Adam Kuzdraliński

The composition of Fusarium species in wheat husks and grains in south-eastern Poland

Abstract Fusarium populations were investigated on 53 samples of wheat grains and husks collected approximately three weeks before harvest in 53 wheat fields in south-eastern Poland. A limited area of sample collection was chosen intentionally to avoid the effect of climate and weather variability. The study was conducted to assess the occurrence of 13 Fusarium species using species-specific PCR assays separately on grains and husks of winter wheat. The obtained data suggest that husks could take a protective role of wheat grain against Fusarium spp. The incidence of Fusarium species decreased in grains vs. husks from 29 to 100%. While Fusarium species were present in husks at 11.32% and less, they were absent in the grain. The presence of Fusarium species on husks is inversely proportional to the percentage reduction of Fusarium spp. in grain. There was a correlation of the presence of certain species of Fusarium in husks and in grains. The number of Fusarium species found on husks was about three times higher in comparison to wheat grain. In conclusion, the presented data indicate the importance of Fusarium populations analysis on wheat husk in seeds pathological studies.

A Review of Conventional PCR Assays for the Detection of Selected Phytopathogens of Wheat

Infection of phyllosphere (stems, leaves, husks, and grains) by pathogenic fungi reduces the wheat yield and grain quality. Detection of the main wheat pathogenic fungi provides information about species composition and allows effective and targeted plant treatment. Since conventional procedures for the detection of these organisms are unreliable and time consuming, diagnostic DNA-based methods are required. Nucleic acid amplification technologies are independent of the morphological and biochemical characteristics of fungi. Microorganisms do not need to be cultured. Therefore, a number of PCR-based methodologies have been developed for the identification of key pathogenic fungi, such as Fusarium spp., Puccinia spp., Zymoseptoria tritici, Parastagonospora nodorum, Blumeria graminis f. sp. tritici, and Pyrenophora tritici-repentis. This article reviews frequently used DNA regions for fungus identification and discusses already known PCR assays for detection of the aforementioned wheat pathogens. We demonstrate that PCR-based wheat pathogen identification assays require further research. In particular, the number of diagnostic tests for Fusarium graminearum, Puccinia spp., and P. tritici-repentis are insufficient.

Genetic mechanisms of variation in erythromycin resistance in Lactobacillus rhamnosus strains.

Genetic mechanisms of variation in erythromycin resistance in Lactobacillus rhamnosus strains

The Ability of a Novel Strain Scheffersomyces (Syn. Candida) shehatae Isolated from Rotten Wood to Produce Arabitol

Arabitol is a polyalcohol which has about 70% of the sweetness of sucrose and an energy density of 0.2 kcal/g. Similarly to xylitol, it can be used in the food and pharmaceutical industries as a natural sweetener, a texturing agent, a dental caries reducer, and a humectant. Biotechnological production of arabitol from sugars represents an interesting alternative to chemical production. The yeast Scheffersomyces shehatae strain 20BM-3 isolated from rotten wood was screened for its ability to produce arabitol from L-arabinose, glucose, and xylose. This isolate, cultured at 28°C and 150 rpm, secreted 4.03 ± 0.00 to 7.97 ± 0.67 g/l of arabitol from 17-30 g/l of L-arabinose assimilated from a medium containing 20-80 g/l of this pentose with yields of 0.24 ± 0.00 to 0.36 ± 0.02 g/g. An optimization study demonstrated that pH 4.0, 32°C, and a shaking frequency of 150 rpm were the optimum conditions for arabitol production by the investigated strain. Under these conditions, strain 20BM-3 produced 6.2 ± 0.17 g/l of arabitol from 17.5 g/l of arabinose after 4 days with a yield of 0.35 ± 0.01 g/g. This strain also produced arabitol from glucose, giving much lower yields, but did not produce it from xylose. The new strain can be successfully used for arabitol production from abundantly available sugars found in plant biomass.

Novel PCR Assays for the Detection of Biological Agents Responsible for Wheat Rust Diseases: Puccinia triticina and Puccinia striiformis f. sp. tritici

The species Puccinia triticina (Pt) and Puccinia striiformis f. sp. tritici (Pst) are devastating cereal pathogens that cause leaf and stripe rust diseases. We developed PCR assays for the species-specific detection of Pt and Pst, 2 biological agents that cause wheat rust disease. For each pathogen, we validated 3 primer sets that target the second largest subunits of the RNA polymerase II (rpb2) and β-tubulin 1 (tub1) genes. The specificities of the primers were verified using naturally infected plant materials with visual symptoms of disease. All primer sets amplified a single DNA fragment of the expected length. The primer sets LidPr15/16, LidPr1/2, and LidPs13/14 were able to detect small amounts of pure fungal DNA with sensitivities of 0.1, 1, and 10 pg/μL, respectively. A sufficient detection limit (1 pg/μL to 5 ng/μL) was observed for all assays when the sensitivity test was performed with host plant DNA. The study also evaluated the simultaneous detection of both rust pathogens, and the multiplex PCR assay generated amplicons of 240 and 144 bp in length for Pts (LidPs9/10) and Pt (LidPr1/2), respectively.

The production of arabitol by a novel plant yeast isolate Candida parapsilosis 27RL-4

Abstract Polyalcohol arabitol can be used in the food and pharmaceutical industries as a natural sweetener, a dental caries reducer, and texturing agent. Environmental samples were screened to isolate effective yeast producers of arabitol. The most promising isolate 27RL-4, obtained from raspberry leaves, was identified genetically and biochemically as Candida parapsilosis. It secreted 10.42– 10.72 g l-1 of product from 20 g l-1 of L-arabinose with a yield of 0.51 - 0.53 g g-1 at 28°C and a rotational speed of 150 rpm. Batch cultures showed that optimal pH value for arabitol production was 5.5. High yields and productivities of arabitol were obtained during incubation of the yeast at 200 rpm, or at 32°C, but the concentrations of the polyol did not exceed 10 g l-1. In modified medium, with reduced amounts of nitrogen compounds and pH 5.5-6.5, lower yeast biomass produced a similar concentration of arabitol, suggesting higher efficiency of yeast cells. This strain also produced arabitol from glucose, with much lower yields. The search for new strains able to successfully produce arabitol is important for allowing the utilization of sugars abundant in plant biomass.