IRANIAN JOURNAL OF PLANT PATHOLOGY
Year:2018 | Volume:54 | Issue:2|Papers Count:7

Smut is the most important disease of sugarcane in Iran, and most of the plant growing areas in the world. The most effective method of disease management, is identification and cultivation of resistant varieties. The aim of this study was to investigate changes in the level of phenolic compounds in resistant and susceptible cultivars to disease and detection phenolic compounds resistance index, to accelerate the identification of resistant cultivars. Two cultivars NCO-310 and CP78-1628, susceptible and resistant to the disease were selected, and with apical meristem and lateral buds culture method, their seedlings with four leaves were produced. Seedlings were inoculated with a suspension of a mixture of two compatible mating type of pathogen. Stem of plants were sampled at 0-120 hour post-inoculation. Soluble and cell-wall binding phenolic acids were extracted from samples, and presence and concentration of phenolic acids p-coumaric, ferulic, p-hydroxybenzoic and syringic acids were detected and determined by high performance liquid chromatography (HPLC) method. Comparison the data obtained from HPLC device showed only titer of cell wall-bound phenolic acids ferulic and syringic showed enhancement, in the resistant cultivar, this reflects the role of these phenolic acids in the resistance reaction. Thus, these phenolic acids can be considered as an indicator of resistance, and in this way quickly identify resistant cultivars and management disease.

Turnip curly top virus (TCTV) is a type member of the genus Turncurtovirus previously reported from Iran. TCTV has a wide host range among vegetables and weeds. In this study, the TCTV infection of the symptomatic jimsonweed (Datura stramonium L. ) showing general yellowing, severe curling and cupshaped leaves was confirmed by PCR. Full-length genome of this isolate was amplified using combination of the PCR and rolling circle amplification (RCA) and cloned into the pJET1. 2 vector. Resulted nucleotide sequence indicated that the jimsonweed isolate of TCTV shares maximum and minimum identities (85. 8-99. 2%) with turnip and radish isolates of TCTV, respectively. In spite of high similarity between full-length nucleotide sequence of jimsonweed and several GenBank isolates, predicted rep protein of the jimsonweed isolate has an additional 14 amino acid residues at the N-terminal. Among five TCTV strains, the jimsonweed isolate was classified in the strain C with turnip and leafhopper isolates of the virus. Results of this study again confirm wide host range of turncurtoviruses in weeds and the role of wild species in infection of vegetables.

Didymellaceae is a species-rich family including saprophytic, endophytic, and pathogenic species that are associated with different types of substrates. Some species of this family, such as Phoma sensu lato, are among the most important and widespread plant pathogens. Despite the economic significance of species belonging to this family in Iran, no coherent study has been conducted on their biodiversity. Many of presently known Didymellaceae members in Iran have been identified based on herbarium materials and in most of the cases there is no living culture available for molecular studies. The aim of present study was to explore species diversity of the family Didymellaceae in East and West Azarbaijan provinces. After isolation and establishing single spore cultures from different substrates, the isolates were identified based on morphological and molecular data using sequence data of ITS-rDNA, LSU-rDNA, and beta-tubulin gene. In this study Epicoccum nigrum, Boeremia exigua, Boeremia strasseri, Didymella glomerata, Didymella tanaceti, Ascochyta medicaginicola, Ascochyta herbicola, Phoma eupyrena and Heterophoma novae-verbascicola were identified from different host plants, soil and also as mycoparasites. Boeremia strasseri, D. tanaceti, P. eupyrena and H. novae-verbascicola are new records for the mycobiota of Iran. Furthermore, for each species new hosts/substrates are reported. Our results confirm that the sole reliance on morphological features for the identifaction of these fungi, is insufficient both at species and genus level.

Citrus vein enation virus (CVEV), a tentative species of the genus Enamovirus, family Luteoviridae, which causes vein enation and trunk woody gall symptoms on citrus, has been recently reported from Iran. In the present research, biological and molecular properties of CVEV different isolates were studied. Following graft transmission of 29 CVEV isolates on sour orange (Citrus aurantium), volkamer lemon (C. volkameriana ) and rough lemon (C. jambhiri), the results indicated that the incidence, type and severity of symptoms depend on the CVEV isolate and host (rootstock), accordingly virus isolates were classified into three groups. CVEV was transmitted by Aphis fabae with a significantly higher efficiency than that by Aphis gossypii. This is the first report of CVEV transmissibility by A. fabae in the world. Based on RT-qPCR results, the maximal and minimal concentrations of CVEV were determined in young bark and petioles tissues of infected sour orange seedlings, respectively. Monthly monitoring of the virus throughout the year by RT-PCR showed that CVEV was only detectable during two periods of late April to early July along with mid-September to early October, however, sensitivity of virus detection raised up to 60 percent in early December by using RT-qPCR. In the phylogenetic analysis of CVEV isolates based on nucleotide sequence of overlapped regions of ORF1 and ORF2, isolates were grouped into three clades which showed some correlation with symptomology groups.

In this research the effect of mixed infection of witches’ broom disease of lime (WBDL) (16SrII-B) and lettuce phyllody (LP) (16SrIX-D) phytoplasmas on symptom expression and phytoplasma density in periwinkle plants (Catharanthus roseus (L. ) G. Don) were investigated. Four healthy periwinkle plants of the same age were first inoculated with LP phytoplasma and after three weeks with WBDL phytoplasma using detached fragments of inoculative dodder (Cuscuta campestris Yank. ). Disease symptoms and phytoplasma population in plants inoculated with both phytoplasmas were compared with those in plants inoculated with either WBDL or LP phytoplasma. In doubly inoculated periwinkle plants the disease symptoms mitigated to mild reduction of leaf size and internodes which strongly differed from those in periwinkle plants singly inoculated with either WBDL or LP phytoplasma. Plants with mixed infection lived longer than those inoculated singly with either phytoplasma. Both WBDL and LP phytoplasmas could be detected in singly and doubly infected plants by conventional and real time PCR assays using specific primer pairs. Analysis of the data obtained by real-time PCR showed that the population of both WBDL and LP phytoplasmas in the mixed infection was significantly lower than that in plants singly inoculated with WBDL or LP phytoplasma. It seems that interaction of WBDL and LP phytoplasmas in mixed infection of periwinkle is of the mutual suppression type.

In recent years a lesser known disease that causes necrotic spots on flower and fruit surface of pomegranate have been observed in orcahrds of Golestan and Mazandaran provinces, Iran. The present study was aimed to characterize and determine the causal agent of this disease. Towards this aim, during spring 2016 pomegranate orchards were inspected in Golestan and Mazandaran provinces and symptomtic flowers and fruits were collected and transported to the laboratory. Isolation was made using routine plant pathology methods on Potato dextrose Agar supplemented with sulphate streptomycin. Pure cultures were established using hyphal technqiue. Colonies on MEA grew very slowly (attained a diameter of 3-4 mm after 7 days at 25℃ ), raised, floded, dense aerial mycelium in centre, white in centre and pink in margin. Conidiomata did not develop in culture. Acervuli were observed on lesions in fruit surface, subcuticular, subepidermal, 50-200 μ m diam; conidiophores dense, individual, short, and hyaline; conidiogenous cells hyaline to subhyalaine, phialidic. Conidia ellipsoidal, aseptate, hyalaine, 4-8 × 2-3. 5 μ m. The identity of the species was further investigated by PCR amplification and sequence of ITS-rDNA region. A BLAST serach against sequence data in GenBank, showed 100 percent similarity with some sequences avaibale in GenBank. Based on morphological and molecular data the fungus was identified as Elsinoë punicea. Inoculation of healthy pomegranate fruit (Yazd Cultivar) using mycelial suspension of the fungal isolates, resulted in the disease symptoms resembling those observed in field conditions; while, controls did not develop disease symptoms. The causal agent was re-isolated from inoculated tissues. With identification and determination of the causal agent, it is necessary to study the incidence of this disease in other pomegranate producing areas in country, biology of the causal agent, diseases cycle and finally provide proper management strategies for this disease.

Oxalis triangularis A. St.-Hil. (Oxalidaceae) known as “ False Shamrock” , is a perennial ornamental plant native to Brazil. The plant is used as indoor pot plant in Iran. In June 2018, rust-infected leaves were sampled from an indoor pot plant in University of Maragheh, located in Maragheh, East Azarbaijan. The following morphological features were observed on infected leaves: Spermogonia and aecia not seen. Uredinia round, 0. 2-0. 4 mm in diameter, in orbicular groups forming concentric circles up to 9 mm in diameter, soon naked, erumpent, powdery, yellowish white to orangeyellow, without paraphyses, urediniospores 16-23 × 13-19 μ m, ellipsoid, globoid or obovoid, wall 0. 5-1(1. 5) μ m thick, minutely and densely echinulate, colorless, germ pores obscure. Telia not seen, teliospores were sporadically present in uredinia, 21-28 × 15-18 μ m, ellipsoid, oblong or broadly oblong, rounded or obtuse at apex, slightly constricted at septum, wall quite colorless, smooth, thin, 0. 5-0. 8 μ m, pedicel colorless, as long as spores or shorter (Fig. 1). The above features fit well with those of Puccinia oxalidis Dietel & Ellis (Arthur 1920). This rust species originally described from Mexico and has been reported from tropical and subtropical America from Argentina to the United States on several species of Oxalis. The rust has also been introduced into Canada, Australia, New Zealand, Hawaii, Madeira Islands, China, India, Nepal, Japan, United Kingdom, Azores, Canary Islands and Uganda (Farr & Rossman 2018). There is a recent report of P. oxalidis on O. triangularis subsp. papilionaceae cv. Atropurpurea from Czech Republic (Š afrá nková 2014). Puccinia bakshii A. B. De, is another Puccinia species producing uredinial and telial states on Oxalis (De 1997). The fungus published invalidly due to article 40. 7 (Melbourne code). However, it differs from P. oxalidis in having epiphyllous uredinia and telia and smaller urediniospores and teliospores. There is at least one confirmed report from United States indicating that spermogonia and aecia of P. oxalidis occur on Mahonia repens (Lindl. ) G. Don (Berberidaceae) (Long & Harsch 1918). This is the first report of P. oxalidis from Iran. The fungus is also newly reported from western Asia. A voucher specimen has been preserved at the IRAN fungus collection under the reference number 17110F. Oxalis triangularis is an introduced ornamental plant into Iran. There is no doubt that P. oxalidis has been introduced to the country via infected host plants and should be considered as a Neomycetes. Material examined: On Oxalis triangularis, Maragheh university campus, Maragheh, East Azarbaijan, June 2018, S. M. Damadi, (IRAN17110F), II+(III).