Abstract
Xanthomonas campestris pv. campestris (Xcc) causes the black rot of cruciferous plants. This seed-borne bacterium is considered as the most destructive disease to cruciferous crops. Although sources of contamination are various, seeds are the main source of transmission. Typical symptoms of black rot were first observed in 2011 on cabbage and cauliflower fields in the main production areas of Algeria. Leaf samples displaying typical symptoms were collected during 2011 to 2014, and 170 strains were isolated from 45 commercial fields. Xcc isolates were very homogeneous in morphological, physiological and biochemical characteristics similar to reference strains, and gave positive pathogenicity and molecular test results (multiplex PCR with specific primers). This is the first record of Xcc in Algeria. Genetic diversity within the isolates was assessed in comparison with strains isolated elsewhere. A multilocus sequence analysis based on two housekeeping genes (gyrB and rpoD) was carried out on 77 strains representative isolates. The isolates grouped into 20 haplotypes defined with 68 polymorphic sites. The phylogenetic tree obtained showed that Xcc is in two groups, and all Algerian strains clustered in group 1 in three subgroups. No relationships were detected between haplotypes and the origins of the seed lots, the varieties of host cabbage, the years of isolation and agroclimatic regions.
Highlights
Xanthomonas campestris pv. campestris (Xcc) isolates were very homogeneous in morphological, physiological and biochemical characteristics similar to reference strains, and gave positive pathogenicity and molecular test results. This is the first record of Xcc in Algeria
A multilocus sequence analysis based on two housekeeping genes was carried out on 77 strains representative isolates
The phylogenetic tree obtained showed that Xcc is in two groups, and all Algerian strains clustered in group 1 in three subgroups
Summary
Black rot caused by Xanthomonas campestris pv. campestris (Xcc), is the most widespread disease of cruciferous crops. Campestris (Xcc), is the most widespread disease of cruciferous crops. It was first reported in the United States of America in 1895 by Pammel (Swing and Civerolo, 1993), and. Several Brassica species can be infected (cabbage, cauliflower, kale, broccoli, turnip, radish and mustard). Many weeds can be infected by the bacterium, and these ensure the conservation of the pathogen throughout the year as inoculum sources (Schaad and White, 1974; Rat and Chauveau, 1985). Xcc is a seed-borne pathogen, this being the primary inoculum source (Cook et al, 1952; Schaad et al, 1980; Schultz and Gabrielson, 1986), but Xcc can survive for months in leaves and other plant debris in the soil
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