Species diversity of Trichoderma in Poland

In the present study, we reinvestigate the diversity of Trichoderma in Poland utilizing a combination of morphological and molecular/phylogenetic methods. A total of 170 isolates were collected from six different substrata at 49 sites in Poland. These were divided among 14 taxa as follows: 110 of 170 Trichoderma isolates were identified to the species level by the analysis of their ITS1, ITS2 rDNA sequences as: T. harzianum (43 isolates), T. aggressivum (35), T. citrinoviride (11), T. hamatum (9), T. virens (6), T. longibrachiatum (4), T. polysporum (1), and T. tomentosum (1); 60 isolates belonging to the Viride clade were identified based on a fragment of the translation-elongation factor 1-alpha (tef1) gene as: T. atroviride (20 isolates), T. gamsii (2), T. koningii (17), T. viridescens (13), T. viride (7), and T. koningiopsis (1). Identifications were made using the BLAST interface in TrichOKEY and TrichoBLAST (http://www.isth.info). The most diverse substrata were soil (nine species per 22 isolates) and decaying wood (nine species per 75 isolates). The most abundant species (25%) isolated from all substrata was T. harzianum

Assimilation of alternative sulfur sources in fungi

Fungi are well known for their metabolic versatility, whether it is the degradation of complex organic substrates or the biosynthesis of intricate secondary metabolites. The vast majority of studies concerning fungal metabolic pathways for sulfur assimilation have focused on conventional sources of sulfur such as inorganic sulfur ions and sulfur-containing biomolecules. Less is known about the metabolic pathways involved in the assimilation of so-called “alternative” sulfur sources such as sulfides, sulfoxides, sulfones, sulfonates, sulfate esters and sulfamates. This review summarizes our current knowledge regarding the structural diversity of sulfur compounds assimilated by fungi as well as the biochemistry and genetics of metabolic pathways involved in this process. Shared sequence homology between bacterial and fungal sulfur assimilation genes have lead to the identification of several candidate genes in fungi while other enzyme activities and pathways so far appear to be specific to the fungal kingdom. Increased knowledge of how fungi catabolize this group of compounds will ultimately contribute to a more complete understanding of sulfur cycling in nature as well as the environmental fate of sulfur-containing xenobiotics

Infection of stem bases and grains of winter wheat by Fusarium culmorum and F. graminearum and effects of tillage method and maize-stalk residues

The effects of tillage (ploughing vs minimum tillage) and application of chopped maize stalks on winter wheat cv. Here-ward by Fusarium culmorum and F. graminearum were investigated in two 2-year experiments in eastern England. Supplementary inoculum of each fungus (five isolates) was applied to the ground to the first wheat crop in each experiment. Infection of shoot bases (spring), stem bases (summer) and harvested grain were determined by isolating the fungi on agar media and by quantitative PCR. Stem bases were infected more frequently by F. culmorum (up to 35% where inoculum was applied) than F. grammearum (up to 22% where inoculum applied; otherwise scarce). Despite mist-irrigation to encourage ear infection, the incidence of pathogens in grain was usually low, always less than 4% for F. culmorum, but up to 30% for F grammearum where inoculum was applied to the ground. Lack of rainfall probably limited the dispersal of conidia from the ground to the ears. Ascospores, produced by F. graminearum (Gibberella zeae) but not F. culmorum, are less dependent on rainfall for dispersal. Infection of grains by F. grammearum was usually correlated significantly with stem infection and sometimes, negatively, with grain yield. Both conidia and ascospores were produced on the previous crop's debris, apparently in small amounts, throughout much of the year. Little horizontal (plot to plot) dispersal was evident. Non-inversion cultivation and maize-stalk amendments tended to decrease stem-base disease, presumably through the effects of microbial antagonism or competition. However, the incidence of F. grammearum was increased in stem bases where maize stalks were present and in grain by both the presence of maize stalks and minimum tillage. The results support experimental data and UK survey data that non-inversion tillage increases the risk of ear infection, especially by F. grammearum, and hence of mycotoxin contamination of grain. Maize presents an additional risk where weather conditions do not limit the proliferation of the pathogens. This is consistent with evidence from surveys that the region in which the wheat crop is grown is the main risk factor for ear infection and mycotoxin accumulation in grain

Molecular characterization of ochratoxigenic fungi associated with poultry feedstuffs in Saudi Arabia

Fungal and mycotoxins contamination of food and poultry feeds can occur at each step along the chain from grain production, storage, and processing. A total of 200 samples comprising of mixed poultry feedstuffs (n = 100) and their ingredients (n = 100) were collected from Riyadh, Alhassa, Qassium, and Jeddah cities in Saudi Arabia. These samples were screened for contamination by fungi. Penicillium chrysogenum was the predominant species taking into its account and frequency, respectively, in both mixed poultry feedstuff and barley samples (4,561.9 and 687 fungal colony-forming units (CFU)/g) and (66% and 17%). Moisture content was an important indicator for the count of fungi and ochratoxin A. Ochratoxin analysis of plate cultures was performed by a HPLC technique. Sample of mixed poultry feedstuff which was collected from Jeddah displayed the highest level of ochratoxin (14.8 µg/kg) and moisture content (11.5%). Corn grains samples were highly contaminated by ochratoxin A (450 and 423 µg/kg) and recorded the highest moisture contents (14.1 and 14.5%). Ochratoxin A production in fungal species isolated from mixed poultry feedstuff samples were high with P. verrucosum (5.5 μg/kg) and A. niger (1.1 μg/kg). In sorghum and corn grains, the highest ochratoxins producing species were P. viridicatum (5.9 μg/kg) and A. niger (1.3 μg/kg), respectively. Sixty-three isolates of A. niger were ochratoxigenic, and all of them showed the presence of pks genes using PKS15C-MeT and PKS15KS primer pairs. The detection technique of A. niger in poultry feedstuff samples described in the present study was successfully used as a rapid and specific protocol for early detection of A. niger without cultivation on specific media

Selection and characterization of Argentine isolates of Trichoderma harzianum for effective biocontrol of Septoria leaf blotch of wheat

Species of the genus Trichoderma are economically important as biocontrol agents, serving as a potential alternative to chemical control. The applicability of Trichoderma isolates to different ecozones will depend on the behavior of the strains selected from each zone. The present study was undertaken to isolate biocontrol populations of Trichoderma spp. from the Argentine wheat regions and to select and characterize the best strains of Trichoderma harzianum by means of molecular techniques. A total of 84 out of the 240 strains of Trichoderma were able to reduce the disease severity of the leaf blotch of wheat. Thirty-seven strains were selected for the reduction equal to or greater than 50 % of the severity, compared with the control. The percentage values of reduction of the pycnidial coverage ranged between 45 and 80 %. The same last strains were confirmed as T. harzianum by polymerase chain reaction amplification of internal transcribed spacers, followed by sequencing. Inter-simple sequence repeat was used to examine the genetic variability among isolates. This resulted in a total of 132 bands. Further numerical analysis revealed 19 haplotypes, grouped in three clusters (I, II, III). Shared strains, with different geographical origins and isolated in different years, were observed within each cluster. The origin of the isolates and the genetic group were partially related. All isolates from Parana were in cluster I, all isolates from Loberia were in cluster II, and all isolates from Pergamino and Santa Fe were in cluster III. Our results suggest that the 37 native strains of T. harzianum are important in biocontrol programs and could be advantageous for the preparation of biopesticides adapted to the agroecological conditions of wheat culture.Centro de Investigaciones en Fitopatologí