Effects of various dietary factors on astaxanthin absorption in Atlantic salmon (Salmo salar)

The experiment was designed to investigate the dietary factors that might enhance or interfere with astaxanthin (Ax) absorption in salmon including potentially interfering factors such as certain carotenoids (zeaxanthin and lutein), plant sterols, fibre and enhancing compounds such as cholesterol and vitamin E. Two hundred and eighty‐eight salmon (778 ± 78 g) were reared in sea water under controlled conditions and fed practical experimental diets. The experimental diets were supplemented with 40 mg Ax kg^?1, in addition to various dietary factors, including cholesterol (2%), vitamin E (450 IU kg^?1), wheat bran (5%), lutein (40 mg kg^?1), zeaxanthin (40 mg kg^?1) and phytosterol (2%). After 26 days of feeding, blood was collected and plasma was separated to determine the plasma Ax concentration. Ax was not detected in the plasma of fish fed the non‐pigmented diet. Fish fed diet containing 2% cholesterol significantly improved Ax absorption, which was reflected in the higher Ax concentration in plasma of Atlantic salmon. Other supplements including vitamin E, wheat bran, lutein, zeaxanthin and phytosterols in diet had no significant effect on plasma Ax concentration . Fish fed diet containing 2% cholesterol significantly increased cholesterol concentration in fish plasma. Phytosterol had no benefit to lower cholesterol plasma level in fish fed 2% phytosterol‐supplemented diet.     

Metapopulation approach for landscape level management of western tarnished plant bug, Lygus hesperus, in Texas (Hemiptera, Miridae)

Insect source-sink dynamics are vital to ecologically intensive pest management. Maintaining sink plant hosts, or "trap crops", and destroying alternate hosts or breeding places adjacent to the field crop are effective pest management strategies for some arthropods. However, determining whether a host acts as a source or a sink is challenging, especially when the pest species is highly mobile and polyphagous. The western tarnished plant bug, Lygus hesperus, is highly polyphagous, and can utilize >300 hosts. Its presence has been documented in 26 roadside weed hosts in the Texas High Plains. Previous studies demonstrated that L. hesperus prefer alfalfa over cotton and several alternate weed hosts. A four-year project involved surveying and sampling for L. hesperus in the agricultural landscapes of several sub-regions of the southwestern United States, including the Texas High Plains. In Texas, geographic information of the landscape vegetation complex was compiled from a 150 km radius in the Texas High Plains. In one study, fifty irrigated cotton fields representing the crop diversity within this region were sampled via sweep-net for 10 weeks. This effort also included sampling of up to six non-cotton insect habitats within a 3 km radius of each field. Seasonal average L. hesperus abundance data were regressed with 27 field characteristics (variables), including habitat-specific land cover, distance between focal cotton fields and non-cotton habitats, longitude, latitude, elevation, habitat heterogeneity index, and several environmental/ecological variables. Significant variables were selected using a stepwise regression at 15% probability rate. A 10-parameter linear model explained 93% of the variation in the data. Major parameters contributing significantly to variation in L. hesperus abundance in cotton were corn and sunflower acreages, focal cotton field distances from several non-cotton hosts, and habitat heterogeneity index. In addition, field marking-and-capture studies were conducted using protein markers and enzyme-linked immunosorbent assays to characterize L. hesperus intercrop movement behavior. The field marking-and-capture approach can be used to study the effects of various crop management practices on L. hesperus intercrop movement and can potentially be applied to other pests and cropping systems.     

Leaf and neck blast resistance reaction in tropical rice lines under green house condition

Rice blast (Magnaporthe oryzae) is the most destructive and epidemic disease of rice. Use of host resistance is the best alternative for disease management. The leaf and neck blast resistance of 182 rice breeding lines were assessed for leaf and neck blast and classified relative to a susceptible check-Masuli and resistant check-Laxmi, from greenhouse experiment in 2005 and 2006. The test plants were inoculated with 10⁵ conidial suspension/ml of M. oryzae at 21 days old seedlings for the leaf blast, and at neck base for the neck blast. Among them, for leaf blast, 77 rice lines were resistant, 43 were moderately resistant, 39 were moderately susceptible and 23 were susceptible. While among the selected 31 rice lines evaluated for neck blast, 4 lines were resistant, 4 were moderately resistant, 16 were moderately susceptible and 7 were susceptible. Leaf and neck infection was significant and positively correlated (r = 0.30, P = 0.05). The rice lines, Barkhe 1032, Barkhe 1034, Barkhe 1035, Barkhe 1036, Barkhe 2014, Barkhe 2024, Barkhe 3019, Super 3004 were resistant to leaf blast and Barkhe 1006, Barkhe 1032, Barkhe 1035, Barkhe 3004 were resistant to neck blast. The rice lines with identification # 11, 69, 137, 168, 182 from Masuli × MT4 parentage, and Barkhe 3017 were susceptible to both leaf and neck blast. Progenies of Irradiated Pusa Basmati (IPB), Kalinga III/IR64 (KIII/IR64), and Masuli/IR64 were resistant to both leaf and neck blast. However, most progenies from Masuli/MT4 showed susceptible reaction to both leaf and neck blast. Thus, rice lines form the IPB, KIII/IR64 and Masuli/IR64 will be promising resistant sources for rice blast in breeding programme.     

Potential biopesticides for crucifer flea beetle, <Emphasis Type="Italic">Phyllotreta cruciferae</Emphasis> (Coleoptera: Chrysomelidae) management under dryland canola production in Montana

The crucifer flea beetle, Phyllotreta cruciferae (Goeze), is an economically important and dominant pest of canola (Brassica napus L) in the Northern Great Plains of the USA. The current flea beetle management strategy is based on using synthetic chemical treated seeds and if necessary, foliar spray of chemicals at canola seedlings in early spring for targeting adult population. However, there is an increasing demand for development of alternative management strategies for P. cruciferae pertaining to concerns over the development of resistance to synthetic insecticides and non-target effects on pollinators and other beneficial insects. Replicated field trials were conducted to test the efficacy of several commercially available biopesticides including Entrust® (spinosad), entomopathogenic nematode Steinernema feltiae?+?Barricade® (polymer gel 1%), Aza-Direct® (azadirachtin), Pyganic 1.4® EC (pyrethrin), Grandevo® SC (Chromobacterium subtsugae), Venerate® XC (Heat killed Burkholderia sp. strain A396 as seed treatment and foliar application) and Gaucho® (imidacloprid) (chemical check) for the P. cruciferae management at two locations (Conrad and Sweetgrass) of Montana in 2016. Biopesticide products were evaluated based on canola leaf area injury ratings and seed yield levels. Although, there was no clear trend of canola yield increase, selected biopesticide treatments were effective in maintaining low leaf area injury ratings as compared to untreated control. Entrust was able to maintain low leaf area injury ratings (8.5–14.5%) when compared to untreated control (16.0–21.4%) at both the locations. Entomopathogenic nematodes, Steinernema feltiae?+?Barricade® and Venerate® applied as foliar treatments maintained significantly lower feeding injury pressure at Sweetgrass (11.8%) and Conrad (13.4%) locations respectively, when compared to the untreated control. Our study results suggest that these biopesticide treatment results were comparable in efficacy to the chemical seed treatment Gaucho®. Other two biopesticide products- Aza-Direct® and Pyganic 1.4® EC treatments did not provide effective control of P. cruciferae at both the locations.     

Efficacy of vaccination with La Sota strain vaccine to control Newcastle disease in village chickens in Nepal

The efficacy of vaccination with Newcastle disease (ND) La Sota and R₂B (Mukteswar) modified live strain vaccines was determined by experimental challenge and with ND La Sota vaccine under field conditions in Nepal. Booster vaccination with ND La Sota vaccine after a primary vaccination with ND La Sota vaccine, induced a geometric mean titre (GMT) of 5.0 log₂ haemagglutination inhibition (HI) units, compared to a GMT of 6.0 log₂ HI units following booster vaccination with R₂B vaccine 1 month after primary vaccination with ND La Sota vaccine. Both vaccines provided 100% protection against challenge with a local field ND strain. Furthermore, booster vaccination with ND La Sota vaccine induced protective levels of antibody after field use in villages in Jhapa, and no outbreaks of ND occurred during the study period. The ND La Sota modified live vaccine is immunogenic and efficacious and is a suitable vaccine for use in vaccination programmes in village chickens in the rural areas of Nepal.

     

Effect of two-component cultivar mixtures on development of wheat yellow rust disease in the field and greenhouse in the Nepal Himalayas

Wheat yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (PST), is a major disease of wheat, and deployment of a single cultivar often leads to disease epidemics. Effect of inoculum level, foliar fungicide spray, and wheat cultivar mixtures were evaluated on disease development in the field and greenhouse in Nepal. Treatments were arranged in a split–split plot design with three replications in both experiments. Two inoculum levels of PST (low and high) were main plot factors; nontreated control and foliar spray of fungicides (Mancozeb and Bayleton) were subplot factors; and two-component cultivar mixtures, composed of different ratios of a susceptible (S) and a resistant (R) cultivars (90:10, 80:20, and 50:50, 100:0, and 0:100) were sub–subplot factors. WYR severity was assessed at different time intervals, and disease development was calculated as area under the disease progress curve (AUDPC). Inoculum level did not cause significant differences in AUDPC in the field but did in the greenhouse. Foliar spray of fungicides reduced the AUDPC in the greenhouse and field. In both experiments, AUDPC values were low in cultivar mixtures compared with a pure stand of a susceptible cultivar. As the proportion of resistant cultivar increased compared with the susceptible cultivar in the S:R mixture component, disease severity decreased with a consequent increase in grain yield. The greater yield obtained with cultivar mixtures compared with only the susceptible cultivar, independent of inoculum level and fungicide spray in the field, revealed a promising strategy to manage WYR in Nepal.     

Comparative studies on egg,meat, and semen qualities of native and improved chicken varieties developed for backyard poultry production

The objective of the present study was to evaluate/compare the sensory attributes of eggs and meat, egg qualities, proximate composition of eggs, and semen qualities of slow growing native (Miri and Mizo-local) and fast growing improved chicken varieties (Gramapriya and Vanaraja) under hill ecosystem of northeastern India. Significantly higher egg weight, egg volume, and albumen volume were observed in Gramapriya followed by Vanaraja, Mizo-local, and Miri chickens. However, yolk volume was significantly higher in Vanaraja and Gramapriya varieties as compared to native chickens. Yolk to albumen ratio was significantly lower in Gramapriya as compared to Vanaraja and Miri chicken. Consumer liking of eggs for aroma, flavor, and overall acceptability of Miri, Mizo-local, and Vanaraja were significantly higher than that of Gramapriya. Genetic groups did not differ significantly in appearance and proximate composition of eggs. No significant differences were observed between various genetic groups for sensory attributes of meat samples. Semen volume was significantly (p ≤ 0.01) lower while sperm concentration was significantly (p ≤ 0.01) higher in native chicken as compared to the improved chicken varieties. However, pH, mass activity, sperm motility, and livability did not differ significantly among genetic groups although Mizo-local had significantly higher abnormal sperm count. The study concluded that the genetic groups with different growth rate differed significantly for various egg quality parameters and semen characteristics but not for sensory attributes of meat and proximate composition of eggs.