The influence of local factors on the prediction of fumonisin contamination in maize.

BACKGROUND: Contamination by mycotoxins is a major concern to the maize industry in north-east Italy where maize grain is often spoiled by Fusarium spp. In this work, fumonisins, deoxynivalenol and zearalenone were determined and an artificial neural network (ANN) model suitable for predicting mycotoxin contamination of maize at harvest time was developed. RESULTS: The occurrence of deoxynivalenol and zearalenone was very limited, while fumonisins concentration ranged from 163 and to 3663 µg kg(-1) in 2007, and from 333 to 11473 µg kg(-1) in 2008. Statistical data analysis of factors affecting fumonisins concentration revealed that irrigation, chemical treatment against the European corn borer and harvest date significantly affected the level of contamination (P < 0.05), although the relevance of the factors was different in 2007 and 2008. The neural network approach showed a significant correlation between ascertained values and predictions based on agronomic data. CONCLUSION: This is the first time that an artificial neural network has been used to predict fumonisin accumulation in maize: the prediction has been shown to have the potential for the development of a new approach for the rapid cataloging of grain lots.

Air analysis in the assessment of fumonisin contamination risk in maize.

BACKGROUND: In maize-growing areas where fumonisin contamination is endemic, there is an urgent need for novel methods to assess the quality of grain lots before their delivery to common drying and storage collection centres. Aerobiological samples of fungal spores released during harvest were analysed to establish a relationship between fumonisin contamination and the abundance of pathogen propagules collected in the combine harvester using a cyclone and membrane filters. Filter-captured propagules were analysed by direct plating, immunoenzymatic assay of specific Fusarium extracellular polysaccharides and real time polymerase chain reaction of the extracted DNA using fum1, a gene involved in the biosynthesis of fumonisin, as a target. RESULTS: The results showed that time of harvest and environmental conditions strongly influenced the efficiency and performance of the collection system. The data obtained were informative in comparing individual samples collected under similar conditions. The immunoenzymatic assay provided the most reliable data, which improved the ability of a neural network to predict the fumonisin content of lots, when added to agronomic, environmental and phytosanitary data. CONCLUSION: This is the first attempt to evaluate the Fusarium propagules dispersed during harvesting as a predictive means to assess maize quality. A method based on cyclone/filter capture and immunological detection has been shown to be feasible and to have the potential for the development of a continuous monitoring system, but the prediction capabilities in the present implementation were limited.

Evolutionary analysis of endopolygalacturonase-encoding genes of Botrytis cinerea.

Sequence analysis of five of the six endopolygalacturonase-encoding genes (Bcpg1, Bcpg2, Bcpg3, Bcpg4, Bcpg5) from 32 strains of Botrytis cinerea showed marked gene to gene differences in the amount of among-strains diversity. Bcpg4 was almost invariable in all strains; Bcpg3 and Bcpg5 showed a moderate variability, similar to that of non-pathogenicity-associated genes examined in other studies. Conversely, Bcpg1 and Bcpg2 were highly variable and were shown to be under positive selection based on the McDonald-Kreitman test and likelihood ratio test. The evolution of the five endopolygalacturonase genes is explained by their different ecophysiological role. Diversification and balancing selection, as detected in Bcpg1 and Bcpg2, can be used by the pathogen to escape recognition by the host and delay plant reaction in the early phases of infection. The analysis of the polymorphisms and the location of the sites with high probability of being positively selected highlighted the relevance of variability of the BcPG1 and BcPG2 proteins at their C-terminal end. By contrast, the absence of variability in Bcpg4 suggests that the efficiency of the product of this gene is critical for B. cinerea growth in late phases of infection or during intraspecific competition, thus markedly affecting strain fitness.

Degradation of fumonisin B1 by a bacterial strain isolated from soil.

A mixed microbial culture degrading fumonisin B l was obtained from soil samples using an enrichment culture procedure. A bacterial isolate from the enrichment culture (strain NCB 1492) degraded fumonisin B1 after incubation for 3 h, as indicated by TLC and HPLC analysis. On the basis of the sequence analysis of 16S rDNA, strain NCB 1492 was related to the Delftia/Comamonas group. Thin-layer chromatographic analysis indicated the presence of metabolites in the NCB 1492 culture filtrates after degradation of fumonisin B1 supplied as sole carbon and nitrogen source in phosphate buffer. Four metabolites were identified by mass spectrometry analysis.

Ochratoxin A-producing strains of Penicillium spp. isolated from grapes used for the production of "passito" wines.

The post-harvest mycobiota of dried grapes, used in Friuli Venezia Giulia (Northern-East Italy) for the production of "passito" dessert wines, was investigated in order to detect potential ochratoxin A (OTA)-producers. Five grape cultivars were analysed and only isolates belonging to the genera Aspergillus and Penicillium were evaluated. No Aspergillus spp. was found while 379 strains of Penicillium spp. were isolated. Four strains produced UV fluorescent metabolites on grape juice agar and synthetic liquid media as observed by thin-layer chromatography (TLC). Three of these resulted OTA producers when analyzed by high pressure liquid chromatography (HPLC), following immunoaffinity column purification. According to the results of morphological examinations and ribosomal DNA sequencing, the OTA producer strains did not belong to the species P. verrucosum or P. nordicum. The corresponding passito wines did not contain OTA.

Mapping and characterization of polymorphism in mtDNA of Cryphonectria parasitica: evidence of the presence of an optional intron.

The mitochondrial DNA (mtDNA) of the filamentous ascomycete Cryphonectria parasitica is large and polymorphic so, to better understand the nature of the polymorphisms within populations, a small collection of Italian strains of the fungus was examined. Known mtDNA polymorphisms were mapped and found to cluster in four regions of the mtDNA molecule, particularly in the RFLP region 2 where five different mtDNA haplotypes out of 13 strains were identified. This region included an area of 8.4kbp which was entirely sequenced in strain Ep155 showing the presence of two introns. An internal 3.2kbp portion was sequenced also in six additional strains. Sequence comparison of the C. parasitica mitochondrial intronic ORFs revealed similarities to known endonucleases such as those of Podospora anserina and Neurospora crassa. DNA sequence analysis showed that three polymorphisms of this mtDNA region within this population of 12 strains were due to the optional presence in the ND5 gene of an intron and of an intervening sequence within the intron. Evidence was also found within this population of mixed mitochondrial types within a single strain.

Geminivirus-related extrachromosomal DNAs of the X-clade phytoplasmas share high sequence similarity.

Southern blot hybridization analysis revealed that the extrachromosomal DNAs (EC-DNAs) associated with Vaccinium witches' broom (VAC) and walnut witches' broom phytoplasmas and various strains of the Italian clover phyllody phytoplasma (ICPh) were highly homologous among themselves but distinct from EC-DNAs of aster yellows related phytoplasmas occurring in the same insect and plant hosts and collected at the same site as the ICPh strains. The EC-DNAs of various strains of the ICPh differed significantly in number and size, more markedly among samples from different host plant species than among samples from the same host plant species. However, experiments on insect-mediated transmission suggested that the size variation is not associated with plant host specificity. Sequence analysis of cloned fragments revealed the presence of highly conserved ORFs (with substantially invariant putative translation products) but also the presence of regions rich in short direct and inverted repeats, which may be the cause of the size variations. The partial sequence of an EC-DNA associated with VAC encoding a putative replication-associated protein indicated their close phylogenetic relationship with geminiviruses.