فصلنامه گیاه پزشکی
سال سی و هفتم شماره 4 (زمستان 1393)

Rhizoctonia zeae causes root rot and sheath blight on corn (Zea mays) and several other gramineous plants. In order to determine the genetic diversity of the R. zeae population in Mazandaran and Golestan provinces، samples were collected from cultivatd soils of both provinces in 2011 and 2012. The identity of isolates as R. zeae were verified by amplification and sequencing of the 18S and 28S rDNA of five representative isolates. Genetic diversity of 20 isolates from different geographic regions were assessed by amplification of the ITS region of rDNA by PCR، using ITS4 and ITS5 primers and sequencing of the amplified fragments. The isolates appeared to be genetically heterogeneous and were differentiated into four clusters based on their ITS sequences. There was substantial correlation between the morphological variation and genetic heterogeneity observed among isolates.

The golden nematode، Globodera rostochiensis which was reported from Hamadan in 2008، is one of the most important pests of potatoe world wide which causes serious yield reduction. Damage to plant occures with invasion of the roots and production of specialized feeding cells. Since the nematode is fairly new for the region، its pathogenicity needs to be monitored on potato cultivars. In a preliminary test، the relation between nematode and a common potato cultivar in Hamadan was studied. Marfona was planted in microplots infested with 0. 05، 4، 9 and 15 eggs and J2/g soil and weights of plant growth parameters and final nematode density were taken after 75 days. As nematode density increased at planting، plant and tuber weights decreased. Nematode reproduction increased with increasing nematode population at planting. The highest final nematode density occurred at highest initial population.

The early blight disease of potato، Alternaria alternata and A. solani، is one of the worldwide diseases، which occurs epidemically in potato growing areas. Thus، because of the economic importance of potato، in Iran، there is a great need for the management planning to be taken into consideration. Movements toward a sustainable agriculture need to consider the managements which are to be economical، free of chemical hazards، applicable in large scales and adoptable by the farmers. Thus، searching for resistant sources، breeding and cultural practices become important as far as the disease and pests managements are concerned. In this study، with reference to the above scales، the factors including type and date of sowing، irrigation types، genetic sources and chemical controls by few systemic and non-systemic fungicides were assessed against the early blight disease of potato for three continuous years in Freidan، Isfahan، Iran. The results revealed that، almost all the treatments were having great influence on disease reduction with significant effects individually، and in combination. Also، the treatments enhanced the potato productions. Sprinkler and dripper irrigations were very effective in comparison to furrow one respectively. Also، single and double rows had no any considerable effect. Late sowing by a month and or two weeks reduced the disease by 77 and 84 percent effectively and respectively. The resistance sources and varieties such as Diamante، Granola، Maradona، Picasso and Kaiser reduced the disease respectively. In respect to fungicides with lower dosage، Trifloxystrobin (WG 50%) with 250 and 200 g/ha، greatly reduced the disease severity، respectively. Investigation onto the integration of these scales showed that in addition to disease reduction، the integration of various methods of control، resistant source، cultural practices and chemical measurements not only caused the reduction of the cost product، but also، reduced the chemical hazards greatly.

Nowadays، use of herbal essences has been considered as superseded high risk insecticides especially in case of stored-product pests. The purpose of this study was to determine the persistence of herbal essences Ferulago angulata (schlecht) Boiss، Ballota aucheri Boiss on three stored product pests. The experiments were carried out at 27±1 Ċ and 60±5 R. H. under dark conditions. LT50 values showed the mortality''s speed of mature insects of Rhyzopertha dominica (Fabricous)، Oryzaephilus surinemensis (Linnaeus) and Tribolium castaneum (Herbst) in F. angulata was significantly more than B. aucheri. In addition، the respiratory toxicity of F. angulata on these pests showed more stability than that of B. aucheri. The findings of this research indicate effective influence of these essences on mentioned insects.

Using plant natural compounds for the control of diseases has been subject to a host of research، due to their advantages on synthetic compounds. In this research، the effectiveness of leaf tissues extracts of radish، cabbage and celery was evaluated for preventive and curative control of cucumber powdery mildew in greenhouse tests. The acetonic، methanolic and water extracts of these plants at concentrations of 1 and 5% (w/v) were sprayed on the plants at either 1 day before or 1 day after the plant inoculation with spore suspension of pathogen. Then، disease severity was evaluated based on the number of disease spots per leaf 10 days after inoculation. The effectiveness of the extracts was also compared with Penconazole fungicide and Reynoutria sachalinensis (Rs) extracts، two commercial compounds for the control of disease. Results showed that the tested extracts reduced the disease severity on the cucumber leaves when applied at 1 day interval before or after the pathogen inoculation، but in varying degrees. In comparison with other extracts، acetonic extract of celery at the concentration of 5% (w/v) had the most preventive effect against disease، and its preventive efficacy was the same as Rs extract. Acetonic extract of celery and methanolic extract of cabbage at the concentration of 5% had the highest curative effect against disease، respectively، and their efficacy for disease cure was comparable to that of Penconazole. Our results showed that all extracts have potential for controlling cucumber powdery mildew.

Determination of resistance sources is essential for development of varieties resistant to biotic and abiotic stresses. Germplasm evaluation can offer valuable breeding materaials which result in different tolerant combinations. In this study، 47 sugar beet monogerm o-type lines (male strile maintainer) along with two susceptible and two resistant checks were evaluated for resistance to Cercospora leaf spot in in vitro conditions using leaf disk method. The test was conducted based on a completely randomized design with three replications. In each replication، 10 leaf disks from 10 plants were checked for every genotype. The leaf disks were sprayed with fungal spores in in vitro conditions and after 8 days the number of spots was counted in leaf area index. Based on the results، most of the genotypes showed susceptibility، but 5 monogerm lines had no significant difference with resistant check. The selected genotypes along with three susceptible genotypes، a susceptible check and a resistant check were evaluated in natural infected conditions. The trial was carried out using to a completely randomized block design with four replicates. Plots were scored three times according to a 1-9 scale and the mean of four replications was used as the score of each genotype every time. According to the results، the susceptible genotypes recevived high score and were susceptible in the field condition. From 5 selected genotypes، only one line acted in a similar way to resistant check and had no significant difference with it.

Faba bean (Vicia faba L.) is one of the important legumes in most countries and an important source of protein for human diet and animal feed as well as nitrogen fixation. Viral disease symptoms including mosaic، leaf curl and deformation suspected of being due to viruses have been observed in faba bean fields in Khuzestan province for a long time. Evaluation of the seed borne nature of the disease showed that the agent (s) of the disease was/were seed-borne. Therefore، the objective of this study was to determine the causal agents of this disease in faba bean fields in Khuzestan province. Samples were collected and infections of Bean common mosaic virus، Bean common mosaic necrosis virus and Cucumber mosaic virus were confirmed by ELISA using 15 antibodies against different viruses. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed using NIb2F/NIb3R and CMVF/CMVR primer pairs and the expected bands of 350 and 520 bp were amplified، respectively، confirming the serological assays. Results of the study showed that Khuzestan faba bean fields were infected at least by three seed-borne viruses including CMV، BCMV and BCMNV. This is the first report of BCMV and BCMNV infection in faba bean in Iran.

Cellulosic and non-cellulosic building materials، such as wood-plastic composite، MDF، particleboard and polystyrene have been widely used recently in the construction industry. The resistance of building materials to termite attack is one of the most important parameters in the evaluation of their quality. In this study، the resistance of composite wood-plastic، MDF، particleboard and polystyrene building materials to M. diversus attack was evaluated under choice and non-choice laboratory assays and under field conditions. Polystyrene، particleboard and MDF were attacked by M. diversus and considerable damage was observed in non-choice assays، but wood-plastic composite was resistant. Particleboard and MDF were the most highly attacked materials in choice and field assays. Due to its lack of nutritional value، polystyrene was not attractive and it showed a low level of damage. Wood-plastic composite showed a high level of resistance to termite attack. There was a significant correlation between the material’s increased density and reduced weight loss.

Soilborne fungal plant pathogens which cause damping-off، root and crown rot and reduce the seed germination lead to crop loss. The biocontrol fungus Trichoderma species is known as the most important antagonists against soilborne fungal diseases. In this study، to improve the efficiency of biological control of antagonists، mutation induction by gamma irradiation was conducted in Gamacell with optimized dose of 250 Gy per second (rate of 0. 23 Gy)، and 24 mutants of Trichoderma harzianum 65 (wild type) isolate were selected. The study of antagonistic properties against Macrophomina phaseolina، Rhizoctonia solani AG4، Sclerotinia sclerotiorum and Fusarium graminearum was done in dual culture، volatile metabolites and extracellular extracts tests in a completely randomized design with three replications.، Th15، Th11، Th5، Th1، Th4 and Th 22 mutants showed the maximum growth inhibition and was inroduced as superior mutants. These mutants have capaibility of evaluation in greenhouse biocontrol tests.

In this research، the effect of host instars was evaluated on time allocation to various foraging behaviors in sexual population of the parasitoid wasp، Lysiphlebus fabarum (Marshall) (Hym.، Braconidae: Aphidiinae). For this purpose، the parasitoid wasps reared in the second instar of black been aphid، Aphis fabae Scopoli (Hem.، Aphididae) were introduced separately to leaf patches that included 15 of the second or fourth instar of the aphid. Next، foraging behaviors of wasp females and host defensive behaviors of aphids were recorded for 30 minutes. According to the results، the host instars did not affect time allocation to various foraging behaviors within a patch. The results also showed that the number of defensive behaviors of two host instars، including kicking and producing droplets of cornicle secretions was significantly different when exposed to parasitoid wasps. The second and fourth instar aphids displayed significantly more kicking and cornicle secretions behaviors، respectively. Frequency of attack orientations relative to the aphid body (anterior، posterior، and lateral) was also tallied. The most attacks on second instar were launched from a lateral orientation، which may present a lower risk of kicking and smearing with cornicle secretions.