‘Candidatus Phytoplasma palmicola’, associated with a lethal yellowing-type disease of coconut (Cocos nucifera L.) in Mozambique

Abstract

In this study, the taxonomic position and group classification of the phytoplasma associated with a lethal yellowing-type disease (LYD) of coconut (Cocos nucifera L.) in Mozambique were addressed. Pairwise similarity values based on alignment of nearly full-length 16S rRNA gene sequences (1530 bp) revealed that the Mozambique coconut phytoplasma (LYDM) shared 100 % identity with a comparable sequence derived from a phytoplasma strain (LDN) responsible for Awka wilt disease of coconut in Nigeria, and shared 99.0–99.6 % identity with 16S rRNA gene sequences from strains associated with Cape St Paul wilt (CSPW) disease of coconut in Ghana and Côte d’Ivoire. Similarity scores further determined that the 16S rRNA gene of the LYDM phytoplasma shared <97.5 % sequence identity with all previously described members of ‘Candidatus Phytoplasma ’. The presence of unique regions in the 16S rRNA gene sequence distinguished the LYDM phytoplasma from all currently described members of ‘Candidatus Phytoplasma ’, justifying its recognition as the reference strain of a novel taxon, ‘Candidatus Phytoplasma palmicola’. Virtual RFLP profiles of the F2n/R2 portion (1251 bp) of the 16S rRNA gene and pattern similarity coefficients delineated coconut LYDM phytoplasma strains from Mozambique as novel members of established group 16SrXXII, subgroup A (16SrXXII-A). Similarity coefficients of 0.97 were obtained for comparisons between subgroup 16SrXXII-A strains and CSPW phytoplasmas from Ghana and Côte d’Ivoire. On this basis, the CSPW phytoplasma strains were designated members of a novel subgroup, 16SrXXII-B.

The underestimated diversity of phytoplasmas in Latin America

“…Mexico is one of the main producers of corn, tomatoes, coffee and avocados, and Brazil is one of the main producers of a wide variety of citrus crops, soybean and many other economically important crops (FAO, 2012). Latin America, like the rest of the world, has been affected by plant diseases caused by phytoplasmas, with a significant impact on the production of corn, coconut, papaya and strawberries (Nault, 1983;Acosta et al, 2011;Harrison et al, 2014;Fernández et al, 2015;Luis-Pantoja et al, 2015). Therefore, Latin America is an important area for the development and application of effective strategies for the detection, characterization and management of phytoplasmal diseases.…”

“…Phytoplasmas comprise a broad group of small, wall-less, insect-vectored bacteria that cause disease in a diverse array of economically important crops around the world (Lee et al, 2000;Harrison et al, 2014). In plants, phytoplasmas are located in the sieve elements of phloem tissue while, in insect vectors, mostly leafhoppers, they are detected at higher concentrations in the salivary glands (Hogenhout et al, 2008).…”

“…To date, 37 candidate species of 'Ca. Phytoplasma' have been formally described, and more than ten potentially novel species have been suggested based on the similarity of 16S rRNA-encoding gene sequences (IRPCM, 2004;Nejat et al, 2013;Harrison et al, 2014). Phylogenetic analysis of 16S rRNA-encoding gene sequences from reference strains of candidate species of 'Ca.…”

‘Candidatus Phytoplasma hispanicum’, a novel taxon associated with Mexican periwinkle virescence disease of Catharanthus roseus

“…Importantly, newly discovered plant diseases and diseases of previously unknown cause are increasingly being attributed to phytoplasmas (Zhao et al, 2014). The phytoplasmas have been classified into a series of groups and subgroups on the basis of RFLP patterns of 16S rRNA gene sequences (16S rDNA) (Lee et al, 1998;Wei et al, 2007;Zhao et al, 2010), and 38 'Candidatus Phytoplasma' species have been described and named on the basis of nucleotide sequence differences in 16S rDNA (Table 1) (Harrison et al, 2014;Šafarova et al, 2016;IRPCM, 2004). Additional phytoplasmas that warrant recognition as distinct 'Candidatus Phytoplasma' taxa have remained undescribed as such (Wei et al, 2007); one of these phytoplasmas is the Mexican periwinkle virescence (MPV) phytoplasma.…”

Identification of a novel subgroup 16SrII-U phytoplasma associated with papaya little leaf disease

“…To date, 37 'Candidatus (Ca.) Phytoplasma' species have been formally described based on 16S rRNA gene sequence phylogeny and/or biological/phytopathological characteristics (Firrao et al, 2004;Harrison et al, 2014). Based on their identification and classification by RFLP analysis of 16S rRNA gene sequences, 32 phytoplasma/16Sr groups and more than 100 subgroups have been identified (Lee et al, 1993(Lee et al, , 1998Nejat et al, 2013).…”