Distribution and characterization of sugar cane yellows phytoplasma in Mauritius

摘要

To better understand the nature of recent outbreaks of yellow leaf syndrome (YLS) of sugar cane in Mauritius, a study was carried out to assess the distribution and genetic diversity of Sugar cane yellows phytoplasma (SCYP) one of the pathogens associated with the disease. A total of 150 varieties with or without YLS symptoms obtained from quarantine, a variety collection plot and commercial fields were examined. A 1.25 kb DNA fragment encoding for the phytoplasma 16S rRNA operon was amplified by nested-PCR in 85 (57 percent) varieties, showing the wide distribution of SCYP in Mauritius. Restriction fragment length polymorphism analysis of the amplified PCR products after digestion with Rsal and comparison with five specific phytoplasma groups revealed the existence of three groups of the pathogen amongst the isolates tested as well as the occurrence of a mixed group. Cloning of the PCR products of three samples followed by RFLP analysis demonstrated that two strains of the phytoplasma or the existence of two 16S rRNA operons within the same phytoplasma could occur within the same plant. In addition to base substitution, DNA sequencing showed variation in size of the different fragments sequenced.