Sylwia Okoń

Avena sterilis L. Genotypes as a Potential Source of Resistance to Oat Powdery Mildew

The aim of the present study was to identify Avena sterilis genotypes demonstrating a high level of resistance against oat powdery mildew, using host-pathogen tests. The study was conducted on 350 A. sterilis genotypes from different parts of the world. Six single-spore isolates of Blumeria graminis (DC.) f. sp. avenae, which demonstrated different levels of virulence to control lines and cultivars, were used in host-pathogen screening tests. To confirm the resistant response of selected genotypes, 13 other isolates were used. Reactions to the isolates were grouped into three classes: resistant, intermediate, and susceptible. Susceptible cultivars Sam and Fuchs were used as controls to estimate the degree of infection. The results of the screening test showed that 10 genotypes were classified as resistant. The second test based on 13 other isolates revealed that only four of the 10 genotypes were a valuable source of resistance against powdery mildew. The identified genotypes may be used in oat breeding programs to increase the level of resistance against powdery mildew. First, however, further studies aimed at identifying whether this resistance is conditioned by a single gene or combinations of different genes are required.

Virulence structure of the Blumeria graminis DC.f. sp. avenae populations occurring in Poland across 2010–2013

The aim of the present study was to determine the virulence structure of powdery mildew of oats (Blumeria graminis DC.f. sp. avena) in Poland in the years 2010–2013. For this purpose, powdery mildew isolates were collected from three experimental stations in Poland. To assess the virulence of the isolates, eight oat varieties with different responses to the pathogen were used. The results showed that a significant proportion of powdery mildew isolates found in Poland overcame the resistance genes of varieties Bruno (Pm6), Jumbo (Pm1) and Mostyn (Pm3). In contrast, lines Av1860 (Pm4), Am27 (Pm5) and Cc3678 (Pm2) were completely resistant to all pathogen isolates involved in the experiment. Changes constantly occurring in the powdery mildew population perfectly reflect diversity indexes, which were the smallest in the first year of observation, where in the following years these parameters were significantly higher. It is worth noting that the presence of powdery mildew is seasonal and local, which is reflected in the prevalence of the disease in a defined area of the country.

Resistance to Puccinia coronata f. sp. avenae in Avena magna, A. murphyi, and A. insularis

Wild oat tetraploids of the section Pachycarpa have already been proven to be a rich source of useful genes but have largely been unexploited for Puccinia coronata resistance. In this study, accessions of Avena magna, A. murphyi, and A. insularis gathered from European and North American gene banks were evaluated at the seedling stage for crown rust reaction using the host-pathogen test and six highly diverse and virulent P. coronata isolates. Of the 92 Avena accessions analyzed, 58.7% were resistant to at least one crown rust race. In all, 37% of the tested accessions reacted nonuniformly, which indicated their heterogeneity. The highest level of resistance was observed in three of the accessions, one of which was verified by flow cytometry as being hexaploid and two of which were verified as being tetraploids. The infection profiles of 19 accessions corresponded to resistance determined by the genes Pc14, Pc39, Pc40, Pc48, Pc50, Pc54, Pc55, Pc61, Pc67, Pc68, Pc97, Pc101, or Pc104. The patterns of infection of the remaining resistant A. magna and A. murphyi accessions allowed us to postulate the presence of potentially novel crown rust resistance genes.

Identification of new sources of resistance to powdery mildew in oat

Powdery mildew caused by Blumeria graminis DC. f. sp. avenae Em. Marchal. is a deleterious foliar disease of common oat which occurs in many parts of the world. Resistance existing in oat cultivars is broken down by new races of this pathogen and because of this fact there is necessity to look for new and effective sources of resistance to powdery mildew in oat. To identify new potential resistance sources to powdery mildew, a total of 67 oat genotypes from five different species Avena sterilis, A. fatua, A. sativa, A. maroccana and A. murphyi and 20 powdery mildew isolates were investigated for disease reactions. Among tested oat accessions the highest level of resistance was associated with A. maroccana genotypes. Genotypes belonging to species of A. murphi and A. sterilis also showed a good level of resistance. Identified genotypes could be used in oat breeding programmes to improve levels of resistance to powdery mildew.

Identification of SCAR markers linked to resistance to powdery mildew in common oat (Avena sativa)

The aim of the present study was to identify SCAR (sequence characterised amplified regions) markers linked to oat mildew resistance group 2 (OMR2). The bulked segregant analysis was used to determine RAPD markers linked to OMR2. Four products were identified that were able to differentiating between resistant and susceptible plants. The products were cloned and sequenced and primers for PCR were designed. Our examinations showed that only the BG8 marker was linked to OMR group 2 at a distance of 4.5 cM from the analysed region. The obtained SCAR-BG8 marker might be used to select genotypes that are resistant to powdery mildew and that contain OMR2.

Genetic variability within Septoria carvi Syd.- a pathogen of caraway Carum carvi L

Genetic variability within Septoria carvi isolates obtained from various organs of caraway cultivated in south-eastern and central Poland was studied using the RAPD-PCR technique. The tests were performed using randomly selected primers. The DNA profiles obtained using four primers proved useful in determining genetic variability among the genotypes of Septoria carvi isolates. The present study characterized the differences in the nucleotide sequence within the internal transcribed spacer region of rDNA (ITS1, 5.8S, ITS2) of selected S. carvi isolates and reference strains of Septoria spp. Moreover, eight isolates were sequenced for three loci: actin, calmodulin and translation elongation factor 1-alpha, and the obtained sequences were compared with the sequences of Septoria reference strains affecting other plants of the family Apiaceae. Phylogenetic analysis showed distinct differences of the tested isolates, which allowed to treat them Septoria carvi species affecting the above-ground organs of caraway Carum carvi L. This study is the first report on the genetic characteristics of the species S. carvi.