جستجوی مقالات مرتبط با کلیدواژه "phytoplasma" در نشریات گروه "بیوتکنولوژی و ژنتیک گیاهی"

In order to detection and differentiation of two complications of disorder and lack of podding in soybeans, while visiting 185 soybean fields in Golestan and Mazandaran provinces, only from the summer cultivation of 17 fields from five different places in Golestan province, plants with signs of disorder and the lack of acute podding were identified and 17 samples were selected from each field and sampling was done from the leaves or stems of the mentioned plants in order to extract RNA and DNA. Then, PCR was performed to detect nepovirus using the degenerate primer of nepovirus and to detect phytoplasma using a pair of general primers and a nested PCR test. The results of electrophoresis confirmed the amplification of the 1800 bp band in the general PCR, the 1250 bp fragment in the nested PCR related to phytoplasma, and also the amplification of the 640 bp band related to a nepovirus. Besides, no band of healthy plants was observed. at the same time, tissue grafting and mechanical inoculation were performed on GPX soybean benchmark plant using the mentioned samples and two types of symptoms appeared. From the sequencing of the disordered samples (production of a small number of seeds and small pods), Tomato ring spot virus strain ep31_63026 and from the sequencing of the samples with non-encapsulation (grassiness and no formation of pods and seeds), Aster yellows phytoplasma from the 16SrI-B group were identified, which confirmed the results of the reference plant. The phylogenetic analysis of sequencing results confirmed the presence of Phytoplasma and Nepovirus only in the summer culture of samples that had symptoms of disorder and lack of podding.

Tomato big bud is one of the most important diseases of tomato caused by phytoplasma in Iran and all over the world. In infected tomato plants, leaves turn to purple and buds become large, swollen and green that fail to develop normally and do not set fruit. For detection of the causal pathogen, we collected some samples from leaves and swollen buds of infected tomato plants as well as from leaves of some weeds in tomato fields such as Orobanche purpurea, Reseda sp, Amaranthus sp. Xanthium strumarium. Total DNA from all collected samples was extracted. To survey the pathogen in the body of some insects that are known as vectors, samples of two species that appeared more frequently in the tomato fields (leafhoppers and whiteflies) were collected and the total DNA was extracted. Molecular detection of the big bud phytoplasma in all samples was carried out by PCR using two specific primers (P1/P7). The results showed that in infected samples of the tomato plants, a DNA fragment of 1800 bp in size was multiplied while in the control plant no DNA fragment was observed when the PCR products were visualized in the gel electrophoresis. The same size specific DNA fragment was detected only in PCR reaction coming from leafhoppers and samples of the Orbanche plant parasite. This research showed that the pathogen can be transmitted by leafhoppers and Orbanche while it cannot be transmitted by seeds and whiteflies. This molecular approach could be an effective and fast method for detection and survey of phytoplasma and other fastidious plant pathogens.

In 2017, leaf stunting and yellowing were observed on twigs and branches of stone fruit trees in production regions in Razavi and North Khorasan provinces of Iran. For diagnosis of disease and identification of the causal agent, symptomatic leaf samples were collected in these orchards and were carried to the laboratory. The disease agent was successfully transmitted by grafting from naturally symptomatic samples to peach (Prunus persica) seedlings. Total DNA was extracted from plant samples and indexed by nested PCR using phytoplasma generic primers, P1/P7 and R16F2n/R2. PCR products were sequenced and the nucleotide sequences were compared with those of other phytoplasmas in GenBank and analyzed by virtual restriction fragment length polymorphism (RFLP). The phytoplasmas associated with leaf stunting and yellowing disease in Razavi and North Khorasan provinces were identified as members of the 16SrIX group or Pigeon pea witches broom (Candidatus Phytoplasma phoenicium). This is the first report of leaf stunting and yellowing disease and characterization of associated phytoplasma in these regions.

‘Candidatus Phytoplasma aurantifolia’ has been reported as causal agent of witches’ broom disease in Mexican lime (Citrus aurantifolia L.), Bakraee (Citrus sp.) and Grapefruit (Citrus paradisi Macfad) trees in Iran. Almost all of the lime orchards in Hormozgan, Sistan & Baluchistan and Kerman provinces are infected by this pathogen now. The pathogen is not naturally associated with other citrus varieties in Iran. During 2010, a several number of Citron (Citrus medica L) trees in commercial citrus orchards in Southern Kerman, Iran with witches’ broom symptoms were found. In order to detection and identification of the associated phytoplasma, nucleic acid was extracted from leaf midribs of symptomatic citron plants showing witches’ broom symptoms. Healthy citron plants were used as negative control. Mexican lime trees infected with ‘Ca. Phytoplasma aurantifolia’ were used as positive control. Nested PCR analysis of symptomatic citron as well as mexican lime trees showing witches’ broom symptoms produced an amplicon of the expected size using phytoplasma universal p1/p7 primer pair in first step and 16F2n/16R2 in second step. The healthy citron trees did not. Sequences obtained from all the amplicons were identical and consisted of 1250 bp nucleotide which had a high sequence similarity (99.8%) with ‘Ca. Phytoplasma aurantifolia’. This is the first report of a natural phytoplasma infection on citron in Iran.