Antifeedant and sublethal effects of imidacloprid on Asian citrus psyllid,Diaphorina citri

BACKGROUND: Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, transmits the causal bacteria of the devastating citrus disease huanglongbing (HLB). Because of the variation in spatial and temporal uptake and systemic distribution of imidacloprid applied to citrus trees and its degradation over time in citrus trees, ACP adults and nymphs are exposed to concentrations that may not cause immediate mortality but rather sublethal effects. The objective of this laboratory study was to determine the effects of sublethal concentrations of imidacloprid on ACP life stages. RESULTS: Feeding by ACP adults and nymphs on plants treated daily with a sublethal concentration (0.1 µg mL^?1) of imidacloprid significantly decreased adult longevity (8 days), fecundity (33%) and fertility (6%), as well as nymph survival (12%) and developmental rate compared with untreated controls. The magnitude of these negative effects was directly related to exposure duration and concentration. Furthermore, ACP adults that fed on citrus leaves treated systemically with lethal and sublethal concentrations of imidacloprid excreted significantly less honeydew (7–94%) compared with controls in a concentration‐dependent manner suggesting antifeedant activity of imidacloprid. CONCLUSIONS: Sublethal concentrations of imidacloprid negatively affect development, reproduction, survival and longevity of ACP, which likely contributes to population reductions over time. Also, reduced feeding by ACP adults on plants treated with sublethal concentrations of imidacloprid may potentially decrease the capacity of ACP to successfully acquire and transmit the HLB causal pathogen. Copyright © 2009 Society of Chemical Industry     

Imposed starvation for in vitro maintenance and high regeneration of elite key lime (Citrus aurantifolia)

Preservation of elite key lime (Citrus aurantifolia) genotypes using efficient micropropagation and regeneration protocols is very important for new breeding programmes. The objective of the present study was to develop an efficient protocol for micropropagation and maintenance of elite genotypes of key lime based on slow growth and starvation strategy. To do this, regenerated shoots were starved, and the growth was compromised via avoiding subcultures for 4, 8, 12 and 24 months. The numbers of responsive explants and adventitious shoots per each explant were evaluated in the presence of benzylaminopurine (BAP). The results showed that the 12- and 24-month starved explants treated with 1 mg/l BAP were able to produce four times more shoots than the control. In addition, the influences of horizontal or vertical layering explants over medium were evaluated. The results indicated that all horizontally layered explants significantly produced 25% adventitious shoots more than vertical explants, most likely owing to more contact with the surface medium. Finally, it could be concluded that application of slow growth, starvation strategy and also horizontally layering of the explants could efficiently enhance micropropagation and maintenance of threatened elite key lime genotypes with a low cost.     

Response of oriental beech (Fagus orientalis Lipsky) seedlings to canopy gap size

The response of nursery seedlings and wildings of oriental beech(Fagus orientalis Lipsky) to canopy gap size was studied ina climax beech forest in northern Iran with respect to seedlingsurvival, shoot growth and vitality. These parameters were followedfor 2 years after planting in gaps of 50, 200 and 600 m², aswell as in the open field. Foliage coloration was used as acriterion for vitality. The survival rate of nursery seedlingsand wildings dropped rapidly with increasing gap size from 84per cent in 50-m² canopy openings to     

Risk factors for <Emphasis Type="Italic">Mycobacterium avium</Emphasis> subspecies <Emphasis Type="Italic">paratuberculosis</Emphasis> in Fars province (Southern Iran) dairy herds

A cross-sectional study was conducted from March to August 2006 in dairy herds in Fars province, southern Iran to determine the herd-level risk factors for infection with Mycobacterium avium subspecies paratuberculosis (MAP). Statistical analysis using multivariable logistic regression showed that contamination of udders of periparturient cows with manure (OR = 6.4, P = 0.02) and history of having suspected cases of Johne's disease in the herd (OR = 6.7, P = 0.04) were significantly associated with the herd infection status. No relationship between breed, herd size and other management practices with the infection status of the herd were found in this study. Implementing high sanitary measures in the farm, particularly with respect to manure handling and cleaning could be considered as one of the important aspects in controlling disease in the region as well as in the future educational effort.     

Effect of topical 1% tropicamide on Schirmer tear test results in clinically normal horses

Objective  To observe the effect of topical 1% tropicamide on equine tear production as measured by Schirmer I tear test.
Materials and methods  Fourteen adult horses received one drop of 1% tropicamide ophthalmic solution in one eye and the opposite eye served as the control. The tear production in both eyes was tested at 1, 2, 4, 6, and 24 h after 1% tropicamide administration.
Results  Measurements made 1 h after treatment revealed a significant reduction in Schirmer tear test values in tropicamide treated eyes ( P  = 0.002). The observed decrease in tear production was maintained up to 4 h after treatment ( P  = 0.002). Although tropicamide-induced decrease in STT values was observed in the treated eyes, the contralateral eyes did not show significant changes in Schirmer tear test results.
Conclusion  Single dose of topical 1% tropicamide resulted in statistically significant reduction in Schirmer tear test values in clinically normal horses.     

The nutritional effect of Isochrysis galbana and Chaetoceros muelleri cultured with different seaweed extracts on the larval development,growth and survival of the marine shrimp,Penaeus indicus

The microalgae Isochrysis galbana and Chaetoceros muelleri were cultured with seaweed extract (SWE) from six different seaweeds and each SWE was used either as a supplement or as an alternative media to conventional f/2 medium. Microalgae cultured with only the f/2 media acted as the control treatment. I. galbana and C. muelleri were then fed to Penaeus indicus larvae, either singly or in combination, for 8 days to evaluate its nutritional quality. Shrimp larvae fed on microalgae cultured in f/2 media supplemented with SWE from Ulva lactuca or Enteromorpha intestinalis moulted faster (P < 0.05) to the second mysis stage compared with the control. Survival, total length and growth rates were better in shrimp larvae fed on microalgae previously cultured in media supplemented with SWE. In general, shrimp larvae fed microalgae cultured entirely in SWE performed equally well compared with the control. Shrimp larvae fed on mixed microalgae (I. galbana + C. muelleri) showed significantly better growth, survival and development compared with larvae on either single microalgal diet. It was concluded that microalgae cultured with SWE could be used as a low‐cost alternative media in producing live food for the hatchery production of shrimp larvae.     

Genetic structure,clonality and diversity in commercial pomegranate (Punica granatum L.) cultivars

Genetic Resources and Crop Evolution - The pomegranate fruit is one of the most important horticultural products due to the presence of polyphenols, anti-oxidant and anti-fungal compounds. In the...     

Optimization of elecrospinning process of zein using central composite design

Biodegradable edible sub-micron electrospun zein fibers were prepared using acetic acid as solvent. The solution concentration at three levels: 22, 26 and 30 w/v %, the electrospinning voltage at three levels: 10, 20 and 30 kV, the solution flow rate at three levels: 4, 8 and 12 ml/h and the distance between needle tip and collector at three levels: 10, 15 and 20 cm were studied. Central composite design (CCD) was utilized to modeling the effect of electrospinning parameters of zein solution on average fiber diameters and the data were analyzed using response surface methodology (RSM). Coefficient of determination, R², of fitted regression model was higher than 0.9 for response. The analysis of variance table showed that the lack of fit was not significant for response surface model at 95 %. Therefore, the model for response variable was highly adequate. Results also indicated that the solution concentration had significant influence (P<0.0001) on morphology and diameter of fibers. By increasing the solution concentration, uniform and bead-free fibers were obtained. As the solution concentration was increased, the average fiber diameters were also increased. Furthermore, the electrospinning voltage had significant effect (P<0.0001) on average fiber diameters. By increasing the electrospinning voltage, the average fiber diameters increased. The solution flow rate and the distance between needle tip and collector had no significant influence on the average fiber diameters. According to model optimization, the minimum average fiber diameter of electrospun zein fiber is given by following conditions: 24 w/v % zein concentration, 10 kV of the applied voltage, 10 cm of needle tip to collector distance, and 4 ml/h of solution flow rate.     

Foliar Nitrogen as an Indicator of Nitrogen Deposition and Critical Loads Exceedance on a European Scale

The foliar N content of bryophytes and Calluna vulgaris (L.) has been shown to be an indicator of atmospheric N deposition in the UK at a regional scale (1000km) and more recently on a smaller scale in the vicinity of intensive livestock farms. This work extends the geographical scale of the relationship between foliar N concentration of Calluna vulgaris and other ericaceous shrubs and N deposition with 2 measurement transects, one extending from northern Finland to southern Norway (2000 km) and the other extending from central Sweden to Stockholm, south east Sweden (330 km). Included in the second transect is a region of complex terrain in the Transtrand uplands, where the variation in N deposition with altitude and canopy cover was quantified using ²¹⁰Pb inventories in organic soil. The relationship between foliar N (F_N) and N deposition was shown to increase linearly with N deposition (N_D) over the range 0.8% N to 1.4% N according to F_N = 0.040N_D + 0.793 (r² = 0.70). The data are entirely consistent with earlier studies which together provide a valuable indicator of critical loads exceedance, the threshold value being approximately 1.5% N, which is equivalent to a N deposition of 20 kg N ha^?1 y^?1.     

Biosystematics relationships among Marrubium L. (Lamiaceae) species in Iran

Genetic Resources and Crop Evolution - Marrubium L., is a problematic genus of Lamiaceae family with approximately 40 taxa that some of its species grow in Iran. In the current study, we studied...