Evidence of 16SrXI group phytoplasma DNA in embryos of root wilt diseased coconut palms

The root wilt disease (RWD) is a major phytoplasma disease of coconut palms in South India. Phytoplasma belonging to the 16SrXI group has been associated with the disease. In our earlier studies we detected phytoplasma from leaves, inflorescence and roots of symptomatic palms in the nested PCR. In this work we examined the embryo from diseased palms for the presence of phytoplasma through semi-nested PCR assay with primers 1F7/7R3 - 1F7/7R2 specific for phytoplasma 16S rRNA gene. Out of 270 embryos collected in four rounds of sampling from two different locations, positive amplification was obtained for 45 (16.67 %) embryos. Sequencing and blastn analysis confirmed the presence of coconut root wilt phytoplasma. To check the potential seed transmission of phytoplasma, mature nuts from diseased palms were germinated in poly bags under disease free conditions and seedlings were sampled for DNA isolation and nested PCR analysis. But phytoplasma DNA could not be detected in any of the seedlings raised in poly bags.