Inoculation methods and aggressiveness of five Fusarium species against peach palm

ABSTRACT: Fusarium wilt is a major disease which affects peach palm (Bactris gasipaes Kunth.var gasipaes Henderson). This study aimed to evaluate inoculation methods and aggressiveness of isolates of five Fusarium species on peach palm. Fusarium proliferatum can infect the leaves, stem, and roots of peach palm. F. proliferatum, F. oxysporum species complex (FOSC), F. verticillioides, F. solani species complex (FSSC), and Gibberella fujikuroi species complex (GFSC) are pathogenic to peach palm. The use of Fusarium-colonized ground corn for root inoculation was effective and reduced the level of damage to plants.

Toxigenicity of Fusarium Species in Gibberella fujikuroi Species Complex (GFSC) Associated With Stalk and Ear Rot Disease of Corn

Fusarium stalk and ear rot disease did not only cause significant losses of yield but also produced mycotoxins that are harmful to animals and human. This study was conducted to elucidate three major mycotoxins i.e. fumonisin B1 (FUMB1), moniliformin (MON), and beauvericin (BEA) produced by the Fusarium spp. isolated from corn showing typical stalk and ear rot symptoms in Indonesia, Malaysia and Thailand. Twenty selected strains of Fusarium species in Gibberella fujikuroi species complex i.e. F.verticillioides, F. proliferatum, F. subglutinans, and F. konzum were analyzed for production of the three mycotoxins by using an Ultra Performance Liquid Chromatography (UPLC). All strains of F. verticillioides and F. proliferatum produced FUMB1 at high levelsand MON at low levels. Many strains of F. verticillioides (67%) and F. proliferatum (50%) did not produce BEA while the others produced BEA at low levels. Two strains of F. subglutinans did not produce FUMB1 but produced MON at low levels. One strain of F. subglutinans produced BEA and the other one did not produce the toxin. Two strains of F. konzum produced both MON and BEA at low levels but only one strain produced FUMB1 at a low level. These mycotoxins have not been reported from Fusarium spp. in Gibberella fujikuroi species complex isolated form stalk and ear rot diseases of corn in these areas. Therefore, concerted efforts must be made to educate all stake holders about the presence and health hazards of these mycotoxins.

Structural variation and dynamics of the nuclear ribosomal intergenic spacer region in key members of the Gibberella fujikuroi species complex

The intergenic spacer (IGS) region of the ribosomal DNA was cloned and sequenced in eight species within the Gibberella fujikuroi species complex with anamorphs in the genus Fusarium, a group that includes the most relevant toxigenic species. DNA sequence analyses revealed two categories of repeated elements: long repeats and short repeats of 125 and 8 bp, respectively. Long repeats were present in two copies and were conserved in all the species analyzed, whereas different numbers of short repeat elements were observed, leading to species-specific IGS sequences with different length. In Fusarium subglutinans and Fusarium nygamai, these differences seemed to be the result of duplication and deletion events. Here, we propose a model based on unequal crossing over that can explain these processes. The partial IGS sequence of 22 Fusarium proliferatum isolates was also obtained to study variation at the intraspecific level. The results revealed no differences in terms of number or pattern of repeated elements and detected frequent gene conversion events. These results suggest that the homogenization observed at the intraspecific level might not be achieved primarily by unequal crossing-over events but rather by processes associated with recombination such as gene conversion events.