Characterization and pathogenicity of Fusarium proliferatum and Fusarium verticillioides, causal agents of Fusarium ear rot of corn

Fusarium ear rot is a significant disease of corn caused by several toxigenic Fusarium species including Fusarium proliferatum and Fusarium verticillioides. Forty-one Fusarium isolates were recovered from corn with Fusarium ear rot disease symptoms collected from Peninsular Malaysia. Isolates were classified into three described species known as F. proliferatum, F. verticillioides, and F. solani. Based on sexual compatibility test, four isolates from F. proliferatum (MATD-1) were crossed-fertile with tester isolate F. proliferatum D024853 (MATD-2), producing perithecia in the presence of ascospores. Meanwhile, the isolates from F. verticillioides (MATA-2) were crossed with tester isolate F. verticillioides A00149 (MATA-1), but were found producing 11 isolates with barren perithecia and three infertile isolates, whereas in 11 isolates of F. verticillioides (MATA-1), seven isolates produced barren perithecia with four nonfertile isolates. In the pathogenicity test, all isolates were found pathogenic and displayed disease symptoms with variation in severity. The highest disease severity index value was observed in F. proliferatum B68c at 4.67, which was obtained in an updated report on the mating type of F. verticillioides and F. proliferatum isolated from Fusarium ear rot disease

Morphological and molecular characterization of Curvularia and related species associated with leaf spot disease of rice in Peninsular Malaysia

Curvularia species are important phytopathogens reported worldwide. They are closely related; consist of major destructive pathogens mainly for grasses and cereal plants including rice (Oryza sativa). A leaf spot symptom of rice is one of the common symptoms found in the rice field and caused reduction of rice yield. However, there are no reports on Curvularia species associated with rice leaves showing spot symptoms. The objectives are to isolate and characterize Curvularia and related species from leaf spot of rice by using morphological and molecular characterization and to determine the phylogenetic relationship between the isolated fungi. Fungal isolation was done from diseased rice leaves showing leaf spot symptoms collected throughout Peninsular Malaysia. Thirty-three isolates were recovered and identified based on their morphological characteristics such as conidia morphology, colony appearance, pigmentation and growth rate for species delimitation. Internal transcribed spacer (ITS) region was amplified to confirm the species identification. The 33 isolates were identified as Bipolaris sorokiniana (10 isolates), Curvularia hawaiiensis (8 isolates), C. geniculata (6 isolates), C. eragrostidis (6 isolates), C. aeria (2 isolates) and C. lunata (1 isolate). A phylogenetic tree was constructed based on ITS sequences using neighbour-joining method. The tree grouped members of Curvularia and Bipolaris into different clades. The phylogenetic tree indicated that the presence of two groups of fungi species; highly virulent and mild pathogens. In conclusion, Curvularia species and Bipolaris sorokiniana were present in rice field in Malaysia and associated with leaf spot of rice

Phenotypic, molecular and mating type analyses of Exserohilum rostratum associated with leaf spots of rice

Exserohilum rostratum is one of the plant pathogens causing leaf spot disease, which affects wide range of plant species, mainly grasses. There has been no report of E. rostratum causes the disease on rice plant particularly on leaves, therefore this study was conducted. During a series of sampling in March to August 2013, leaf spot is one of common symptoms found in rice plantations in Malaysia. The objectives of this study were to identify fungi isolated from leaf spot of rice based on phenotypic and molecular approaches, to determine whether or not E. rostratum isolates were pathogenic, to analyze the mating type of E. rostratum using Polymerase Chain Reaction (PCR) and to examine the sexual development of E. rostratum isolates. All isolated fungi were purified and identified based on their phenotypic features for species delimitation and confirmed by sequencing the internal transcribed spacers (ITS) region. Seventy-eight isolates were identified; E. rostratum (45 isolates), Bipolaris sorokiniana (10 isolates), Curvularia hawaiiensis (8 isolates), C. geniculata (6 isolates), C. eragrostidis (6 isolates), C. aeria (2 isolates) and C. lunata (1 isolate). A phylogenetic tree was constructed using neighbor-joining method showed the same species grouped in the same clade. Clade I consisted of E. rostratum while Clade II were Bipolaris sorokiniana and Curvularia species. Based on pathogenicity test, some isolates of E. rostratum were pathogenic and produced leaf spot symptoms towards rice. In this study, E. rostratum is minor or secondary pathogen to rice because it showed smaller lesion compared to infection by B. oryzae, the main pathogen of brown spot disease. Mating type (MAT) of all isolates of E. rostratum were amplified using two sets of primers (NM162MAT1_1F1Seto and NM163MAT1_1R1Seto for MAT1-1; NM164MAT1_2F1Seto and NM165MAT1_2R1Seto for MAT1-2). Three isolates were confirmed carried MAT1-1 allele while 42 isolates are MAT1-2 isolates. The imbalance distribution of both MAT may caused by ratio of modes of reproduction and selection pressure in the field. The opposite MAT isolates were crossed on Sach’s medium for 3 weeks in quadruplicate. Nine isolates were indicated as fertile, which produced mature pseudothecia and ascospores, 12 isolates produced barren pseudothecia (empty asci) and the remaining 24 isolates were non-fertile without formation of pseudothecia. Three isolates of E. rostratum from this study; one MAT1-1 isolate (UPM1109) and two isolates of MAT1-2 (UPM1247 and UPM1152) are highly fertile and suggested to be used as tester strains. The developed tester strains may facilitate other researchers to access the fertility on other related study on other E. rostratum isolates

Identification and diversity of Fusarium species isolated from tomato fruits

Fruit rot of tomato is a serious disease caused by Fusarium species. Sampling was conducted throughout Selangor, Malaysia and fungal species identification was conducted based on morphological and gene encoding translation elongation factor 1-α (tef1-α) sequence analysis. Five species of Fusarium were discovered namely F. oxysporum (including F. oxysporum f. sp. lycopersici), F. solani, F. equiseti, F. proliferatum and F. verticillioides. Our results provide additional information regarding the diversity of Fusarium species associated with fruit rot disease of tomato