نشریه پژوهش های کاربردی در گیاه پزشکی
سال دهم شماره 4 (زمستان 1400)

Melon aphid Aphis gossypii is one of the economic pests of melon that has a high adaptability to various environmental conditions, including salinity. In this study, the lethal and sub-lethal (LD10) effects of Palizin soap insecticide (0, 450, 696, 1078, 1669, 2583 and 4000 ppm) were investigated on A. gossypii reared on melon seedlings under salinity stress (0, 20, 40 and 60 mM) in a Factorial experiment based on completely random design in growth chamber (25 ± 1°C, %70 ± 5 RH and 16L/8D h photoperiod). Bioassay was performed based on leaf deep bioassay method. The LD50 values after 24 hours were estimated as 1378, 1036, 860 and 749 ppm for treatments, respectively. An inverse relationship was observed between the toxicity of Palizin and increase in salinity. To determine the effect of LD10 of Palizin on aphids, biological parameters of insect fertility in each salinity treatment were determined based on the age-stage, two-sex life table theory. The nymphs had longer development duration in treated aphids than aphids that grew under similar salinity conditions, but adult insects had a shorter longevity and less fecundity. The average of intrinsic rate of increase varied from 0.31 to 0.17 ♀/♀/days-1 and the average of generation time varied from 11.16 to 12.65 days between 0 and 60 mM salinity treatments. Based on the results, Palizin insecticide with salinity stress can be recommended for successful integrated management of aphid on melon under salinity stress conditions.

Western flower thrips (Frankliniella occidentalis) is one of the most important plant pests with a wide range of hosts that causes damage in most parts of the world. In this study, the efficacy of four insecticides including Gracia® (fluxametamide EC 10%) 0.3 and 0.5 ml/l, imidacloprid (SC 35%) 0.5 ml/l, cypermethrin (EC 40%) 0.5 ml/l and Proteus® (thiachlopride + deltamethrin 11% OD) 0.7 ml/l against this pest was based on a randomized complete block design with four replications in a cucumber greenhouse in 2019. The regression relationship between post-spraying intervals and the western flower thrips population was fitted with a quadratic model.  The results of analysis of variance of Western flower thrips mortality by treatments on days 3, 7 and 14 after spraying were significant (P <0.05). Also, two effectiveness indices of chemical compounds on this pest were presented and a significant difference was observed between them. The relationship between the population density of western flower thrips per flower and the density of thrips hunted on each blue card was also determined and their conversion coefficients were obtained. In general, fluxametamide with the highest percentage of mortality and control index and the lowest damage index among the tested treatments is recommended as a suitable insecticide to control this pest in greenhouse conditions.

Bacterial canker disease caused by Pseudomons syringae pv. syringae, is one of the most damaging diseases in sour cherries. In this study, relative resistance of some local sour cherries to this disease was evaluated. Totally, 46 genotypes in adult stage in two repetitive years (2018 and 2019) and 18 genotypes in seedling stage at year 2020 were examined. A mixture of three local P. s. pv. syringae isolates was used as inoculum. Saplings trunks were inoculated in autumn 2019 and canker length was measured one year later. Adult trees were inoculated in autumn 2017 and canker length was recorded one and two years later. Based on result, mean canker length was different among genotypes in both stages. In saplings, the most and the least canker length were rated for genotypes 230 and 125, respectively. Compound analysis of adult trees data showed the least and the most canker lengths were related to genotypes 208 and 104, respectively which were thus rated as the most susceptible and the most resistant genotypes. Based on the results obtained from adult plants, planting of susceptible genotypes like 108, 206 and 220 in risk area is not recommended.

Virulence of the two Iranian isolates of Beauveria bassiana was evaluated against the larvae of Hyphantria cunea through bioassay and immune responses. The median lethal concentrations (LC50) for AM-118 and BB3 isolates calculated as 8.8×105 and 2.3×106 spore/mL. by using dipping method. The LT50 values were calculated as 3.94 and 5.78 days, respectively for AM-118 and BB3 isolates. The highest numbers of the total hemocytes, granulocytes, and plasmatocytes were observed 3-6 hours post-injection of both fungal isolates. On the other hand, the total number of hemocytes increased from 160×104 to 480×104 cell/mL and the numbers of granulocytes and plasmatocytes increased to 200×104 and 140×104 cell/mL, respectively. The larvae injection by the conidia of AM-118 and BB3 led to the increase of nodule numbers at time intervals of 12-24 hours and the activity of phenoloxidase after 6-12 hours of post-injection from 0.12 to 0.2 U/mg protein. The isolate AM-118 showed the higher virulence compared to BB3 and it caused the more mortality in the lower time and spore concentrations. Moreover, the immune responses of the larvae toward this isolate were lower than BB3 isolate. The current results demonstrate that the two Iranian isolates of the entomopathogenic fungus, B. bassiana, are virulent against the larvae but they induce immune responses indicating physiological conflict between the pathogen and host.

Lentil wilt caused by Fusarium oxysporum f. sp. lentis is one of the most important diseases of this plant in dryland areas of the country. In this study, the effect of lentil seed priming with different concentrations of resistance inducing materials, biopriming (with bacterial antagonist Bacillus methylotrophicus), hydropriming and application of fungicide Rovral TS were evaluated for enhance resistance in plants and reduction in disease severity under laboratory, glasshouse and field conditions. In the laboratory, oxalic acid 2 and 4 mM, fungicide and the bacterium inhibited the mycelial growth ofpathogen. Most of the treatments increased seed germination and rootlet length significantly. Treatments of Bacillus, hydropriming, silicon 2, silicon nanoparticles 4, methyl salicylate 0.2 and 0.4 and salicylic acid 0.5 mM increased the wet and dry weight of rootlet and plumule significantly. In the greenhouse conditions, all experimental treatments were able to significantly reduce the disease severity in the plants compared with the control and the best result was achieved using Rovral TS, antagonist, methyl salicylate 0.1 and salicylic acid 0.25 mM, respectively. In the field conditions, the hormones were applied individually or in combination with the antagonistic bacterium. The least percentage of mortality obtained through silicon nanoparticles 1 mM in the individual application, while silicon along with silicon nanoparticles both in 2 and 4 mM were the best in combination form. This study showed that the application of antagonistic bacterium and hormones in combination with eachother or individually is an effective way to decrease disease severity in lentil.

In this study, the effect of Rhizophagus irregulariss mycorrhiza and nitroxin bio-fertilizers alone and in combination form was evaluated on control of chickpea wilt disease caused by Fusarium oxysporum f. sp. ciceris. Evaluation of effectiveness of these treatments was done through measurement of chlorophyll and carotenoid pigments, and disease severity. A factorial experiment based on randomized complete block design by eight treatments with three replications was conducted under greenhouse condition. Our results showed that the amount of chlorophyll and carotenoid pigments were significantly decreased in infected plants without biofertilizer treatment while disease severity was increased. The highest increase in  chlorophyll a and carotenoid pigments was observed in nitroxin treatment while the highest increase in  chlorophyll b and ab was recorded in mycorrhizae treatment. Approximately, the maximum change in measured parameters was related to mycorrhiza treatment while all treatments were able to increase yield components compared to control plant. The results of disease severity assessment in infected plant inoculated with bio-fertilizers showed that application of these bio-fertilizers in combination form caused a significant reduction in disease severity. Based on these results, use of both bio-fertilizers combined with soil could increase plant resistance to disease stress by the  increase of yield components

 Viroids are classified in two families including Avsunviroid that consists of three genera (Pelamoviroid, Avsunviroid and Elaviroid) and pospiviroid including five genera (Apscaviroid, Hostuviroid, Cocaviroid, Coleviroid and Pospiviroid). Grapevine-infecting viroids belong to the three genera in the pospiviroid family. A total of 121 symptomatic and non- symptomatic leaf and green shoot samples were collected from the main vineyards in Zanjan province to detect the important viroids infecting grapevines. Total RNAs were extracted from the samples and then cDNAs were synthesized by cDNA synthesize Kit with a random hexamer primer. Specific primers used to detect Grapevine yellow speckle viroid 1(GYSVd-1), (GYSVd-2) Grapevine yellow speckle viroid 2, (HSVd) Hop stunt viroid, Australian grapevine viroid (ASGVd) in reverse transcription polymerase chain reaction (RT-PCR). The results revealed that the specific DNA fragments corresponding to each viroids were amplified in PCR. Percentage of infections were 14%, 16%, 20% and 22% for GYSVd-1, GYSVD-2, HSVd and ASGVd relative to total number of examined samples, respectively. Sequencing of seven selected PCR-amplified fragments showed that each newly sequenced segment was classified in a clade with the previously reported respective isolates from Iran. In addition, the most mixed infection related to HSVd and other viroids. This is the first assay to detect the four important viroids infecting vineyards form Zanjan province.

 Downy mildew is one of the most important diseases of cucumber. The use of multi-site fungicides in disease control programs is recommended to ensure adequate crop protection and to delay the potential resistance of high-risk groups of single-site fungicides. The efficacy of 15 different copper oxychloride (WP 35%) brands of Iranian formulators with a concentration of 2 g/L, in control of cucumber downy mildew were assayed. Other treatments were two registered fungicides flopicolide + propamocarb hydrochloride SC 68.75% (Infinito) 2 ml/L and cyazofamid SC 400 (Ranman®) 0.5 ml/L with control treatment. Trials were performed in Tehran (Varamin) and Mazandaran (Amol) provinces with 16 treatments and southern Kerman province (Jiroft) with 17 treatments in a randomized complete block design with four replications. The experiments were carried out in greenhouse production systems (Varamin and Jiroft) and open field (Amol). Foliar spray began with the appearance of first symptoms of the disease and was repeated at intervals of 5 to 7 days. In Jiroft, Tehran and Mazandaran experiments, 2, 3 and 4 sprays were performed with experimental treatments, respectively. Experimental plots were evaluated at the stage of disease severity with a grade of 9 in the scoring index in control plots. Analysis of variance showed significant differences in all experiments between treatments and control. Comparison of the mean of the experiments showed that the brands of copper oxychloride had not the same effect and were divided into several statistical groups. Their efficiency was 65.9-72% in greenhouse conditions and 29-43% in open field conditions.

Tuta absoluta is one of the most important pests of tomato in many countries. Emamectin benzoate (EB) is widely used in the control of lepidopteran pests, but there is sparse information available regarding its sublethal effects on T. absoluta. In this research, the lethal and sublethal effects of EB were investigated on T. absoluta under laboratory conditions. Acute toxicity bioassay was carried out on 2nd instar larvae using residue contact method. The LC50 value was 14.50 mg a.i. L−1, for 24 h exposure time. LC10 and LC30 of the insecticide was used for sublethal effect study. The insecticide significantly extended the larval developmental time at LC30. Pupal weight, fecundity and longevity of female adults were decreased at both tested concentrations. However, the LC10 and LC30 of the insecticide had no significant effects on pupal period, egg hatchability, and male adults’ longevity at sublethal effect study. These results suggest that the sublethal effects of EB might affect pest population dynamics significantly by delaying its development, and decreasing its reproduction. Hence, this bioinsecticide can be used in integrated pest management program of T. absoluta if its efficacy proven under the field and greenhouse conditions.