جستجوی مقالات مرتبط با کلیدواژه "tan spot" در نشریات گروه "گیاهپزشکی"

Tan spot (Pyrenophora tritici-repentis) is one of the most destructive leaf diseases that causes significant damages to wheat during epidemic periods. The application of fungicides is a rapid control practice of the disease during epidemic periods. Under the Integrated Management of Diseases (IDM), fungicides application for controlling leaf diseases is recommended based on disease level (disease pressure), plant growth stages, and only for susceptible cultivars. Several fungicides have been proposed for controlling tan spot, but the efficiency of recommended fungicides is effective when they are used to reduce the disease pressure on important plant leaves especially flag leaf. According to growth stages, four timing have been recommended to fungicides application including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The results of fungicides application at different growth stages of wheat are inconsistent and also there is no comprehensive study about the timing of fungicides application for controlling this disease in Iran. Therefore, the present study was carried out to determine the appropriate timing of fungicides application at four wheat growth stages. A field experiment was conducted in a split plot design with four replications. The main and sub-main factors of the experiment were cultivars (Karim and Koohdasht) and the spraying treatments, respectively, and common fungicides (such as Tilte, Folicur, Falcon, and Rexduo) were sprayed at four timings including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The spraying treatments were as follows: one, two, three and four spraying times. The efficiency of spraying treatments was evaluated one week after the last spraying by determining the disease index (incidence, severity and area under the disease progress curve; AUDPC) and also comparing the yield and yield components. The results showed that spraying treatments from the full flag leaf emergence to flowering stages (Tr3, Tr5, Tr6, Tr8 and Tr9) decreased the values of AUDPC-I by 42.1 to 80.5% and 33 to 76.6% for Koohdasht and Karim cultivars, respectively, whereas the values of AUDPC-S decreased by 30.7 to 47% and 33 to 58% in Koohdasht and Karim cultivars, respectively. The effect of spraying treatments on damage reduction showed that the damage reduction ranged between 1.4-30.8% and 1.1-29.7% in Koohdasht and Karim cultivars, respectively. The highest damage reduction was observed at the full flag leaf emergence to flowering stages. The highest yield increase was observed at the full flag leaf emergence to flowering stages, which was more than 36% (1071.2 to 1298.9 kg/ ha) and 34% (1054.5 to 1313.8 Kg/ ha) in Koohdasht and Karim cultivars, respectively. The spraying treatments at the node formation stages had the least effect on the yield improvement, which were, respectively, 2.1-7.1% and 1.5-5% in Koohdasht and Karim cultivars. In both cultivars, the comparison of economic profit showed that treatment of Tr3 (flag leaf emergence stage), in addition to decreasing the disease severity and yield increase, and reduction of spraying costs had the highest economic profit compared to other spraying treatments (Tr6, Tr8 and Tr9). Spraying prior to the appearance of flag leaf stage (node formation) was not effective for reducing tan spot severity. The treatment of Tr3 (spraying once at the full flag leaf emergence stage), was the best timing of fungicide application for the disease pressure reduction, and the yield and economic profit increase. In addition to the timing and spraying frequency, the disease pressure reduction rate and yield enhancement, economic profit should be also considered to decide on spraying application.

Tan spot disease incited by Pyrenophora tritici-repentis, is an important disease of wheat throughout the world, including Iran. The disease inflicts considerable losses to the crop in the epidemic conditions. Application of fungicides is a quick method for control of the disease in epidemic years. In this study, the effect of some registered fungicides was evaluated on growth inhibition of the causal agent as in vitro, and also for control of the disease in greenhouse and field conditions on a susceptible wheat line (N-80-19). The experimental design was carried out as completely randomized in in vitro condition and as split plot in greenhouse and field conditions with 3 replications. Main plots were included the fungicides Cyproconazole, Cyproconazoleপ�睚츩 (Altocombi), Flusilazoleপ�睚츩 (Alert), Iprodioneপ�睚츩 (Rovral T-S), Propiconazole, Tebuconazole, Carbendazim and Benomyl), and sub-plots were consisted of the spraying times (flag leaf, head appearance and flag leafꖩ appearance stages). The treatments were evaluated by recording the infection index, 10 days after the last spraying simultaneously with disease development on control plots. The grain yield was also calculated after wheat harvesting. The results demonstrated Rovral T-S (73.83%), Altocombi (71.92%) and Alert (69.42%) had maximum in vitro growth inhibition of the fungus. The three fungicides showed considerable advantages on reduction of infection index and increase of yield in greenhouse and field tests, compared to other fungicides. For infection index, no-significant difference was recorded among spraying times. The highest thousand grain weight was respectively obtained by spraying at flag leaf head appearance (increasing 10.11 and 9.94 grams), flag leaf (increasing 9.26 and 9.18 grams) and head appearance stages (increasing 9.15 and 8.68 grams, respectively, for greenhouse and field), compared to their control.

In order to study the reaction of 23 different advanced wheat cultivars and lines against major foliar diseases in Golestan province، including powdery mildew، brown rust and tan spot، an experiment was conducted in a randomized complete block design with three replications during winter of 2009. Infection was created naturally in the field by planting susceptible rows between the treatments. Evaluation of the treatments was done based on the intensity of different diseases (disease incidence، disease severity، area under disease progress curve (AUDPC) and standardized AUDPC، total seed weight and thousand kernel weight (TKW). Analysis of variance showed that treatments were statistically different (P≤0. 01) based on all recorded data. Results of multiple range test (LSD) showed that the highest and lowest severity of powdery mildew were observed in line 17 (72. 74%) and Gaspard (0%)، respectively. The highest and lowest severity of brown rust was observed in Bolani and Morocco (11. 11%) and Gaspard (0. 12%)، respectively. The highest and lowest severity of tan spot disease was recorded in Morvarid (94. 56%) and Morocco (0%)، respectively. The highest grain yields were recorded in line 11 (4340. 97g) and Morvarid (4013. 19g)، and lowest grain yields recorded in Bolani (184. 03g) and Morocco (250g). The highest and lowest TKW were observed in Cultivars Shiroudi (36. 33g) and Morocco (13. 53g)، respectively

Tan spot disease of wheat with the causal agent of Pyrenophora tritici-repentis is a very serious disease throughout the world causing severe yield losses. Out of 163 isolates of the pathogen، collected from Golestan and Mazandaran provinces، 58 were selected for a study of population genetic structure. Selecting the real representatives from the whole population was carried out according to the results of the rep-PCR with BOX primers، and as well the locations of the isolates and the fields where the isolates had been collected. Population genetic structure of the pathogen was evaluated using rep-PCR as a molecular marker with three primers namely BOX، ERIC and REP. Three softwares of POPGENE، NTSYS-pc and GenALEx6 were utilized for data analysis. Population structure study among six sub-populations of the Iranian isolates revealed that 73% of the total variance was related to the variations within sub-populations while 27% of that related to the variance among sub populations. Mean gene diversity of the population was estimated as 0. 3147. A dendrogram، based upon genetic similarity with Dice coefficient and UPGMA method showed no clear separations among isolates belonging to different races 1 and 2، so racial distribution of isolates is not found consistent with rep-PCR classification of the isolates in the dendrogram. There exists some consistency between geographical origin of the isolates and their genetic similarity. This is the first study covering population genetic structure of P. tritici-repentis in Iran. An evaluation of telemorph production regarding the pathogen، showed that pseudothecia (with asci and ascospores) were produced for 54% of the isolates while 17% of the isolates produced pseudothecia without asici and 29% while produced no sexual structures. It seems that beside the MAT gene and some other independent genetic factors، some macronutrients as well as humidity effect telemorph production.