New horizons in the Biodiversity of Ralastonia solanacearum Associated with Tomato through Biochemical and Molecular Analysis

Abstract

Current study aimed to detect the spread of new strains of bacterial wilt disease on tomato in Iraq particularly some areas of Najaf province for the agricultural season 2024. Results of the pathogenicity test of Ralastonia solanacearum on tomato for the 22 studied isolates showed that the two isolates, R. solanacearum 1 and R. solanacearum 4, outperformed the other isolates in the severity of the disease and reached 46.67% and 42.74% respectively. Based on the diagnostic keys, the results confirmed that the bacterial isolates belong to R. solanacearum. Results of microscopic and morphological examination indicated that the bacteria were Gram-negative, rod-shaped, and had the appearance of white colonies with red centers on the (TZC) medium, while in the SPA medium, transparent colonies appeared. Biochemical tests also indicated that R. solanacearum gave positive results for some tests, including Catalase test, Oxidase test, and Pectolytic test. The tests that gave negative results included KOH, Livan, Hydrolysis of Gelatein, Arginine, Starch Hydrolysis, Aesculin Hydrolysis, and Indol test. Biovar test results showed that it was from Race 3, which infects the Solanaceae family, including tomatoes. The molecular diagnosis, which was based on the 16 SrRNA gene, showed that new strains were obtained for the first time and were registered in (NCBI) with the accession numbers (PP473560 and PP473561).