Characterization and pathogenicity of Fusarium proliferatum causing stem rot of Hylocereus polyrhizus in Malaysia

During a series of sampling in 2008 and 2009, stem rot disease was detected in Hylocereus polyrhizus plantations in Malaysia, with symptom appeared as circular, brown sunken lesion with orange sporodochia and white mycelium formation on the lesion surface. Eighty‐three isolates of Fusarium were isolated from 20 plantations and were morphologically identified as F. proliferatum based on the variability of colony appearance, pigmentation, growth rate, length of chains, production of bluish sclerotia, concentric ring aerial mycelium and sporodochia. Three species‐specific primers, namely ITS1/proITS‐R, PRO1/2 and Fp3‐F/4‐R successfully produced PCR products and confirmed that the isolates from stem rot of H. polyrhizus were F. proliferatum isolates. From BLAST search of translation elongation factor 1‐alpha (TEF1‐α) sequences, the isolates showed 99–100% similarity with F. proliferatum deposited in GenBank which further confirmed that the isolates were F. proliferatum. The results from amplification of MAT‐allele specific primers indicated that 14.5% of F. proliferatum isolates carried MAT‐1 allele and 85.5% carried MAT‐2. Crossing results showed that all 83 F. proliferatum isolates were male fertile showing positive crosses with the tester strains of MATD‐1 and MATD‐2. Perithecia oozing ascospore were produced. Forty isolates as representative were evaluated for pathogenicity test, produced rot symptoms similar to those observed in the fields which confirmed the isolates as the causal agent of stem rot of H. polyrhizus. To our knowledge, this is the first report of stem rot of H. polyrhizus caused by F. proliferatum in Malaysia.     

Identification and Molecular Characterizations of Neoscytalidium dimidiatum Causing Stem Canker of Red‐fleshed Dragon Fruit (Hylocereus polyrhizus) in Malaysia

During the year 2008 to 2009, a new disease of stem canker was noticed in most red‐fleshed dragon fruit (Hylocereus polyrhizus) plantations in Malaysia. The symptoms observed were small circular sunken orange spot, black pycnidia and rotted stem. This study was conducted to determine the occurrence of the stem canker on H. polyrhizus in Malaysia, subsequently to isolate, identify and characterize the fungal pathogen based on morphology and molecular characteristics and pathogenicity test. From the surveyed 20 plantations in Malaysia, stem canker was detected in all the plantations. A total of 40 isolates of Scytalidium‐like fungus were isolated and identified as Neoscytalidium dimidiatum based on morphological characteristics and ITS region sequences, which showed 99% similarity to N. dimidiatum (FJ648577). From the phylogenetic analysis using maximum‐likelihood tree, isolates of N. dimidiatum from stem canker of H. polyrhizus were grouped together and did not show any sequence variation. From pathogenicity test, all 40 isolates of N. dimidiatum were pathogenic causing stem canker on H. polyrhizus. To our knowledge, this is the first report of stem canker of H. polyrhizus caused by N. dimidiatum in Malaysia.     

Characterization of Fusarium spp. associated with pineapple fruit rot and leaf spot in Peninsular Malaysia

Pineapple (Ananas comosus) is one the important fruit crops planted in Malaysia, and this study was conducted to determine Fusarium spp. associated with diseases of the fruit crop as Fusarium is prevalent in tropical countries. Our objective was to identify and characterize Fusarium spp. associated with pineapple fruit rot and leaf spot mainly found on the fruits and leaves in Peninsular Malaysia. Fusarium isolates (n = 108) associated with pineapple fruit rot and leaf spot were characterized by morphological, molecular and phylogenetic analyses, a mating study and pathogenicity testing. TEF‐1α sequence analysis identified Fusarium proliferatum, Fusarium verticillioides, Fusarium sacchari and Fusarium sp. Mating was successful only between tester strains of F. proliferatum and F. verticillioides. Sexual crosses with standard tester strains showed that 82 isolates of F. proliferatum produced fertile crosses with mating population D (Gibberella intermedia) and three isolates of F. verticillioides were fertile with the tester strain of mating population A (Gibberella moniliformis). All isolates were pathogenic, causing pineapple fruit rot and leaf spot, thus fulfilling Koch's postulates.     

Characterization and Pathogenicity of Colletotrichum truncatum Causing Stem Anthracnose of Red‐Fleshed Dragon Fruit (Hylocereus polyrhizus) in Malaysia

During August 2010 and January 2011, 10 isolates of Colletotrichum were recovered from stem anthracnose lesions of Hylocereus polyrhizus in the states of Kedah and Penang, Malaysia. Based on the morphological characteristics of colony colour and appearance, and shapes of conidia as well as sequences of internal transcribed spacer regions (ITS), β‐tubulin, actin (ACT) and glyceraldehyde 3‐phosphate dehydrogenase (GAPDH), the fungus was identified as Colletotrichum truncatum. Pathogenicity test showed that C. truncatum isolates were pathogenic to the artificially inoculated H. polyrhizus stem. This is the first report of C. truncatum causing anthracnose on H. polyrhizus stems in Malaysia.     

Homologous recombination and allele replacement in transformants of Fusarium fujikuroi

The ascomycete Fusarium fujikuroi could be transformed stably to hygromycin resistance only when the transforming plasmid contained a fragment of DNA from the fungus. The transformation frequencies were roughly independent of the sequence of the particular fungal DNA fragment used, of its size (1.8 or 6 kb), and of whether this DNA was present only once in the fungal genome or about forty times (the genes for ribosomal RNA). The plasmid was integrated into the fungal genome by homologous recombination in the eighteen transformants tested; ectopic integration was never observed. The carB gene of F. fujikuroi was cloned and shown to complement unpigmented mutants deficient in phytoene dehydrogenase. A mutant carB allele was prepared in vitro and used to transform wild-type protoplasts; the transformants contained a genomic duplication and were heterozygous for carB; the mutant allele replaced the original wild-type allele when this was spontaneously lost in the transformants. This loss was due to gene conversion in some cases and to recombination between repeated sequences in others. Received: 5 November 1999 / Accepted: 16 March 2000     

Fusarium incarnatum is associated with postharvest fruit rot of muskmelon (Cucumis melo)

Postharvest fruit rot was observed on muskmelon (Cucumis melo) on market shelves at a melon farm in the city of Hatyai, Songkhla, Thailand. Diseased muskmelon fruit displayed cotton-like mycelia on wounds and had brown to dark brown internal tissue. Based on morphological characteristics and molecular analysis of internal transcribed spacer (ITS) and translation elongation factor 1-α (TEF1-α) DNA sequences, the fungal pathogen was identified as Fusarium incarnatum. This species belongs to the Fusarium incarnatum-equiseti species complex (FIESC). A pathogenicity test was conducted to verify Koch's postulates, and F. incarnatum was observed to cause fruit rot on muskmelon; symptoms of the disease were similar to those seen in the field. However, only artificially wounded melons became infected, suggesting that F. incarnatum is an obligate wound-infecting pathogen. To our knowledge, this is the first report of F. incarnatum causing fruit rot of muskmelon in Thailand.     

Pathogenicity of Epicoccum sorghinum towards dragon fruits (Hylocereus species) and in vitro evaluation of chemicals with antifungal activity

Recent reports of plant diseases that result in yield reduction and increasing demand for dragon fruits raise concerns of fruit supply shortage. Emerging plant diseases may play an important role in increasing yield losses and reducing the availability of stem cuttings (source of planting materials). Understanding the aetiology of current and new diseases of dragon fruit is important to address production issues and to formulate effective disease control measures. This study reports Epicoccum sorghinum as a potential emerging pathogen of dragon fruit. Epicoccum sorghinum MBDF0024a was isolated from dragon fruit stems (Hylocereus monacanthus) showing brown spot symptoms. DNA sequence of the internal transcribed spacer (ITS-rDNA), beta tubulin and actin gene regions of fungal isolate MBDF0024a had high similarities to E. sorghinum stains. Epicoccum sorghinum MBDF0024a was pathogenic to three cultivated dragon fruit species (Hylocereus undatus, H. monacanthus and H. megalanthus) in repeated laboratory and glasshouse trials. Large brown lesions developed on 3-week-old inoculated rooted stem cuttings 3 days postinoculation (dpi). Yellowing of the lesion (advance part) started at five dpi, and at seven dpi, yellowing was observed in the stem. As there are no reported control measures for diseases caused by E. sorghinum, this study screened chemicals with antifungal properties. A biopesticide containing B. subtilis (2 ml/400 ml), and chemicals isoprothiolane (2.25 ml/400 ml), mancozeb (2 g/400 ml) and pyraclostrobin (1 ml/400 ml) (chemical control) completely inhibited the in vitro growth of E. sorghinum MBDF0024a. The results establish E. sorghinum as a new and emerging pathogen of dragon fruit that could be a major yield-limiting disease if left uncontrolled. The biopesticide can be considered a fairly safe option for disease management, but glasshouse and field studies are needed for validation.     

Ability of plant pathogenic fungi Gibberella fujikuroi and Fusarium commune to react with airborne methyl jasmonate

ABSTRACT

The pathogenic fungi Gibberella fujikuroi and Fusarium commune produce jasmonic acid. The application of volatile deuterium-labeled methyl jasmonate increased the amount of nonlabeled JA present in G. fujikuroi and F. commune. These results indicate that the fungi have the ability to react with airborne methyl jasmonate in a manner similar to a plant.     

Fusarium rot in cucumber greenhouses of Jiroft region

The present work was done to identify Fusarium species that cause Fusarium rot in greenhouse cucumber crop in Jiroft region (Kerman, Iran), in 2006–2007. During these years, a vast sampling was done from several greenhouses of Jiroft. The plants with rot symptoms as well as the soil samples of greenhouse were transferred to lab. The isolates of plants and soil samples were detached by direct isolation of the infected tissue and soil suspension methods, respectively. Totally 120 isolates were obtained, which were classified into the following six species according to their morphological and physiological characteristics: Fusarium oxysporum, Fusarium solani, Fusarium culmorum, Fusarium monoliforme, Fusarium sambucinum, Fusarium subglutinans. It is the first time that three of these taxons, i.e. F. culmorum, F. monoliforme and F. subglutinan are reported in cucumber of Iran. Pathogenesis studies of the isolates were done by mycelium placement and spore suspension injection methods in sterile soil under greenhouse conditions. Then the disease symptoms were investigated.     

Molecular characterisation of Fusarium oxysporum causing rot diseases in small cardamom (Elettaria cardamomum Maton)

Incidence of root rot and foliar yellowing, rhizome rot, panicle wilt and stem rot diseases of small cardamom (Elettaria cardamomum Maton) are caused by Fusarium oxysporum Schlecht., and were surveyed in the high ranges of Idukki district, Kerala during 2010–2011. The diseases were noticed in different areas to varying degrees. Root rot was found to be most severe, followed by pseudostem rot, rhizome rot and panicle wilt. The Fusarium infections were prevalent throughout the year (January–December) and varied from 1.5 to 10.6%. Even though the pathogen was isolated from different plant parts, during pathogenicity studies, all the isolates could cross-infect other plant parts too. Twenty different isolates of F. oxysporum were obtained from diseased samples, and five morphologically distinct isolates were analysed with Randomly Amplified Polymorphic DNA (RAPD) markers to study the genetic variability, if any, among them. PCR amplification of total genomic DNA with random oligonucleotide primers generated unique banding patterns, depending upon primers and isolates. Nine oligunucleotide primers were selected for the RAPD assays, which resulted in 221 bands for the five isolates of F. oxysporum. The number of bands obtained was entered into an NTSYS, and the results showed moderate genetic variability among F. oxysporum isolates causing root rot, rhizome rot, panicle wilt and pseudostem rot, collected from different locations. The dendrogram of different isolates into groups resulted in one major cluster at 0.61 similarity index comprising of four isolates (CRT 3, CRR 3, CPW 2 and CSR 1) and one isolate (CRT 5) formed in a separate cluster. Among the five isolates of F. oxysporum, CRT 5 was entirely different from the other four isolates. The isolates also differ according to the geographical area, as revealed from the genetic variability observed in different root rot isolates (CRT 3 and CRT 5). It is inferred that despite moderate variability, F. oxysporum, infecting small cardamom in Idukki district of Kerala, consists of a single clonal lineage.     

A high‐resolution genetic map of the cereal crown rot pathogen Fusarium pseudograminearum provides a near‐complete genome assembly

Fusarium pseudograminearum is an important pathogen of wheat and barley, particularly in semi‐arid environments. Previous genome assemblies for this organism were based entirely on short read data and are highly fragmented. In this work, a genetic map of F. pseudograminearum has been constructed for the first time based on a mapping population of 178 individuals. The genetic map, together with long read scaffolding of a short read‐based genome assembly, was used to give a near‐complete assembly of the four F. pseudograminearum chromosomes. Large regions of synteny between F. pseudograminearum and F. graminearum, the related pathogen that is the primary causal agent of cereal head blight disease, were previously proposed in the core conserved genome, but the construction of a genetic map to order and orient contigs is critical to the validation of synteny and the placing of species‐specific regions. Indeed, our comparative analyses of the genomes of these two related pathogens suggest that rearrangements in the F. pseudograminearum genome have occurred in the chromosome ends. One of these rearrangements includes the transposition of an entire gene cluster involved in the detoxification of the benzoxazolinone (BOA) class of plant phytoalexins. This work provides an important genomic and genetic resource for F. pseudograminearum, which is less well characterized than F. graminearum. In addition, this study provides new insights into a better understanding of the sexual reproduction process in F. pseudograminearum, which informs us of the potential of this pathogen to evolve.     

人工授粉对火龙果果实发育的影响

于开花期对红皮红肉类型火龙果进行人工授粉与自然授粉处理,并对不同发育阶段的子房或果实进行解剖观察,以研究人工授粉对果实发育的影响.结果表明:人工授粉可提高火龙果的平均单果重和商品果率,平均单果重与果实内种子数呈显著正相关关系;火龙果子房为多胚珠结构,子房内有若干“珠柄-胚珠”单元,胚珠在开花后发育成种子,珠柄则发育成肉...     

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.     

甘肃大葱贮藏期镰孢菌腐烂病病原鉴定

【目的】大葱在贮藏期频繁发生镰孢菌腐烂病,损失严重。明确该病害病原种类对病害防治具有重要意义。【方法】利用组织分离法对采集自甘肃省兰州市(区)蔬菜市场的16份大葱贮藏期镰孢菌腐烂病病样进行病原物的分离、纯化培养,经单孢分离后根据形态学特征,再结合r DNA-ITS、EF-1a(tef)基因序列分析的方法进行鉴定。【结果】共分离得到80株镰孢菌,经鉴定分属3个种,即层出镰孢菌(Fusarium proliferatum)、尖孢镰孢菌(F.oxysporum)和燕麦镰孢菌(F.avenaceum),其中层出镰孢菌为大葱镰孢菌腐烂病的优势致病菌,分离频率为52.50%。对兰州白葱不同部位进行致病性测定,结果表明层出镰孢菌对大葱鳞茎的致病力最强,而燕麦镰孢菌对大葱鳞茎的致病力最弱。【结论】3种镰孢菌作为该病害的病原,属国内首次报道。     

Identification and genetic diversity of Fusarium sacchari associated with pokkah boeng disease of sugarcane in Northeast Brazil

Isolates from the Fusarium fujikuroi species complex, mainly F. sacchari, have been reported to be the causal agents of pokkah boeng in sugarcane in Brazil. However, inadequate information was available on the occurrence and genetic diversity of F. sacchari in Northeast Brazil, which is a limiting factor on management. Thus, isolates of F. subglutinans sensu lato from sugarcane plants with symptoms of pokkah boeng were evaluated using the sexual cross-fertility to determine species. All the isolates produced black perithecia when they were crossed with the test isolates of F. sacchari. Three weeks after the crossing, the formation of fertile ascospores cirri was observed. Thirty-four isolates were self-sterile hermaphrodites, while 21 were fertile only as males. Five isolates were homothallic. The effective size [N_e(f)] of the population as a function of the frequency of hermaphrodites and female sterile strains was 95.5%. The F. sacchari isolates were separated into four genetic groups independent of geographic location. The mean of polymorphism among all populations was 79%, and the average unbiased genetic diversity (uh) was considered moderate (0.31). This study in addition to confirming that F. sacchari as the main species associated with pokkah boeng in sugarcane in Northeast Brazil, reveals the relationship of mating type and genetic diversity of F. sacchari. The unrestricted gene flow between regions is probably the best explanation for the low geographic correlation. This knowledge will help in the adoption of management measures with fungicides or resistant cultivars.     

First morphogenetic identification of <i>Fusarium solani</i> isolated from orange fruit in Egypt

Losses due to postharvest decay may occur at any time during postharvest handling, from harvest to consumption affecting the produce quality and quantity. Accurate identification of the pathogen causing postharvest disease is essential to the selection of an appropriate disease control approach. Nine isolates of Fusarium recovered from orange fruit were identified as Fusarium solani. The fungus is involved with fruit decay. The obtained cultures were purified and grown on potato-dextrose agar (PDA), malt yeast agar (MYA), and Czapek's nutrient media (CNM) under light for identification. A pathogenicity test was carried out to fulfil Koch's postulates. The pathogen could only enter ripe orange fruit through wounds and cracks causing the rot disease. The identification of the fungal isolates was confirmed to be F. solani by DNA sequencing, which was 99 to 100% homologous to those deposited in the Gen- Bank. The identity of nine fungal isolates was confirmed to be F. solani by DNA sequencing of the internal transcribed spacer (ITS) rDNA region (GenBank Accession Nos. DQ486874 to DQ486881 and KC758879). To our knowledge, this is the first morphogenetic identification of F. solani isolated from orange fruit in Egypt.     

Molecular diversity of Fusarium oxysporum causing rot diseases of vanilla in south India

Incidence of root, stem and beans rot of vanilla (Vanilla planifolia Andrews) caused by Fusarium oxysporum Schlecht was surveyed in vanilla growing areas of south India during December 2008. The incidence of the disease varied from 1 to 100% in different locations. A total of 60 isolates of F. oxysporum were obtained from diseased samples, and nine morphologically different isolates were taken for molecular characterization using Randomly Amplified Polymorphic DNA (RAPD) markers to study the genetic variability if any, among them. PCR amplification of total genomic DNA with random oligonucleotide primers generated unique banding patterns depending upon primers and isolates. Nine oligonucleotide primers were selected for the RAPD assays, which resulted in 384 bands for nine isolates of F. oxysporum. The number of bands obtained was entered into a NTSYS and the results showed that the variability among the pathogen isolates was moderate. The nine isolates studied were grouped into single major cluster at 0.66 similarity index. Hence, it is inferred that F. oxysporum infecting vanilla in south India consists of a single clonal lineage with a moderate level of genetic diversification.     

Variation in pathogenicity of Fusarium verticillioides and resistance of maize genotypes to Fusarium ear rot

Abstract

The ineffective control measures of pathogens is due to variability among their populations. Hence, the study of pathogenic variation of Fusarium verticillioides strains on maize genotypes. Six F. verticillioides infected maize ear were randomly obtained from three agro-ecological zones in Southwest Nigeria. Pathogenicity of F. verticillioides strains at 1.0?×?10⁶ spores/mL were examined in vivo based on the rating scale of 1–7 on maize genotypes T2L COMP.1.STR SYN-W-1, PVA SYN 8F2, and T2L COMP.4. The pathogens were inoculated to the maize genotypes on 8th week for disease severity and were all moderately susceptible, however, genotype T2L COMP.4 was the most susceptible. It was observed that, 9.4% were classified as highly virulent, 12.5% as virulent, 37.5% as moderately virulent, 21.8% as slightly virulent, and 18.8% as non-virulent. In all, Fusarium verticillioides strains displayed different degrees of virulence, however, maize genotype T2L COMP.4 was the most susceptible to ear rot.