نشریه پژوهش های کاربردی در گیاه پزشکی
سال نهم شماره 2 (تابستان 1399)

Basal stem rot caused by Sclerotinia sclerotiorum is considered the most important fungal disease of sunflower in Iran. Application of resistant genotypes is one of economic strategies for the disease management. Recently, in association mapping for resistance to sclerotinia rot disease in sunflower, a significant relationship has been observed between the lower Sclerotinia-induced necrosis and HaRIC_B gene expression. On the other hand, expression of defense genes is highly regulated by transcription factors. In this study, using real time PCR technique, the expression level of HaRIC_B gene and MYB-related transcription factor were studied in partial resistant (LC1064C/ 8*A) and susceptible (SDR19) lines of sunflower inoculated with the S. sclerotiorum isolate A37. In studying the expression pattern of HaRIC_B gene in two lines, it was seen that the expression pattern in the LC1064C/8*A line was increased regularly from one sampling time to another and the expression rate at any time was more in LC1064C/8*A line than SDR19. Comparison of HaRIC_B gene expression and MYB-related transcription factor revealed a reasonable relationship between the expression level of both genes, especially in the LC1064C/8*A ine. This finding highlight the possible major role of MYB-related transcription factor in stimulating HaRIC_B gene expression and consequently inducing resistance to Sclerotinia in sunflower which, of course, needs further investigation. By confirming the resistance of the LC1064C/8*A line to Sclerotinia at the molecular level, this line could potentially be used in the production of resistant hybrid cultivars in conventional plant breeding programs.

Two spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae)isone of the most important pests of beans that large amount of acaricides are used to control it every year.The experiment was conducted to evaluate the resistance of 11 bean genotypes (KS-21494, KS-21493, KS-21492, KS-21498, KS-21517, KS-21529) and red (Dadfar cultivar, KS-31287 and KS-31286) to two-spotted spider mite at Khomein Bean Research Station during 2017 and 2018. This study was conducted in the randomized complete block design with three replications and in two experiments with spraying and without spraying in field and greenhouse conditions. Resistance mechanisms (tolerance, antibiosis and antixenosis) and plant resistance index were determined in greenhouse conditions. Sampling was performed by selecting 10 plants from each plot randomly and two leaves from the bottom and the top, then the density and damage of the pest were evaluated in the selected samples. Pest life stages including eggs and active stages (larvae, nymphs and adults) were counted and recorded. The results of this study showed that there was a significant difference among the cultivars and genotypes of beans in yield and its components and the population and damage of two-spotted spider mite. The results of comparing the means showed that the highest and lowest density of two-spotted spider mite eggs were observed in Sadri cultivar and KS-21517 genotype with 198.55 and 41.95, respectively. The highest and lowest yield were recorded 2437 kg/ha and 1221 kg/h on KS-31287 and KS-21529, respectively. KS-31286, KS-21492 and Dadfar were selected as tolerant genotypes and cultivar to two-spotted spider mite with damage scale of 3.6, 4 and 3.8, respectively. Antibiosis resistance mechanism was recorded on Dadfar and genotype KS-31286 with 18.4 and 15.2 adult mites, respectively. The antixenosis mechanism was recorded on genotype KS-31286 and Dadfar cultivar with 1.8 and 1 adult mites, respectively. The results of the calculation of the plant resistance index to two-spotted spider mite showed that the genotype KS-31286 and Dadfar cultivars had the highest resistance index at 9.09 and 14.28, respectively. Therefore, Dadfar cultivar is recommended in the first priority and genotype KS-31286 in the second priority for cultivation in the region. KS-31287 genotype was not selected as resistant genotype due to low plant resistance index despite high yield.

Use of resistant cultivars is an effective way to manage Zymoseptoria tritici blotch. This study was performed to identify new sources of resistance to among 135 wheat genotypes. Genotypes were cultivated in the Augment design and at the research field of Aliabad Katoul Agricultural high school. Artificial contamination of genotypes was done by spreading infected leaves and inoculating with pathogenic fungal spore suspension. The notes were taken five times, seven days apart. Cluster analysis categorized genotypes into four groups. Genotypes 51, 68, 79 (Shiraz), 85, 87, 89, 97, 110, 115 (Narin), 116, 123 (Mehregan) and 130 were classified in group three (resistant). This group had the lowest area under disease progress curve and showed high resistance to disease. Little frequency of genotypes in two susceptible (four) and resistant (three) groups showed that this trait was controlled by several genes with additive epistasis. Therefore, gene pyramiding and selection in early generations can be effective. Resistance genotypes identified in this study can be used in breeding programs for the pyramiding of resistance genes or backcross methods.

The root-knot nematodes (Meloidogyne spp.) are the most important group of plant parasitic nematodes in terms of economic damage to agricultural products. Biological control is one of the new and environmentally friendly methods to control of these pathogens. One way of biological control of nematodes is the use of anti-nematode plants. In the present study, the effect of Datura stramonium, Datura metel and Hyoscyamus niger extracts was evaluated against native nematode population of Meloidogyne javanica. Evaluations were based on the effect of extracts on nematode egg hatching and mortality of second stage juveniles (J2s) in laboratory conditions. For this purpose, the plants were cultured in the phytotron and the leaves of grown plants were harvested and dried. The aquatic extracts of powdered leaves (1gr to 30ml) were prepared and different concentrations of each extract were used to evaluate the rate of hatching and mortality of J2s. In terms of the effect of extracts on nematode egg hatching, all three plants were had inhibitory effects. High concentrations of the extract was more effective, so that the 50% concentration had the best effect in reducing hatching and the concentration of 25% had also good effect. The effect of extracts on the mortality of J2s was also significant, and all three plants, caused a significant percentage of J2 mortality compared with control, especially at higher concentrations. Of these, the concentration of 25% of all three plants had an appropriate inhibitory effect on J2s death. In another experiment, the effect of these extracts on seed germination of tomato (Super Strain B) was examined. Different concentrations of extracts were placed in sterile petri dishes covered with sterile filter paper and the seeds were placed inside them. The percentage of seed germination was recorded within a week. In general, it can be said that the extract of the plants had no negative effect on the germination of tomato seeds.

In current research, the effect of four artificial diets containing cowpea, red kidney bean, navy bean and corn seed flour on protein content of 4th instars whole body; 5th and 6th instars larval and pre-pupal gut and fat bodies; and pupal whole body of the cotton bollworm (Helicoverpa armigera Hübner), were investigated. Also, the effect of different diets on the digestive α-amylase and pectinase was studied. Protein patterns were also compared using SDS-PAGE. According to the results, the lowest amount of protein in 4 th instars whole body and 5 th instars gut and fat bodies was seen in corn as diet and highest one was in navy bean diet. Insects reared on the corn as diet did not developed to 6 th larval stage during the experiment. Except for the protein content of 6 th instars fat bodies, no significant differences were observed in the other treatments of the 6 th instars and pre-pupa. The lowest amount of pupal protein was found in red kidney bean diet and the highest one was in navy bean diet. Due to the decrease in protein content in different diets, insect weight and the activity of digestive α-amylase and pectinase were also affected and significant differences were observed. The least weight and activity of enzymes were recorded in corn diet. Diferences in the amount of protein was also detected in SDS-PAGE. Consequently, artificial diets of corn and red kidney bean are not suitable for this insect rearing and white bean and cowpea are reported as appropriate diets.

Stem or black rust caused by Puccinia graminis f. sp. tritici (Pgt) is one of the most destructive wheat diseases in the world, including Iran. Investigation of virulence factors on wheat resistance genes, identification of resistance sources to stem rust among host genotypes and determination of effective resistance genes in resistant wheat genotypes are the requirements of using genetic resistance (production of resistant cultivars) as the most efficient and healthy way to control this disease. To assess the seedling resistance of 30 wheat genotypes, which produced CIMMYT Center (International Maize and Wheat Improvement Center), and introduced as resistance sources to stem rust was investigated with six different Pgt races base on randomized complete block design with three replications. Race analysis of Pgt isolates was done to identify of their virulence on resistance genes (Sr) of stem rust at the greenhouses of the cereal section of the Seed and Plant Improvement Institute. The results indicated that the races were TKTTF, TTTTF, PKSTC, TTRTF, TKSTF and PTRTF. Genotypes carrying the genes Sr22, Sr24, Sr26, Sr31, Sr32, Sr33 and Sr40 were resistance against all the Pgt races, and are introduced as the differential cultivars with effective Sr resistance genes. Genetic resistance components including infection type and latent period for each genotype were recorded under greenhouse conditions. The results of the genetic resistance components showed the existence of phenotypic variation in the response of genotypes to stem rust races. Resistant genotypes identified in this study (genotypes 4, 5, 6, 7, 8, 9, 11, 13, 14, 16, 17, 18, 20, 21, 22, 25, 26, 27, 28 and 29) can be used as seedling resistance resources in national wheat breeding programs for genetic resistance to stem rust in different climates of the country.

Downy mildew is the most important disease of cucumber. Efficacy of the fungicides Cyazofamid (Regnant® SC 20%) and Pyraclostrobin + Dimethomorph (Pyradim® DF 18.7%), in controlling cucumber downy mildew disease were assessed in Tehran and Mazandaran provinces in a Randomized Complete Block Design (RCBD) with 10 treatments and four replications. Treatments included the Regnant fungicide at three concentrations of 0.5, 0.6 and 0.75 ml/L and the Pyradim fungicide at three concentrationse of 0.25, 0.3 and 0.35 ml/L as target fungicides and Propamocarb hydrochloride + Fluopicolide (Infinito® SC 68.75%) 2ml/L and Cyazofamid (Ranman® SC 400) 0.5 ml/L as standard fungicides including two controls as with and without water spray. The combined Analyses of Variance (ANOVA) revealed a significant diference between treatments at level of 1%, but no significant difference was detected between locations and treatment × location intractions. Means comparison based on Duncan Multiple Range Test revealed that the Ranman® and Infinito® fungicides together with the Regnant at the dose of 0.75 ml/L decreased disease severity by 79.1, 72.8 and 71.9% compared to water spray treatment (control), respectively. On the contrary, the fungicides Regnant at the dose of 0.5 ml/L and Pyradim at the concentrations of 0.25 and 0.3 ml/L decreased disease severity by 46.7, 46.7 and 43.2% showing the lowest efficacy compared to water spray treatment (control), respectively.. Based on the results, the concentrations 0.6 and 0.75 ml/L of the Regnant and the dose of 0.35 ml/L of the Pyradim fungicides are recommended as the proper concentrations for control of the disease with 7-10 days intervals.

Integration of different pest control tactics into a larger program is a principle in modern IPM. Interaction between different tactics and possible antagonism between them then will become important. A popular integration is integration of egg parasitoids, Trichogramma spp. and larvicidal microbial agent, Bacillus thuringiensis Berliner against some field crop moth-pests, particularly in bollworm-cotton system. Although sequence of application allow avoiding direct antagonism, but indirect effects on the next generation of the parasitoid via treating the target pest’s larvae is not impossible. Some direct effect via overlapping of different stages of the pest is also possible. Therefore, studying possible maternal effects on parasitoids of the next generation that are developing on B.t.-treated host larvae is required. In this study, response of Trichogramma brassicae Bezdenko, was studied on two kinds of hosts; first bollworm, Helicoverpa armigera Hubner eggs laid by those females that treated by LC20 of B. thuringiensis in third instar. The second one control (untreated) individuals. Life history parameters were compared between the two groups by two-sided t-test. Fortunately no significant difference was observed between the two groups. It means that B.t. had no undesirable effect on T. brassicae. The mean value of R0, rm and T were 41.22 ± 3.85 female/female/generation, 0.3545 ± 0.009 /d and 10.49 ± 0.19 d as average of the two treatments. Thus, B. t. is safe for integration into Trichogramma application programs.