Apricot yellows associated with ‘Candidatus Phytoplasma phoenicium’ in Iran

Almond witches\u2019 broom associated with \u2018Candidatus Phytoplasma phoenicium\u2019 is an economically important disease of almond in Iran and Lebanon. During surveys of almond witches\u2019 broom in 2012\u20132015, an apricot yellows disease was observed in Fars Province of Iran. The characteristic symptoms of the disease were leaf yellowing, inward leaf curl, scorch of leaf margins, shortened internodes, production of rosettes at the tips of the branches, and decline, stunting, and death of affected trees. Healthy bitter almond and apricot seedlings, grafted with shoots from symptomatic trees, exhibited phytoplasma-type symptoms. A 16S rDNA fragment of 1,250 bp was amplified by nested-PCR from affected trees and grafted seedlings. Nucleotide sequence identity, presence of species-specific signature sequences, and phylogenetic analysis of 16S rDNA allowed the assignation of the phytoplasma strains identified to the \u2018Ca. P. phoenicium\u2019. In vitro and in silico RFLP analyses of the amplified fragment allowed affiliation of the apricot yellows phytoplasma to a molecular variant in the subgroup 16SrIX-B. Within the population strains identified in this and previous studies, 16 genetic lineages were determined within 16S rDNA nucleotide sequences by the combination of 19 single nucleotide polymorphisms. The apricot yellows phytoplasma strains belong to a unique genetic lineage distinguished by the presence of three lineage-specific SNPs. This first report of \u2018Ca. P. phoenicium\u2019 in association with apricot yellows in Iran opens new perspectives on the epidemiology of almond witches\u2019 broom, suggesting possible adaptation of the phytoplasma to other fruit tree species

Apricot yellows disease associated with 'Candidatus Phytoplasma phoenicium' in Iran

Almond witches\u2019 broom (AlmWB) associated with 'Candidatus Phytoplasma phoenicium' is one of the economically important diseases of almond in Iran and Lebanon. In 2012-2015 surveys of AlmWB, apricot yellows (AprY) disease was observed in Fars province of Iran. The characteristic symptoms of the disease were leaf yellowing, inward leaf curl, scorch of leaf margins, shortened internodes, production of rosettes at the tip of branches, decline, stunting, and death. Healthy bitter almond and apricot seedlings, grafted with shoots of AprY-affected trees, exhibited phytoplasma-type symptoms. The 16S rDNA fragment F2n/R2 was amplified by nested-PCR from both AprY-affected trees and grafted seedlings. Nucleotide sequence identity, presence of species-specific signature sequences, and phylogenetic analysis of 16S rDNA allowed the assignation of detected phytoplasma strains to the species 'Ca. P. phoenicium'. In vitro and in silico RFLP analysis of the fragment F2n/R2 allowed the affiliation of AprY phytoplasma to a variant of subgroup 16SrIX-B. Within 'Ca. P. phoenicium' (16SrIX-B) population strains, identified in this and previous studies, 16 genetic lineages were determined by the combination of 19 single nucleotide polymorphisms (SNPs) identified within 16S rDNA nucleotide sequences. Interestingly, AprY phytoplasma strains belong to a unique genetic lineage distinguished by the presence of three lineage-specific SNPs. This first report of 'Ca. P. phoenicium' in association with AprY disease in Iran opens new perspectives on the epidemiology of AlmWB phytoplasma, suggesting its possible adaptation to other fruit tree

Diversity of phytoplasmas associated with Almond Witches’-Broom disease in the Middle East

Almond witches\u2019-broom (AlmWB) is a phytoplasma disease devastating almond production in Lebanon and Iran. Here, 34 leaf samples were collected from symptomatic almond trees in Iran and assayed for phytoplasma detection and characterization. Based on 16S rRNA gene sequence analyses, \u2018Candidatus Phytoplasma phoenicium\u2019 (subgroup 16SrIX-B) and \u2018Ca. P. solani\u2019 (16SrXII-A) were identified. Comparison with NCBI GenBank revealed that Iranian and Lebanese \u2018Ca. P. phoenicium\u2019 strain populations were genetically homogeneous

Genetic diversity of ‘Candidatus Phytoplasma phoenicium’ strain populations associated with almond witches’ broom in Lebanon and Iran

Candidatus Phytoplasma phoenicium\u2019 (subgroup 16SrIX-B) strains associated with almond witches\u2019 broom disease in Lebanon and Iran were typed by PCR-based amplification and sequence analyses of rplV-rpsC and secY genes. Results showed that Iranian and Lebanese AlmWB-associated phytoplasma strain populations constitute at least two distinct genetic lineages, supporting previous evidence obtained through 16S rDNA analysis. Such genetic diversity reflects differences in biological features (i.e. insect vectors and plant hosts) of \u2018Ca. P. phoenicium\u2019 in Lebanon and Iran. Molecular markers identified within rplVrpsC and secY genes should be employed to improve the knowledge about \u2018Ca. P. phoenicium\u2019 ecology and almond witches\u2019 broom epidemiology in the Middle East