فصلنامه بیماریهای گیاهی
سال پنجاه و هشتم شماره 4 (تابستان 1402)

Chickpea chlorotic dwarf virus (Mastrevirus, Geminiviridae) is a destructive geminivirus worldwide. In this study, symptomatic okra and wild jute samples showing typical geminivirus symptoms were collected from Jiroft farms and circular molecules of extracted DNA were enriched using rolling circle amplification (RCA) method followed by cloning and sequencing of RCA products of two selective samples from okra and wild jute. Sequence analysis showed that two isolates belong to strain CpCDV-F. Attempts to recover associated alpha- and betasatellite molecules from two plant samples using polymerase chain reaction assay resulted in detection of Gossypium darwinii symptomless alphasatellite (GDarSLA) only in wild jute sample. Sequence analyses indicated that two new CpCDV isolates shared nucleotide identity of 98% with each other and two viral and one alphasatellite sequences are closely related to Iranian Genbank isolates. Pathogenesis tests using previously constructed infectious clone of CpCDV led to appearance of yellowing and dwarfing in agroinoculated okra seedlings. Based on the results of this study, okra and wild jute plants are reported as new hosts of the CpCDV in Iran and wild jute is the new virus host in the world.

Internal boll rot disease is one of the important diseases of cotton. All commercial cotton cultivars, especially the native varietes, are susceptible to the disease. The disease has been reported in pistachio, soybean, and pepper. Changes in the shape and weight of bolls, shedding of buds, flowers and bolls, and the appearance of brown spots on the fibers are symptoms of the disease in cotton. In order to identify the casual agent of the disease, 178 infected boll samples were collected from Tehran, Golestan and Hormozgan provinces, and 17 isolates were obtained from them, and their pathogenicity was evaluated in cotton and bell peppers. Agents were isolated in PDA medium containing yeast extract at a temperature of 30 degrees Celsius. Molecular identification was done by amplification of a part of ribosomal DNA by polymerase chain reaction and ITS1- ITS4 primers. All 17 samples isolated in cotton were pathogenic in Cotton and bell pepper. Two yeast species were identified, Filobasidium magnum was identified for the first time from Tehran province and Meyerozyma guilliermondii is reported for the first time from Iran in the Golestan province .

This study was conducted with the aim of isolation, identification, frequency determination and pathogenicity of fungal and oomycota species associated with citrus decline in six different locations of Hormozgan province. Isolation of fungi and oomycota was carried out from Bakraee and Mexican lime roots and local tangerine branches on general and semi-selective culture media. The isolates were identified at genus or species level based on morphological characteristics and sequence of ITS-rDNA and a part of TEF-1α gene. Frequency percentage of identified species was determined in surveyed locations based on numbers of cultivated plant pieces. Fusarium solani, Macrophomina phaseolina, Fusarium proliferatum, Alternaria sp., Rhizoctonia solani, Fusarium acutatum, Phoma sp., Fusarium sp.1 and Fusarium sp.2 with the frequency of 93.51%, 1.1%, 0.26%, 0.26%, 0.17%, 0.08%, 0.04% and 0.04%, respectively, and Pythium spp. and Phytophthora nicotianae with the frequency of 4.96% and 3.12%, respectively, were isolated from roots with rot. Fungal species isolated from branches with dieback symptoms were Alternaria spp., Neofusicoccum mediterraneum and Colletotrichum gloeosporioides with the frequency of 81.7%, 10.56% and 0.92%, respectively. Pathogenicity of three isolates from each species was tested on one-year-old seedlings of local tangerine on Bakraee. All the investigated isolates, except for Alternaria sp. and Pythium sp., were pathogenic on seedlings and caused symptoms similar to decline symptoms observed in citrus orchards. Pathogenicity of Alternaria sp.1 and N. mediterraneum isolates was tested on detached branches of local tangerine and pathogenicity of C. gloeosporioides was tested on one-year-old seedlings of local tangerine and all tested isolates were pathogenic.

The oomycete pathogens causing white blister rusts on members of Asteridae comprise different species within the genus Pustula (Albuginales, Oomycota). During the collection of white blister rust specimens in the South Khorasan province (eastern Iran) in April 2019, a specimen collected from Takhtajaniantha pusilla (Asteraceae), was identified morphologically as Pustula junggarensis (Albuginales, Oomycota). BLAST search using the ITS nrDNA sequence data, confirmed the identification. Also, the phylogenetic analysis using cox2 sequences clustered the species in the same clade with P. junggarensis sequences from China. This is the first record of P. junggarensis in Iran. To the best of our knowledge, this is the first report of a disease caused by a causative fungal/fungal-like agent on T. pusilla in Iran.

Rhizoctonia root rot disease of common bean (Phaseolus vulgaris L.), caused by Rhizoctonia solani AG4, is one of the most important bean diseases worldwide. The use of biological and non-biological prime agents has become a promising and environmentally friendly alternative to the management of soil-borne pathogens. Therefore, the present study aimed to compare the effect of Bacillus subtilis isolate A4 (biological prime) and beta-aminobutyric acid (BABA) (non-biological prime) on the management of Rhizoctonia root rot disease in Talash and Sadri cultivars of common bean plants. The seeds were coated with the mentioned priming agents and after drying, they were planted and kept in the greenhouse at a temperature of 20±2 °C. Plants at the cotyledon stage were inoculated by R. solani AG4 inoculum. The induction of resistance in plants was evaluated by measuring disease severity, morphological, and physiological factors three weeks after inoculation. The priming factors increased almost all morphological and physiological measured traits, compared to the control. The plants treated with prime agents had a lower disease severity index (DSI) compared to the control plants and the Talash cultivar treated with B. subtilis had the lowest DSI, with a 59% reduction. The phenol content, catalase and peroxidase enzyme activities under bio-priming and chemo-priming treatments in the presence of the pathogen showed a significant increase compared to the control plants.

In recent years, yield losses due to chickpea chlorotic dwarf virus (CpCDV, Mastrevirus, Geminiviridae) infection have been intensified in a large number of plants such as watermelon, okra and cotton and the virus has been reported around the world (Kanakala and Kuria 2018). In the current study, natural infection of watermelon with CpCDV was investigated. Watermelon samples showing leaf chlorosis, hardness and discoloration of the flesh with whitish stripes, deformation and increasing seed abortion of fruits (Fig. 1) were collected from watermelon-growing farms in Behbahan (Khuzestan Province) in 2018. Total DNA of the samples was extracted from leaf tissue using the cetyltrimethylammonium bromide (CTAB) method followed by the enrichment of the extracted circular DNA molecules by rolling circle amplification (RCA) method using phi 29 DNA polymerase (TempliPhi kit, GE Healthcare, USA). Polymerase chain reaction (PCR) tests using RCA product as DNA template and the primer pair CpCDV-752-F/CpCDV-1326-R (Askari et al. 2021) resulted in the amplification of an expected 575 bp DNA fragment (Fig. 2) indicating the infection of the all tested samples with CpCDV. The definitive infection of a PCR positive sample (W1) with CpCDV was confirmed by sequencing of PCR product.