فصلنامه گیاه پزشکی
سال چهل و یکم شماره 4 (زمستان 1397)

Legumes are an important source of protein for humans in the world. Leguminous food is mostly attacked in storage environments by several pests. Callosobruchus maculatus (F.) is considered as the main pest of pulses. Chemical insecticides and fumigants are the main methods to control stored product pests. By considering adverse effects of these compounds, it is needed to develop alternative control strategies that will be effective, biodegradable, cost-effective, and without any adverse effect on non-target organisms. Nano particles are the new generation of these safe products. In this study, the effect of two silicon dioxide nanoparticles, Aerosil® and Nanosav was investigated on oviposition deterrence of C. maculatus in four concentrations viz. 50, 100, 200, and 300 mg.kg-1 on 5 pulse seeds of cowpea, black gram, green gram, chickpea, and lentil. Pulse seeds after treatment were exposed to one-day old male and female adults. Five days after treatment the laid eggs were counted. The second experiment was carried out to evaluate the effect of two silica nanoparticles on egg hatching and adult emergence of pulse bruchid. For this purpose, the legume seeds each with a one-day old egg were treated with the same concentrations; then the seeds were assessed for hatching eggs and emerging adults. In another experiment, the effect of these formulations was checked out on weight loss and progeny production after 3 months. Declared pulses were treated with the same concentrations and then exposed to 1-day old male and female adults. After 3 months, the percentage of weight loss and the number of produced progeny were recorded. The most oviposition deterrence was on black gram with the mean percentage of 96% in 300 mg.kg-1 of Aerosil®. The least percentage of hatched eggs and emerged adults was on lentil with the mean of 13 and 1% with 300 mg.kg-1 of Aerosil®, respectively.
The least weight loss was on lentil with the mean percentage of 10 with 300 mg.kg-1 of Nanosav. The least progeny production was induced with 300 mg.kg-1 of Nanosav on lentil with the mean number of 40 progeny. The results of this study showed that Aerosil® was more effective than Nanosav, but two silica nanoparticles had enough efficiency against infestation of C. maculatus and can be used effectively in the integrated management of C. maculatus in pulses.

Spot blotch (Bipolaris sorokiniana)is one of the most destructive leaf diseases that causes significant damages to barley during epidemic periods. Fungicide application is a rapid control practice for this disease during epidemic periods. Several fungicides have been proposed for controlling of spot blotch, but these fungicides are effective if they reduce the disease pressure on important plant leaves, especially flag leaf. The results of fungicides application at different growth stages of barley are inconsistent, and also there is no comprehensive study on the timing of fungicides application for controlling of this disease in Iran. Therefore, the present study was designed to determine the appropriate timing of fungicides application at four growth stages of barley to decrease the disease pressure on the upper leaves of the plant, the timing of spraying on reduction of disease damage, and to increase yield and economic profit. A field experiment was conducted in a split plot design with four replications. The main and sub-main factors of the experiment were cultivars (Sahra and Yousef) and the spraying treatments, respectively, and the 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 selected as once, twice, three and four times spraying that were Tr1 (once spraying at early stem elongation to node forming 1), Tr2 (once spraying at node formation 2-3), Tr3 (once spraying at full flag leaf emergence), Tr4 (once spraying at flowering), Tr5 (twice spraying at node formation 2-3 + full flag leaf emergence), Tr6 (twice spraying at full flag leaf emergence+ flowering), Tr7 (twice spraying at early stem elongation to node forming 1+ node formation 2-3), Tr8 (three times spraying at node formation 2-3+ full flag leaf emergence+ flowering), Tr9 (four times spraying at early stem elongation to node forming 1+ node formation 2-3+ full flag leaf emergence+ flowering) and Tr10 (check). The efficiency of spraying treatments was evaluated one week after the last spraying by determining the index of disease (e.g., incidence and severity, area under the disease progress curve, AUDPC) as well as comparing the yield and yield components. The results of this study showed that treatments with more than once spraying from the node formation 2-3 to flowering stages (Tr5, Tr6, Tr8 and Tr9 treatments) could decrease the values of AUDPC-I between 76.8-86.1% and 68.3-81.2% in Sahra and Yousef cultivars, respectively. Whereas the values of AUDPC-S decreased between 62-65.7% and 60.1-62.7% in Sahra and Yousef cultivars, respectively. The highest percentage of yield increase was observed in the treatments with more than once spraying from the node formation 2-3 to flowering stages, which was more than 37% (1092.8 to 1284.1 kg/ ha) and 41% (1167.8 to 1290 Kg/ ha) in Sahra and Yousef cultivars, respectively. In both cultivars, the comparison of economic profit showed that Tr5 treatment (node formation 2-3 to flag leaf emergence stage) not only decreased the disease severity, but also increased the yield. It also reduced costs and had the highest economic profit compared to other spraying treatments (Tr6, Tr8 and Tr9). According to obtained results, the treatment of Tr5 (twice spraying at T1+T2 timing) was the best timing of fungicide application for the reduction of the disease pressure and the increase of yield and economic profit.

Gorgan in Golestan province is substantially considered as an important region for production of agricultural crops in Iran. Plant-parasitic nematodes may cause direct or indirect damages to the plants in this region. Although some members of Merliniidae, Telotylenchidae or Pratylenchidae (Nematoda: Tylenchoidea( have been reported from different crops of Gorgan so far, there is no adequate and accurate information on these nematodes in association with many agricultural crops in Gorgan for making decisions on their management. The aim of the present study is to identify plant-parasitic nematodes of these three families in the agricultural field crops of Gorgan region and to determine their frequencies in the studied area. In order to identify the plant parasitic nematodes from the families of Merliniidae, Telotylenchidae and Pratylenchidae associated with the important field crops of Gorgan, Iran, 64 soil samples were collected from different parts of the region during 2014-2015. The nematodes were extracted, fixed and transferred to anhydrous glycerin. The permanent slides were prepared from the extracted nematodes and necessary measurements were made. Finally, the nematodes were identified based on morphological and morphometric characters, using available identification keys. In this study, 11 species belonging to seven genera were identified as Amplimerlinius macrurus, Merlinius brevidens, M. microdorus, Paramerlinius hexagrammus and Pratylenchoides ritteri from family Merliniidae, Tylenchorhynchus brassicae and T. crassicaudatus from family Telotylenchidae, and Pratylenchus neglectus, P. sefaensis, P. thornei and Zygotylenchus guevarai from family Pratylenchidae. Tylenchorhynchus crassicaudatus was found in the rhizosphere of soybean plants in Gorgan. Description, morphometrics, line drawings and photomicrographs were provided for this new record of nematodes. Among the identified species, P. sefaensis, M. brevidens and M. microdorus were the most distributed species, with 26.6, 25.0 and 23.4 % relative frequencies, respectively. Tylenchorhynchus crassicaudatus is reported for the first time in Iran and cited here. Furthermore, differences of morphological and morphometric characters of this species with other closely related species namely T. thermophiles, T. paratriversus, T. kashmirensis and T. mashhoodi are discussed. The morphological and morphometric characters of the present population are congruent to those of the type population type, except for hyaline region of tail being slightly shorter (4-7 vs 7-13 µm). Our population differs from the closely related species in some features related to female tail (shape, length and the number of annuli on the ventral side), in the absence of post-rectal sac, spicules and gubernaculum lengths, distance of DGO from stylet knobs and position of vulva.

Cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), is an important world-wide pest of wheat and barley. Adults and larvae feed on the upper side of leaves and chew long strips of tissue between the leaf veins especially on flag leaf, which can reduce grain yield. However, the greater damage is usually caused by feeding activity of larvae rather than adults. This paper presents the results of an investigation on the damage caused by this pest in wheat fields. This study was carried out in three wheat (Line: N8019) fields located at Neka, Sari, and Joybar, in Mazandaran province, Iran. Occurrence and activity of the pest in the fields was monitored weekly from mid-February until mid-May during 2013 and 2014. Coinciding with the end of larval feeding-activity (early May), 10 spots were selected in each field, and 10 beetle-infested wheat stems (showing pest damage symptoms on flag leaf surface) and 10 intact stems (without damage symptoms) in each spot were randomly selected and labeled. The flag leaves of infested stems were photographed and infestation rates (% leaf surface damage) were assessed and categorized in four groups (<10%; 10-20%; 20-40%; >40%) using UTHSCSA image tool for windows version 3. At harvest time, the spikes of all labeled stems (infested and intact) were separately collected and grain weight and grain number per spike as well as 1000-kernel weight was measured. The relationship between percentage of flag leaf damage and yield (grain number and grain weight per spike) and 1000-kernel weight was calculated using regression analysis. Overwintered adult beetles were observed in the fields from early March, with a peak activity occurring at mid-March. Larval feeding activity started during late March and continued until early May. In both sampling years, the highest grain weight loss and number of grains per spike, and 1000-weight loss were observed in the >40% of infestation rate. Grain weight loss, number of grains reduction per spike, and 1000-kernel weight loss in the >40% infestation rate were 42.58%, 25.86% and 32.76% in 2013 and 32.42%, 15.59% and 19.82% in 2014, respectively. Results showed that the infestation rate of flag leaves can negatively affect grain weight per spike and 1000-kernel weight. With increasing percentage of flag leaf infestation, grain weight and grain number per spike, and yield decreased. However, in this study the infestation rates of flag leaves were mostly <10% or 10-20% and rarely reached >40% rate. During two-year sampling, only 10% out of 566 beetle-infested stems showed more than 40% leaf surface damage. In contrast, 46% and 62.3% of collected samples in 2013 and 2014, had less than 20% flag leaf surface damage. Therefore, the probability of severe damage caused by O. melanopus was low to moderate in the study sites.

Cotton whitefly, Bemisia tabaci (Gennadius), is one of the most important pests of field crops, vegetables, and ornamental plants. Parasitoid wasps, Eretmocerus mundus Mercet and Eretmocerus eremicus Rose and Zolnerowich, as well as predatory bug Orius albidipennis Rueter are natural enemies which are used as biocontrol agents to control B. tabaci and play a critical role in reduction of chemical insecticide application. In this study, experiments were carried out using a Y-tube olfactometer to determine the impact of volatiles emitted from leaves infested by B. tabaci on attraction of natural enemies. Moreover, the effect of presence of one natural enemy on attraction or repellency of another natural enemy was studied. Results of olfactory responses showed that infested cucumber leaves were more attractive for all species of natural enemy species, O. albidipennis, E. mundus and E. eremicus, than healthy leaves. The results also showed that O. albidipennis avoided leaves that both species of parasitoid wasps coexist on them. However, presence of O. albidipennis on the leaves as a competitor did not affect the attraction of the parasitoid wasps to infested leaves. Induced reactions in damaged plants increase their resistance to invasive pests. These changes can affect the reactions of all organisms around the plants including herbivores, pollinators, natural enemies, and even other plants nearby. Previous research confirms our results on attraction of natural enemies to plants injured by B. tabaci. Avoidance of O. albidipennis of patches containing parasitoids may be due to escape from intraguild predation or other reasons like low quality food in such patches. On the other hand, in this study both parasitoids preferred leaves containing O. albidipennis and whitefly nymphs to leaves with only whitefly nymphs. There is a hypothesis that female parasitoids should not avoid the polyphagous predators because they will lose many oviposition locations, as the number of polyphagous predators is too far in agroecosystems. This theory is corresponding well with the results of our study.

DNA extraction is the first step of genetic experiments. In this regard, quality and quantity of extracted DNA plays an important role in molecular studies. This experiment was conducted in order to achieve a novel method that helps us to extract DNA from Apis florea F (one of two important Iranian honeybee). This species is regarded as an important honeybee due to its world-wide distribution and direct role in pollination of field crops, orchards and forests. Samples were collected randomly from the hives of dwarf honeybee in Khuzestan province. In the current research, DNA was extracted from the thorax tissues of worker bees. Totally, four DNA extraction methods were evaluated including the optimal salting out, phenol-chloroform, CTAB and CTAB+SDS. To evaluate the quality of extracted DNA, spectrophotometry, electrophoresis and agarose gel methods were applied to compare quantity and quality of DNA extraction. Quantity and quality of extracted DNA was evaluated by spectrophotometry based on the absorption ratio 260/280 and electrophoresis on agarose gel. Based on the absorption ratio, for the methods of salting out, phenol-chloroform, CTAB and CTAB + SDS were 1.15 ± 0.01, 1.37 ± 0.01, 1.72 ± 0.02 and 1.82 ± 0.01, respectively. Duncan multiple range test revealed that CTAB+SDS was significantly different from other methods for evaluation of DNA extraction. Based on the results, the quality of DNA visible bands on the agarose gel can be considered as the option to evaluate the quality of DNA. On the other hand, twice washing in the CTAB + SDS method reduced protein contamination significantly. Furthermore, it could be mentioned that all the DNA extraction methods used in this study seems to be suitable in polymerase chain reaction test, but CTAB+SDS resulted in higher DNA quality and quantity. We referred to this thorax tissue as “thoracic muscle mass”, which could be as candidate tissue to obtain larger quantities of DNA.

The predatory mite, Neoseiulus barkeri, is one of the most important biocontrol agents of the two-spotted spider mite Tetranychus urticae Koch or other pests. Some of the phytoseiid mites utilize pollen as a food source and develop and reproduce on a pollen diet as well. They require pollen for successful development and reproduction. The predatory mite was collected from cucumber field infested with two-spotted spider mite in Khoramabad in Lorestan province. In this research, the effect of diets such as, maize pollen, walnut pollen, sunflower pollen, date pollen, bee pollen with or without two-spotted spider mite eggs in laboratory conditions (27±1˚C, 16L: 8D photoperiod and 70-80% RH) was compared. The life tables of the predator were constructed based on two- sex life table. The population parameters were estimated based on Chi & Liu’s model, using data of both sexes and the variable developmental rate among individuals. The results showed that total immature mortality when N. barkeri fed on only sunflower pollen or bee pollen was 100%.The developmental times of different stages on tested plant pollen showed significant differences. The progeny sex ratio when fed on date pollen (58%) and spider mite eggs (77%) and tested plant pollen plus spider mite was more female biased. The highest intrinsic rate of natural increase (r) was recorded when N. barkeri fed on corn pollen + spider mite (0.244 day-1) and on date pollen + spider mite (0.225 day-1). The female longevity when fed on date pollen +spider mite egg (12.12 days) and walnut pollen + spider mite egg (11.15 days) were longer than the other treatments. The comparison between predatory mite that fed on pollen only and mites that fed on pollen+spider mite showed that longevity of mites when fed on pollen only was longer, however, the fecundity rate of predatory mite when fed on pollens and spider mite was higher. The predatory mite fed on maize, walnut and date pollens, was able to complete the developmental stages and oviposit. Maize, walnut and date pollens were suitable alternative foods for the mass rearing of this predator.