Occurrence, genetic diversity and pathogenicity characteristics of Pseudomonas viridiflava inducing alfalfa bacterial wilt and crown root rot disease in Iran

Abstract

Alfalfa (Medicago sativa), the world’s most influential forage crop, is infected by many diseases such as alfalfa bacterial wilt disease. The causal agent of bacterial crown and root rot and wilt disease is Pseudomonas viridiflava, which is a substantial pathogen of alfalfa worldwide. This pathogen spreads through the xylem and under field conditions, plants show growth stunting, chlorosis and wilting symptoms not previously reported. In this study- the first on Pseudomonas viridiflava on alfalfa from Iran, we have investigated the pathogenicity and genetic diversity of Pseudomonas viridiflava in some parts of Iran. To survey the causal agent of the disease, symptomatic plants were collected from the main alfalfa growing area. Pathogenicity of the collected strains was confirmed on alfalfa plants under green-house conditions using a completely randomized design. Determination of bacterial strains was done based on standard bacteriological methods and PCR assay using specific primers. Effects of bacterial strains on wet weight, dry weight, stem length and root length of infected plants were measured and the data were analyzed by SAS software and Duncan’s assessment. The diversity of liquid cellular proteins of bacterial strains was examined on Polyacrylamide gel. To delineate of genetic diversity the total DNA was drawn out. Fourteen random primers were used in a RAPD test. To sketch the dendrogram, RAPD fragments were used to calculate genetic diversity with NTSYS software. This data showed pathogenicity and genetic diversity of Pseudomonas viridiflava in Iran.