فصلنامه بیماریهای گیاهی
سال پنجاه و هفتم شماره 1 (پاییز 1400)

Our objective was to investigate the effect of glyphosate in induction of resistance to two plant bacterial pathogens. To do so, glyphosate at an optimal concentration of 1.8 mg / l was used on the transgenic potato, Odyssay cultivar, to induce resistance to two strains of pathogenic bacteria (21A of Pectobacterium atrosepticum and ENA49 of Dickeya dadantii). RT-PCR analysis on RNA isolated from transgenic plants, showed overexpression of aroA and potato defense response genes. Transgenic potato leaves infected with potato pathogenic bacteria, and then treated with glyphosate showed a high level of expression of pathogenesis-related genes (PR-2, PR-3, PR-5), especially PR-2 and defense response genes (HSR-203j, HIN1), especially HSR-203j. However; the plants infected with bacteria and non-treated by glyphosate did not significantly change the expression of these genes. The results showed that the treatment of plants by glyphosate may not only eliminate weeds of farmland but can also induces a systemic acquired resistance to pathogenic bacteria by expressing of PR proteins and defense response genes.

Pyricularia oryzae is the cause of blast leaf spot disease on rice and more than 50 plant species of crops and weeds in Poaceae family. Sampling was performed in 2017 in rice fields of Guilan and Mazandaran provinces. Morphological studies showed that the isolates obtained from Oryza sativa, Setaria viridis, Echinochloa crus-galli, Sorghum halepense, and Paspalum dilatatum were belonged to P. oryzae. The pathogenicity test revealed that isolates obtained from each host had higher pathogenicity on the same host and were either not pathogenic or less pathogenic on other hosts. Cluster analysis of DNA fingerprinting data using rep-PCR showed that isolates obtained from different hosts were located in three clonal lineages. In general, there were isolates from different hosts in all three identified clonal lineages, and no correlation was found between the similarities of the band pattern with their collection areas.

The pathogens causing white blister rusts (Albuginales, Oomycota) comprises three genera including Albugo, Pustula and Wilsoniana infecting species of Brassicaceae, Caryophyllales and Asteridae, respectively. The current study contributes with new knowledge on Albuginales in Iran. An extensive survey for sampling white blister rust specimens was performed during the 2017-2020 growing season in some regions in Eastern and Northern Iran. Based on morphological and molecular (Cox2 and ITS) data Albugo lepidii on Lepidium sativum, A. koreana on Camelina transcaspica, Albugo arenosa on Strigosella africana, A. candida on various hosts, A. occidentalis on spinach and Wilsoniana portulacae on Portulaca sp. were identified. Our results, represent the first morphologically and molecularly verified report of A. candida on Goldbachia laevigata, Raphanus sativus, Eruca sativa from Iran and on Sinapis arvensis, Savignya parviflora, Isatis leuconeura and Sisymbrium altissimum worldwide. Sisymbrium septulatum is reported as Matrix nova for A. candida. White blister rust caused by A. candida is reported for the first time on a member of the genus Savignya in Iran. Albugo lepidii and A. koreana are new records for Iranian mycobiota. Detailed descriptions and illustrations along with phylogenetic placement here are provided for Wilsoniana portulacae and Albugo occidentalis.

Reducing the damage of the cyst nematode Heterodera schachtii is one of the research fields in sugar beet producing countries. Using chemical fertilizers can improve soil fertility and reduce damages of plant parasitic nematodes. In this study, the effects of ammonium sulfate, calcium sulfate, zinc sulfate, potassium sulfate, potassium nitrate, sodium silicate, triple superphosphate, iron sequesterine and sulfur on H. schachtii and growth parameters of susceptible sugar beet cultivar (cv Sharif) were investigated in two experiments. The first experiment was performed in plastic pots containing 6 kg of pasteurized field soil and river sand (1:1), and the second one in pots filled with 9 kg of field soil for four and five months, respectively, both under microplot conditions. Fertilizers were mixed with pots soils before sowing and the nematode was inoculated by adding 200 g of infested soil containing 18 cysts with 4200 eggs. The results showed that chemical fertilizers and sulfur did not have significant effects on growth of the infected sugar beet plants in pasteurized mixed or field soils, and some of them reduced it. In the pasteurized soil, zinc sulfate 50 kg/ha, iron sequestrene 5 kg/ha, sodium silicate 10 kg/ha and triple superphosphate 100 kg/ha caused a relative decrease of more than 67% in the nematode final population and reproduction factor. In the field soil, these indices in triple superphosphate 100 kg/ha and sulfur 100 and 200 kg/ha were lower than other treatments, but were at the same statistical level with the control. The third experiment was performed in small containers filled with infested soil to investigate the effects of treatments on nematode egg hatching in greenhouse. The results showed that the highest hatching was happened in the treatment of ammonium sulfate 200 kg/ha, which was statistically at the same level with triple superphosphate 100 kg/ha.

Stem or black rust caused by Puccinia graminis f. sp. tritici (Pgt) is one of the most common and harmful wheat diseases in Iran and worldwide. Under favorable conditions and the formation of the disease pyramid, the pathogen can destroy the wheat crops in a short time. Pgt has high genetic variability in the population structure due to the completion of the sexual cycle, which causes the creation of new races (race diversity) with a completely different pathogenicity pattern. TTKSK (Ug99) is one of the most critical race of Pgt that has appeared in recent decades and has caused much damage to wheat crops worldwide. This race had identified and reported in the country. However, the safest and at the same time most cost-effective way to manage and control this disease is to use genetic resistance. Accurate knowledge of the genetic structure of the pathogen population (existing races) in each region and knowledge of the virulence factors (genes) of stem rust races is the first step and similar to the roadmap to achieve effective and stable genetic resistance. One way to study the trend of changing pathogenicity patterns of races in each region is to observe virulence factors on stem rust differential genotypes in a trap nursery. For this purpose, virulence factors of Pgt races and the effectiveness of resistance genes in international differential genotypes investigated for three consecutive years (2017-2020) in the Ardabil province.

The pistachio is a commercial nut crop that belongs to the family Anacardiaceae. Reports for viral agents of this plant are limited to hop stunt viroid, pistachio ampelovirus A, and pistacia virus B. We investigated of the presence of viruses in Iranian Pistacia vera by analyzing publicly available RNA-Seq data. Twelve paired-end datasets were retrieved from the Sequence Read Archive (SRA) database of NCBI. Transcriptomic data were mapped to P. vera reference genome using Hisat2 to eliminate plant RNAs. The remaining data were de novo assembled by MEGAHIT and Trinity programs and the resultant contigs subsequently were queried versus viral reference sequences using BLASTx. Two novel viruses related to the family Kitaviridae were identified and tentatively named “pistachio virus x” (MT334618-20) and “pistachio virus y” (MT362605-06). Based on the genome structure, sequences similarity, and phylogenetic relationships we propose these novel viruses as possible members of genera Higrevirus and Cilevirus. High reads number on different plant tissues, root and leaf, of pistachio virus x led us to make a conclusion on possible systemic infection of this virus on Pistacia vera. To the best of our knowledge, it is the first report of possible viral agent from Iranian pistachios.