Genetic variability among isolates of Fusarium oxysporum from sugar beet

Fusarium yellows, caused by the soil‐borne fungus Fusarium oxysporum f. sp. betae (Fob), can lead to significant yield losses in sugar beet. This fungus is variable in pathogenicity, morphology, host range and symptom production, and is not a well characterized pathogen on sugar beet. From 1998 to 2003, 86 isolates of F. oxysporum and 20 other Fusarium species from sugar beet, along with four F. oxysporum isolates from dry bean and five from spinach, were obtained from diseased plants and characterized for pathogenicity to sugar beet. A group of sugar beet Fusarium isolates from different geographic areas (including nonpathogenic and pathogenic F. oxysporum, F. solani, F. proliferatum and F. avenaceum), F. oxysporum from dry bean and spinach, and Fusarium DNA from Europe were chosen for phylogenetic analysis. Sequence data from β‐ tubulin, EF1α and ITS DNA were used to examine whether Fusarium diversity is related to geographic origin and pathogenicity. Parsimony and Bayesian MCMC analyses of individual and combined datasets revealed no clades based on geographic origin and a single clade consisting exclusively of pathogens. The presence of FOB and nonpathogenic isolates in clades predominately made up of Fusarium species from sugar beet and other hosts indicates that F. oxysporum f. sp. betae is not monophyletic.     

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.     

Pathogenic variation and molecular characterization of <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from wilted Welsh onion in Japan

Thirty-two isolates of Fusarium species were obtained from wilted Welsh onion (Allium fistulosum) grown on nine farms from six regions in Japan and identified as F. oxysporum (18 isolates), F. verticillioides (7 isolates), and F. solani (7 isolates). The pathogenicity of 32 isolates was tested on five commercial cultivars of Welsh onion and two cultivars of bulb onion in a seedling assay in a greenhouse. The Fusarium isolates varied in the degree of disease severity on the cultivars. Five F. oxysporum isolates (08, 15, 17, 22, and 30) had a higher virulence on the cultivars than the other isolates. The host range of these five isolates was limited to Allium species. Molecular characterization of Fusarium isolates was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer (ITS) regions of ribosomal DNA. The 32 isolates were grouped into eight types (four types for F. oxysporum, one for F. verticillioides, and three for F. solani). Restriction patterns of the ITS region were not related to pathogenicity. However, the haplotypes obtained with five enzymes (RsaI, HinfI, HaeIII, ScrFI, and MspI) and the phylogenetic analysis permitted the discernment of the three Fusarium species. The PCR-RFLP analysis should provide a rapid, simple method for differentiating Fusaruim species isolated from wilted Welsh onion in Japan.     

Fusarium oxysporum,F. proliferatum and F. redolens associated with basal rot of onion in Finland

In recent years in Finland, Fusarium infections in onions have increased, both in the field and in storage, and Fusarium species have taken the place of Botrytis as the worst pathogens causing post‐harvest rot of onion. To study Fusarium occurrence, samples were taken from onion sets, harvested onions and also from other plants grown in the onion fields. Isolates of five Fusarium species found in the survey were tested for pathogenicity on onion. Fusarium oxysporum was frequently found in onions and other plants, and, of the isolates tested, 31% caused disease symptoms and 15% caused growth stunting in onion seedlings. Fusarium proliferatum, a species previously not reported in Finland, was also identified. Over 50% of the diseased onion crop samples were infected with F. proliferatum, and all the F. proliferatum isolates tested were pathogenic to onion. Thus, compared to F. oxysporum, F. proliferatum seems to be more aggressive on onion. Also some of the F. redolens isolates were highly virulent, killing onion seedlings. Comparison of the translation elongation factor 1α gene sequences revealed that the majority of the aggressive isolates of F. oxysporum f. sp. cepae group together and are distinct from the other isolates. Incidence and relative proportions of the different Fusarium species differed between the sets and the mature bulbs. More research is required to determine to what extent Fusarium infections spoiling onions originate from infected onion sets rather than the field soil.     

A new ‘forma specialis’ of Fusarium solani causing leaf yellowing of Phalaenopsis

The pathogenicity of 35 Fusarium solani isolates obtained from diseased leaves of greenhouse‐grown Phalaenopsis plants in Taiwan was tested on different orchids, including Phalaenopsis sp., Cymbidium spp., Oncidium sp., Dendrobium sp. and Cattleya sp., plus pea (Pisum sativum), chrysanthemum (Chrysanthemum indicum) and cucurbit [melon (Cucumis melo) and cucmber (C. sativus)] plants. Isolates of F. solani from Phalaenopsis spp. caused severe leaf yellowing on Phalaenopsis and mild symptoms on Cymbidium spp., but no visual symptoms on Oncidium sp., Dendrobium sp., Cattleya sp., pea, chrysanthemum or melon. Fusarium solani isolates collected from Phalaenopsis, pea and cucurbits were molecularly characterized by internal transcribed spacer (ITS), intergenic spacer (IGS) and β‐tubulin gene analyses. Phylogenetic trees constructed by distance and parsimony methods indicated that isolates from Phalaenopsis were grouped into one type based on ITS, IGS and β‐tubulin sequences with high bootstrap value (> 84%) support, compared to ‘formae speciales’ of F. solani from the other hosts. These analyses show that isolates of F. solani from Phalaenopsis are distinct from F. solani isolates from other hosts in Taiwan. Therefore, it is proposed that F. solani isolates that incite Phalaenopsis leaf yellowing be designated F. solani f. sp. phalaenopsis.     

Molecular identification and mycotoxin production of <Emphasis Type="Italic">Lilium longiflorum</Emphasis>-associated fusaria isolated from two geographic locations in the United States

Fusarium diseases of Liliaceae crops cause significant losses worldwide. Yet some Fusarium species are found in planta without causing disease or even in a symbiotic relationship with its host. In this study we identified and characterized the Fusarium species isolated from soil, and from healthy and diseased bulbs of Lilium longiflorum grown in New Jersey and Oregon in the United States. The predominant Fusarium species from the Oregon location were F. solani (74%) and F. oxysporum (20%), whereas F. concentricum (43%) and F. proliferatum (26%), both belonging to the Gibberella fujikuroi species complex (GFSC), were the most commonly isolated species from New Jersey. To our knowledge, this is the first report of F. concentricum associated with Liliaceae. All of the isolates were characterized with sequences of the internal transcribed spacer and translation elongation factor 1-alpha genes. The 24 GFSC isolates were further characterized with mating type, mating population, and mycotoxin analysis. Results showed that all GFSC isolates were MAT-2, suggesting that the populations may be asexually reproducing in the region examined. The majority of the GFSC isolates produced beauvericin. Enniatin A, B, B₁ and fusaproliferin were produced by a few isolates. Enniatin A₁ and fumonisins were not detected in any of the isolates. Although F. oxysporum and F. solani are well-known bulb pathogens, many isolates of F. oxysporum and F. solani, and all of the F. concentricum and F. proliferatum were isolated from asymptomatic bulbs, suggesting their endophytic association with lilies.     

Fusarium proliferatum, an additional bulb rot pathogen of Chinese chive

This is the first report of a disease of Chinese chive caused by Fusarium proliferatum. Because the symptoms are similar to those of the bulb rot (kampu-byo in Japanese) caused by F. oxysporum, we propose F. proliferatum as another causal agent of bulb rot of Chinese chive. Symptoms are wilting of leaves and brown rot on the basal bulbs of Chinese chive. A Fusarium sp., frequently isolated from symptomatic plants, produced identical symptoms on Chinese chive after inoculation, and was reisolated from the diseased plants. The fungus was identified as F. proliferatum based on morphological, cultural, and molecular characteristics.     

PCR-SSCP analysis of <Emphasis Type="Italic">Fusarium</Emphasis> diversity in asparagus decline in Japan

The diversity of Fusarium populations in asparagus (Asparagus officinalis L.) decline fields in Japan was estimated by PCR-SSCP (single-stranded conformational polymorphism) analysis of the ITS2 regions of the nuclear rRNA genes. This method was used to rapidly and objectively identify pathogens associated with roots of plants showing symptoms of asparagus decline collected from fields in five regions across Japan. Over 651 fusarial isolates were obtained, and were easily differentiated into three principal species. Fusarium oxysporum f. sp. asparagi was most frequently isolated from the domestic five regions (68%), whereas Fusarium proliferatum (28.6%) was less frequent. Fusarium solani was found much rarely (2.5%). The frequency of isolation of Fusarium proliferatum increased gradually from the north to the south of Japan, though considerable differences were found between fields in each region, as well as regional differences among the Fusarium populations. Most of the fusarial isolates were highly pathogenic in vitro. These results reveal that Fusarium oxysporum f. sp. asparagi and Fusarium proliferatum are important biotic factors which lead to asparagus decline in Japan.     

Auftreten und Nachweis von Fusarium oxysporum und F. proliferatum an Steck- und Saatzwiebeln

The pathogen Fusarium oxysporum f. sp. cepae inducing the Fusarium basal rot mainly spreads in warmer cultivation regions due to its adaptibility to high temperature. Meanwhile the pathogen occurs in Germany as well, especially in years with relatively high average temperature during the growing season. Phytopathological investigations of 300 symptomless onion bulbs showed a contamination rate of approximately 10% with regard to Fusarium spp, with F.?oxysporum proving to be the predominant species. Onion sets planted in these fields were latently infected with F.?oxysporum at rates of 19?C98%. Unexpectedly, the contaminated sets did not indispensably lead to a high occurrence of plants exhibiting characteristic symptoms of Fusarium basal rot such as wet and dry rot. Presumably, the development of symptoms is particularly affected by given climatic conditions. The results of pathogenicity tests of isolated Fusarium spp. isolates under controlled conditions support this assumption. The inoculation of the substrate with selected Fusarium spp. isolates resulted in a reduction of emergence by up to 70% under controlled conditions, which are suboptimal with regard to the cultivation of onions. The emergence of plants was not affected by Fusarium spp. under optimal cultivation of onions. However, under optimal cultivation conditions a reduction of plant growth occurred in a subsequent growth stage. Beside F.?oxysporum, F.?proliferatum could be detected in onion bulbs as well as seeds. The proportion of contaminated seeds accounted to 62%. Both species F.?oxysporum and F.?proliferatum proved to be pathogenic in onion although their isolates varied much in their virulence.     

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.     

Morphology,phylogeny and pathogenicity of Fusarium species from Sansevieria trifasciata in Malaysia

Leaf blight is a common disease affecting Sansevieria trifasciata in many countries, including Malaysia. In the present study, Fusarium isolates were consistently recovered from the diseased leaves collected from various locations throughout the country. Based on morphology and multigene phylogenetic analysis using mitochondrial small subunit (mtSSU), intergenic spacer region (IGS) and translation elongation factor 1-α (TEF1-α) gene sequences, seven Fusarium species were identified, with F. oxysporum being the most prevalent (67.6%) among 34 isolates. Pathogenicity tests resulted in the discovery of pathogenic isolates that belonged to F. oxysporum, F. proliferatum, and F. pseudocircinatum, whereas all isolates of F. brachygibbosum, F. concentricum, F. mangiferae, and F. solani were nonpathogenic. The results suggest that several Fusarium species are accountable for causing disease on S. trifasciata in Malaysia.     

Characterization of Fusarium diseases on commercially grown orchids in Hawaii

A decline of unknown aetiology has become a major problem for commercial orchid production in Hawaii, one of the primary orchid‐producing states in the USA. The major symptoms of decline include root degradation, foliar blight, pseudobulb rot and sheath rot. It was unclear whether all these symptoms are caused by the same or different pathogens, but preliminary research indicated that Fusarium species may be involved. In this study, the incidence of Fusarium species was examined across 186 plants, from 29 orchid genera and intergeneric hybrids across three islands in the state of Hawaii. The main five species associated with diseased orchids were F. proliferatum (38% of samples), F. solani (16%), F. oxysporum (16%) and two previously undescribed species (8% for both species combined). The two undescribed species were similar in appearance to F. subglutinans, and were designated FS‐A and FS‐B. Pathogenicity tests established that both F. proliferatum and FS‐B caused foliar spots, foliar blight and pseudostem rot on Dendrobium orchids, and that F. proliferatum isolates from diseased tissue of several genera could also induce symptoms on Dendrobium orchids. Although orchids have increasing importance in floriculture, relatively little is known about orchid pathogens, and previous studies focused primarily on Cymbidium and Phalaenopsis. This study provides new information concerning Dendrobium orchid pathogens and suggests a much wider host range than previously recognized for the five Fusarium species recovered from tissue with symptoms. These findings can contribute to better management of Fusarium diseases, which represent a significant challenge to orchid production in Hawaii.     

Molecular identification and pathogenicity of Fusarium and Alternaria species associated with root rot disease of wolfberry in Gansu and Ningxia provinces,China

Wolfberry (Lycium barbarum) ranks in the top 10 best-selling medicinal plants in China and it has been used for centuries as a medicine and a food supplement. It is suggested to have benefits on human health due to the rich content of polysaccharides, carotenoids, flavonoids, and alkaloids contained in its fruits, leaves, and root bark. Recently, severe root rot diseases have been causing plant losses in major growing areas. Here, we report fungi causing root rot disease in Chinese wolfberry plants. The analysis of nucleotide sequences of the internal transcribed spacer (ITS) region revealed a total of 92 isolates isolated from both soil and plant material samples. Fusarium spp. were the most abundant (58%), followed by Penicillium spp. (9%), and Alternaria spp. (5%). Fusarium spp. included F. oxysporum (36%), F. solani (30%), F. chlamydosporum (9%), F. nematophilum (9%), and F. tricinctum (8%). Sequences from the translation elongation factor 1-α gene (TEF-1α) were used to confirm the identity of Fusarium spp. and showed the predominance of F. oxysporum and F. solani. To confirm the pathogenicity of isolates, four isolates belonging to Fusarium spp. and one isolate belonging to Alternaria spp., isolated from wolfberry root tissues with root rot symptoms, were tested in outdoor and laboratory conditions. Results revealed that the five tested isolates were pathogenic with varying degrees of aggressiveness and ability to induce symptoms of root rot in wolfberry seedlings. The five isolates were recovered from inoculated seedlings, completing Koch's postulates. This is the first report on causative agents of root rot in Chinese wolfberry.     

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.     

Molecular identification of Fusarium spp. associated with bakanae disease of rice in Italy and assessment of their pathogenicity

Between 2006 and 2008, 146 isolates of Fusarium spp. were obtained from bakanae‐diseased rice plants and seeds from the major rice‐growing regions of Italy. These isolates were identified based on translation elongation factor (EF‐1α) sequence and pathogenicity tests were used to assess their aggressiveness against the susceptible rice cultivar Galileo. Use of the EF‐1α sequence gave reliable identification and showed that Fusarium fujikuroi, the causal agent of bakanae disease, was the most abundant Fusarium spp. isolated. These data were confirmed by inoculation of the isolates to rice seeds which were then germinated in the greenhouse, showing that only F. fujikuroi isolates were able to cause bakanae disease. Pathogenic isolates were identified with different levels of aggressiveness. Phylogenetic analysis based on EF‐1α sequences generated a tree which separated the various Fusarium species into different clusters with high bootstrap values.     

Pathogenicity of plant and soil isolates of <Emphasis Type="Italic">Phytophthora parasitica</Emphasis> on tomato and pepper

Crown and root rot of tomato and sweet pepper can be caused by Phytophthora parasitica. In this work, 23 P. parasitica isolates from diseased pepper or tomato plants as well as 54 isolates from 23 monocrop tomato soils (from Spain and Chile) and one from a pepper soil were studied for their host–pathogen response. Results show significant host specificity for the isolates from tomato plants and tomato soils (63 of 64 isolates were unable to cause disease in pepper). None of the pepper plant/soil isolates showed pathogenicity on tomato, and only four of 14 reproduced their pathogenicity on pepper. Only one tomato isolate was pathogenic to both Solanaceae species. Two different inoculation protocols were evaluated (substrate irrigation and stem cutting). All isolates which expressed pathogenicity when stem inoculated also did it when root inoculated, but not vice-versa. Therefore, the recommended test protocol for tomato and pepper breeding programmes is that based on root inoculation by irrigation.     

Conventional and real-time PCR for the identification of Fusarium fujikuroi and Fusarium proliferatum from diseased rice tissues and seeds

Fusarium fujikuroi is a species of the Gibberella fujikuroi species complex (GFSC) and the causal agent of bakanae disease on rice. Even if F. fujikuroi is the most abundant Fusarium species found on rice, other species can also be isolated from rice, such as F. proliferatum. Multiple alignment of translation elongation factor (TEF) gene sequences of different Fusarium spp., showed a deletion of six nucleotides in F. fujikuroi sequence and a two nucleotide polymorphism in the same region of F. proliferatum sequence. These elements of variability were used to develop a conventional and Real-Time PCR assay for diagnosis. The species specific primer pairs (Fuji1F/TEF1R and Proli1F/TEF1R) gave a product of 179 and 188?bp for F. fujikuroi and F. proliferatum respectively. Primer specificity was confirmed by analyzing the DNA of the most representative species of the GFSC and 298 strains of Fusarium spp. isolated from rice plants and seeds in Italy. The specific primers were also successfully used to detect fungal presence directly from infected rice tissues and seeds, providing a rapid tool for the early detection of pathogen contamination.     

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.     

Identification of Colletotrichum siamense causing litchi pepper spot disease in mainland China

Litchi (Litchi chinensis) pepper spot disease results in black spotting symptoms on litchi fruits. This disease was first observed on litchi cultivar Guiwei, in Guangzhou, China, in 2009, and then found widespread in other litchi-growing regions of China. Colletotrichum isolates were consistently recovered from typical black spot lesions of diseased fruits with frequency ranging from 83% to 100%. Three representative Colletotrichum isolates from Maoming, Guangzhou and Shenzhen were selected for identification and pathogenicity testing in the field. Based on morphology and phylogenetic analysis using the ribosomal internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT), β-tubulin (TUB2) and glutamine synthetase (GS) gene sequences, the three isolates were identified as C. siamense. In the pathogenicity experiments, typical symptoms appeared on the inoculated litchi fruits, including black spots and green patches around these black spots. These symptoms were consistent with the symptoms originally observed in the field. Colletotrichum siamense was successfully reisolated from the typical black spot lesions of the inoculated litchi fruits. To the authors' knowledge, this is the first report on characterization of C. siamense as the causal agent of litchi pepper spot disease in mainland China by successful inoculation on fruits under field conditions.     

A selective agar medium for isolation,enumeration and morphological identification of Fusarium proliferatum

A selective agar medium based on macerated date fruits was developed for the isolation, enumeration and morphological identification of Fusarium proliferatum from soil and from infected tissues of various plants (including: onion bulbs, corn ears and stems, and various weed tissues). The selective date medium enhances the formation of polyphialide and longer chains of conidia for better separation from other related Fusarium species which also grow and proliferate on this medium. Furthermore, the date medium enables microscopic distinction among other closely related Fusarium species, e.g. F. oxysporum and F. verticillioides. Fruits of the date cultivars Medjoul and Deglet Noor provided the most useful results as compared with other cultivars tested. The date medium can serve as a selective medium for direct isolation and enumeration of F. proliferatum, as it suppresses the development of other soil fungi and plant pathogens such as Macrophomina phaseolina, Sclerotium rolfsii and Rhizoctonia solani, as well as bacteria.