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Artemisia sieberi showing symptoms resembling those caused by phytoplasma were observed in Geno Mountain, Hormozgan Province, Iran, and were examined for phytoplasma presence by PCR assays. In addition, the essential oils hydrodistilled from the aerial parts of phytoplasma-infected and healthy plants have been analyzed and compared by GC and GC/MS. Phylogenetic and virtual RFLP analysis of the 16S rRNA gene sequences revealed that the phytoplasma associated with A. sieberi witches' broom (AsWB) was a strain of 'Candidatus Phytoplasma aurantifolia'. The presence of the disease, however, induced a further enrichment (from 4.9 to 45.2%, a relative increase of 90%) of the entire monoterpene class as compared to the abundance in healthy samples. Conversely, a matching decrease in monoterpenoid (from 48.7 to 2%, a relative decrease of 90.2%) was observed in the infected plants. Besides the first report of phytoplasma infection of A. sieberi, the changes of its essential oils are reported.

Phytoplasmas, prokaryotic wall-less microorganisms, are important pathogens of several plant species in most parts of the world. Phytoplasmas have been reported associated with various symptoms on hundreds of plant species. Witches’ broom disease (WBD) is one of the most common disease symptoms, which is caused by phytoplasma strains belonging to different phytoplasma groups. Symptoms of the disease differ from one host to the other as well as from one phytoplasma strain to the other. However, WBD symptoms are usually characterized by the production of a large number of small leaves, accompanied in some host plants by the production of several branches/shoots. Phytoplasma strains belonging to more than 13 groups and 39 subgroups have been reported associated with WBD in more than 116 plant species. Most of the phytoplasma strains causing WBD symptoms in plant species belong to the 16SrII and 16SrI groups, mainly 16SrII-D and 16SrI-B subgroups. The current review provides information on the different types of phytoplasma strains associated with WBD symptoms in ornamental plants, medicinal plants, forest trees, weeds, vegetable crops, field crops, and fruit trees. Emphasis is on WBD on acid limes, almonds, peanuts, jujube, and cassava that have resulted in significant economic losses in different countries. Description of the symptoms, phytoplasma groups, and management options is also provided for some of the diseases.

In 2017 growing season numerous examinations of Cosmos bipinnatus in Hormozgan province, Iran revealed the disease symptoms similar to those associated with phytoplasmas. Phytoplasmas were detected from all symptomatic plants by the specific polymerase chain reaction (PCR) utilizing phytoplasma universal primer pairs. Amplification, sequencing and blast analysis of 16S rDNA fragment (ca. 1.2 kb) demonstrated that C. bipinnatus plants were infected by a phytoplasma belonging to the 16SrII group. This is the first report of association of a ‘Candidatus Phytoplasma aurantifolia’-related strain with C. bipinnatus phyllody in Iran.

Aerva javanica plants showing symptoms of witches’ broom, little leaf, and leaf roll were observed in 50% of the A. javanica plants grown in the deserts of Hormozgan province, Iran. This study was carried out to verify possible phytoplasma association with this disease, insect vector, and modification of the chemical composition of symptomatic A. javanica. Aerial parts were collected at the full flowering stage from symptomatic and asymptomatic plants and samples were examined for phytoplasma presence by nested-PCR assays. PCR and sequencing analysis showed that a phytoplasma was associated with the disease sharing 99% sequence identity with ‘Candidatus Phytoplasma aurantifolia’-related strains (16SrII). Furthermore, this phytoplasma was transmitted to healthy periwinkle plants under experimental conditions by the leafhopper Austroagallia sinuata that was then demonstrated to be a vector of this phytoplasma. Analysis of the oils carried out by GC–MS revealed the enrichment of the triterpene hydrocarbons (2.3% in asymptomatic vs. 11.8% in symptomatic samples) and the hydrocarbons (69.3% vs. 85.93%) as compared to the abundance in asymptomatic samples. Conversely, a matching decrease in ketone (3.51% vs. 0.6%) was observed in the symptomatic plants. These results indicate that phytoplasma presence is influencing the secondary metabolites production in infected plants.

Taverniera cuneifolia plants showing shoots proliferation and witches' broom symptoms were observed in Minab, Iran. A study was performed to detect and identify the possible phytoplasma associated with the disease, identify the putative insect vector and possible modification in fatty acid composition of symptomatic plant roots. Sequence analysis revealed that the associated phytoplasma shared 99.92% sequence identity with ‘Candidatus Phytoplasma australasia'-related strains. Successful transmission of phytoplasma by Orosius albicinctus to healthy periwinkle demonstrated its putative vector status. Moreover, analysis of the oil composition of the plant roots revealed an increased rate of fatty acid composition in the infected plants.

Hishimonus phycitis is one of the main insect vectors of phytoplasmas, in particular of ‘Candidatus Phytoplasma aurantifolia’-related strains associated with witches' broom disease in many crops. A study was conducted to investigate the relationship between H. phycitis infection by phytoplasmas and some of its biological parameters. H. phycitis harboring phytoplasmas resulted in more fecundity (higher number of offspring produced) and higher nymph developmental rate compared to uninfected insects. The finite rate of population increase (λ) and net reproductive rate (R0) were higher in phytoplasma-infected H. phycitis indicating that the overall fitness of the infected population was improved. The survival of phytoplasma-infected female was lower compared with infected male, which suggest that they may be a fitness trade-off in response to phytoplasma infection. A beneficial effect of a plant pathogen on vector fitness may indicate that the pathogen developed a relationship with the insect first, then moving to the plant secondarily. Taken together, our findings suggest that elimination of the infected trees (as a source of inoculum) should be a relevant part of the lime witches' broom disease management.

Samples of Cota tinctoria with phytoplasma symptoms including witches’ broom, stunting, twisting of the shoots and little leaf were observed in Bandar Abbas, Iran, in 2017. Phylogenetic analysis revealed that the phytoplasma associated with Cota tinctoria witches’ broom (CtWB) is a strain of ‘Candidatus Phytoplasma trifolii’. Furthermore, the phytoplasma was successfully detected in the leafhopper, Orosius albicinctus collected from the symptom-bearing plants. This work therefore reports a new phytoplasma-associated disease on Cota tinctoria and its putative insect vector.

The fitness of Plutella xylostella L. on different genetically manipulated Brassica plants, including canola's progenitor (Brassica rapa L.), two cultivated canola cultivars (Opera and RGS003), one hybrid (Hyula401), one gamma-ray mutant-RGS003, and one transgenic (PF) genotype was compared using two-sex and female-based life table parameters. All experiments were conducted in a growth chamber at 25±1°C, 65±5% relative humidity, and a photoperiod of 16:8 (L:D) h. There were significant differences in duration of different life stages of P. xylostella on different plant genotypes. The shortest (13.92 d) and longest (24.61 d) total developmental time were on Opera and PF, respectively. The intrinsic rate of increase of P. xylostella ranged between 0.236 (Opera) and 0.071 day(-1) (PF). The highest (60.79 offspring) and lowest (7.88 offspring) net reproductive rates were observed on Opera and PF, respectively. Comparison of intrinsic rate of increase, net reproductive rates, finite rate of increase, mean generation time, fecundity, and survivorship of P. xylostella on the plant genotypes suggested that this pest performed well on cultivars (RGS003 and Opera) and performed poorly on the other manipulated genotypes especially on mutant-RGS003 and PF. Glucosinolate levels were significantly higher in damaged plants than undamaged ones and the lowest and highest concentrations of glucosinolates were found in transgenic genotype and canola's progenitor, respectively. Interestingly, our results showed that performance and fitness of this pest was better on canola's progenitor and cultivated plants, which had high levels of glucosinolate.

Zinnia elegans plants showing symptoms of phyllody, virescence, witches’ broom, little leaf and yellowing were observed in Bandar Abbas, Hormozgan Province, Iran. Analysis showed that the phytoplasma shares a 99% sequence identity with “Candidatus Phytoplasma aurantifolia” and is a strain related to this species. To the authors’ knowledge, this is the first report of the occurrence of a 16SrII phytoplasma infecting Zinnia elegans flowers.