نشریه پژوهش های کاربردی در گیاه پزشکی
سال دهم شماره 3 (پاییز 1400)

The beet armyworm, Spodoptera exigua, is one of the most important polyphagous ubiquitous pests of the sugar beet. Because of adverse effects of conventional pesticides, introduction of new safe control methods in beet army worm management is essential. The aim of this study was evaluating compatibility of two EPN species, Steinernema carpocapsae and S. feltiae with cypermethrin against beet army worm larvae. Contact and oral toxicity of EPNs and cypermethrin was evaluated against six days old beet armyworm larvae. The recorded LC50 values of S. carpocapsae and S. feltiae were 6.63 and 4.41 IJ/Larvae, respectively. This value for cypermethrin was 465.4 ppm. Combination effects were tested at three concentrations of EPNs including 2, 4, and 6 IJs/Larvae and 160 and 320 ppm of cypermethrin. Nevertheless, the negative effect of cypermethrin on EPNs, synergistic effects on larvae mortality were recorded at combination treatments 160 ppm Cyp+2 IJs/Larvae EPNs, similar effect was also recorded at treatment contained 320 ppm cypermethrin and same level of IJs of S. feltiae. Larvae mortality was enhanced by increasing the exposure time to cypermethrin and also in combination with EPNs. This increasing trend was also recorded for 48 hours of post-exposure to EPNs and then the curve became plateau.

The emergence and rapid spread of virulent races of wheat rusts has driven a search for sources of resistance for durable resistance. Slow rusting resistance, a kind of race-nonspecific resistance, has been reported to be more durable. In this study in order to identify possible sources of durable stem rust resistance between elite wheat lines, slow rusting parameters including coefficient of infection (CI), final rust severity (FRS), apparent infection rate (r) and relative area under disease progress curve (rAUDPC) were evaluated in a set of forty six wheat lines along with susceptible control (mixture of McNair and the line CD-90-12) in 2015-2016 and 2016-2017 cropping seasons. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran). All lines were evaluated under natural infection conditions against race population having virulence to resistance genes including Sr25, Sr5, Sr6, Sr7a, Sr23, Sr28, Sr29, Sr30, Sr33, Sr34, Sr37, SrDP2, SrGT, SrPL, SrWLD, SrH and SrTmp < /em>. Results of evaluations for resistance parameters showed that the lines M-93-13, M-93-14, M-93-16 and M-93-20 had low level of CI, FRS, r and rAUDPC so were considered as lines having high levels of slow rusting resistance. The lines C-93-10, C-94-6, C-94-8, CD-94-6, M-93-3, M-93-12 and M-93-18 had moderate level of slow rusting and 25 lines with high values of CI, FRS, r and rAUDPC were grouped as lines having low level of slow rusting resistance. The remaining lines without slow rusting resistance were considered as susceptible group. The lines with high and moderate levels of slow rusting resistance can be used in breeding programs or releasing new resistant cultivars.

The cigarette beetle, Lasioderma serricorne damages a wide range of stored products. Despite a great deal of research, control of this pest still relies on the use of phostoxin tablets, which is becoming less effective as the insect develops resistance to this compound. In this research mortality effect of carbon dioxide and nitrogen gases evaluated individually and in combination, against adults of L. serricorne. Mortality was recorded after 24 h. Results indicated that nitrogen did not have a significant lethal effect on adults of pest. The LC50 value of carbon dioxide was estimated 2498.59 ppm. In combination tests of these gases, concentrations of 254, 381 and 508 ppm of nitrogen were combined with the LC50 value of carbon dioxide. Results showed that insect mortality was increased by decreasing the concentration of nitrogen or by increasing that of carbon dioxide. According to the results of this study, the cost of using phostoxin tablets was much higher than that of carbon dioxide. Linear programming can be introduced as a useful method for optimizing control managing of this pest. Also, by considering the low cost control and high insecticidal effect of carbon dioxide and evaluating other aspects, this fumigant can be introduced as a suitable alternative to phostoxin.

During spring and summer of 2018, suspected symptoms of the phytoplasma disease such as leaf shrinkage and yellowing as well as leaves with abnormally-enlarged stipules were observed in apple orchards in Khorasan Razavi province and 33 leaf samples were collected. Samples of symptomatic apple tree were assayed for infection with phytoplasma, using universal primer pairs P1 / P7 and nested PCR using primer pair R16F2n / R16R2, fU5 / rU3 and R16MF2 / R16MR2 in Polymerase Chain Reaction (PCR). The universal PCR products were 1800 bp fragments and the nested-PCR products were 1250, 876 and 1400 bp fragments, respectively, which were amplified by primer pairs. Of 33 leaf samples from apple, 18 samples were tested positive for phytoplasmas. The R16MF2/R16MR2 primed nested PCR products were cloned, sequenced and submitted into GenBank. Comparison of the obtained sequences with the sequences of NCBI using BLAST software and Restriction Fragment Length Polymorphism (RFLP) analysis of the nested PCR products using the enzymes AluI, RsaI and TruI (MseI) indicated that phytoplasma in apple trees in Razavi Khorasan province was most similar to Candidatus Phytoplasma trifolii related to Clover Proliferation (CP) 16SrVI group. Analysis of sequences using iPhyClassifier software, determination of nucleotide similarity, and phylogenetic analysis of full-length 16S rDNA showed that phytoplasma in apple tress of Razavi Khorasan province belongs to 16SrVI-A subgroup. This is the first report on Ca. Phytoplasma trifolii infections in apple trees in Iran and other regions across the world.

Common pistachio psyllid, is one of the most important pests of pistachio in Iran. In this study, the effect of spirotetramate (SP), salicylic acid (SA), methanolic and n-hexane extracts of walnut husk (MW & NW, respectively), methanolic and n-hexane extracts of dill seed (MD & ND, respectively) and the combined application of spirotetramate with these compounds (SP + SA, SP + MW, SP + NW, SP + MD and SP + ND) were studied on pistachio psyllid population during two years. Distilled water was also considered as control. The amount of secondary compounds (total phenol and flavonoid contents) in pistachio leaves in different treatments was determined. In the first year, the highest percentage of population reduction of pistachio psyllid was observed in combined treatment of spirotetramate and methanolic extract of dill seed (SP + MD) with an average of -91.26 ± 3.21 % and in the second year in methanolic extract of dill seed (MD) with an average of 36.70 ± 8.43% and SP + MD combined treatment with an average of -35.17 ± 17.9%. In both years, the combined use of n-hexanic extract of green walnut husk with spirotratram (SP + NW) reduced significantly the population of pistachio psyllids compared to the use of spirotratram alone. The amount of total phenol and flavonoid compounds in the leaves of pistachio trees treated with the studied compounds showed a significant difference. The highest level of total phenol was obtained in SP + MD treatment (75.48 ± 1.94) that showed significant differences with SP, MD and SP + ND treatments. The results of this study during two years showed that methanolic extract of dill seed in combination with spirotetramate (SP + MD) had the greatest effect in the population control of pistachio psylla nymphs and therefore can be considered in the integrated management programmes of this pest.

Chickpea is the third most important food legume in the world. Ascochyta blight is the most destructive disease of chickpea caused by the fungus Didymella rabiei. Identification of resistance sources in germ plasm of chickpea is essential for breeding programs and management of disease. In order to investigate the effects of spore concentration and virulence severity of isolate on intensity of ascochyta blight in chickpea genotypes, a factorial experiment was conducted based on completely randomized design with three replications. Effect of two isolates (A3: moderately virulent & A6: highly virulent) and different spore concentrations (105, 2 × 105, 5 × 105 spores ml-1) were investigated on disease rate of 20 genotypes. Results showed that disease scale and its severity were affected by spore concentration, virulence severity of isolates and chickpea genotypes and there was significant difference between genotypes, isolates and spore concentrations. The disease severity increased with spore concentration from 2 × 105 to 5 × 105 spores ml-1 for resistant lines including, ILC 202, ILC72, ILC3279, ICC3996 and ICC12004, while the susceptible lines were affected by all of the conidial concentrations. The chickpea differential lines including ILC202, ILC72, ILC3279, ICC3996 and ICC12004 were resistant to all of the conidial concentrations of A3 (moderately virulent) while were susceptible to 2 × 105 spores ml-1 of A6 (highly virulent). The spore concentration of 2 × 105 spores ml-1 with A3 isolate developed the most discrimination between chickpea genotypes on the basis of mean disease scale. The obtained information can be used in breeding programs of chickpea and pathogenic diversity studies.

The lemon butterfly, Papilio demoleus is one of the most important citrus pests in nursery and newly planted trees in most citrus growing areas of Iran, particularly in Mazandaran province. In this research, nutritional indices of Lemon butterfly larvae, was investigated on different host plants (Citrus sinensis c.v. Thompson navel, Citrus aurantium, Citrus sinensis c.v. Sangin and Citrus reticulata) under the laboratory conditions (24 ± 2˚C, 65-75% RH and photoperiod of 14L:10D h) in 2008. Results indicated that the relative growth rate (RGR), efficiency of conversion of digested food (ECD) and approximate digestibility (AD) were significantly different among host plants. However, there was no significant difference between relative consumption rate (RCR) and efficiency of conversion of ingested food (ECI) among citrus varieties. The highest and lowest relative consumption rate related to Thompson navel and Sangin as 6.92 ± 0.36 and 3.71 ± 0.19, respectively. ECI and ECD were the highest on Thompson navel as 41.19 ± 6.6 and 96.63 ± 33.42, respectively.

Take-all disease of wheat caused by Gaeumannomyces graminis var. tritici is one of the important diseases of wheat worldwide. In this study, application of two Trichoderma species on the control of this disease was evaluated under laboratory and greenhouse conditions. The causal agent of disease was isolated from suspected diseased plants in wheat fields of Khorrramabad district, identified according to scientific mycological literatures and its pathogenicity was proven in greenhouse. The mycelial inhibition potential of Trichoderma harzianum and T.viride in dual culture and volatile metabolite effects against the pathogen were tested in vitro. Then, single and combined greenhouse application of the two Trichoderma isolates and triadimenole fungicide for control of take-all disease were investigated using a completely randomized design with 16 treatments and four replications and disease severity and growth indices were recorded and analyzed statistically. In vitro experiments showed that both of the Trichoderma species disintegrated the hypha and inhibited the mycelia growth of G. graminis. Combined application of triadimenole fungicide with the two antagonists, triadimenole, and single application of T. harzianum and T. viride reduced take-all severity by 70.6, 58, 47.06 and 47.06 percent, respectively in greenhouse after 30 days of sowing. Trichoderma biocontrol agent and integration of chemical compounds with antagonists would provide promising strategy for management of wheat talke-all disease.

Monilinia fructicola causes disease on peaches and nectarines, and is an economic concern in the South Eastern United States. This experiment was designed to try and understand the mechanisms that allow M. fructicola to be resistant to Demethylation Inhibitor (DMI) fungicides, which is an interest among agronomists. Isolates of M. fructicola were analyzed with High Performance Liquid Chromatography to measure differences in ergosterol concentration between selected groups of isolates. This was done to determine if M. fructicola is using an alternate sterol other than ergosterol as the final end product of the sterol biosynthesis pathway, or is using a different enzyme other than 14-a demethylase, to synthesize ergosterol. This experiment showed differences in ergosterol concentration between the groups of isolates that were analyzed. The three groups analyzed in this study included isolates without the ‘Mona’ element while susceptible to DMI fungicides, isolates with the ‘Mona’ element and resistant to DMI fungicides, isolates with the ‘Mona’ element while susceptible to DMI fungicides. Statistical analysis revealed significant differences between the three groups of isolates, which suggesting that M. fructicola uses a different enzyme, other than 14-a demethylase, to synthesize ergosterol.