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Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), is an important and threatening disease for the citru s industry in southeast Iran. In the present study, seasonal dynamic monitoring of CLas was conducted by absolute real-time PCR. Plant materials were obtained across 7 and 6 months from December 2014 to October 2015 from three parts of the canopy of two naturally infected citrus species, Mexican lime (Citrus aurantifolia) and sweet orange (C. sinensis) located in two distinct geographical regions, Sistan-o-Baluchestan and Kerman provinces, respectively. Results showed significant variation (α = 0.001) in the bacterial titers in both infected hosts. These notable changes have also been observed in all tree’s canopy parts and a particular part of tree canopy during sampling months, exhibited by sudden changes in bacterial titers. It was also found that in both locations maximum titers of HLB occurred in summer. The data obtained by correlation assessment suggests a significant relationship between temperature and pathogen population variations that probably in warmer months correlated with the sap flow rate changes in the host, the bacterial titer was increased. In this study, no consistent pattern of the disease agent distribution was found between two different plant hosts. The results of this research on the quantification of CLas in the host plant can be a great help in making proper decisions for disease management by providing the possibility of early detection and rapid removal of inoculum sources.

Sweet orange (Citrus sinensis) and Orlando tangelo (C. paradisi × C. reticulata) trees showing witches’-broom symptoms were observed during 2018 in southern Kerman province, Iran. Detection of phytoplasmas in the symptomatic trees was confirmed by nested PCR assays using the phytoplasma specific primers. Sequence analysis indicated that the phytoplasmas associated with the witches’-broom affected trees belong to the 16SrII-C subgroup phytoplasma. This is the first report of a 16SrII-C phytoplasma associated with witches’-broom symptoms of Sweet orange and Orlando tangelo trees in the world.

Citrus Decline Disease was recently reported to affect several citrus species in Iran when grafted on a local rootstock variety, Bakraee. Preliminary studies found “Candidatus Phytoplasma aurantifoliae” and “Candidatus Liberibacter asiaticus” as putative etiological agents, but were not ultimately able to determine which one, or if an association of both, were causing the disease. The current study has the aim of characterizing the microbiota of citrus plants that are either asymptomatic, showing early symptoms, or showing late symptoms through amplification of the V1–V3 region of 16S rRNA gene using an Illumina sequencer in order to (i) clarify the etiology of the disease, and (ii) describe the microbiota associated to different symptom stages. Our results suggest that liberibacter may be the main pathogen causing Citrus Decline Disease, but cannot rule out the possibility of phytoplasma being involved as well. The characterization of microbiota shows that the leaves show only two kinds of communities, either symptomatic or asymptomatic, while roots show clear distinction between early and late symptoms. These results could lead to the identification of bacteria that are related to successful plant defense response and, therefore, to immunity to the Citrus Decline Disease.

The lebbek tree, Albizia lebbeck, family Fabaceae is a deciduous, perennial tree mainly distributed in tropical and subtropical areas of the world. Lebbek is widely used as a shade tree on the margin of agricultural fields and urban parks …

Phylogenic relationships and genetic diversity in citrus are considered to be important in clarifying their genetic relationships, germplasm characterization and the registration of new varieties. The ‘Bakraee’ ( Citrus sp.) is an unknown natural biotype which is being used widely as rootstock as well as edible fruit in some regions of Iran. In the present research work, phylogenic relationships among ‘Bakraee’ and some commercially important citrus varieties were investigated through SSR and PCR-RFLP molecular markers. Two UPGMA dendrograms were generated using SSR and PCR-RFLP data. SSR data showed 0.87 and 0.65 genetic similarities between ‘Bakraee’ and rough lemon ( Citrus jambhiri Lush.) and sweet lime ( Citrus limettioides Tan.), respectively. PCR-RFLP analysis demonstrated that all of the amplified fragments in ‘Bakraee’ are also present in rough lemon. Our study confirmed a close relationship between ‘Bakraee’ and rough lemon and support the possibility of rough lemon as maternal parent in the hybrid origin of ‘Bakraee’.

Phyllody disease associated with 16SrIX phytoplasma was observed in the range of 4.1–11% in 10 different lines of toria [Brassica rapa L. subsp. dichotoma (Roxb.)] in experimental fields of the Indian Agricultural Research Institute, New Delhi, India during 2008 and 2009. The toria phyllody (TP) phytoplasma was detected in all the symptomatic and 13.3% of asymptomatic toria plants by nested PCR. The phytoplasma was detected in midrib, flower part, siliquae, stem, and root of infected plants as well as seeds. TP was transmitted by grafting and by dodder to toria and nine other rapeseed/mustard species as confirmed by nested PCR. However, symptoms of phytoplasma infection were induced only in toria, yellow sarson [Brassicarapa L. subsp. trilocularis (Roxb.)], brown sarson [Brassicarapa L. subsp. sarson (Prain)], rapeseed (B. napus subsp. oleifera), and rocket or taramira (Eruca sativa) but not in mustard (B. juncea), black mustard (B. nigra), Ethiopian mustard (B. carinata), B. tournefortii and white mustard (Sinapis alba). Transmission of TP phytoplasma to periwinkle (Catharanthus roseus) was successful only through dodder, but no transmission to tomato (Lycopersicon esculentum) or brinjal (Solanum melongena) was found. TP phytoplasma was detected in Laodelpax striatellus, an abundant planthopper in toria fields, which indicates that this planthopper may be a potential vector for TP phytoplasma.

Samples from toria plants (Brassica rapa L. subsp. dichotoma (Roxb.)) exhibiting phyllody, virescence, witches broom, extensive malformation of floral parts, formation of bladder like siliquae and flower sterility were collected from four different locations in India. Sequencing and phylogenetic analysis of the 16S rRNA, a part of 23S rRNA, partial sec A genes, rp gene and 16S–23S intergenic spacer region indicated that the phytoplasmas associated with toria phyllody (TP) symptoms were identical and belonged to 16SrIX phytoplasma Pigeon pea witches’-broom (PPWB) group. The iPhyClassifier generated virtual RFLP pattern of 1.25 kb 16S rDNA sequences indicated that TP phytoplasma belongs to 16SrIX-C phytoplasma subgroup. Complete 23S rRNA gene of TP phytoplasma had 2,787 nucleotides and is the first sequence of 16SrIX phytoplasma group. Restriction digestion of 16S rDNA and 23S rDNA PCR products has also shown that TP phytoplasmas from all the four locations in India were identical. Toria is a previously unreported host for a phytoplasma in16SrIX-C subgroup.

Brinjal little leaf is a phytoplasmas-associated disease widespread in India that induces severe economic losses in the crop. In this study phytoplasmas infecting brinjal plants in New Delhi, India were characterized by RFLP analysis and DNA sequencing of 16S rRNA, ribosomal protein rpl22, secA and 23S rRNA genes. Collective actual and virtual RFLP patterns, sequence analysis and sequence based phylogenetic analysis of the studied loci showed that the phytoplasma associated with brinjal little leaf disease in New Delhi, India is a member of 16SrVI-D subgroup. PCR amplification and sequencing of 16S rRNA of phytoplasma from Hishimonus phycitis confirmed that the phytoplasma in vector is molecularly indistinguishable from the one in the host plant.