JOURNAL OF CROP PROTECTION
Year:2012 | Volume:1 | Issue:4|Papers Count:10

Mycosphaerella graminicola, the causal agent of septoria tritici blotch (STB), is a widespread and significant pathogen of wheat. To determine mating types, 89 isolates were collected randomly from wheat fields of Khuzestan, East Azerbaijan, Ardebil, Kermanshah and Golestan provinces of Iran, during 2006-7.DNA was extracted based on standard protocols. Multiplex PCR was conducted using two pairs of mating type-specific primers forMAT1-1 and MAT1-2.Sensitivity to strobilurin fungicide was determined using strobSNPrc7 and strobSNPrc1 primers. The results showed that in 35 isolates, a fragment of 340 bp amplified withMAT1-1 idiomorph specific primers and in 54 isolates a fragment of 660 bp was amplified withMAT1-2 idiomorph specific primers.While the mating type frequencies were highly unequal, theMAT1-1 was predominant. All isolates were sensitive to strobilurin and amplified a fragment of 639 bp. It is concluded that both mating types are present in Iran, although with different frequencies, which may affect genetic variation through sexual cycle. Meanwhile the studied isolates were not resistant to strobilurin fungicides which may be due to growing wheat cultivars resistant to STB rather than using strobilurin fungicides as a dominant control method.

Biological efficacy of Trichoderma species may differ due to variations in ecosystems. This study was conducted to assess the biocontrol efficacy of some native Trichoderma isolates against Fusarium oxysporum, an important causal agent of potato wilt disease under laboratory and greenhouse conditions in Shahrood Agricultural Research Center, Shahrood, Iran during 2006-2007. Fourteen isolates were collected among which eight showed promising ability in inhibiting growth of the pathogen through dual culture and production of volatile and non-volatile metabolites but T. asperellum (T2) and T. atroviride (T3) were almost more efficient than other isolates in inhibiting the mycelial growth of the pathogen in comparison to control (P£0.01). Eight isolates were evaluated against the disease under green house condition. Potted plants treated with Trichoderma isolates+F. oxysporum showed lower disease incidence in comparison to Fusarium infested control (P £0.05). Best disease control was observed in potted plants treated with F. Oxysporum+T. asperellum (T2) showing 2.5% disease incidence in contrast to Fusarium infested control, in which disease incidence was 73%.

A survey on the hover flies (Diptera: Syrphidae) fauna of northern Iran, between 2010 and 2011, led to the discovery of the species Pipiza accola Violovitsh, 1985. Both the genus and species are newly recorded from Iran. All the specimens were collected from Gilan and Mazandaran provinces, using Malaise traps. The diagnostic characters of P. accola and its geographical distribution is presented.

Race-specific resistance of wheat to yellow rust caused by Puccinia striiformis f. sp. tritici has been reported as short-lived. Partial resistance, a kind of quantitative resistance, has been reported to be more stable. Partial resistance in terms of slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC), and coefficient of infection (CI) was evaluated in a set of twenty six wheat genotypes along with susceptible control during 2010-2011 cropping year. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran) under natural infection conditions with twice artificial inoculation. Artificial inoculation was carried out by yellow rust inoculum having virulence againstYr2, Yr6, Yr7, Yr9, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, YrA, and YrSU. Seedling reaction was also evaluated in greenhouse by using race 66E0A+, Yr27+. Results of mean comparison for resistance parameters showed that, lines C-89-4, C-89-17 and C-89-16 along with susceptible had the highest values of FRS, CI, r and rAUDPC, therefore were selected as moderately susceptible or susceptible lines. The lines C-89-7, C- 89-8, C-89-9, C-89-10, C-89-13, C-89-14 and C-89-20 had susceptible reactions at seedling stage and low level infection at adult plant stage.Accordingly these lines with low level of different parameters supposed to be having gene/s for varying degrees of partial resistance or high temperature adult plant resistance (HTAP) that can be used for future manipulation in wheat improvement program after confirmatory studies. The remaining lines (except for C-89-2) were immune or had low level of infection. Thus, these were selected as resistant lines. In this study correlation coefficient between different parameters of slow rusting was highly significant. Based on the results, the reaction of the studied genotypes to stripe rust varied from sensitive to immune.

The Meloidae, known as blister beetles, a widespread family of Tenebrionoidea that includes approximately 2500 species, is still scarcely known faunistically in several areas of the world. Because of specific biogeographical feature, Iran harbors a rich diversity of meloids and due to the lack of basic and integrated studies, particularly in eastern parts of Iran, our current knowledge of Iranian meloids should be considered preliminary. In order to improve the knowledge of the meloidae species of north eastern Iran, faunistic investigations on blister beetles of this region were carried out during 2011-2012. Collected specimens as well as deposited specimens in Insect Museum of Ferdowsi University of Mashhad were examined, in detail. As a result, 31 species belonging to 11 genera from 2 subfamilies were identified. Among the identified specimens, 24 species were new for fauna of Khorasan provinces. Ctenopus sinuatipennis Fairmaire (1892) is reported for the first time from Iran.

Essential oil extracted from the leaves of Lemon verbena, Lippia citriodoraKunth (Verbenaceae) was tested for fumigant toxicity in the laboratory against two stored-product insectsTribolium confusum Jacquelin du Val andCallosobruchus maculatus (F.). The chemical composition of the isolated oil was examined by GC-MS. The major compounds were citral (11.3%), limonene (10.6%), neral (7.9%), 4-phenyl undecan-4-ol (7.7%), a- curcumene (6.5%), a-cedrol (4.5%) and caryophyllene oxide (4.5%).Furthermore, lesser amounts of the other components include carveol (3.7%), linalool (3.5%), a-pinene (3.2%), caryophyllene (2.8%) and geranyl acetat (1.8%) were existed in the essential oil. In the fumigant toxicity set at 27±1 oC and 65±5% R. H., darkness condition and 24 h exposure time, considerable differences in mortality of insect to essential oil vapor were observed. C. maculatus (LC50=10.2 ml/l air) was significantly more susceptible than T. confusum (LC50=497.8 ml/l air). These results suggested that essential oil of L. citriodoracould be used as a potential control agent against stored-product insects.

Life table parameters of Aphis pomi DeGeer (Hemiptera: Aphididae) were determined on two host plants: apple (Malus pumila L.) and flowering quince (Chaenomeles japonica Lindl.). This study was carried out under laboratory conditions (25±1 oC and RH of 70±5 % and a photoperiod of 16: 8 h (L: D). The survivorship from first instar nymphs to adult was very close in M. pumila and C. japonica. The longevity of A. pomi was 8.1±0.458 and 9.65±0.412 days and the fecundity of female was 37.25 ± 2.198 and 32.9±1.802 nymphs on M. pumila and C. japonica, respectively. Peaks of reproductive value occurred at ages of 8 and 9 days when reared on M. pumila and C. japonica, respectively. The intrinsic rate of increase (r) on M. pumila was higher than that on C. japonica, as it was 0.396±0.015 on M. pumila and 0.329±0.006 day-1 on C. japonica. The mean generation time (T) was 9.13±0.35 and 10.62±0.18 days, on M. pumila and C. japonica, respectively. The results showed that the two closely related host plants had significant influence on life table parameters of A. pomi and the aphid showed a better performance on M. pumila than on C. japonica.

Fungi belonging to the Mycosphaerella s. l. are widely distributed all over the world. Most taxa cause leaf spot diseases, and have considerable impact on cultivation of many economically important crops. On Eucalyptus species, for example, Mycosphaerella leaf spots are one of the major diseases responsible for severe damage in most parts of the word especially outside of their native cultivation range. Mycosphaerella leaf blotches on Eucalyptus have little been studied in Iran. During a study on fungi associated with leaf spots on Eucalyptus spp. several specimens of mitosporic fungi which have been collected from Guilan province were examined and two species viz. Kirramyces epicoccoides and Pseudocercospora eucalyptorum were found to be new records for Iran mycobiota. Moreover, another species of Pseudocercospora is described on Eucalyptus. This species is clearly distinguished from related taxa by its conidium morphology, and appears to represent a new species; however, due to complicated taxonomy of the genus Pseudocercospora (especially on Eucalyptus spp.) further information is required to confirm its taxonomical position.

Asiatic citrus canker is a devastating disease resulting in drastic economic losses in citriculture worldwide. Amongst three different types of the disease, i.e. A, A* and Aw, the A* type is genetically less known. In order to comprehend the behavior of the Asiatic citrus canker A*-type strain (Xanthomonas citri subsp. citri) in the vicinity of the host cells, a targeted semi-quantitative transcript analysis approach via RT-PCR was carried out. A subset of sixteen genes, as representative of different steps involved in phytopathogencity, was analyzed on the culture medium (as uninduced) and compared with the subset isolated from the infected Mexican lime (Citrus auarntifoliaL.) plants (as induced). The results showed that certain genes were up-regulated in induced condition, suggesting a putative role in bacteria-host interaction. Furthermore, the transcripts in induced condition could be classified into constitutive, early- and late-responsive genes, demonstrating their functional relevance during the host-pathogen interaction.

Root rot and vine decline caused by Monosporascus cannonballus is a major challenge for melon production world-wide. In recent years, a disease suggested to be related to this pathogen was observed 1-2 weeks prior to harvest in many melon production areas across Iran. In this study, melon plants with symptoms of chlorosis, wilting, decline and/or sudden death were collected from melon growing areas. Pieces of the roots with rot symptoms or discoloration were surface-sterilized and placed on PDA culture medium.DNA was extracted from the rest of the sterilized roots and used in polymerase chain reaction (PCR) using specific primers designed from ribosomal DNA of M. cannonballus. The pathogenicity of the fungus for 24 of its isolates was examined on a muskmelon genotype, Zard-e-Garmsar. In addition, the presence of M. cannonballus was tested on the symptomless melon plants at early growing stages as well as those inoculated with this pathogen using the specific primers. The presence of M. cannonballus was confirmed in 95 melon samples (63% of total samples tested) based on the morphological criteria of the isolated fungus and molecular techniques, where a unique band specific to this pathogen was amplified in diagnostic PCR.M. cannonballus was also detected in the roots of symptomless and inoculated melon plants as early as 2 days post-inoculation. This study demonstrated that M. cannonballus is the major causal organism for melon collapse in all sampling regions and that the pathogen is detectable in melon plants suspected of infection using molecular tools at early growth stages.