فصلنامه بیماریهای گیاهی
سال پنجاه و هفتم شماره 2 (زمستان 1400)

Identifying resistance related metabolites as biomarker for screening wheat germplasms resistant to leaf rust (Puccinia triticina) is a useful approach to increase the speed, accuracy and cost effectiveness of screening disease resistance. The relatively polar metabolites were extracted in a mixture of methanol-water from near isogenic line (NILs) of wheat susceptible (Thatcher Lr22b) or resistant (Thatcher Lr25) to leaf rust in the two leaf stage, 24 h after inoculation with the pathogen, talcum powder or sterilized distilled water, in three replications. Metabolites were analyzed using a GC/MS. ANOVA showed that abundance of 26 metabolites had significant differences among experimental factors including near isogenic lines (NILs), inoculation (I) and NILs ×I interaction. Abundance of 26 significant metabolites was subjected to canonical discriminant analysis and hierarchical cluster analysis to group observations of metabolite profiles based on similarities and differences in the investigated metabolic space. Finally 13 resistance related metabolites (RR) and 13 Pathogenesis related metabolites (PR) were identified that the majority of RR metabolites involved in induced resistance and constitutive resistance. Significant metabolites included metabolites with potential signaling and/or antimicrobial activity as well as molecules used as precursors for cell wall reinforcement, phenolic and alkaloids compounds, and accumulation of amino acids and proteins associated with resistance. Up-regulation of the number pathways upon infection of wheat to leaf rust fungus is discussed.Key words: metabolic profiling, Wheat leaf rust, screening resistance, gas chromatography/mass spectrometry.

Fungal diseases are considered as main causes of yield loss and increased costs in wheat production. Stem rust caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating fungal disease of wheat, worldwide. Identification of new stem rust resistance sources, and the involved genes are required to achieve resistant cultivars and durable resistance as the most efficient control method of wheat stem rust. In order to identify new seedling resistance sources, virulence pattern of eight Pgt isolates was studied on 27 wheat commercial cultivars and elite lines of national breeding programs in a randomized block design with three replications.

The septoria leaf spot caused by Zymoseptoria tritici، is one of the most destructive wheat diseases in the world, which causes lots of damage to this crop annually. The aim of this study was to investigate the effect of 0 and 200 ppm of chitosan on the expression of defense genes and antioxidant enzymes (peroxidase, catalase and ascorbate peroxidase) activity, in Koohdasht wheat cultivar (susceptible cultivar) in interaction with the pathogen. Therefore, two-week plants were sprayed with chitosan, and then treated plants along with control plants were inoculated with Z. tritici pathogen. Finally, the expression rate of PR1, PR2 and PR5 genes were examined using qRT-PCR technique at 0, 12, 24, 48, 96, and 240 hours after inoculation (hai). According to the results, disease severity reduced by about 55% in chitosan pre-treated plants compared to control. The results of qPCR showed that expression of mentioned genes increased in treated and control plants, but the expression of PR1, PR2 and PR5 genes increased by 7.5, 4.15 and 3.76 times more in treated plants compared to control in 24 hai, respectively. Comparing enzyme activity in chitosan pre-treated plants and control, indicates an increasing trend of peroxidase enzyme and a decreasing trend of catalase and ascorbate peroxidase in the first group of plants. The examined gene expression and antioxidants pattern changed in both groups of plants indicates the effectiveness of chitosan in inducing resistance against septoria leaf blotch in wheat.

Faba bean necrotic yellows virus (FBNYV) (Nanovirus, Nanoviridae) is a common nanovirus of leguminous plant in Asia, Africa and Europe continents. In this research, natural hosts of FBNYV in three eastern provinces of Iran have been studied and full-length genome components of a Rabor isolate (Kerman province) has been sequenced. To identify FBNYV natural hosts, leguminous plants and leaf vegetables were sampled in Kerman, Razavi Khorasan and Northern Khorasan, and the FBNYV infection of the samples was tested by PCR and/or nucleotide sequence of DNA-S component. Results indicated that lentil, faba bean, broad bean, chickpea, alfalfa, fenugreek, parsley and dill are infected with FBNYV and DNA-S of seven isolates from seven plant species share 89.6-99.7% nucleotide sequence identities. Among infected hosts, full-length genome components of a chickpea isolate of FBNYV from Rabor (Kerman province) was determined and compared with the related components of the GenBank isolates. Accordingly, all genome components of the Rabor isolate shared 88.57-99.81% nucleotide sequence identities with the corresponding sequence of other Iranian and GenBank isolates. To conclude, FBNYV has a broad host range in leguminous plants and even can infect non-leguminous leaf vegetables. It is the first report of the FBNYV infection of fenugreek, parsley and dill in the world.

In 2018, a drastic Ascochyta blight epidemic on chickpea crops occurred in the Northwest of Iran. A survey was conducted in the region to identify races of Ascochyta rabiei and estimate the yield loss. Infected plant samples were taken from an infected field in Pasvah region and transferred to the lab at Dryland Agricultural Research Institute (DARI), Maragheh. In addition to A. rabiei, a Cladosporium-like taxa is also isolated from plants showing disease symptoms. Based on morphological characteristics and DNA sequence comparisons, isolates of this fungus were identified as Cladosporium halotolerans. Pathogenicity tests and Koch’s postulates were verified and fulfilled on chickpeas under controlled conditions. The disease symptoms developed on the host plant after 5 days after inoculation (dai) under controlled conditions included appearing yellow-brownish leaflets on the branches that latterly turned to wilt and were covered with gray-black mold. Histological studies also confirmed the pathogenicity of this fungus on chickpeas. Host range investigations were carried out on the further six species belonging to the Fabaceae, including garden pea, lentil, garden vetch, narbon vetch, bitter vetch, and grass pea. Results showed that this pathogen can produce the same disease symptoms on all inoculated, as well. This study represents the first attempt to pathogenicity of C. halotolerans on legumes in the world.

The genus Chronogaster Cobb, 1913 of the family Chronogasteridae Gagarin, 1975 included 55 valid species which have been reported from terrestrial, marine and freshwater habitats in different localities in the world. In the of nematode fauna of Gurigol Lake, East Azarbaijan province (GPS, 37˚ 54ʹ 40ʹ Nʺ and 46˚ 42ʹ 10ʺ E) and soil in Khaki Beig, Divandarreh Kordestan province (GPS: 36˚ 11ʹ 21ʹ Nʺ and 6˚ 54ʹ 26ʺ E) two populations of Chronogater were collected. The nematodes extracted by using sieves and centrifugation, and transferred to anhydrous glycerin. The nematodes were mounted on microscopic slides and their morphological and morphometric characters studied using Olympus BX 41 optical microscope and digital images prepared by a DP50 camera. Both populations were identified as C. rotundicauda Heyns & Coomans, 1983.