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

Abstract

Papaya is an important fruit crop cultivated in tropical and subtropical regions. Papaya little leaf (PLL) disease was observed in China. The phytoplasma 16S rRNA gene was detected from symptomatic papaya trees via PCR using phytoplasma universal primers P1/P7 followed by R16F2n/R16R2. No amplification products were obtained from templates of asymptomatic papaya trees. These results indicated a direct association between phytoplasma infection and PLL disease. Comparative and phylogenetic analyses of 16S rRNA gene sequences indicated that the papaya-infecting phytoplasmas under study belonged to the peanut witches' broom phytoplasma group (16SrII). Genotyping through use of computer-simulated RFLP analysis of 16S rRNA genes and coefficients of RFLP pattern similarities (0.97) reveal that the PLL phytoplasma was placed in a new subgroup. In this article, we describe the molecular characterization of a new phytoplasma associated with PLL disease and propose that the PLL phytoplasma be considered as a novel subgroup, 16SrII-U.

Multilocus sequence analysis of phytoplasma strains of 16SrII group in Iran and their comparison with related strains

“…Among 23 subgroups described within the phytoplasma group 16SrII, the natural occurrence of 21 subgroups (except for subgroups 16SrII‐C and II‐D), is reported from narrow geographical and host ranges (Al‐Subhi et al, ; Yang et al, , ). For example, phytoplasma strains of seven 16SrII subgroups (16SrII‐F to II‐L) have only been recognised in cactus plants in China.…”

“…In this study, we applied MLSA to assess the genetic divergence among the representative phytoplasmas within the group 16SrII reported from Iran and other countries. As the phytoplasma strains of subgroups 16SrII‐F to II‐W were phylogenetically close to phytoplasmas of 16SrII‐A, II‐B, II‐C and II‐D (Al‐Subhi et al, ; Cai et al, ; Yang et al, , ), it is likely that the subgroups 16SrII‐A to 16SrII‐E are the main and core subgroups within the group 16SrII.…”

“…Using virtual and actual restriction fragment length polymorphisms (RFLP) analysis of 16S rRNA gene, phytoplasmas have been classified into 32 16Sr RFLP groups (Lee, Gundersen‐Rindal, Davis, & Bartoszyk, ; Lee, Hammond, Davis, & Gundersen, ; Nejat et al, ). Of these, the 16SrII related phytoplasmas have a diverse ecology, as they have been identified in association with diseases in various cultivated plants widespread in different geographical areas (Cai, Wei, Davis, Chen, & Zhao, ; Yang, Jiang, Che, Cao, & Luo, ). By virtue of their vast distribution, Asia is believed to be the geographical origin of these phytoplasmas (Cai et al, ).…”

“…In Iran, for example, phytoplasmas of 16SrII have been characterised in association with diseases in numerous plant species, but despite their importance, they have been poorly characterised at the molecular, biological and ecological levels. By RFLP analysis of 16S rRNA gene sequences, the phytoplasma strains of group 16SrII have been classified into 23 subgroups (Al‐Subhi, Hogenhout, Al‐Yahyai, & Al‐Sadi, ; Yang et al, , ). Until sufficient molecular and ecological evidence is obtained, all phytoplasmas belonging to this group are considered as relatives of “ Ca .…”

Classification of a new phytoplasmas subgroup 16SrII-W associated with Crotalaria witches’ broom diseases in Oman based on multigene sequence analysis

“…Above all, the phytoplasma associated with Crotalaria witches’ broom in Oman seemed to be distinguishable from all the other phytoplasmas belonging to Peanut WB group (16SrII). The 16SrII group has 21 subgroups including 16SrII-A, −B, −C, −D, −E, and –F [ 66 ] therefore, we propose to assign the Crotalaria witches’ broom from Oman in a new lineage 16SrII-W subgroup. The Orosius sp.…”