Diversity and virulence of Streptomyces spp. causing potato common scab in Prince Edward Island, Canada

Common scab (CS) is a potato disease that significantly decreases the market value of potato tubers following the development of necrotic lesions on their surface. Streptomyces scabiei is the main causal agent of CS; however, other closely related species, including S. acidiscabies and S. turgidiscabies, have also been shown to cause the disease. In this study, we characterized the genetic and phenotypic diversity of Streptomyces spp. causing CS in Prince Edward Island, the main potato-producing province in Canada. Two hundred and ninety-six pathogenic Streptomyces spp. isolates were retrieved from diseased tubers harvested from six fields located across a longitudinal geographical gradient. Genome fingerprinting analyses using Repetitive elements Polymerase Chain Reactions (PCR) (ERIC- and BOX-PCR) revealed 14 distinct genetic groups. Thirteen of them were taxonomically affiliated with S. scabiei, while the fourteenth group was affiliated with S. acidiscabies. Their geographical distribution was characterized and revealed that on average between six and eight different genetic groups were detected per field, with variable abundance. Virulence assays showed strong differences in virulence between the genetic groups, ranging them from low to highly virulent. Interestingly, pathogenic Streptomyces spp. populations in each field seem to be dominated by the most virulent genetic groups. The results obtained will contribute to better understand the population dynamic of pathogenic Streptomyces spp. causing common scab of potato and promoting the development of more efficient detection and intervention tools to manage this important potato disease.

New Findings on the Resistance Mechanism of an Elite Diploid Wild Potato Species JAM1-4 in Response to a Super Race Strain of Phytophthora infestans

Late blight is a devastating potato disease worldwide, caused by Phytophthora infestans. The P. infestans strain 2013-18-306 from Yunnan is a “supervirulent race” that overcomes all 11 known late blight resistance genes (R1 to R11) from Solanum demissum. In a previous study, we identified a diploid wild-type potato JAM1-4 (S. jamesii) with high resistance to 2013-18-306. dRenSeq analysis indicated the presence of novel R genes in JAM1-4. RNA-Seq was used to analyze the late blight resistance response genes and defense regulatory mechanisms of JAM1-4 against 2013-18-306. Gene ontology enrichment and KEGG pathway analysis showed that many disease-resistant pathways were significantly enriched. Analysis of differentially expressed genes (DEGs) revealed an active disease resistance mechanism of JAM1-4, and the essential role of multiple signal transduction pathways and secondary metabolic pathways comprised of SA-JA-ET in plant immunity. We also found that photosynthesis in JAM1-4 was inhibited to promote the immune response. Our study reveals the pattern of resistance-related gene expression in response to a super race strain of potato late blight and provides a theoretical basis for further exploration of potato disease resistance mechanisms, discovery of new late blight resistance genes, and disease resistance breeding.

Development of an express method for the quantitative assessment of the contamination of wheat flour with Bac. spores. subtilis

The causative agent of potato bread disease (Bacillus subtilis, ssp. Mesentericus) develops in the crumb of wheat bread. To prevent potato disease of bread, it is necessary to control raw materials and finished products in order to identify their microbiological contamination. Various methods can be used to determine the presence of bacteria that cause potato bread disease. These methods are usually subdivided into four groups: 1) bacteriological; 2) technological; 3) biochemical and 4) physical. Within the framework of all four groups of methods, there is no single method for analyzing the detection of pathogens of potato disease in bread, which would be easily reproduced in any laboratory and would have a correct assessment of the results.At the Department of Nutrition Technology of the Ural State University of Economics, an express method for the colorimetric determination of the contamination of wheat flour with Bac spores has been developed. subtilis by the content of erythrodextrins in it, which give a reddish-brown color when interacting with iodine solution. The advantages of the improved method for determining the potato disease of bread include: speed and rapidity; the possibility of both qualitative and quantitative determination of Bac. subtilis in flour to predict the occurrence of potato bread disease in wheat flour bread.