ABSTRACT
Phytoplasmas that are associated with fruit crops, vegetables, cereal and oilseed crops, trees, ornamental, and weeds are increasing at an alarming rate in the Middle East. Up to now, fourteen 16Sr groups of phytoplasma have been identified in association with more than 164 plant species in this region. Peanut witches' broom phytoplasma strains (16SrII) are the prevalent group, especially in the south of Iran and Gulf states, and have been found to be associated with 81 host plant species. In addition, phytoplasmas belonging to the 16SrVI, 16SrIX, and 16SrXII groups have been frequently reported from a wide range of crops. On the other hand, phytoplasmas belonging to 16SrIV, 16SrV, 16SrX, 16SrXI, 16SrXIV, and 16SrXXIX groups have limited geographical distribution and host range. Twenty-two insect vectors have been reported as putative phytoplasma vectors in the Middle East, of which Orosius albicinctus can transmit diverse phytoplasma strains. Almond witches' broom, tomato big bud, lime witches' broom, and alfalfa witches' broom are known as the most destructive diseases. The review summarizes phytoplasma diseases in the Middle East, with specific emphasis on the occurrence, host range, and transmission of the most common phytoplasma groups.
ABSTRACT
Cacti are evergreen perennial succulent plants that are used as ornamental and hedge plants. The fruits and leaves are also used as forage in some areas (Dewir, 2016). Cactus species are susceptible to several pathogens, including phytoplasma. In March 2020, three cactus plants (Opuntia cylindrica) out of ten (30% incidence) exhibited phytoplasma symptoms, including stunted growth, fasciation in stems and cladodes, color changes of the tips of cladodes to purple, and having clusters of highly proliferating cladodes. The plants were located in the Botanic Garden at Sultan Qaboos University, Muscat, Oman (N:23º59'14"; E:58º16'34"). PCR assays were carried out on the DNA samples extracted from young cladodes of three each of symptomatic and asymptomatic plants using phytoplasma-universal 16S rRNA primers, P1/P7 in direct PCR followed by R16F2n/R16R2, P4/P7 in the nested PCR. Distilled water (DW) and Alfalfa witches' broom phytoplasma (AlfWB) were used as negative and positive controls in each assay, respectively. In addition, amplification of the partial translocase protein A (secA) gene in the symptomatic cactus samples was done using SecA-II-F1/SecA-II-R1 (targeting 2140 bp) followed by SecA-II-F1/SecAR4 (targeting 1510 bp) (Al-Subhi et al., 2018). All the symptomatic plants and the positive control were positive for both genes (16S and secA), but no amplification was observed from the asymptomatic samples and DW. Sequence analysis and similarity searches against BLASTn revealed that the phytoplasma 16S rRNA (MT327813) shared 100% sequence identity with that of 'Candidatus Phytoplasma aurantifolia' isolate CB04 (MT555412) from India. The secA gene sequence (MT331815) analysis showed 100% identity with Cicer arietinum phyllody (KX358585). The associated phytoplasma was designated as cactus fasciated phytoplasma (CFP). Phylogenetic trees based on CFP 16Sr rRNA,secA genes, and a combined phylogenetic tree showed clustering of the CFP with the 16SrII-D subgroup phytoplasmas. The association of the aster yellows and peanut witches'-broom phytoplasma groups with other cactus species has already been reported from Lebanon, Mexico, China, Italy and Egypt (Dewir, 2016). The 16SrII phytoplasma in association with O. cylindrica showing fasciated stem has been reported from Egypt (Omar et al., 2014). A series of diverse plant species in association with 16SrII-D phytoplasma has been reported from Oman (Al-Subhi et al., 2018). However, this is the first report of a cactus phytoplasma disease in Oman belonging to the 16SrII-D subgroup phytoplasmas. Some fasciated cactus species are attractive and therefore cultivated as new ornamental plants and transported around the world, which may pose a new threat to other economically important crops.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
To find out the potential condition for diapause induction in the potato tuber moth Phthorimaea operculella (Zeller), combination of constant temperatures (15, 20, and 30°C) and photoperiods (8, 9, 10, 11, 12, 14, and 16 h) were employed from egg to adult emergence. In addition, changes in the total phospholipid fatty acid content and cold tolerance of non-diapausing and diapausing pupae were examined. The critical daylength for diapause induction were 12.43 h at 20°C and lower temperatures that can induce in 50% of population. Moreover, the composition of total phospholipid fatty acids in the pupae revealed seven major fatty acids in both non-diapausing and diapausing pupae: oleic (26-32%), palmitic (21-29%), linoleic (18-21%), palmitoleic (4-10%), stearic (9%), linolenic (7-8%), and pentadecanoic acids (3-5%) with an increase in proportion of unsaturated fatty acids in diapause state. In contrast to increase of oleic acid (C18:1) from 26 to 32% in non-diapausing to diapausing pupae, a decrement trend from 29 to 21% in palmitic acid (C16:0) was observed at the same state. Additionally, supercooling point was observed to be significantly lower in diapausing (-22.6°C) than in non-diapausing pupae (-18.5°C) and the fresh weight of diapausing pupae was found to be significantly higher than non-diapausing ones. The significance of these findings would allow us a better understanding of interrelationship between diapause and cold tolerance.
