Sublethal concentrations of azoles induce tri transcript levels and trichothecene production in Fusarium graminearum.

The effect of sublethal concentrations (below the recommended field doses) of propiconazole and tebuconazole on the amount of tri transcripts and accumulation of trichothecenes by three Fusarium graminearum isolates of 3ADON, 15ADON, and NIV chemotypes was examined on yeast extract sucrose agar (YES) medium. RT-qPCR analyses showed higher tri4, tri5, and tri11 transcript levels in cultures of all three F. graminearum isolates supplemented with sublethal concentrations of azoles as compared to those in nontreated control, although the fold changes in the amount of tri transcripts differed according to the type of azole used. Mycotoxin analysis revealed higher increase in trichothecene accumulation in most of the tebuconazole-treated samples of all chemotypes tested. A huge increase in all trichothecene compounds was revealed in samples of all F. graminearum isolates treated with 5 mg L(-1) of tebuconazole. An inducing effect of azoles on trichothecene accumulation in the grain was confirmed in an in planta experiment; however, the results obtained were inconsistent. A higher amount of trichothecenes and fungal DNA was quantitated in two grain samples treated with sublethal propiconazole concentrations. In contrast, no significant increase in trichothecene levels was revealed in grain samples treated with sublethal concentrations of tebuconazole.

Multilocus phylogenetics show high intraspecific variability within Fusarium avenaceum.

Fusarium avenaceum is a common soil saprophyte and plant pathogen of a variety of hosts worldwide. This pathogen is often involved in the crown rot and head blight of cereals that affects grain yield and quality. F. avenaceum contaminates grain with enniatins more than any species, and they are often detected at the highest prevalence among fusarial toxins in certain geographic areas. We studied intraspecific variability of F. avenaceum based on partial sequences of elongation factor-1 alpha, enniatin synthase, intergenic spacer of rDNA, arylamine N-acetyltransferase and RNA polymerase II data sets. The phylogenetic analyses incorporated a collection of 63 F. avenaceum isolates of various origin among which 41 were associated with wheat. Analyses of the multilocus sequence (MLS) data indicated a high level of genetic variation within the isolates studied with no significant linkage disequilibrium. Correspondingly, maximum parsimony analyses of both MLS and individual data sets showed lack of clear phylogenetic structure within F. avenaceum in relation to host (wheat) and geographic origin. Lack of host specialization indicates no host selective pressure in driving F. avenaceum evolution, while no geographic lineage structure indicates widespread distribution of genotypes that resulted in nullifying the effects of geographic isolation on the evolution of this species. Moreover, significant incongruence between all individual tree topologies and little clonality is consistent with frequent recombination within F. avenaceum.