جستجوی مقالات مرتبط با کلیدواژه "dieback" در نشریات گروه "گیاهپزشکی"

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.

Accurate identification of the host species is critically important for disease detection and informing appropriate disease management decisions. Paecilomyces formosus, a causal agent of dieback and decline of oak, is an emerging threat that may cause severe risk to the Zagros forests of Iran in the future. In this study, a nested PCR assay for the identification of P. formosus was developed with the species-specific primer pairs PaMF and PaMR designed from the comparisons of nucleotide sequences of the nuclear ribosomal DNA internal transcribed space regions (ITS) from P. formosus isolates and other closely related taxa. To accomplish this, we sampled forest trees with dieback symptoms in Kermanshah and Ilam provinces. The Paecilomyces isolates were identified based on morphological characteristics, acid production on keratin sucrose agar medium, and sequencing of the ITS-rDNA region and part of the beta tubulin gene. Nested PCR was successfully amplified a 441 bp product exclusively from P. formosus genomic DNA, and no cross-reactions were observed with any other species, and also P. variotii. The nested PCR method can detect 100 fg of P. formosus genomic DNA. Sixty of symptomatic forest trees from seven locations in Zagros foreste were assayed, resulting in the discovery of Amygdalus lycioides, Cerasus avium, Cerasus microcarpa, Quercus libani, Acer spp., Acer monspessulanum, Ficus carica, Ziziphus spina-christi, Tamarix ramosissima and Ziziphus spina-christi as new host species, and all seven infested areas. To fulfill Koch’s postulates, the experiments were carried out on detached branches and attached healthy branches of trees at the forests in Kermanshah and Ilam provinces, Iran. The PCR-based method developed here can be used for a fast and reliable diagnosis of P. formosus, monitoring the epidemics, and assessing management strategies in Zagros forests.

 Ornamental trees decline is an important disease that threatens many ornamental and forest trees in the world, including ash, acacia, black locust, maple, elm and ornamental palms. In the present research, in order to characterize the fungal agents associated with black locust decline in Ardabil, samples were collected from black locust trees with typical dieback and canker symptoms from green spaces. 150 fungal isolates were isolated and purified using routine plant pathology methods. Identification of species was carried out using morphological and molecular sequence data of the ITS regions or TEF gene. In this study, 10 fungal species including Fusarium oxysporum, F. solani, Acremonium sp., Cytospora chrysosperma, Camarosporidiella elongata, Nigrospora sp., Alternaria alternata, Epicoccum nigrum, Chaetomium sp. and Sordaria macrospora were identified. It seems that Camarosporidiella elongata, Cytospora chrysosperma, Fusarium oxysporum and F. solani are likelyinvolved in the vascular obstruction, dieback and eventually black locust trees decline in green space of Ardabil. This is the first study on the occurrence of black locust decline in Iran. Among the identified isolates, Ca. elongata is reported for the first time in Iran. Acremonium sp. and S. macrospora are new reports on black locust host worldwide.

Pistachio die-back is one of the most important and prevalent diseases of pistachio orchards, causing severe reduction of pistachio yield. Due to the important role of bacteria in the occurrence and development of pistachio die-back, the interaction of Bacillus spp. and Paecilomyces formosus was investigated in this research. The isolates of both groups were injected beneath of the inner bark of branches (Ohadi cultivar) using sterile syringes alone or in mixture. According to the results, Bacillus pumilus and P. formosus isolates were able to cause disease on the branches, with longitudinal developments in vascular tissue. Bacterial isolates alone caused lesions ranged 4.5-14 cm in inoculation sites. Mix inoculations, significantly, increased disease development in xylem varied 10-32 cm. Based on morphological, biochemical and molecular properties, isolation of B. pumilus strains is reported for the first time as one of the causal agents of pistachio die-back in Iran.

Hazelnut tree has natural habitats in northwestern Iran in the forests of Ardabil and Gilan provinces. Decline disease is a threatening agent of hazelnut trees in these areas. Symptoms of the disease include weakness, reduced growth, leaf fall and dieback of the branches, branch and trunk canker and root rot that eventually lead to the gradual death or decline of the tree. In Iran the fungi cause hazelnut decline disease, Diaporthe amygdali, and Cytospora fuckelii as canker and Fusarium semitectum, F. lateritium, F. anthophilum and Armillaria mellea as root rot causative agents. This article describes symptoms of hazelnut decline in Iran, pathogenic fungi and management strategies.

Elm is one of the most important ornamental trees and is used extensively in design of urban green space. Dieback and canker disease of elm has been widespread in Tabriz green space and other cities in province in recent years. In order to identify the factors involved in dieback and canker of elm trees in Tabriz city, symptomatic and healthy samples were taken and 208 fungal isolates from 64 plant samples were purified. Identification of species was carried out using morphological and sequence data of the ITS or TEF regions for some species. In this study, 16 species of fungi including, Ophiostoma novo-ulmi, Fusarium solani, F. proliferatum, F. tricinctum, Pestalotiopsis brassicae, Cytospora rhodophila, C. chrysosperma, Didymella glomerata, Chaetomium globosum, Ch. rectanguare, Clonostachys rosea, Seimatosporium lichenicola, Coniolariella macrothecia, Pleurostomophora ochracea, Sordaria sp. and Geosmithia sp were isolated from sapwood and wood parts of trunk and main branches with vascular discoloration and healthy trees. Among the identified isolates, Fusarium and Chaetomium were the most abundant taxa. Chaetomium globosum, Ch. rectangulare, F. proliferatum, S. lichenicola, P. brassicae, Co. macrothecia, Pl. ochracea, C. rhodophila, Geosmithia sp., Cl. rosea and D. glomerata are new reports on elm host worldwide.

Ash tree is an important symbol of the urban green space in the world, which is also used in the construction of home and sport equipment. Ash dieback disease caused by Hymenoscyphus fraxineus is widespread in the most forests and green areas of the European countries. The disease was first observed in Poland and Lithuania in the early 1990s. The geographical spread of the pathogen has increased in the last two decades and so it is now is considered as a serious threat to the Ash trees. Initial infection is caused by ascospores released from apothecia formed on the previous year's leaves dropped. Disease management can be achieved by prevention and quarantine methods, sanitation, identification and cultivation of resistant cultivars and the use of chemical fungicides. The disease has not been reported from Iran so far, however, the possibility of entering the disease in the future is unclear. Therefore in this article we discuss the various aspects related to this disease including symptoms, pathologic biology, and management methods.

During recent years, citrus trees decline has becoming one of the most important factors of limiting the area of citrus orchards in the south of Iran including Fars province. Different biotic and abiotic agents were attributed to citrus decline worldwide, but it appears that some abiotic stresses including soil drought, and soil or water salinity, as well as some infectious diseases including gummosis, dieback, citrus nematode and witch’s broom are more important in Fars province. This is an attempt to gather information of the potential agents of complex diseases known as “citrus trees decline”, as well as, discussion on management strategies of citrus decline in Fars province.

Citrus gummosis disease cause canker accompanied by gum exudates, crown and root rot, twig dieback, and decline of citrus trees. This disease has been reported from Khuzestan and Fars provinces, now infected by in parts of Kohgiluyeh and Boyerahmad province (southwest Iran), namely: Molabarfi, Bidestan, Posht-e-koh, Tol-e-mavizi, Bidzard, Chaharbish-e-olia and Chaharbish-e-sofla from Gachsaran town and Cheshm-e-belghis, Dehborji, Spar and Marin from Kohgiluyeh town. Sour lemon, sweet lemon, big sour lemon and orange were more infected respectively. Pathogen identified as Phytophthora nicotianae. As it is epidemic in this province for planting diseased seedlings, incorrect planting method, stalk sensitivity, incorrect irrigation method, can manage by planting healthy certified seedlings on sour orange stalk, correction planting and irrigation methods, chemical control, and biological control with antagonistic fungi or bacteria.