Histological and chemical Susceptibility of some Potato cultivars Infected with new Strains of Pectobacterium carotovorum

Abstract

The potential losses of potato yield due to soft rot disease caused by Pectobacterium carotovorum constitute a major threat to this crop, as the pathogen adapts to environmental and nutritional changes resulting in genetic patterns that are more virulent in infection of plant tissue. Therefore, the current study aimed to determine the tissue and chemical sensitivity of some potato varieties infected with this bacteria. Results confirmed that the bacterial isolates belong to P. carotovorum according to diagnostic keys, microscopic and morphological examinations that indicated the bacteria is Gram-negative grew on the differential medium Yeast extract-dextrose-CaCO3 (YDC) as a yellow to cream colonies, convex, shiny, and circular. While on the D-3 agar medium, the colonies were white to cream, and on the Nutrient Agar medium (NA) was cream to shiny white. The outcomes of the biochemical tests indicated that P. carotovorum isolates gave positive results for some tests including Catalase and Hydrolysis of Gelatin. Other tests such as Oxidase, Starch hydrolysis, voges-proskauer, phynelalanen, and methyl red were negative. The isolates were molecularly diagnosed based on the 16 S rRNA gene, as new strains were obtained for the first time in the Iraq, which were deposited in GenBank (NCBI) under the accession numbers PP824981, PP824982, and PP824983. The highest percentage of infection and severity with the disease were recorded in Elmundo variety, which reached 42.10 and 22.14%, respectively. The results of the sensitivity test of some potato varieties to P. carotovorum showed that the highest rotted tissue was in Elmundo variety, which reached 4.98cm, compared to the control which reached 0.00cm. Based on the percentage of carbohydrates, protein and fats, Burren variety outperformed other studied varieties significantly reaching 8.44%, 1.17 mg/g and 0.15 mg/g, respectively, compared to the control treatment which reached 16.81%, 3.92 mg/g and 1.81 mg/g, respectively. While for phenols, flavonoids, nitrates and organic acids, Volare variety outperformed the other varieties, reaching 6.67 mg/g, 1.61 mg/g, 0.21% and 0.10%, respectively, compared to the control which reached 18.31 mg/g, 3.24 mg/g, 0.27% and 0.22%, respectively.