Extraction of high quality DNA from polysaccharides-secreting xanthomonads

A DNA extraction method using CTAB was used for the isolation of genomic DNA from ten Xanthomonas  campestris pathovars, ten isolates of Xanthomonas albilineans and one isolate of Pseudomonas  rubrisubalbicans. High quality DNA was obtained that was ideal for molecular analyses. Extracellular polysaccharides were effectively removed thus resulting in DNA that dissolved easily and was well digested by restriction enzymes. All of the other methods tested resulted in the coprecipitation of the polysaccharides together with the nucleic acids upon addition of alcohol so that even high yields could not compensate for this contamination. DNA obtained by the CTAB method was used for cloning, Southern hybridizations and PCR for up to three years after the extraction.Keywords: Polysaccharides, CTAB, polymerase chain reaction, DNA

DETECTION AND CHARACTERISATION OF SUGARCANE YELLOWS PHYTOPLASMA

Abstract A study was carried out to assess the distribution and association of sugarcane yellows phytoplasma-ScYP in sugarcane affected by yellow leaf syndrome (YLS) in Mauritius. The polymerase chain reaction was used to detect and characterise the phytoplasma. Samples were collected from clones undergoing quarantine, in a variety collection plot, in mature commercial fields and from 6 month old commercial fields. A 1.25 kb DNA fragment encoding for the phytoplasma 16s rRNA was consistently amplified by nested-PCR. Of the 204 samples with and without symptoms derived from 166 varieties, 95 (57%) tested positive for ScYP by PCR. Restriction fragment length polymorphism analysis of the phytoplasma 16s rDNA amplified product indicated that 3 phytoplasma groups are present in sugarcane in Mauritius. The results indicated that detection of YLS based on symptoms only is not reliable, since many asymptomatic varieties were positive for the phytoplasma early in the growing season

CONTRIBUTION OF MICROSATELLITES TO SUGAR CANE BREEDING PROGRAM IN MAURITIUS

Abstract Sugar cane microsatellite libraries have recently been developed. Here, we report the efficiency of some rnicrosatellite primers to generate polymorphic and easily scorable markers in sugar cane. Primers selected proved to be very efficient when applied to test for legitimacy of clones, to identify contaminants in nurseries and for diversity studies. We also investigated the amplification of microsatellite primers on DNA extracted using an alkaline treatment method, and this technique looks promising