نشریه آفات و بیماریهای گیاهی
سال هشتاد و هشتم شماره 2 (پیاپی 111، اسفند 1399)

In order to investigate the soybean competitive ability (DPX cultivar) under interference condition different densities of Asian spider flower (0, 3, 5, 10, 15, 20, 30, 45 plant/m-2); an experiment was conducted based on randomized complete blocks design with three replications in 2015–2016 growing season in Kalaleh, Golestan province. Different densities of Asian spider flower had a significant effect on biological yield, economic yield, 100 grain weight and pods per plant of soybean. The highest grain and biological yields of soybean were 374.9 and 734.30 g/m2, respectively which observed in weed-free treatment. However, these traits declined nonlinearly as weed density increased, so that in 45 plant/m-2interference treatment, economic and biological yields reached 172 and 344.38 g/m2, respectively.

Lycoriella auripila (Winn.) (Diptera: Sciaridae) and Megaselia halterata (wood.) (Diptera: Phoridae) are major pests of cultivated mushroom, Agaricus bisporus (Lge.) Imbach. They are controlled by chemical insecticides. It is necessary to study the toxicity of insecticides against the dipteran pests of mushrooms. This research investigated the toxicity of four commercial insecticides against the larval stage of the pests including pyriproxyfen and cyromazine from insect growth regulator group (IGRs), trichlorfon and cypermethrin from organophosphorus and pyrethroid groups respectively. The insecticides bioassay with sciarid and phorid larvae were conducted in the growing medium of mushroom. Insecticide treatments were incorporated into growing medium. The LC50 values of the insecticides were determined by emerged adults. The values of LC50 against the sciarid larvae for pyriproxyfen, cyromazine, cypermethrin and trichlorfon were 1.46, 31.15, 47.96 and 103.8 and for phorid larvae7.25, 189.65, 69.96 and 86.8 mg ai/L respectively. Pyriproxyfen was more toxic insecticide on larvae of both the pests.

The fungi, Macrophomina  phaseolina  and Fusarium oxysporum are the main causal agents of sesame wilt making a great loss in Iran and worldwide. In this research, 25 cultivars and genotypes of sesame including 14 yield comparison test lines, four improved lines and six commercial cultivars (Dashtestan2, Darab1, Halil, Naz-uniculm and Naz branched grew in 3 replicates in randomized complete blocks in a hotspot field in 400-ha farm of Seed and Plant Improvement Institute (SPII) in Karaj. Each genotype was cultivated in two meters length. Disease scores were recorded at the maturity stage. The results showed that all genotypes were affected by disease to some extent among which Dashtestan 2 had the highest mean of disease score. The lines 92-10 and 90-10 with the lowest record of wilting (less than 20%) were grouped as resistant lines. Correlation analysis between five important agronomic traits related to yield with wilt disease data showed that damping-off data has a significant correlation with the number of seeds per capsule. Although a significant correlation was observed between wilting with capsule length, the coefficient was low. There was a non-significant correlation between wilt disease and 1000 seed weight, SPAD no. and capsule weight without seeds.

To evaluate the different doses of mesosulfuron + iodosulfuron (Atlantis) and application time on two Kurdistan and Fars populations in crop year 2013-2014, a split spilt plot experiment was carried out in the field in Fars province. The different doses of herbicide (0, 6, 12, 18, 24 g ai/ha) as the main plot, two populations of wild oat (Kurdistan and Fars respectively) as sub-plot and application time at stages of 18 (8 leaves) and 23 zadoks (tillering) as sub-sub plot were considered. The regrowth percentage of wild oat Fars and Kurdistan populations in highest dose (24 g ai/ha) at two herbicide application times in 8 leaves (16.16 and 4.5%) and tillernig (23 and 6%) were obtained respectively. It is remarkable that the regrowth percentage of wild oat at reduced dosage (12 g ai/ha) at tillernig time was more than 8 leaves in two Kurdistan and Fars populations. Dose-response equations for dry weight of wild oat showed that the required level of dose for reaching a 50% decrease in two populations of wild oat and application times was different. Doses of 7.93 and 8.38 g ai/ha in order to achieve a 50% decrease in the dry weight of Kurdistan population in two application times of 8 leaves and tillering was required. These amounts for a 50% reduction in dry weight of Fars were 9.89 and 9.66 g ai/ha, respectively. In reduced doses of herbicide with delayed application time, regrowth and dry weight of wild oat increase and effect on grain yield and number of spike in wheat. The application of reduced doses (12 g ai/ha) is recommended at stages of 18 zadoks (8 leaves).

Late blight (PLB), caused by Phytophthora infestans, is the most important diseases of potato in the world and Iran that 16 models have been developed for forecasting so far. Gorgan county had the largest potato cultivated area in the province and during recent 17 years, PLB appeared in 11 years with different severities. In order to developing a forecasting model based on “blight favorable day” concept, daily weather data converted to periodic and conditional variables, at last three predictor variables were developed. FTP was the best predictor variable which composed of three temperature variables and two precipitation variables and its daily score was -2 to 4. Accumulated FTR from 21 March to disease appearance was 64 and in no-disease years was 4. Prediction accuracy of the model was 75% and 89% based on logistic regression and discriminant analysis, respectively and sensitivity and specificity of final model was 92 and 100%, respectively.

Functional response is one of the standard criterions to detect the efficiency of a predator as a biocontrol agent. Classic functional response experiments include two fundamental assumptions: 1) the prey is evenly distributed in space; 2) predation rate is often time-limited. In this article, the limiting factor of Nesidiocoris tenuis (Hem.: Miridae) was investigated on tomato leafminer eggs. Multi-patch functional response experiments were carried out using first and fifth instar nymphs and females of the predator. Two set of prey densities exposed to the predator included the upper density or the total number of prey available in all patches equated satiation level. Experiments were conducted by three available times; 1, 2 and 3h for fifth instar nymphs and females, and 1, 1.5 and 2h for the first instar nymphs. The results showed that the predator is limited by volume of its gut rather than by time.  The functional response of all stages was from type II. The values of Th and a' were estimated as 4.033 min and 0.0385 min-1 for first instar nymph, 3.517 min and 0.0305 min-1 for fifth instar nymph and 2.512 min and 0.0278 min-1 for female. According to this study, N. tenuis could be considered as an efficient biocontrol agent of tomato leafminer.

Common scab is one of the most important bacterial diseases of potato which restricts the optimal production of this economical crop. Following sampling in 2018-2019, the powdery colonies with Streptomyces morphology were purified and evaluated based on phenotypic features, pathogenicity and detecting the genes on Pathogenicity Island including txtAB, nec1 and tomA. The colony morphology of the strains on malt yeaste extract agar was variable and pathogenic strains showed symptoms such as no germination, dwarfing and necrosis on radish seedlings which were divided into six phenotypic groups. 11 out of 20 pathogenic strains on radish, were capable of causing necrosis or pitting on potato slices and eight of them showed chlorosis or necrosis on tobacco leaves after 10 days. The results of pathogenicity including superficial or raised lesions with the lesion severity index of 1-4 were recorded in greenhouse conditions. The 700 bp fragment was detected in six out of eight selected strains. While, txtAB and tomA were amplified in JR-12 and TM-29, respectively. Based on 16rSRNA sequencing results, JR-12 and TM-29 strains were characterized as Streptomyces bottropensis and Streptomyces sp. Respectively.It seems that the Razavi-Khorasan strains have a virulence factor other than Thaxtomine A, which needs further experiments to confirm.

Scald and covered smut, caused by Rhynchosporium secalis and Ustilago hordei, respectively, are two important diseases of barley in Khuzestan province in the southwest of Iran. The present study was conducted to evaluate the resistance of 100 selected genotypes of barley from different sources to these diseases under field conditions in two research stations of Ahvaz and Shavar in 2019. Evaluation for barley scald leaf disease was performed based on the double digit method 00-99 scale. In the case of covered smut, barley seeds were inoculated by spore suspension of pathogen three times every two days before sowing, and the number and percentage of infected spikes were recorded after the emergence of the disease. According to the results, 6, 15, and 7 genotypes were immune, resistant, and moderately resistant, respectively, and the rest of genotypes were susceptible or moderately susceptible to scald. The barley cultivar Bahman was determined as immune and the cultivars Sahra, Norouz, Lout, Makoui, and Jolgeh were shown to be resistant. In the case of covered smut, 28 genotypes were determined as resistant or moderately resistant and 72 genotypes were shown to be susceptible or moderately susceptible. The barley cultivars Sahra, Goharan, Lout, Valfajr, and Bahman were resistant to the covered smut disease. In this study, the highest percentage of resistance sources for both diseases was related to cold climate and the lowest percentage was related to warm climate.

Apple powdery mildew is one of the most important apple diseases (Malus domestica Borkh) in the world. The aim of this study was to evaluate interaction effects between some common cultivars and rootstocks to apple powdery mildew. The experiment was conducted in a factorial randomized block design with four replications under natural conditions using MM.111, MM.106, M9 seedling rootstock and four cultivars include Red Delicious, Golden Delcious, Golab e Kohanz and Golab e Esfahan, in four years. The evaluation was performed based on incidence and severity disease percentage on the leaves during two years. It was concluded that M.9 rootstock have a negative effect on Esfahan's Golab and made the cultivar more susceptible to the disease.  However, this rootstock had a positive effect on Red Delicious, Golden Delicious and Golab e Kohanz. M.9 × Golab e Esfahan and Seedling × Golab e Esfahan combinations with 52.% and 48.10% disease incidence and 56.77 and 53.33 disease severity percentage respectively, showed the most suceptibility, while, M.9 × Red Delicious and MM.106 × Red Delicious with 12.50 %and 16.76% disease incidence and 16.47% and 19.61% disease severity respectively, showed the highest resistance. So Golab e Kohanz and Red Delicious on M.9 rootstock, Red Delicious on M.9 and M.106 rootstock are recommended.

Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap), is one of the major diseases in common bean fields leading to significant losses in yield and seed quality. Application of resistant varieties is the effective disease management. In this study, 15 bean genotypes with the Sadri cultivar as a check varaiety were cultivated in the field of Agricultural and Natural Resources Research Center of Markazi province during 2015 and 2016 which were inoculated with bacterial suspension (107 cell/ml) before flowering stage. The resistance of genotypes was assessed in the pre-physiological maturity stage. The results showed that CBB reduced yield average 33.2% in the studied lines. Also, yield components including number of pods per plant, number of seeds per pod and one hundred seed weight reduced 28.9%, 17% and 15.6% respectively.Finally, based on factor and cluster statistic analysis, five bean lines with the highest geometric mean productivity and steress tolerance index and the lowest stress susceptibility index were selected. VAX3 and Ks31118 genotypes were released as CBB resistant red bean varieties due to their marketability and suitable grain color. Also VAX1, VAX5 and VAX6 lines can be used as the parents in bean hybridization programs to release resistant varieties to this disease.

In this research, possibility of induced systemic resistance in tow tomato cultivars Termeh and Capitan was assayed by exogenous application of methyl jasmonat (MeJA). Tomato plants were treated with methyl jasmonat at concentration of 0, 0.1 and 0.2 mM by spraying at 2-4 leaf stage and then were inoculated withpathogen agent at 6- leaf stages. Gene expression level of npr1, pds and eds1 genes and catalase, peroxidase, polyphenol oxidase activity and total phenol continent was investigated using qRT-PCR and spectrophotometery methods, repectively. The results of this research showed that enzyme activity was variable in tested cultivars and interval times after inoculation. The highest enzyme activity was observed in Termeh cultivar under disease stress. The highest and lowest expression level was occured in npr1 and pds genes, respectively. These results indicated that methyl jasmonat is able to iduces resistance in tomato against wilting disease throught change on bio-chemical and molecular activities.