stricto (s.s.), six were F. proliferatum, four were F. culmorum, three isolates belonged to each of F. subglutinans and F. meridionale species and one isolate of F. asiaticum was identified. Among Fusarium isolates, the nivalenol (NIV) genotype could be found more frequently, followed by 3-acetyl deoxynivalenol (3-ADON) and 15-acetyl deoxynivalenol (15-ADON) genotypes. Production of trichothecenes in autoclaved rice cultures was analyzed by gas chromatography (GC) and confirmed by GC–MS. The mean levels of NIV, 3-ADON and 15-ADON produced by Fusarium spp. were 824, 665 and 622 μg kg^?1, respectively. All Fusarium isolates were capable of producing CWDEs, mainly cellulase and xylanase. Lipase and pectinase activities appeared later and at less quantities. In overall, the isolates FH1 of F. graminearum and FH8 of F. proliferatum showed the maximum activity of CWDEs, which was correlated with high level of their virulence and aggressiveness on wheat. On the other hand, correlation was observed between the level and type of trichothecene produced by each isolate and its virulence on wheat. Virulence of trichothecene producing isolates was higher than that of non-trichothecene producing isolates. Our results suggested that CWDEs and trichothecenes, as virulence factors, have considerable roles on virulence and aggressiveness of the pathogen. This is the first report on the effect of trichothecenes and CWDEs on virulence and aggressiveness of Fusarium spp. associated with FHB disease in wheat growing regions of Iran.     

Identity and pathogenicity of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with crown rot on wheat (<Emphasis Type="Italic">Triticum</Emphasis> spp.) in Turkey

An extensive survey was carried out to collect Fusarium species colonizing the lower stems (crowns) of bread wheat (Triticum aestivum L.) and durum wheat (T. durum Desf.) from different wheat growing regions of Turkey in summer 2013. Samples were collected from 200 fields representing the major wheat cultivation areas in Turkey, and fungi were isolated from symptomatic crowns. The isolates were identified to species level by sequencing the translation elongation factor 1-alpha (TEF1-α) gene region using primers ef1 and ef2. A total of 339 isolates representing 17 Fusarium species were isolated. The isolates were identified as F. culmorum, F. pseudograminearum, F. graminearum, F. equiseti, F. acuminatum, F. brachygibbosum, F. hostae, F. redolens, F. avenaceum, F. oxysporum, F. torulosum, F. proliferatum, F. flocciferum, F. solani, F. incarnatum, F. tricinctum and F. reticulatum. Fusarium equiseti was the most commonly isolated species, accounting for 36% of the total Fusarium species isolated. Among the damaging species, F. culmorum was the predominant species being isolated from 13.6% of sites surveyed while F. pseudograminearum and F. graminearum were isolated only from 1% and 0.5% of surveyed sites, respectively. Six out of the 17 Fusarium species tested for pathogenicity caused crown rot with different levels of severity. Fusarium culmorum, F. pseudograminearum and F. graminearum caused severe crown rot disease on durum wheat. Fusarium avenaceum and F. hostae were weakly to moderately virulent. Fusarium redolens was weakly virulent. However, F. oxysporum, F. equiseti, F. solani, F. incarnatum, F. reticulatum, F. flocciferum, F. tricinctum, F. brachygibbosum, F. torulosum, F. acuminatum and F. proliferatum were non-pathogenic. The result of this study reveal the existence of a wide range of Fusarium species associated with crown rot of wheat in Turkey.     

Natural occurrence of <Emphasis Type="Italic">Fusarium</Emphasis> species and fumonisin on maize grains in Ethiopia

Fusarium species causing maize kernel rot are major threats to maize production, due to reduction in yield as well as contamination of kernels by mycotoxins that poses a health risk to humans and animals. Two-hundred maize kernel samples, collected from 20 major maize growing areas in Ethiopia were analyzed for the identity, species composition and prevalence of Fusarium species and fumonisin contamination. On average, 38 % (range: 16 to 68 %) of maize kernels were found to be contaminated by different fungal species. Total of eleven Fusarium spp. were identified based on morphological characteristics and by sequencing the partial region of translation elongation factor 1-alpha (EF-1α) gene. Fusarium verticillioides was the dominant species associated with maize kernels (42 %), followed by F. graminearum species complex (22.5 %) and F. pseudoanthophilium (13.4 %). The species composition and prevalence of Fusarium species differed among the areas investigated. Fusarium species composition was as many as eight and as few as four in some growing area. The majority of the maize samples (77 %) were found positive for fumonisin, with concentrations ranging from 25 μg kg^?1 to 4500 μg kg^?1 (mean: 348 μg kg^?1 and median: 258 μg kg^?1). Slight variation in fumonisin concentration was also observed among areas. Overall results indicate widespread occurrence of several Fusarium species and contamination by fumonisin mycotoxins. These findings are useful for intervention measures to reduce the impact of the main fungal species and their associated mycotoxins, by creating awareness and implementation of good agricultural practices.     

Characterization of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with tobacco diseases in Northwestern Argentina

Phenotypic traits are regularly used to diagnose the development of Fusarium head blight (FHB) in the field, whereas mycotoxin accumulation in wheat grains can only be accurately evaluated through costly methods, such as high–performance liquid chromatography (HPLC). The aim of this study was to determine whether: (i) the results provided by existing commercial decision support tools could be anticipated using phenotypic measurements, including a novel technique of computer–assisted image analysis of spikes; and (ii) these measurements could avoid using HPLC. We monitored the FHB development during two consecutive years in highly contaminated plots in the Burgundy region (France). Contamination by crop residues was simulated through a field inoculation with barley grains artificially colonized by Fusarium graminearum. The development of the disease on spikes and harvested grains was assessed on one tolerant and two susceptible wheat varieties. The accumulated amounts of mycotoxins were measured in harvested grains using HPLC. As expected, the measured traits revealed that the inoculum responsible for infection on spikes mainly came from residues left on the soil surface, and the susceptible varieties were more diseased than the tolerant variety. Weather conditions had a strong effect on disease development. The novel computer–assisted image analysis technique had a better prediction power of deoxynivalenol accumulation, was more objective and time–saving than classical visual symptom assessments. This assessment method could be suitable to supplement the use of existing prediction tools and might avoid systematic and costly mycotoxin measurements in likely infected plots.     

Five plant families support natural sporulation of <Emphasis Type="Italic">Cronartium ribicola</Emphasis> and <Emphasis Type="Italic">C. flaccidum</Emphasis> in Finland

Fusarium is one of the most destructive fungal genera whose members cause many diseases on plants, animals, and humans. Moreover, many Fusarium species secrete mycotoxins (e.g. trichothecenes and fumonisins) that are toxic to humans and animals. Fusarium isolates from date palm trees showing disease symptoms, e.g. chlorosis, necrosis and whitening, were collected from seven regions across Saudi Arabia. After single-sporing, the fungal strains were morphologically characterized. To confirm the identity of morphologically characterized Fusarium strains, three nuclear loci, two partial genes of translation elongation factor 1 α (tef1α) and β-tubulin (tub2), and the rDNA-ITS region, were amplified and sequenced. Of the 70 Fusarium strains, 70 % were identified as F. proliferatum that were recovered from six regions across Saudi Arabia. Fusarium solani (13 %), as well as one strain each of the following species: F. brachygibbosum, F. oxysporum, and F. verticillioides were also recovered. In addition, five Fusarium-like strains were recognized as Sarocladium kiliense by DNA-based data. The preliminary in vitro pathogenicity results showed that F. proliferatum had the highest colonization abilities on date palm leaflets, followed by F. solani. Although F. oxysporum f. sp. albedinis is the most serious date palm pathogen, F. proliferatum and F. solani are becoming serious pathogens and efforts should be made to restrict and control them. In addition, the potential toxin risks of strains belonging to F. proliferatum should be evaluated.     

Trichothecene genotype and genetic variability of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> and <Emphasis Type="Italic">F. cerealis</Emphasis> isolated from durum wheat in Argentina

Fusarium head blight (FHB) is one of the most important fungal diseases affecting wheat worldwide and it is caused mainly by species within the Fusarium graminearum species complex (FGSC). This study evaluated the presence of FGSC in durum wheat from the main growing area in Argentina and analyzed the trichothecene genotype and chemotype of the strains isolated. Also, the genetic variability of the strains was assayed using ISSR markers. Molecular analysis revealed that among the strains isolated and identified morphologically as F. graminearum, there were 14 strains identified as F. cerealis. Also, it revealed that durum wheat grains were mostly contaminated by F. graminearum, being this the only species reported so far, within the FGSC, affecting durum wheat in Argentina. Analysis of molecular variance (AMOVA) indicated a high genetic variability within rather than between F. graminearum populations. All F. graminearum strains presented 15ADON genotype and were able to produce DON while all F. cerealis strains presented the NIV genotype and most of them were able to produce this toxin. The finding of F. cerealis in durum wheat grains indicates the need for investigating if this fungus is the responsible for the NIV contamination found in wheat in Argentina.     

Hyperspectral quantification of wheat resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight: comparison of two <Emphasis Type="Italic">Fusarium</Emphasis> species

Experiments were conducted to determine the extent of Fusarium langsethiae infection in wheat, barley and oats grown under identical experimental conditions. In total, four experiments were conducted with both winter and spring sown experiments at two locations. The amount of F. langsethiae infection was determined by quantifying F. langsethiae DNA and quantifying the combined concentration of the trichothecene mycotoxins HT-2 and T-2 (HT-2 + T-2) in cereal head fractions (grain and rest of the head) after threshing at harvest. Results of the study showed that under identical experimental conditions, oats had the highest F. langsethiae DNA and HT-2 + T-2 concentrations compared to wheat and barley. This indicates that the high levels detected on UK oats compared to wheat and barley from surveys of commercial crops is a consequence of genetic differences rather than differences in agronomy applied to the cereal species. The concentration of HT-2 and T-2 per unit of F. langsethiae DNA in oats compared to wheat and barley was also significantly higher indicating host differences in either the stimulation of HT-2 and T-2 production or in the metabolism of HT-2 and T-2. The study also showed that the proportion of F. langsethiae DNA in threshed grains was significantly lower than that in the rest of the cereal head.     

Impact of primary infection site of <Emphasis Type="Italic">Fusarium</Emphasis> species on head blight development in wheat ears evaluated by IR-thermography

The effect of the primary infection site by Fusarium graminearum and F. culmorum within wheat ears on Fusarium head blight (FHB) was investigated under controlled conditions. FHB development was assessed visually and thermographically following inoculation by: (i) spraying ears, or injecting inoculum into spikelets on (ii) tip, (iii) centre and (iv) base of the ears, separately. Fusarium infection significantly increased the temperature span within ears 6 days post inoculation (dpi), especially infections starting at the ear tip. The temperature difference between air and ear was negatively correlated to FHB severity and enabled disease detection even 29 dpi. F. culmorum caused significant higher disease severity neither reflected in the frequency of infected kernels nor in thousand kernel weight (TKW). Spray inoculations had the strongest effect on TKW, whereas tip inoculations had no effect. Centre and base inoculations had intermediate effects on TKW, although FHB levels did not differ with the same trend among inoculation scenarios. The overall low correlations among FHB severity, infected kernels and TKW are explained by the pathogen spread within ears – downwards more than upwards – and the effect on yield formation which is lower for infections of the upper parts of ears. An exponential model showed high goodness of fit for gradients of infected kernels within ears (R ²  ≥ 70) except tip infection with F. culmorum. This study confirmed that FHB is a function of the primary infection site within ears. Thermography was useful to differentiate among infection scenarios and may be applied in breeding for FHB resistance.     

Diversity of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with root rot of sugar beet in China

Sugar beet is widely grown throughout the world and represents the second largest crop used to produce sugar. Root rot in sugar beet, caused by Fusarium, significantly reduces yield, juice purity, and sugar concentration. Here, 307 Fusarium isolates were collected from sugar beet roots exhibiting typical root rot symptoms in eight provinces or autonomous regions of China from 2009 to 2012. Based on morphological characteristics and sequence data of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) and the translation elongation factor 1α (EF-1α), Fusarium oxysporum (38.4%) was identified as the most prevalent species, followed by F. solani (20.9%), and F. equiseti (18.9%). These three species were widely distributed in all eight of the provinces and autonomous regions. F. tricinctum (5.9%), F. brachygibbosum (4.6%), F. redolens (3.3%), F. proliferatum (3.3%), F. graminearum (2.3%), F. verticillioides (1.6%), F. nygamai (0.7%), and F. culmorum (0.3%) were less frequently obtained. Of the 307 Fusarium isolates, 117 representing different species and geographic locations were demonstrated to cause tip rot and vascular discoloration in sugar beet roots, with disease incidence ranging from 84.2 to 100.0% and disease index ranging from 41.94 to 75.83. This is the first detailed report of Fusarium species, in particular F. tricinctum, F. brachygibbosum, F. redolens, F. proliferatum, F. nygamai, and F. culmorum, causing sugar beet root rot in China.     

Identification of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with soybean root rot in Sichuan Province,China

Soybean root rot is a worldwide soil-borne fungal disease threatening soybean production, causing large loss in yield and quality of soybean. Fusarium species are well recognized as the important causal agent of Fusarium root rot, which are often distinct with respect to various factors in different soybean-producing regions around the world. Recently, Fusarium root rot has been frequently reported in Sichuan Province of China, where is unique in its climate and diverse cropping patterns, but it is still unclear about the predominant Fusarium species and their pathogenicity on soybean. In this study, diseased soybean roots were collected from three regions of Sichuan Province during 2014–2015. Based on morphological characteristics and phylogenetic analysis of nucleotide sequences of the ribosomal internal transcribed spacer region and the translation elongation factor 1-α gene, 78 isolates of Fusarium were identified as nine distinct species. Pathogenicity tests showed that seven species of Fusarium were able to infect soybean, but differed in pathogenicity. F. oxysporum, F. equiseti and F. graminearum were the most aggressive species to soybean, whereas F. fujikuroi and F. verticillioides were not pathogenic to soybean. There was a strong positive correlation of the pathogenicity of Fusarium species with seedling emergence and fresh root weight. In addition, the diversity of Fusarium species varied among soybean-growing regions. To our knowledge, this report on population and pathogenicity of Fusarium species, in particular, F. graminearum, associated with soybean root rot in Sichuan Province of southwest China, will be helpful to provide effective control strategies for the disease.     

<Emphasis Type="Italic">Fusarium ershadii</Emphasis> sp. nov., a Pathogen on <Emphasis Type="Italic">Asparagus officinalis</Emphasis> and <Emphasis Type="Italic">Musa acuminata</Emphasis>

Two Fusarium strains, isolated from Asparagus in Italy and Musa in Vietnam respectively, proved to be members of an undescribed clade within the Fusarium solani species complex based on phylogenetic species recognition on ITS, partial RPB2 and EF-1α gene fragments. Macro- and micro-morphological investigations followed with physiological studies done on this new species: Fusarium ershadii sp. nov can be distinguished by its conidial morphology. Both isolates of Fusarium ershadii were shown to be pathogenic to the monocot Asparagus officinalis when inoculated on roots and induced hollow root symptoms within two weeks in Asparagus officinalis seedlings. In comparison mild disease symptoms were observed by the same strains on Musa acuminata seedlings.     

<Emphasis Type="Italic">Fusarium oxysporum</Emphasis> and <Emphasis Type="Italic">Fusarium avenaceum</Emphasis> associated with yield-decline of pyrethrum in Australia

Fusarium wilt, one of the destructive diseases of cucumber can be effectively controlled by using biocontrol agents such as Trichoderma harzianum. However, the mechanisms controlling T. harzianum-induced enhanced resistance remain largely unknown in cucumber plants. Here we screened the potent T. harzianum isolate TH58 that could effectively control F. oxysporum (FO). Glasshouse efficacy trials also showed that TH58 decreased disease incidence by 69.7 %. FO induced ROS over accumulation, while TH58 inoculation suppressed ROS over accumulation and improved root cell viability under F. oxysporum infection. TH58 inoculation could reverse the FO-induced cell division block and regulate the proportional distribution of nuclear DNA content through inducing 2C fraction. Moreover, the expression levels of cell cycle-related genes such as CDKA, CDKB, CycA, CycB, CycD3;1 and CycD3;2 in TH58 - pre-inoculated seedlings were up-regulated compared with those infected with FO alone. Taken together, these results suggest that T. harzianum improved plant resistance against Fusarium wilt disease via alterations in nuclear DNA content and cell cycle-related genes expression that might maintain a lower ROS accumulation and higher root cell viability in cucumber seedlings.     

<Emphasis Type="Italic">In vitro</Emphasis> bacterization of banana (<Emphasis Type="Italic">Musa</Emphasis> spp.) with native endophytic and rhizospheric bacterial isolates: Novel ways to combat <Emphasis Type="Italic">Fusarium</Emphasis> wilt

Compared to conventional planting material, micropropagated plantlets are highly susceptible to Fusarium wilt because they are free from beneficial root inhabitants. We aimed to introduce mixtures of beneficial microbes in the plantlets in the rooting medium under in vitro conditions rather than by field applications. Endophytes and rhizobacteria from different banana cultivars and plantation areas were screened and characterized. Under in vitro conditions, banana tissue culture plantlets were bacterized with the prospective endophytes, Bacillus subtilis strain EPB56 and EPB10 and the rhizobacteria, Pseudomonas fluorescens strain Pf1 and effects of in vitro bacterization were investigated against Fusarium oxysporum f. sp. cubense race 1 under glasshouse and field conditions. Inoculation of bananas during micropropagation allowed for the omission of minerals and salts as well as vitamins from the growing media while resulting in plantlets close to double size compared to the controls with full strength media. All endophyte and rhizobacteria strains tested resulted in significant reductions in Fusarium infection in the glasshouse and field and in significantly better plant growth. The three-way combination of bacteria resulted in 78% disease reduction and more than doubled the yields compared to the untreated controls across two field experiments. Three-way inoculation led to yields of 23 and 24 kg/ bunch compared to chemical disease control (13; 15 kg/bunch) and untreated controls (10; 13 kg/bunch) in the two field experiments. Under glasshouse conditions, activity of defence enzymes was significantly increased by all inoculation treatments. Inoculation in vitro led to the establishment of the microorganisms in the plant system before delivering to the farming community. Micropropagation combined with the establishment of a beneficial microbial consortium should complement the micropropagated plants for easier adaptation under field conditions.     

The chemotaxis regulator <Emphasis Type="Italic">pilG</Emphasis> of <Emphasis Type="Italic">Xylella fastidiosa</Emphasis> is required for virulence in <Emphasis Type="Italic">Vitis vinifera</Emphasis> grapevines

Type IV pili of X. fastidiosa are regulated by pilG, a response regulator protein putatively involved in chemotaxis-like operon sensing stimuli through signal transduction pathways. To elucidate the roles of pilG in pathogenicity of X. fastidiosa, the pilG-deletion mutant XfΔpilG and complemented strain XfΔpilG-C were generated. While all strains had similar growth curves in vitro, XfΔpliG showed significant reduction in cell-matrix adherence and biofilm production compared with wild-type X. fastidiosa and XfΔpilG-C. The genes pilE, pilU, pilT, and pilS were down-regulated in XfΔpliG when compared with its complemented strain and wild-type X. fastidiosa. Finally, no Pierce’s disease symptoms were observed in grapevines inoculated with XfΔpilG, whereas grapevines inoculated with the wild-type X. fastidiosa and complemented strain of XfΔpilG-C developed typical Pierce’s Disease (PD) symptoms. The results indicate that pilG has a role in X. fastidiosa virulence in grapevines.     

Genetic structure of <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis> and <Emphasis Type="Italic">P. teres</Emphasis> f. <Emphasis Type="Italic">maculata</Emphasis> populations from western Canada

Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.     

The effects of <Emphasis Type="Italic">Gibberella zeae</Emphasis>, <Emphasis Type="Italic">Barley Yellow Dwarf Virus</Emphasis>, and co-infection on <Emphasis Type="Italic">Rhopalosiphum padi</Emphasis> olfactory preference and performance

Insect-borne viruses promote several changes in plant phenotype, which can modify plant-vector interactions in favor of virus survival and dissemination. Although co-infections commonly occur in the field, little is known about their effects on interactions with the vector. The ecological interactions between Barley Yellow Dwarf Virus (BYDV) and its aphid vector, Rhopalosiphum padi, have been investigated extensively, but the vector’s behavior in more complex scenarios has yet to be examined. We assessed olfactory response and performance of R. padi to wheat singly and doubly infected by the pathogenic fungus Giberella zeae and BYDV. Non-viruliferous aphids preferred odors of BYDV-infected wheat over healthy wheat, as previously reported in the literature, and they were still preferentially attracted to BYDV-infected plant during co-infection. However, around 35% more non-viruliferous aphids chose healthy wheat over G. zeae-infected wheat. Viruliferous aphids did not show any preference to the treatments. BYDV-infected wheat was a superior host than healthy wheat for the aphids whose population increased in 25%. We observed a synergistic effect of the co-infected wheat, which was the best host for aphids, and promoted an elevation of 42% on population growth. Our results indicate that co-infection might be beneficial for virus spread as does not interfere with aphid olfactory preference and provides greater colony growth than in singly infected plants.     

Chitinolytic <Emphasis Type="Italic">Streptomyces griseorubens</Emphasis> E44G enhances the biocontrol efficacy against <Emphasis Type="Italic">Fusarium</Emphasis> wilt disease of tomato

Streptomyces griseorubens E44G is a chitinolytic bacterium isolated from cultivated soil in Saudi Arabia (a hot, arid climatic region). In vitro, antifungal potential of S. griseorubens E44G was assessed against the phytopathogenic fungus, Fusarium oxysporum f. sp. lycopersici (the causative agent of the Fusarium wilt disease of tomato). An inhibition zone of 24 mm was recorded. The chitinolytic activity of S. griseorubens E44G was proved when the colloidal chitin agar plate method was used. A thermostable chitinase enzyme of 45 kDa molecular weight was purified using gel filtration chromatography. The optimum activity was obtained at 60 °C and pH 5.5. The purified enzyme has shown a very pronounced activity against the phytopathogenic fungus, F. oxysporum. The molecular characterization of the chitinase gene indicated that it consists of 1218 bp encoding 407 amino acids. The phylogentic analysis based on the nucleotide DNA sequence and the deduced amino acids sequence showed high similarity percentages with other chitinases isolated from different Streptomyces species. In the field evaluation, application of both S. griseorubens E44G treatments significantly increased all tested growth and yield parameters and decreased the disease severity compared with the infected-untreated tomato plants suggesting potential as a biocontrol agent.     

Gibberella ear rot of corn caused by <Emphasis Type="Italic">Fusarium asiaticum</Emphasis> in Japan

Ear rot with white or pink mold was found on corn (Zea mays L.). A species of Fusarium, not registered previously as a pathogen causing Gibberella ear rot of corn in Japan, was isolated from the rotted ear. The isolates, identified as F. asiaticum based on morphological characteristics and nucleotide sequences, caused white or pink mold on corn ear after inoculation. Moreover, the 3-acetyl deoxynivalenol chemotype and the nivalenol chemotype were found in the isolates. We propose to include F. asiaticum as one of the pathogens causing Gibberella ear rot of corn in Japan.     

Control of infection of tomato fruits by <Emphasis Type="Italic">Alternaria</Emphasis> and mycotoxin production using plant extracts

Tomato fruits are susceptible to infection by Alternaria species. In addition, Alternaria species may contaminate the fruits with mycotoxins. There is thus interest in control systems to minimise pathogenicity and control toxin production. The objectives of this study were to examine the effect of plant extracts of Eucalyptus globulus and Calendula officinalis on the growth of strains of Alternaria alternata and A. arborescens, on pathogenicity of tomato fruits and mycotoxin production. The growth bioassays showed that the ethanolic and chloroformic fractions of E. globulus were the most effective in reducing growth of A. alternata (66–74 %) and A. arborescens (86–88 %), respectively at 2500 μg/g. The effects of plant extracts on mycotoxin biosynthesis were variable and strain dependent. The most effective fractions in decreasing mycotoxin accumulation were the ethanolic and chloroformic extracts of E. globulus, which reduced tenuazonic acid by 89 %, alternariol by 75–94 % and almost complete inhibition of alternariol monomethyl ether. All the tested fractions reduced percentage of infected tomato fruits when compared to the controls. The ethanolic and chloroformic fractions of E. globulus completely inhibited growth of A. alternata and A. arborescens on unwounded fruits and reduced the aggressiveness on wounded fruits of strains of both species significantly.     

Molecular and biological characterization of an isolate of <Emphasis Type="Italic">Tomato mottle mosaic virus</Emphasis> (ToMMV) infecting tomato and other experimental hosts in eastern Spain

Fusarium Head Blight is a major disease of wheat and an important contributor to the reduced cultivation of wheat in South Africa, where the crop often is grown under irrigation. We collected Fusarium isolates from 860 Fusarium Head Blight-infected wheat heads in seven irrigated wheat-growing areas of South Africa. Six Fusarium species, i.e., F. chlamydosporum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum and F. semitectum were recovered, three of which, i.e., F. chlamydosporum, F. equiseti and F. semitectum, were not previously associated with Fusarium Head Blight in South Africa. Fusarium graminearum occurred at high frequencies at all seven locations. Based on polymerase chain reaction (PCR) assays of diagnostic sequences, more isolates were predicted to produce deoxynivalenol than nivalenol. Fusarium graminearum (sensu lato) appears to be the primary causal agent of Fusarium Head Blight in irrigated wheat in South Africa, which may not be the case for wheat cultivated under rain-fed conditions. Rotations of irrigated wheat with other graminaceous crops and maize could increase fungal inoculum and disease pressure. The establishment of Fusarium Head Blight in the irrigated wheat region of the country means that resistant lines and alternative agronomic practices are needed to limit disease severity, yield losses and mycotoxin contamination.