نشریه تحقیقات بیماری های گیاهی
سال ششم شماره 1 (بهار و تابستان 1399)

This study has carried out for distinguishing of Leptosphaeria maculans and L. biglobosa (aggressive and ‎non-aggressive groups respectively) using colony growth, ability for pycnidium and pigment production in four ‎mediums and temperatures of Forty nine isolates (Zaman Mirabadi et al., 2010) (totally 784 treatments) in three ‎replication and three times. The result of analysis variation has shown that significant difference between isolates ‎considering colony growth in the different mediums and temperature treatments. The maximum and the minimum ‎colony growth was observed in 30⁰c –v8 juice Agar (48.05 mm) medium and 15⁰c-Czapek Dox Agar (17.01 mm) ‎respectively after 12 days. The greatest and lowest pigment production in the different temperature was observed in ‎PDA and MEA (except in 30⁰c). The minimum and maximum pigment production was observed in 15⁰c and 30⁰c ‎respectively. The percentage of presence yellow-orange and brown pigment was‏ ‏variable in the different treatments. ‎Brown pigment in V8 and CDA was dominated while yellow- orange was seen in PDA and MEA. 93.78 % isolates ‎produced pigment in Czapek Dox Broth. The maximum pycnidium production was observed in V8 and 20⁰c. ‎According to the obtained results, Dasht-Naz, Eslamabad, Fazelabad, Kohi khail and bykar ayesh were belonged to ‎aggressive species (L.maculans) and Talokola, Lala, Khalkhail and mustard isolate too were located as L.biglobosa.

The Downy mildew of onion, caused by Peronospora destructor Berk, generates a lot of economic damage to onions annually. Fungicides are the main components of plant diseases management. The aim of this study was to determine the efficacy of equalizer to control of onion downy mildew. Experiments were carried out in a randomized complete block design with six treatments and three replications in 2017 in Khuzestan and Hormozgan provinces. treatments consisted of equalizer (0.2, 0.3 and 0.4 kg /h, Infinito 2L /h, water spray and control without spraying). After observing the first signs of the disease, the treatments were conducted and continued every 10 days until the control treatment contamination reached as high as possible. Evaluation of experimental plots was conducted before each spray by selecting 10 plants from two middle rows and disease severity index (DSI) for each treatment was determined using scoring system of 1-9 and Kofoet A and Fischer formula. Analyses of variance revealed that there was significant diference among treatments at 1% level. But between treatments and location there was not significant difference. Also the result showed significant difference between location and treatment × location. The means comparison showed that 0.4kg/h Equalizer treatment creates statistically higest efficiency in Khuzestan and Hormozgan provinces(88/87 and 91/85%) respectivley. The other treatments including 0/2kg/h, 0/3kg /h of Equalizer and Infinito(2L/h) with 55/63,62.40 and 60.15 efficiency in Khuzestan and also 14/81, 76.29 and 67/40% efficiency in Hormozgan province were located in next statistcally groups. So the results of this study suggested 0.4kg/h Equalizer as appropriate rate in comparison to Infinito to control of Downy mildew of onion.

During the summer months until the fall of 2017, 50 diseased samples of ligustrum plants suspected to bacterial disease were collected from all around Tehran and Karaj parks and green spaces. The diseased samples were transferred to the laboratory for further investigation. The dominant single colonies with distinguished morphology were selected and fulfilled their pathogenicity on geranium and detached stems and leaves of the host plant. Seven pathogenic bacterial isolates were further analyzed by morphological, physiological and biochemical traits. Using PCR, the 16S rRNA gene of the selected isolates was amplified DNAs were first extracted by alkaline lysis method and their 16S rRNA genes were amplified with primer pair P6/P1. The PCR products were sequenced by Macrogen Co. (Seoul, Korea) and the edited sequences were compared with deposited sequences in Genbank nucleotide database (http://www.ncbi.nlm.nih.gov). According to the results, heterogeneous species include strains of Stenotrophomonas maltophilia, strains of Pseudomonas plecoglossida, strains of Bacillus sp., strains of Paenibacillus sp., strain of Ochrobactrum sp., strains of Achromobacter sp., and strains of Staphylococcus epidermidls were identified. The presence of a wide range of not-so-well-known bacteria, but the pathogen confirms their importance, at least as secondary pathogens. This is the first report of isolating certain novel bacterial agents on ligustrum in Iran.

Root-knot nematodes (Meloidogyne spp.) are the most important plant pathogenic nematodes that reduce yield of economic plants worldwide. The use of compounds of plant secondary metabolites has been proposed as the best alternative strategy for controlling nematodes due to its properties such as specific mechanism of action, limited spectrum of action and the ability to decompose into non-toxic metabolites. This study was performed to investigate the inhibitory effect of aqueous extracts of Chenopodium album, Amaranthus retroflexus and convolvulus arvensis on mortality of root-knot Nematode, (Meloidogyne javanica) in vitro conditions. Experiment in a completely randomized design with 3 factors (1- type of extract in 3 levels of Ch. album, A. retroflexus and C. arvensis, 2- concentration of extract in 3 levels with ratios of 0.04, 0.2 and 0.4% and 3- Extraction organs were performed at 3 levels of leaves, stems and roots in 3 replications for each treatment in laboratory conditions and the two plants that had the most effect were done in Labratory conditions. The results showed that the extracts of all three plants significantly increased the mortality of second level of nematode larvae. The extract of 0.4% of coriander leaves with 98.3% mortality of age 2 larvae had the highest mortality and the extract of 0.2% and 0.04% of ivy root with 37% had the lowest mortality. The two plants of Ch. album and A. retroflexus, which had the best results in vitro, were studied in greenhouse conditions. The reproductive factor of control with nematode has a significant difference with other treatmentsFrom the results of study,it can be cincluded that it is possible that the weeds of tomato fields especially A.retroflexus and Carvensi,returning to the ground canreduce the J2population of root-knit nematodes in the soil.