Characteristics of the strain VNIIKR-B-0035 Erwinia rhapontici isolated from common barley (Hordeum vulgare L.)

Erwinia rhapontici (Millard 1924) Burkholder 1948 is a phytopathogenic bacterium that causes pink grain of cereals and legumes, as well as various types of rot and other symptoms in a wide range of valuable agricultural plants, and to fully understand the pathogenic potential of this bacterium, it is necessary to study in detail as many strains as possible. The aim of this work is to create a comprehensive characterization of the bacterial strain VNIIKR-B-0035 E. rhapontici, isolated from common winter barley (Hordeum vulgare L.), origin – Republic of Crimea. The paper presents its morphology studied using cell microscopy, as well as photographs of bacterial colonies cultured on R2A nutrient medium. The cells of this strain are rod-shaped, measuring 0.8–1.5 μm long and 0.2–0.4 μm wide. Bacterial colonies of strain VNIIKR-B-0035 on R2A medium are whitish, slimy, and uniform. They have a round, convex shape, a smooth, shiny surface, and are opaque. They do not produce water-soluble pigments. Biochemical characteristics were studied using the API 20E kit for the identification of Enterobacteriaceae and physiologically similar bacteria (Biomerieux, France). Bacteria of this strain are capable of fermenting many types of sugars, reduce nitrites, do not produce arginine dihydrolase, lysine decarboxylase, ornithine decarboxylase, urease, indole, acetoin, gelatinase and H2S, and are also unable to utilize citrates. Molecular genetic characterization was conducted using four PCR tests for various genes specific to this phytopathogenic bacterium. Strain VNIIKR-B-0035 was identified using PCR tests with primers TSU01/TSU02, ERH-1A/ERH-1B, and isoRF/isoRR, as well as by sequencing a portion of the rpoD gene. This is the first molecular genetic identification of E. rhapontici in Russia. This study confirmed that common barley (Hordeum vulgare L.) can serve as a source of E. rhapontici isolation.

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