فصلنامه گیاه پزشکی
سال سی و پنجم شماره 3 (پاییز 1391)

The side effects of three pesticides، hexaflumuron، pymetrozin and spirodiclofen and four plant extractions including، Calotropis procera (Willd.) R. Br. (Asclepiadaceae)، Teucrium polium (Labiatae)، Fumaria parviflora Lam. (Fumariaceae) and Thymus vulgaris L. (Labiatae) were evaluated on survival rate and reproductive parameters of Chrysoperla carnea (Stephens) at 26±1oC، 60±5% RH and 16:8 (L: D) photoperiod. The egg and 3rd instar larvae were assayed using dipping and topical application methods، respectively. The results demonstrated that the developmental period from egg to adults، was longer than controls. Among the pesticides and plant extractions، the pymetrozin (21. 3 days) and the F. parviflora (22. 8 days) had the lowest and highest effect on the developmental period against egg، respectively. In addition، the study was carried out on the 3rd instar larvae، and the results showed that the highest value of the developmental stage from 3rd instar larvae to adult was assayed by pymetrozin (15. 4 days) and F. parviflora (14. 8 days)، and the lowest value was calculated by hexaflumuron (12. 7 days) and spirodiclofen (12. 4). These results revealed that pymetrozin affected the 3rd instar larvae longevity but it didn not have a significant effect on the egg. It would also be expected that this pesticide doesn not have a negative effect on the efficacy of C. carnea as abiological control agent on target pests.

Wheat root and crown rot known as take-all disease caused by Gaeumannomyces graminis var. tritici is one of the most important diseases of wheat worldwide. In Iran,the disease has been reported from provinces such as Markazi and Golestan. In recent years, symptoms of the disease such as stunted and yellow plant, rotted roots and whitened/empty heads have been observed in wheat fields in various areas of Zanjan province. This study was conducted to probe the existence of the disease in the province, to identify its causal agent and to identify wheat rhizobacteria for possible use in the biocontrol of the disease. To this aim, 25 samples were collected from wheat roots and soil surrounding them in various areas of the province. Fungi were isolated on potato dextrose agar (PDA) and identification of Ggt was performed based on CMI Description. Pathogenicity of fungal isolates was proved on wheat in the greenhouse. Isolation and identification of rhizobacteria were performed based on conventional procedures. From 420 bacterial isolates, 140 isolates were selected based on preliminary grouping and were screened for their antagonistic effects in the lab. Thirty-four isolates with the most inhibitory power were selected for identification by biochemical tests. Results showed that antagonistic bacteria mainly belonged to Pseudomonas, Erwinia and Bacillus genera. Finally, three strains representing the three genera were selected and their capability for the control of the disease was studied under greenhouse conditions. Results revealed that bacteria belonging to the mentioned genera can be used for biocontrol of the disease.

In this research, 30 sugar beet breeding populations developed by crossing of sugar beet monogerm and multigerm male strile lines with nematode resistant wild sources (W-1009 contaning resistance gene from Beta procumbens and W-1010 contaning resistance genes from Beta maritima) were compared with resistant and susceptible checks with respect to nematode resistance and yield. The experiments were conducted as randomized complete block design with four replications in 2005- 2006, under beet cyst nematode (BCN) infested fields in Mashhad and Khoy areas. The reproductive factor (RF) of BCN was also estimated. The number of eggs and larvae of the nematode in the first and second year of the trials in the two areas was 424 and 476 cysts or larvae per 100g soil, respectively. The results of field trials and cluster analysis based upon sugar yield showed that the genotypes 231×(MSC2×W-1009)-P, 231×(MSR×W-1009) ×FC709-2, 231×(MSR×W-1010) and 231×(MS261×W-1010) had high yield potential and were grouped with the foreign resistant check in the same cluster. However, the genotypes 231×(MSR×W-1010), 231×(20447×W-1009), 261×(MS20314×W-1009) and 231×(MC2×W-1009) had the lowest reproduction factor (RF) in the field trials. Therefore, the above-mentioned genotypes could be used for developing nematode resistant varieties. Among those, the genotype 231×(MSR×W-1010) was superior to the resistant checks with respect to both traits and thus it was identified as a resistant genotype with a high yield potential.

In order to complete the microbial control of the sawthoothed beetle by the fungus Beauvaria bassiana (isolate 441c) in IPM program of stored date, 9 edible and commercial vegetable oils including Canola, Soybean, Sesame, Corn, Coconut, Grape seed, Olive, Sunflower and Almond were investigated to formulate the fungus. Results showed that B. bassiana formulated with sesame oil was the most suitable among the oils used in this research because of the lowest LC50 with 1.491×104 spore/ml. Sesame oil had also the highest synergistic effect with the quickest mortality effect and almond oil had the highest antagonistic effect on the fungus. The lowest and highest immunity coefficient of the pest population was calculated with sesame and soybean oils formulation, respectively. Among the fatty acids found in vegetable oils, The Margaric and Arashidic acids had additive effects and the fatty acids Palmoletic and linoleic had an impact effect on the pathogenesis of the fungus B. bassiana.

Cytospora canker caused by the fungus Cytospora spp. is one of the most common diseases of walnut trees in many parts of Iran. To identify the species of Cytospora on the walnut trees, during 2008-2009, more than 200 samples of infected twigs and branches with symptoms of Cytospora canker were collected from the major walnut cultivation areas in Iran. Based on morphological characteristics of asexual fruiting bodies on the bark (including presence or absence of conceptacle, shape, size and number of ostiol, shape and color of disk, arrangement of chambers, color of tendrils, size of conidia, conidiophores and conidiogenous cells and branching type of conidiophores) four species, namely Cytospora cincta, C.chrysosperma, C.leucostoma and C.schulzeri were identified. C.chrysosperma consisting of about 80% of collected isolates was determined as prevalent species. Moreover, the walnut tree was known as a new host species for C. schulzeri.

Armillaria root and crown rot is an important disease of woody plants including fruit, forest and ornamental trees in different regions. The disease is common in Isfahan and causes economical losses on a broad range of fruit trees. There only a few tolerant varieties to disease, and there is no efficient method in controlling the disease. Therefore, detection of the pathogen from soil is necessary to establish an IPM program for decreasing losses. In this study, specific primers were successfully used for rapid, sensitive and specific detection of Armillaria isolates from soil and wood samples. DNA was isolated directly from soil and wood samples and ITS region was amplified using universal primers ITS1 and ITS4 and specific primers AR1 and AR2 in nested PCR. The nested PCR method enables the detection of pathogen directly from soil and root samples without the need for isolation and cultivation of mycelium of Armillaria and in earlier steps of the disease progress.

In this study, the effects of four Beauveria bassiana isolates, obtained from the soil of Fashand, Atashgah and Ghare-agaj and one from a grass hopper Sphingonotus sp. on the adults of Russian wheat aphid Diuraphis noxia were studied under laboratory conditions. After determination of the minimum and maximum concentrations, the adult Russian wheat aphid was treated with conidial concentrations of 1×103 to 1×10 6 spore/ml to calculate LC50 & LC90. DEBI002 proved to have the lowest LC50 (4 ×105 spore/ml) whilst DEBI010 showed the highest LC50 (2.5×106 spore/ml). The lowest LT50 was obtained 2.8 days for DEBI002 at 1×10 6 spore/ml. In a completely randomized block design, the mortalities caused by the isolates on 6th & 10th days were as follows: At 1×10 5 spore/ml, on 6th days DEBI002(34.95% ± 3.64), DEBI015(37.1% ± 6.11) & DEBI001 (32.35% ± 1.3) were classified as level A & DEBI010 (18.74% ± 1.91) as level B. On 10th days, at 1×10 5 spore/ml DEBI002(45.1% ± 1.23), DEBI015(39.48% ± 7.21) and DEBI001(39.43% ± 2.65) were classified as level A & DEBI010 (16.23% ± 3.9) as level B (Duncans Muitple Range Test).