Botanica Lithuanica , Volume 11, Number 2

2005 m.

The internal infection of seeds by fungi was determined on potato dextrose medium. During the experimental years (2000–2001 and 2003) the number of seed-borne Alternaria micromycetes was high in winter and spring oilseed rape (Brassica napus var. oleifera), and spring turnip rape (Brassica rapa var. oleifera). In all cases the number of seeds infected with Alternaria spp. increased with an increase in Alternaria blight severity on siliqua. The number of seeds infected with Cladosporium spp. was much lower than the number of seed infected with Alternaria spp. In most cases the amount of seeds infected with Penicillium spp. increased with a reduction of Alternaria blight severity on siliqua. In all experimental years the seeds of oilseed rape and turnip rape was slightly infected with Botrytis spp., Mucor spp., Fusarium spp., Aspergillus spp.

Keywords: winter and spring oilseed rape, spring turnip rape, Alternaria blight, Alternaria spp.

Experiments were carried out at the Upytė Experimental Station of the Lithuanian Institute of Agriculture. They were designed to investigate the occurrence of fungi on the seeds of various oil flax cultivars during harvesting and storage as well as to test the effectiveness of chemical agents intended for their control. The following potential mycotoxin-producing fungi were identified at a genus level: Alternaria spp., Aspergillus spp., Fusarium spp., Penicillium spp., their incidence (%) on seeds was measured and efficiency of fungicides against these fungi was estimated.

Keywords: linseed, Alternaria, Fusarium, mycotoxins, fungicides.

A PCR-based assay analysing the genomic DNA of 60 Fusarium strains, isolated from food grains, using species-specific and TRI5 gene-specific primers, was carried out. Species-specific PCRs were used to confirm the identity of the Fusarium species. These results showed the necessity of combining morphological and molecular identification techniques. The analysis of fungal genomic DNA for the presence or absence of the TRI5 gene, encoding the first step in a trichotecene synthesis pathway, showed contamination by trichotecenes producers in 4 cereal samples out of the 8 tested, and multiplex species-specific PCR detected F. avenaceum and F. culmorum. TRI5 gene specific PCR-based analysis of the fungal genome demonstrated a close correlation of this gene with the production of secondary metabolites, particularly trichotecenes, detected by TLC.

Keywords: Fusarium, trichotecenes, grains, Lithuania.

During the period of 2003–2004, the contamination of grain with micromycetes was investigated before harvesting, at the moment of harvesting, as well as in the course of grain transportation into storehouses and during storage. Isolation of prevailing and potentially toxic micromycetes revealed that during harvesting and transportation microbiological contamination of grain increased, particularly of damaged grain. When wheat was chemically cultivated, the number of micromycete propagules in grain was almost twice lower than when wheat was cultivated ecologically.

Keywords: microbiological contamination, grain storage, crop cultivation technology.

Commercial wheat grain stored in Lithuanian storage enterprises in 2003–2004 was strongly contaminated by mould fungi. In the endomycobiota of the grain 22 genera and 44 species and varieties of micromycetes were identified. The fungi of the Ulocladium, Alternaria, Penicillium, Fusarium, Acremonium, Chrysosporium, Sporotrichum, Aspergillus, and Arthrinium genera were the most common and their percentage of occurrence among isolates made up 93.1 % of fungi found. The Fusarium genus exhibited the most diverse species composition; F. poae, F. sporotrichioides, F. graminearum, and F. avenaceum prevailed. The majority of these fungi are known as potential producers of toxic metabolites responsible for the formation of mycotoxins in infected grain. The species composition and frequency of occurrence of separate species in the internal tissues of stored commercial wheat grain vary depending on climatic conditions, wheat cultivation technology, as well as wheat cultivar.

Keywords: micromycetes, wheat grain, species frequency, mycotoxins.

This paper deals with yeast distribution on various substrata of plant origin: on cereals, vegetables, fruits, and fodder stocked under various storage conditions. The investigation results showed that the yeasts Candida valida, C. pelliculosa, C. graminis, C. utilis, Geotrichum candidum, G. fermentans, and Rhodotorula rubra were isolated from cereal grains. Eight yeast species (Rhodotorula rubra, R. graminis, Rhodosporidium diobovatum, Lipomyces anomalus, Geotrichum candidum, Saccharomyces cerevisiae, Debaryomyces polymorphus, and Metschnikowia pulcherima) were isolated from vegetables and fruits. Metschnikowia pulcherima yeast was isolated for the first time in Lithuania. Geotrichum candidum, G. fermentans, Candida utilis, C. lipolytica, C. scottii, C. parapsilosis, and C. guilliermondii yeasts were isolated from fodder. It was estimated that a broad spectrum of carbon source assimilation and fermentation was characteristic of the yeasts isolated and this allowed them to adapt easily to various substrata of plant origin.

Keywords: yeasts, plant substrata, isolation, identification, fermentation.

Samples of sage (Salvia officinalis L.), lovage (Levisticum officinale W. D. J. Koch), thyme (Thymus vulgaris L.), and marjoram (Majorana hortensis Moench.) were desiccated applying different technologies and examined for the presence of micromycetes. The largest amount of colony forming units of micromycetes was counted on lovage and marjoram desiccated in a convection oven and under natural conditions. In total, 60 species were isolated from studied herbs. The most diverse species composition of micromycetes was found on marjoram (35 species), while species from the Penicillium Link genus were found only on sage. The majority of the isolated species are known to be producers of mycotoxins. The Chrysosporium merdarium 1-Šal strain isolated from sage was estimated as a patulin and sterigmatocystin producer. The selection of suitable desiccation methods can lead to a decrease in the contamination of herbs with toxin producing micromycetes.

Keywords: micromycetes, herbs, desiccation technologies, mycotoxins.