Genetic variability amongst Fusarium spp. in the section Liseola from bakanae-infected rice in Malaysia and Indonesia by RAPD analysis.

RAPD was used to assess genetic relatedness amongst 59 strains of Fusarium spp. in the section Liseola obtained from rice plants showing bakanae symptoms from different major granary areas in Malaysia and Indonesia, as well as 14 strains of standard testers from U.S.A. RAPD analysis using 10 nucleotides with 60 – 70% G+C contents primers i.e. OPA-02 (5’-tgc-cga-gct-g-3’), OPA-04 (5’-aat-cgg-gct-g-3), OPA-09 (5’-ggg-taa-cgc-c-3’), OPA-17 (5’-gac-cgc-ttg-t-3’), OPT-11 (5’-ttc-ccc-gcg-a-3’), OPT-18 (5’-gat-gcc-aga-c-3’), OPU-06 (5’-acc-ttt-gcg-g-3’), OPU-16 (5’-cgt-cgc-tgg-a-3’), OPV-06 (5’-acg-ccc-agg-t-3’) and OPV-16 (5’-aca-ccc-cac-a-3’) showed variations on DNA profiles between the species, indicating the species were genetically heterogeneous. Dendograms from cluster analysis based on UPGMA showed that the six species of Fusariumwere clustered separately

Variability of Fusarium species associated with bakanae disease of rice based on virulence, vegetative and biological compatibility

Bakanae is one of the most important diseases of rice in Southeast Asia. Variability of 212 strains of Fusarium associated with the disease in Malaysia and Indonesia were examined. Most of the strains (59.0%) were classified into five Fusarium species in section Liseola i.e. F. fujikuroi (the most frequent, 37.3%), followed by F. verticillioides, F. proliferatum, F. sacchari and F. subglutinans. Pathogenicity tests on a susceptible rice seedlings variety MR 211 confirmed that only isolates identified as F. fujikuroi were pathogenic and able to produce typical bakanae symptoms. Results on vegetative compatibility tests indicated that there was a substantial genetic diversity within the five species. Several isolates (2.4%) were classified as heterokaryon self-incompatible (HSI) based on their inability to form a heterokaryon. In crosses with seven standard testers of mating populations (MP-A to MP-G), 69.3% of the strains were assigned to five Gibberella fujikuroi species complex i.e. MP-A, MP-B, MP-C, MP-D and MP-E based on their ability to produce viable ascospores. The isolates of F. fujikuroi belong to MP-C. The present data provide baseline information for Fusarium species associated with bakanae disease of rice in Malaysia and Indonesia as well as for the genotypes involved in causing the disease on rice in this region

Secondary metabolite profiles and mating population of Fusarium species in section Liseola associated with bakanae disease of rice

A total of 25 strains of Fusarium species that belong to F. fujikuroi (a pathogen of bakanae disease), F. proliferatum, F.sacchari, F. subglutinans and F. verticillioides were isolated from rice plants showing typical bakanae symptoms in Malaysia and Indonesia and screened for their secondary metabolites. The objectives of the studies were to determine the physiological variability based on production of moniliformin (MON), fumonisin (FB1), gibberellic acid (GA3) and fusaric acid(FA) as well as to ascertain the mating populations (MPs) within the Gibberella fujikuroi species complex based on their ability to produce perithecia and viable ascospores. Production of GA3 could be used to separate F. fujikuroi that belongs to MP-C from other species. In crosses with seven standard testers of MPs, 76% of strains could be assigned to at least one of the G. fujikuroi species complex namely MP-A (G.moniliformis), MP-B (G. sacchari), MP-C (G. fujikuroi) and MP-D (G.intermedia). Single strain (M3237P) that was assigned as MP-C, and has also been identified morphologically as F. fujikuroi was also crossed-fertile with MP-D tester. The secondary metabolites profiles and the presence of MP-A, MP-B, MP-C and MP-D strains on samples of bakanae-infected rice plants are new records in Malaysia

Tolerance and biosorption of copper (Cu) and lead (Pb) by filamentous fungi isolated from a freshwater ecosystem.

Filamentous fungi are able to accumulate significant amount of metals from their environment. The potential of fungal biomass as agents for biosorption of heavy metals from contaminated sediments is currently receiving attention. In the present study, a total of 41 isolates of filamentous fungi obtained from the sediment of the Langat River, Selangor, Malaysia were screened for their tolerance and uptake capability of copper (Cu) and lead (Pb). The isolates were identified as Aspergillus niger, A. fumigatus, Trichoderma asperellum, Penicillium simplicissimum and P. janthinellum. A. niger and P. simplicissimum, were able to survive at 1000 mg/L of Cu(II) concentration on Potato Dextrose Agar (PDA) while for Pb, only A. niger survived at 5000 mg/L concentration. The results showed that A. niger, P. simplicissimum and T. asperellum have a better uptake capacity for Pb compared to Cu and the findings indicated promising biosorption of Cu and Pb by these filamentous fungi from aqueous solution. The present study was also determined the maximum removal of Cu(II) and Pb(II) that was performed by A. niger. The metal removal which occurred at Cu(II) 200 mg/L was (20.910 +/- 0.581) mg/g and at 250 mg/L of Pb(II) was (54.046 +/- 0.328) mg/g

Bakanae disease of rice in Malaysia and Indonesia: eetiology of the causal agent based on morphological, physiological and pathogenicity characteristics

Bakanae disease on rice has been recorded almost in all countries where paddy is grown commercially, especially in Asian countries, including Malaysia and Indonesia. Bakanae disease was widespread in Peninsular Malaysia and three provinces of Indonesia with the range of disease severity from scale 1 to 5 and disease incidence from 0.5 to 12.5% during 2004-2005 main growing seasons. A total of five Fusarium species belonging to section Liseola and their allied i.e. Fusarium fujikuroi, F. proliferatum, F. sacchari, F. subglutinans and F. verticillioides were isolated and identified on the basis of their morphological characteristics. Literature data showed that the bakanae disease of rice all over the world is caused by F. fujikuroi and probably some other Fusarium species from section Liseola or allied. However, from pathogenicity tests that have been carried out by using variety MR 211 of rice it was evident that F. fujikuroi was highly virulent and the only species involved in causing bakanae disease. Therefore, this species was the only one detected to be able to produce gibberellic acid - (GA3) with Rf value 0.40 and 0.62, developed in solvent systems isopropanol:ammonia: water (10 : 1 : 1), v/v/ v and chloroform:ethyl acetate: formic acid (5 : 4 : 1), v/v/v, respectively. This knowledge would be invaluable in developing our understanding on the interaction between F. fujikuroi and the host plants

Characterization of Fusarium proliferatum and Fusarium verticillioides based on species-specific gene and microsatellites analysis

Fusarium species are known to cause various diseases on plantations including fruits and vegetables. The most common Fusarium that can cause plant diseases are Fusarium proliferatum and Fusarium verticillioides. Ear rot disease on maize, wilt disease on cucurbits and fruit rot disease on tomato as well as banana are example of diseases caused by these two species. The objectives of this study were to identify F. proliferatum and F. verticillioides based on species-specific primers and polymerase chain reaction (PCR) amplification and to evaluate the genetic diversity of both species based on microsatellite markers. Fifty isolates of Fusarium species that were previously collected throughout Malaysia from different hosts were identified by using species-specific PCR amplification. Twenty-nine isolates were identified as F. proliferatum and 21 isolates were identified as F. verticillioides based on species-specific primer. The genetic diversity of all the fungal isolates was evaluated by using microsatellite analysis with six established primers. Five out of six primers amplified polymorphic bands with the most effective primer showing high polymorphism were (AG)7C and (TCC)5 meanwhile one primer (TTTC)4 gave negative result with no band amplified. The phylogenetic tree that was constructed showing two different clades distinguished between F. proliferatum and F. verticillioides

Iron, oxidative stress, and virulence : roles of iron-sensitive transcription factor Sre1 and the redox sensor ChAp1 in the maize pathogen Cochliobolus heterostrophus.

The gene SRE1, encoding the GATA transcription factor siderophore biosynthesis repressor (Sre1), was identified in the genome of the maize pathogen Cochliobolus heterostrophus and deleted. Mutants were altered in sensitivity to iron, oxidative stress, and virulence to the host. To gain insight into mechanisms of this combined regulation, genetic interactions among SRE1 (the nonribosomal peptide synthetase encoding gene NPS6, which is responsible for extracellular siderophore biosynthesis) and ChAP1 (encoding a transcription factor regulating redox homeostasis) were studied. To identify members of the Sre1 regulon, expression of candidate iron and oxidative stress-related genes was assessed in wild-type (WT) and sre1 mutants using quantitative reverse-transcription polymerase chain reaction. In sre1 mutants, NPS6 and NPS2 genes, responsible for siderophore biosynthesis, were derepressed under iron replete conditions, whereas the high-affinity reductive iron uptake pathway associated gene, FTR1, was not, in contrast to outcomes with other well-studied fungal models. C. heterostrophus L-ornithine-N(5)- monooxygenase (SIDA2), ATP-binding cassette (ABC6), catalase (CAT1), and superoxide dismutase (SOD1) genes were also derepressed under iron-replete conditions in sre1 mutants. Chap1nps6 double mutants were more sensitive to oxidative stress than either Chap1 or nps6 single mutants, while Chap1sre1 double mutants showed a modest increase in resistance compared with single Chap1 mutants but were much more sensitive than sre1 mutants. These findings suggest that the NPS6 siderophore indirectly contributes to redox homeostasis via iron sequestration, while Sre1 misregulation may render cells more sensitive to oxidative stress. The double-mutant phenotypes are consistent with a model in which iron sequestration by NPS6 defends the pathogen against oxidative stress. C. heterostrophus sre1, nps6, Chap1, Chap1nps6, and Chap1sre1 mutants are all reduced in virulence toward the host, compared with the WT

Identification of Microfungi Isolated from Belian Fruits

Belian tree (Eusideroxylon zwageri Teijsm. & Binn.) is one of the highly demanded commercial timber tree indigenous to the Southeast Asian region. The tree is threatened with over exploitation; habitat destruction and slow regeneration. While vascular plants are known as major reservoirs of fungi species, there have been no studies to identify the microfungi isolated from fruits of this endemic tree. By using internal transcribed spacers (ITS) sequence analysis, five genera were isolated and identified as Annulohypoxylon, Daldinia, Hypoxylon, Lasiodiplodia and Trichoderma. This result will be primarily used as baseline data for further investigations on microfungi diversity associated with Belian tree

Vegetative compatibility of Fusarium oxysporum isolated from various plants

Fusarium oxysporum is common plant pathogen and is classified into divisions called formae speciales according to host specificity. Thirty isolates of F. oxysporum was isolated from various plant samples from various locations in Malaysia. Chlorate-resistant sectors (CRSs) were generated and phenotyped on the phenotyping media that contain different nitrogen sources. Twenty-seven of F. oxysporum isolates were identified as heterokaryon self-compatible (HSC) while three isolates as heterokaryon self-incompatible (HSI) after repeated attempts. Those isolates that formed heterokaryon when the nit mutants merged with different isolates were classified into same vegetative compatibility group (VCG) while those unable were classified into different VCGs. Twenty VCGs were obtained, four VCGs contained more than one isolate and another 16 VCGs contained a single isolate in each group. The percentage of VCG diversity of F. oxysporum was 74%. F. oxysporum isolated from various plants samples in Malaysia were genetically diverse based on their multiple VCGs

Isolation and characterisation of Ascomycetes isolated from Eurycoma Longifolia Jack and Malay traditional vegetables

Plants are the most common host for fungal communities. However, vegetables and herbs traditionally consumed by the Malay community have not been thoroughly investigated for their association with fungi. The main objective of the present study is to identify the Ascomycetes fungi associated with Eurycoma longifolia Jack and vegetables traditionally consumed by the Malay community. In the present study, we isolated and identified 34 isolates of the Ascomycetes fungi obtained from five traditional vegetables (Oenanthe javanica, Cosmos caudatus, Persicaria odorata, Psophocarpus tetragonolobus and Cantella asiatica) and Eurycoma longifolia Jack. The isolates are identified as eight species, which are Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium oxysporum, Fusarium proliferatum, Fusarium solani, Penicillium paraherquei and Trichoderma asperellum. Aspergillus and Fusarium are dominant among the isolated fungi. This report provides additional information on the diversity of fungi isolated from traditional vegetables and Eurycoma longifolia based on the Internal Transcribed Spacer (ITS) sequence analysis