Iranian Journal of Plant Protection Science
Year:2010 | Volume:40 | Issue:2|Papers Count:13

Macrophomina phaseolina is a soilborne pathogen with a worldwide distribution and a host range of over 500 plant species. To study the genetic diversity and host specialization of this fungus in Iran, plants with signs and symptoms of charcoal rot were collected from 12 provinces during years 2006 to 2008. Following isolation and purification, 52 isolates from 24 host plants were identified through morphological methods and by species-specific primer. Genetic diversity was analyzed using Inter-Simple Sequence Repeat (lSSR) markers. From among the nine tested primers, six sets yielded polymorphic and reproducible bands, used in subsequent analyses. Fingerprint data from all primers were analyzed using UPGMA method and Jaccard’s Coefficient. Cluster analysis divided the isolates into four groups at a 60% similarity level. Group 1 comprised 5.76% of the isolates, including all the hemp from Kashan and Isfahan. Group 2 comprised 68.53% of the isolates, including all the ones from kiwi, soybean, melon, olive, maize, and okra. Golestan isolates from hosts of: maize, sorghum, kiwi, soybean and marigold with 64% similarity being placed together with Qazvin isolates from pumpkin and tomato hosts with 100% similarity may be due to similarity of the host origin. Group 3 being comprised of 13.47% of the isolates, included isolates from Fabaceae and Cucurbitaceae. Most of the Group 3 isolates were collected from arid regions. With isolates of mungbean with 88% of similarity being placed together in this group. Qom and Karaj grown cucumber, Kashan cantaloupe, Qazvin common bean, Khorasan common bean isolates with 75% of similarity were placed together in this third group. Group 4 got comprised of 19.23% of isolates including the ones from Solanaceae, Fabaceae and Cucurbitaceae hosts with no specific correlation to geography. Isolates of cantaloupe from Fars and from Khuzestan with 60% similarity and tomato from Qom and eggplant from Hormozgan with 66% similarity and isolates of sesame from Kerman and Kashan with 90% similarity as well as three isolates of sunflower from Markazi, Fars and Khuzestan with 61% of similarity were placed in this fourth group. The results demonstrate that genetic diversity of M phaseolina is high among hosts and geographical regions, with host specialization being detectable in some cases.

Planococcus citri (Risso) is an important pest of crop and of ornamental plants worldwide. The high reproductive potential of P. citri and its fairly short life cycle along with the frequent application of insecticides (required to maintain P.citri populations below economic thresholds), enhances resistance development and results in control failures. In this research, susceptibility to Permethrin in two populations of P. citri were studied. Insecticide bioassays were carried out on 2nd instar nymphs using dipping method and formulated insecticide. The results indicated LC50s of Permethrin on Rasht and Tehran populations as 363.4 and 1102.3 ppm, respectively. There was a significant difference observed between LC50 of Rasht and Tehran populations (P<0.05), with Tehran population being 2.89 times more tolerant to Permethrin than the Rasht population. An assessment of esterase activity indicated on optimal pH of 8. Esterase activity in the case of Tehran population was 1.33 fold Rasht population. The crude extracts of P. citri populations were analyzed through native PAGE. Following esterase activity (staining using a-NA and b-NA substrates), a single band of esterase was detected for either one of the strains and with similar electrophoretic migration. There was not any difference observed between Rasht and Tehran populations as regarded gluthathion-S-transferase activity.

In recent years, anthracnose disease of citrus has caused and continues to cause heavy losses to some citrus commercial tree varieties in Mazandaran Province. This disease is deeply spread out in the citrus orchards of the province. In order to isolate and identify the causal agent or agents of the disease, random sampling was done from infected trees during 2004-2005. In lab, samples were cultured on PDA medium. From among 119 samples cultured, 96 Colletotrichum isolates were isolated. Based upon morphological and some physiological characteristics as well as on growth optimal temperature, all the isolates were identified as Colletotrichum gloeosporioides. Pathogenicity severity tests with selected isolates were done on detached branches and as well on two-year old Valencia orange (Citrus sinensis (L.) Osbeck), Unshio mandarin (Citrus unshio Marcow) scions in laboratory and in greenhouse, respectively. The results showed that all isolates were pathogenic on two original cultivars. There were significant virulence differences observed (at a=%1) among the isolates. On the basis of virulence, the lab Valencia and Unshios were respectively divided- into 17 and 15 groups, whereas the greenhouse ones (Valencia and Unshios) divided into 7 and 8 (groups) respectively.

Mites of the family Ascidae constitute an important group of predator arthropods that live in soil make a living, on plants and an stored products, and some species of which are in close association with humans and animals. A faunestic survey was carried out to identify the mites of the family Ascidae in Guilan province, northern Iran, during 2007-2009. Samples were taken from such different habitats as soil, plants, warehouses, manure and decaying plants. A total of 16 species from 8 genera were collected and identified. One genus (Platyseius Beriese, 1916) and four species are new records for Iran while 14 species for Guilan province mite fauna. The taxonomic characteristics of the four new species new for Iran mite fauna are given. A key is also provided for northern Iran (Guilan, Mazandran and Golestan Provinces) ascid mites. The list of the identified species is as follows with the, new species for Iran mite fauna being marked by an asterisk. Subfamily Arctoseiinae Evans, 1963: A-Genus Arctoseius Thor, 1930 [1-A. cetratus (Sellnick, 1940)]. Subfamily Ascinae Voigts & Oudemans, 1905: B- Genus Blattisocius Keegan, 1944 [2-B. keegani Fox, 1947, 3-B. tarsalis (Berlese, 1918)]; C-Genus Lasioseius Beriese, 1923 [4-L. extremus (Daneshvar, 1987), 5-L. sugawarai Ehara, 1964, 6-L. youcefi Athias-Henriot, 1959, 7-L. frankbakker/ Faraji & Karg, 2005]; D-Genus Proctolaelaps Berlese, 1923 [8-P. pygmaeus (Muller, 1860)]; E- Genus Protogamasellus Karg, 1962 [9-Protogamasellus mica (Athias-Henriot, 1961)]; F-Gamasellodes Athias- Henriot, 1961 [10-Gamasellodes bicolor (Berlese, 1918)]. Subfamily Platyseiinae Evans, 1957: G-Cheiroseius Berlese, 1916 [11-C. longipes* (Willmann, 1951), 12-C. bryophilus* Karg, 1969, 13-C. necorniger (Oudemans, 1903), 14-C. caseadensis (De Leon, 1964) 15-C. curtipes (Halbert, 1923)]; H-Platyseius Berlese, 1916 [16-P. subglabe/ (Oudemans, 1902)].

Rice Blast, caused by Pyricularia grisea is an important injuries fungal disease of Mazandran Province. To identity the fungus's resistance to Edifenphos fungicide, 50 isolates of the pathogen were sampled from some different parts of the province. The inhibition of hyphaI growth in response to different concentrations (1-140 ppm in PDA) of Edifenphose and the EC50 of this fungicide for the isolates were determined after 5, 7 and 14 days following the start of the experiment. Then, the hyphal growth inhibition due to being disposed to different concentrations and as well as EC50 of Tricyclazole was measured for II semi-resistant and resistant against Edifenphos isolates, and after 5, 7, and 14 days from the start of the experiment. In a greenhouse experiment the effect of the fungicide was estimated on the control of leaf blast severity inflicted upon 2 resistant and I sensitive isolates of the pathogen, in Tarom commercial of rice cultivar. Results revealed 34% of the isolates as sensitive, 22% semi-sensitive, 30% semi-resistant and 14% resistant to Edifenphos, while all the semiresistant and resistant isolates being sensitive to Tricyclazole. Also from the greenhouse experiment it was observed that this fungicide controlled the disease (caused by any of the isolates) more effectively than the fungicide Edifenphos. The seeming resistance against Edifenphos among the isolates of this pathogen, the sensitivity of the fungus to Tricyclazole and the more effectivity of this fungicide in the control of the disease is reported for the first time in the province.

The objective of this study was to investigate side effects of two widely used soil-applied herbicides, Trifluralin (EC 48%) and Ethalfluralin (EC 33%) in 0-500 and 0-300 ppm concentrations, respectively, on biological activities of five pathogens of cotton (Gossypium hirsutum c.v Sahel) viz. Rhizoctonia solani, Pythium ultimum, Fusarium moniliforme, Alternaria alternata and Verticillium dahliae. The parameters, including fungal mycelial growth inhibition (%), prapagule germination, virulence, seedling disease and saprophytic growth of R. solani (by use of baiting method), were determined in laboratory as well as in greenhouse. Results showed that, growth inhibition rate was affected by type and concentration of herbicides. The herbicide treatments reduced mycelial growth in nearly all pathogens with various intensities. Verticillium. dahliae and F moniliforme showed low vs. very high susceptibilities, respectively. The growth of other fungi was suppressed in a range of 4.8-66.3%. The herbicides increased germination percentage in F moniliforme chlamydospores and either decreased or inhibited formation or germination percentage in P. ultimum sporangia. Also, Trifluralin was observed to have more addetive effects than Ethalfluralin on saprophytic activity of R. solani. It's finally concluded that tested herbicides caused the cotton seedlings to get predisposed to infection (by Pythium and Fusarium species) thus and increasing the incidence of diseases.

In the framework of a study on the powdery mildew fungi in Iran, several infected plant specimens were collected from around the country during 2001-2009. Based on the results of the study Erysiphe quercicola on Quercus sp. and E. malvae on Malva sp., Golovinomyces ambrosiae on Helianthus spp., Golovinomyces fischeri on Senecio glaucus, are the newly reported for Iranian mycobiota. In addition, some specimens belonging to Golovinomyces cichoracearum s.l. were assessed. According to the new species concept, concerning these taxa, Golovinomyces cichoracearum s.s. prevalent in the country was redescribd, and G. sonchicola on Sonchus spp. is recorded for the first time, although already reported from Iran under the initials of G. cichoracearum s.l.. Moreover, some taxa powdery mildew fungi are reported on new hosts in Iran as follows: Golovinomyces cynoglossii on Symphytum asperum, Leveillula taurica on Daphne mucronata, Podosphaera leucotricha on Photinia serrutata.

Samples were collected from soil and as well from phyllosphere of rice plant and subjected to dilution plate technique on RBSF Trichoderma selective medium. A total of 202 Trichoderma isolates were obtained from rice fields at different geographical locations distributed all over Mazandaran Province. Single spore isolates were obtained and genomic DNA extracted from all the isolates using DNA extraction kit. For an identification of isolates, morphological as well as molecular characteristics were studied. Morphological identifications were accomplished through morphological keys and subsequent descriptions. For molecular identification, the Internal Transcribed Spacer (ITS) region of the rDNA gene complex, including ITS1, the 5. 8S rRNA gene and ITS2 was amplified using primers ITS1 and ITS4. To identify the isolates at the species level, ITS sequence analysis was carried out for all isolates with the aid of the program TrichOKEY 2. The identified isolates belonged to six species of: Trichoderma harzianum, T. virens, T. atroviride, T. hamatum, T. brevicompactum and T. asperellum. More than 90 percent of the isolates belonged to species T. harzianum and T. virens. Therefore, these two important biocontrol agent species of plant diseases are the most common ones occurring in the rice (paddy) fields. T. harzianum is the most dominant Trichoderma species observed in rice phyllosphere while T. virens being more abundant in soil. None of the isolates of the four remaining species were isolated from phyllosphere. In addition, all T. atroviride isolates, except for one, originate from the eastern part of the Mazandaran province.

Pistachio psylla, Agonoscena pistaciae Burckhardt & Lauterer, is a key pest of pistachio trees in the pistachio-producing regions throughout Iran. The investigation of biology of pests under the field condition in each region is the first step that must be taken in developing an integrated pest management program. The seasonal fluctuations of eggs, nymphs and adults of pistachio psylla were investigated in 2007 and 2008. Results indicated that, the pest bears six complete along with one incomplete generation in Rafsanjan region. The mean generation period for adults, eggs and nymphs, from first to the sixth generation during 2007 and 2008 were assessed as 27.8±5.2, 27.4±2.6 and 27.1±1.9 days, respectively. The effect of canopy height on the distribution of eggs and nymphs, in the low, medium and high height conditions revealed that the density of eggs and nymphs increase with increase in the canopy height.

Sheath blight disease, caused by Rhizoctonia solani AG-1 IA, is one of the most serious fungal diseases of rice, worldwide. Rice resistance is a relative phenomenon and disease response varied (due to complex quantitative inheritance and high environmental diversity), so an accurate disease assessment would be difficult. To detect a reliable reaction of rice in a high level of disease development, a new inoculation method was developed, using Mycelial Mass (MM) of R. solani, produced in PD-broth along with application of a water sprayer system. Seedlings from three local and from two improved cultivars (Anbarbo, Ghasroldashti, Ahlemi-Tarom, Khazar and Bahar, respectively) were transplanted into the field. After 45 days past, tillers from each plant were sealed using rubber bands, then inoculated by a virulent isolate of pathogen, in three methods of: mycelial mass, colonized Rice Grain/rice hull (RG) and Freshly Infected rice stem (FI). Inoculated plants were kept moist until the last scoring time by through of a water sprayer system, above the tested plants in the field. Disease scoring was recorded 15 and 25 days following inoculation and at the end of dough grain stage, using the Relative Lesion Height (RLH%) method. Detailed disease assessment introduced the FI method as appearing with a low level of disease development, and of highly varied results. But MM and RG methods were of less varied results within each cultivar and at different times of evaluation. The most conspicuous vertical disease development was observed (among all tested cultivars) at the second evaluation stage and at the end of dough stage (the most susceptible stage of rice growth) in the MM inoculation method. Therefore, the plants were divided into three and two groups, respectively, and were found different from grouping by RG and FI methods (DMRT 5%). Therefore under water sprayer system, MM inoculation method can be used for the measurement of rice reliable reaction to sheath blight disease in the field. Anbarbo, Ghasroldashti, Ahlemi-Tarom and Bahar were identified as moderately resistant with the same statistical group from first screening test, but in this study they fell in different groups and their reliable tolerance were appeared after optimization of the test condition by development of disease, so Ahlemi-Tarom showed very susceptible reaction.

Blast disease is considered as the most serious disease of rice throughout the world. To genetically analyze leaf blast resistance, five rice cultivars namely Khazar, Hashemi, Kadoos, Fuji and Rashti were crossed together in the framework of a defective half diallel design. Parents and the resulting lines were cultured in greenhouse in the form of a randomized complete block design. Following inoculation with five blast isolates of: IA-66, IA-38, IA-79, IA-181, and IA-l77, such characteristics as number of blast lesions on the leaf, percent of leaf infection area as well as lesion size were evaluated using international standard method for evaluation of blast disease (S.E.S). The results recorded from the analysis of variance indicated that there exist significant differences among genotypes. The significance of general combining ability, specific combining ability and also the relationship between general and specific combining ability indicated the effect (simultaneous) effect of additive and non- additive gene action (with a greater share going to additive gene action). In the control of these characteristics a dominant gene also plays its role. High narrow and broad sense heritabilities were reported for all these characteristics. Considering the high heritability in these characteristics and the additive effect of the resistance genes, it can be concluded that Khazar, Kadoos and Fuji resulting lines could suitably be used for cultivars for increasing the resistance against the above mentioned blast disease agents.

Pistachio green stink bug, Acrosternum hegeeri, due to its inflicting damages on crop quantity and quality, is of a great economical importance in pistachio production. On the other hand, a knowledge of digestive enzymes, is quite indispensable in the study and application of new pest management technologies. Results of studeies have shown that midgut in this insect is divided into four sections (m1-m4) all of which are morphologically different with their pHs determined as 6.4±0.1, 6.22±0.13, 6±0.1 and 6.1±0.12, respectively. In addition, salivary gland pH value amounts to 6.04±0.1. Enzymatic assays, using hemoglobin as substrate, revealed maximum proteolytic activity in m1 and m3 at pH 3 and in m2 and m4 at a pH of 4. The specific substrates for cysteine proteases, Z-Arg-Arg-pNA, Z-Phe-Arg-pNA, were hydrolyzed by midgut extract suggesting the strong presence of the cysteine proteinases cathepsin L and a low level of cathepsin B, respectively. The presence of cysteine proteases was supported by strong enhancement (53.12%) of the midgut proteinase activity in the presence of DTT for Z-Phe-Arg-pNA and (13.5%) for Z-Arg-Arg-pNA, respectively. Hydrolyzing activity of the cathepsin L and B in midgut extract against the substrates Z-Phe-Arg-pNA and Z-Arg-Arg-pNA was inhibited by the specific inhibitor, E-64 by 90% and 66%, respectively. During the study a-amylase in the midgut was also investigated, the enzyme optimum pH being 5. The results show that cysteine and acid proteinases should be the major proteases in the midgut of pistachio green stink bug, in consistence with the prevailing pH in the insect’s midgut. Amylolytic activity was also determined in the midgut extract of the green stink bug.

To evaluate the allelopathic effect of essential oil extracted from leaves of Eucalyptus globules against some certain weeds and the possibility of that being employed in weed management strategies, laboratory and greenhouse studies were conducted in Islamic Azad University of Khoy in 2007 in the framework of a factorial expreiment based on a randomized complete block design of four replications. The studied factors consisted of Eucalyptus essence concentrations of: 0.5, 2, 3.5 and 5 nl/ml in laboratory along with 0.25, 0.5, 0.75, and 1 v/v in pots with weeds including: Amaranthus retloflexus and convolvulus arvensis. Distilled water was used as control. Results indicated that germination percentage, germination rate, radicle length, plumule length, primary root length, primary pedicle length, seedling and plantlet lengths decreased, with increase in of essence concentrations. The highest allelopathic effect of the essential oil was observed against A.retloflexus. Plantlet length in A.retloflexus decreased from 39 mm to 9 mm in control, and as affected by the highest concentration of Eucalyptus essential oil application. Therefore, it can be concluded that Eucalyptus essential oil can be further studied, as a biological herbicide in the management and control of the above mentioned weeds.