فصلنامه بیماریهای گیاهی
سال پنجاه و نهم شماره 1 (پاییز 1402)

Tomato leaf curl Palampur virus (ToLCPalV) is a destructive bipartite begomovirus which recently is responsible for huge losses to tomato and cucurbits production in Iran. In this research, the effect of the silicon element, growth regulators including salicylic acid (SA), methyl jasmonate (MJ), brassinosteroids (BR), silicon element (Si) and their interactions to response of ToLCPalV infection of the greenhouse cucumber was studied. The study was performed as factorial experiment based on randomized complete block design and carried out under greenhouse conditions in pots. Before planting, cucumber seeds were presoaked separately in SA (0.5 millimolar), MJ (5 micromolar) and BR (1 micromolar). Subsequently, two or three-leaf stage of cucumber seedlings was sprayed by Si solution (1 ml/lit), one week before agroinoculation with ToLCPalV infectious clone. To analyze morphological and chemical characteristics, plant growth parameters including fresh weight and plant height parameters and amount of the catalase, peroxidase, polyphenol oxidase, ascorbate peroxidase and guaiacol peroxidase enzymes were assessed 30 days post agroinoculation with ToLCPalV infectious clone. Results indicated that, SA and combination of MJ+Si and BR+Si treatments resulted in raising the enzyme levels which leads to delay in appearance of ToLCPalV symptoms and decrease fresh weight and plant height parameters of plants. Based on the results of this research, application of plant growth regulators with or without silicon element including SA, MJ, MJ+Si and BR+Si could be resulted in increasing resistance in greenhouse cucumber against ToLCPalV infection.

The stem and bulb nematode Ditylenchus dipsaci is one of the most important plant-parasitic nematodes with a worldwide distribution, causing damage mainly in temperate regions. Onion, garlic and alfalfa are its main hosts. The use of nematode-free seeds and plant propagation materials, crop rotation, resistant cultivars and chemical nematicides are common methods of its management. Due to the side effects of nematicides on human health and the environment, the use of safe, cost-effective alternative methods are necessary. In this study, the nematicidal effects of the essential oils of mountain thyme, oregano, clove, sage and savory as well as the metabolites of the fungus Scytalidium sp. were studied in comparison to metam sodium under laboratory conditions. To prepare the nematode population, nematodes were extracted from naturally infected garlic from the Gogan region of East Azarbaijan province, reared on carrot discs and incubated at 18 ± 1°C for 60 days. The effects of plant essential oils, fungal metabolites and metam sodium were investigated in bioassays with four replicates, and nematode mortality was recorded after 24 and 48 hours. After a probit analysis, the LC50 and LC90 values were calculated for each of the compounds tested. After 24 hours, the LC50 values for the essential oils clove, oregano, marzeh and thyme were 1748, 769.2, 1662 and 4913 ppm, respectively, and for the fungal metabolite and metam sodium were 207.6 and 6.7 ppm, respectively. Gas chromatography with a mass spectrometer (GC-MS) and a DB5 column was used to identify the components of the essential plant oils and the metabolites, the results of which are presented here. Based on the LC50 values, the compounds tested caused mortality and population decline of D. dipsaci at relatively low concentrations, with the exception of sage-flower.

Begomovirus infecting vegetables is one of the main components of yield losses in south-eastern Iran. In this study, the incidence of chili leaf curl virus (ChiLCV) and the associated satellites were studied in pepper farms and commercial greenhouses of Jiroft and Manoojan (Kerman province). Full-length genome of three ChiLCV isolates was amplified using the rolling circle amplification method followed by cloning and sequencing. Furthermore, associated alpha- and betasatellites genomes were amplified in the PCR assay using specific and degenerate primer pairs, respectively. Sequence comparison showed that three ChiLCV isolates shared >95% pairwise nucleotide identities with the selected GenBank isolates. Gossypium darwinii symptomless alphasatellite (GDarSLA) was also found to be associated with three ChiLCV isolates and shared >89% pairwise identities with the selected GenBank isolates. Furthermore, tomato leaf curl betasatellie (ToLCB) was identified in two pepper isolates from Manoojan and shared >94% pairwise identities with the selected GenBank isolates. To demonstrate the pathogenesis of ChiLCV, a partial dimer of the viral genome was designed, constructed and agroinoculated into pepper seedlings. This led to the appearance of typical ChiLCV symptoms, including dwarfing and yellowing. Collectively, ChiLCV is one of the important begomoviruses infecting pepper in south-eastern Iran and the full-length genome of the virus as well as the associated alphasatellite are reported for the first time in Iran.

Hippeastrum/amaryllis (Hippeastrum hybridum Hort.) belongs to Amaryllidaceae. Plants of the hippeastrum exhibiting virus-like symptoms of chlorotic ring spots and concentric oval patterns were found in the collection of ornamental geophytes of the Ornamental Plants Research Center, Mahallat, Iran. Amplification of the genome using general primers of the Orthotospovirus genus, and specific primers of capsicum chlorosis virus (CaCV) led to the amplification of the expected fragments in some of the collected samples. Sequencing of amplified fragments proved the infection of some of the samples with CaCV and iris yellow spot virus (IYSV).No simultaneous infection with these two viruses was observed in any of the samples. This is the first report of the occurrence of members of the genus Orthotospovirus on the hippeastrum plant from Iran.

Within the framework of the Mycology research laboratory's program at the University of Guilan focusing on the identification and DNA barcoding of powdery mildew fungi (Erysiphaceae, Ascomycota) from Iran, a powdery mildew specimen on Helichrysum was collected from Zanjan-Tarom road and subjected for morphological and molecular identification. Although this species morphologically resembles Leveillula helichrysi, and some other closely related species such as L. taurica complex, the ITS sequence differentiates this fungus from the sequences of L. helichrysi and L. taurica available in GenBank. We suggest this collection may represent a new species or new haplotype within L. helichrysi. Therefore, until we obtain more samples and sequence the type material, we report this fungus as Leveillula cf. helichrysi from Iran.

Emerging plant viral diseases account for serious threats to agricultural crop yields and food security in many parts of the world. Alfalfa mosaic virus (AMV), a member of the Alfamovirus genus within the Bromoviridae family, exhibits a wide host range, infecting more than 150 plant species, including economically important crops such as alfalfa (Medicago sativa), lettuce (Lactuca sativa), potato (Solanum tuberosum), tomato (Licopersicon esculentum), pepper (Capsicum annuum) and bean (Phaseolus vulagris). AMV was initially documented infecting alfalfa in the Fars and Tehran provinces in 1968, subsequently spreading to all alfalfa-growing regions of Iran country (Zainadini et al. 2005). Serological assays have traditionally identified AMV strains, with molecular characterizations also being conducted on Iranian AMV isolates (Golnaraghi et al. 2004; Massumi & Hosseini Pour 2007; Massumi et al. 2012; Mangeli et al. 2012; Pourrahim & Farzadfar 2015). However, a number of Iranian AMV isolates have also been characterized molecularly (Mangeli et al. 2012; Pourrahim & Farzadfar 2015). Notably, based on ELISA tests and molecular examinations, Mangeli and colleagues identified AMV in various weeds, alfalfa, and vegetables such as potatoes and peppers across different Iranian regions (Mangeli et al. 2019). A greenhouse survey in Bandar Abbas, Iran, in spring 2023 revealed severe leaf chlorotic spots, yellowing symptoms, and fruit necrosis in tomato (Haji-Abad) and pepper (Bandar-Abbas) plants (Figure 1). To confirm AMV infections, total RNA was extracted from five symptomatic and one asymptomatic sample of tomato and pepper plants using TRIzol reagent (Sinaclone), followed by reverse transcription-polymerase chain reaction (RT-PCR) assays with a set of specific AMV primers (AMV-R, AMV-F) targeting a 780-nucleotide segment of the coat protein gene (Massumi et al. 2012). PCR products of the expected size (approximately 780 bp) were obtained from all of the symptomatic samples (five samples of tomato and pepper plants), while no amplified products were generated from any of the healthy leaf samples of tomato and pepper plants. Amplified fragments from one sample of each plant were gel purified using a PCR purification kit (Qiagen Co.) and sequenced directly using a paired-end sequencing strategy (Sinohe Co. Iran). Multiple alignments of the obtained nucleotide sequences (corresponding to a part of CP gene) with 15 AMV isolates obtained from GenBank showed the highest identity (97.9%. for IR-To-01 isolate and 98.3% for IR-Pep-03 isolate) with an Italian AMV strain See-1 isolated from Sechium elude and the lowest identity (95.8% for IR-To-01and 95.4% for IR-Pep-03) with an Iranian AMV isolate (IRWS2) from Wisteria sinensis. Phylogenetic analysis grouped Iranian isolates with European strains, while, the other AMV isolates (including Iranian, Asian and American isolates) were grouped into a separate clade (Figure 2), suggesting a possible introduction through seed trade. Further PCR assays targeting other viral groups, using four primer pairs, including a degenerate primer pair of potyviruses Nib1 / Nib3R (Gibbs and Mackenzie 1997); a degenerate primer pair of begomoviruses primer BC (Deng et al. 1994) / primer181V (Rojas et al. 1993) and Tobamovirus degenerate primer pair TobamodF/TobamodR (Li et al. 2018), yielded no positive results, suggesting no mixed infection of AMV with other viruses. Given the economic importance of tomatoes and related industries in southern Iran and the potential of emerging viruses which can rapidly spread and infect tomato crops, leading to reduced fruit production and quality, understanding the epidemiology and genetic variations of emerging viral diseases such as AMV is crucial for effective control measures. Ongoing research aims to elucidate genetic variations, pathogenicity, host range, and distribution of AMV in tomato and pepper plants under greenhouse and open-field conditions in Iran. Based on the results of nucleotide sequencing, based on a small part of the virus envelope protein from tomato (Haji Abad) and pepper (Bandar Abbas) under different cultivation conditions in Iran, particularly in Hormozgan province, a major center for greenhouse and outdoor tomato and pepper cultivation.