Abstract
Four isolates of the phytopathogenic bacterium <i>Xanthomonas albilineans (Xa)</i> from samples taken in commercial fields of different Cuban provinces and two from the cultivar L55-5, artificially infected in the Camagüey and Matanzas Experimental Stations, were used for the extraction of total nucleic acids according to the CTAB protocol. They were amplified by PCR using four primer combinations: A: P1-M1, B: P1-M2, C: P2-M1 and D: P2-M2. Direct sequencing of the PCR products was performed on all samples and the nucleotide sequences were used to generate partial consensus of 16-23S rRNA, which were analyzed with the BLASTn program. In all the isolates evaluated, the presence of a common band at the height of 620 bp was visualized and the AFLP profile showed that there is homology when comparing the sequences corresponding to the 16-23S rDNA of <i>X. albilineans</i> of the different isolates; the phylogenetic analysis reflected a grouping of the isolates of the species, regardless of its geographical origin, different from others of the genus <i>Xanthomonas</i>. The comparison of the Cuban isolates with eight strains published in GenBank, showed marked similarity with them, with 100% nucleotide identity and percentage of coverage with a genome fragment of the GPE PC73 strain from Guadalupe, KO905 from the United States and a strain from Brazil. The predominance of the generalized circulation in Cuba of a single serovar is presumed.
Highlights
Leaf scald disease, caused by Xanthomonas albilineans (Ashby) Dowson, is a lethal disease of sugarcane
Molecular Detection and Studies of Genetic Variability The migration in 1% agarose gel of the amplified product with the primers FGPS1450 and FGPS132 of the four isolates evaluated allowed to visualize the presence of a common band at the height of 620 bp, all corresponding to the expected size, while the control did not originate signals amplification, a result that confirms the identity of the isolates as X. albilineans in the sampled areas (Figure 1)
The amplified fragment length polymorphism (AFLP) analysis (Figure 2) made it possible to compare a small fragment of the genome of an isolate from Jovellanos (Matanzas) and another from Florida (Camagüey); the sequences corresponding to the 16-23S rDNA of X. albilineans showed that there is homology between both isolates
Summary
Leaf scald disease, caused by Xanthomonas albilineans (Ashby) Dowson, is a lethal disease of sugarcane. The bacterium colonizes stems and leaves, mobilizes systemically within plant tissues and manifests itself differently, with symptoms that frequently vary between cultivars, times of the year and localities, a condition that is attributed to environmental influences or pathogenic variations [12, 19, 27]. In Cuba, safely assessing genetic resistance within the management strategy is crucial for the control of the disease, since resistance to leaf scald within the breeding process is considered as a selection criterion. The objective of this work lies in knowing the existence or not of different pathogenic variants of Xa and their influence on characterization of the resistance of cultivars as a measure to control the spread and effects of the disease
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