Establishment of persistent avian infectious bronchitis virus infection in antibody-free and antibody-positive chickens

Avian infectious bronchitis virus (IBV) causes a highly contagious and economically significant disease in chickens. Establishment of a carrier state in IBV infection and the potential for the persistent virus to undergo mutations and recombination in chicken tissues have important consequences for disease management. Nevertheless, whether chickens can maintain persistent IBV infection in the absence of reinfection from exogenous sources or the presence of antibody in the host can modulate virus persistence remains unclear. Indeed, whether or not IBV genome can undergo genetic changes during in vivo infection has not been demonstrated experimentally. In the present study, IBV shedding and tissue persistence were monitored in individual chickens maintained under strict isolation that precluded reinfection from exogenous sources. In the first of two experiments, intranasal exposure of 6-wk-old antibody-free chickens to IBV vaccine virus resulted in intermittent shedding of the virus from both trachea and cloaca of individual birds for up to 63 days. Also, the virus was recovered from the internal organs (spleen, gonad, kidney, lung, cecal tonsil, and cloacal bursa) of six of eight birds killed at various intervals between 27 and 163 days postinoculation (DPI). In the second experiment, IBV exposure of 1-day-old maternal antibody-positive chicks led to periodic virus shedding from the trachea and cloaca in all chickens until 77 days; however, internal organs (lungs and kidneys) of only one of seven birds (killed at 175 DPI) were virus positive, suggesting that presence of antibody at the time of infection protects internal organs from IBV infection. When the lung and kidney isolates of IBV from the latter experiment were compared with the parent-vaccine virus, no changes in their antigenicity, tissue tropism, or the nucleotide sequence of the S1 glycoprotein gene were observed. These findings indicate that, unlike the mammalian coronaviruses, propensity for frequent genetic change may not be inherent in the IBV genome.     

Characterization of infectious bronchitis virus isolates by slot blot hybridization

We used slot blot hybridization of the hypervariable regions of the S1 subunit of spike peplomer gene to identify and characterize infectious bronchitis virus (IBV) strains. Template DNA was created from six reference strain IBVs of different serotypes and immobilized on a nitrocellulose membrane. We synthesized digoxigenin-labeled probes from reference and unknown field viruses and hybridized them to template DNA. All reference strains could be distinguished and isolates identified by serotype if they were at least 95% identical to a reference strain. This slot blot hybridization procedure was specific and reproducible, and strain typing was consistent with the S1 sequencing of the IBV genome. This study thus provides a simple and rapid method for typing of IBV.     

In vitro tuberisation of Gloriosa superba L. on basal medium

A suitable protocol for in vitro tuber production using non-dormant tubers of Gloriosa superba L. on Murashige and Skoog (MS) medium without addition of plant growth regulators is reported in the present study. Among the different basal media tested MS medium was found to be suitable for induction and development of secondary tubers; one in vitro tuber per explant was obtained after 6 weeks and 3 tubers per explant after 12 weeks of culture. These tubers produced healthy green shoots that rooted on basal medium. Best rooting was noted in half strength (half organics and inorganics) MS medium with one-fifth nitrates.     

Improving productivity of Bauhinia purpurea for tree planting farmers in Nepal

Shortage of fodder is a major constraint to livestock production in Nepal. The genetic variation in canopy biomass production of Bauhinia purpurea L, a very important fodder species in Nepal, was estimated in a Breeding Seed Orchard in order to examine the potential of simple, low input breeding. Substantial genetic variation could be observed suggesting that low input breeding based on simple phenotypic selection can provide biomass gain in the order of 2–5% per year. Very high correlation was observed between stem diameter (cross section area) and total biomass, making farmer based selection relevant. Jointly, these results suggest that low input domestication is a promising option for improving fodder production in Nepal and thereby help to improve rural livelihood and development. A multiple population approach is recommended.     

Virulence status,viral accommodation and structural protein profiles of white spot syndrome virus isolates in farmed Penaeus monodon from the southeast coast of India

The objective of this study was to investigate the reason for variation in the virulence of white spot syndrome virus (WSSV) from different shrimp farms in the Southeast coast of India. Six isolates of WSSV from farms experiencing outbreaks (virulent WSSV; vWSSV) and three isolates of WSSV from farms that had infected shrimps but no outbreaks (non‐virulent WSSV; nvWSSV) were collected from different farms in the Southeast coast of India. The sampled animals were all positive for WSSV by first‐step PCR. The viral isolates were compared using histopathology, electron microscopy, SDS‐PAGE analysis of viral structural proteins, an in vivo infectivity experiment and sequence comparison of major structural protein VP28; there were no differences between isolates in these analyses. A significant observation was that the haemolymph protein profile of nvWSSV‐infected shrimps showed three extra polypeptide bands at 41, 33 and 24 kDa that were not found in the haemolymph protein profile of vWSSV‐infected shrimps. The data obtained in this study suggest that the observed difference in the virulence of WSSV may not be due to any change in the virus, rather it could be due to the shrimp defence system producing certain factors that help it to accommodate the virus without causing any mortality.     

Effects of shade on arbuscular mycorrhizal colonization and growth of crops and tree seedlings in Central India

The study was conducted to investigate the effects of different light intensities (25, 50, 67, and 100% of full sun [open]) on arbuscular mycorrhizal (AM) colonization and growth of two intercrops (a rainy season crop, Phaseolus mungo Roxb. var. PU-35 and a winter crop, Triticum aestivum L. var. WH-147) and seedlings of two multipurpose tree species (Eucalyptus tereticornis Sm. [Clone C-7, ITC, Bhadrachalam] and Albizia procera Benth.) of Central India. The results showed that various plant growth parameters viz., shoot length, dry weight and phosphorus (P) uptake were adversely affected by low light intensity. Inoculations with AM fungi (Acaulospora scrobiculata Trappe, Glomus intraradix Schenck & Smith and an unidentified Glomus species) increased the plant growth on account of all measured parameters under tested light conditions. Mycorrhizal efficiency of different AM fungi varied in narrow range. AM inoculants were more efficient at higher light intensity in above mentioned plant species, except wheat. Data on colonization of P. mungo, T. aestivum, E. tereticornis and A. procera showed that formation of arbuscules, vesicles and sporocarp was delayed by lower light intensity. Colonization index of host roots and spore counts increased with increase in light intensity during successive months after inoculation. Data on effect of light regimes on microclimate of net house showed that lux meter reading decreased as per grades of shading nets used during both rainy and winter seasons. With increase in light intensity, ambient temperature, soil surface temperature and sub surface temperature at 15 cm depth increased, except that the ambient and soil surface temperature in control (open) were slightly lower than net house observations during January and February. Value of ambient temperature varied in narrow range, with in treatments as compared to soil surface and sub soil surface temperature at 15 cm depth. Soil surface temperature at 25% of full sunlight was less than respective control values by 2–11°C and sub soil temperature at 15 cm depth was less by 4–12°C. The values of different microclimate parameters varied in narrower range during winter season as compared to rainy season. While ranking the importance of two factors studied—light and AM fungi—for their effect on the growth and P uptake by different plant species, inoculations with AM fungi came in the first place (explained 50–82% variation) and light substantially increased the values of R ² in stepwise regression analysis (forward selection). The results suggest that AM inoculation may enhance the growth and P uptake of intercrops under tree shade and the tree canopy management is likely to increase the efficiency of AM inoculants in agroforestry systems. Use of excessive shading (25% of full sun or more) in nurseries may be avoided and PAR (photosynthetically active radiation) lamps may be used to increase growth and colonization index of tree seedlings.     

Two phenolic glycosides from Curculigo orchioides Gaertn

One new glycoside derivative from syringic acid and one new phenol glycoside, curculigoside E (1) and orchioside D (2), were isolated and characterized from the rootstock of Curculigo orchioides collected in the Nawalparasi District (Nepal). The structures of the new isolated compounds were elucidated by means of spectroscopic methods such as 1D, 2D NMR and MS.     

Supra-nutritional dietary intake of selenite and selenium yeast in normal and stressed rainbow trout (Oncorhynchus mykiss): Implications on selenium status and health responses

Commercial salmonid diets are not typically supplemented with selenium (Se) as they naturally contain relatively high levels of this essential trace element; however supplementation may be necessary to meet requirements during physical stress. Adopting an integrated approach by simultaneously determining Se status, various health parameters and interactions with other trace elements, this study aimed to determine the role of supra-supplemented selenite and Se-yeast (Selplex^®) on the growth and health of rainbow trout (Oncorhynchus mykiss), both under normal conditions and after exposure to chronic physical stress. Fish were fed one of seven diets; a basal un-supplemented diet (0.73 mg kg^− 1 Se) or diets supplemented with Se-yeast or sodium selenite to provide 2, 4, or 8 mg kg^− 1 Se for 10 weeks prior to subjection of daily handling and confinement stressors for seven days. Net whole body Se retention was significantly greater for Se-yeast than selenite at all levels. In normal conditions activities of hepatic glutathione peroxidase (GSH-Px) and thioredoxin reductase (Trx-R) indicate that Se requirements were met by the basal diet. Similarly, pre-stress supra-supplementation of selenite and Se-yeast did not affect oxidative status (total antioxidant capacity of serum and hepatic malondialdehyde), immuno-competence (respiratory burst activity, serum lysozyme, and leukocyte counts) or other haematological and growth parameters (nuclear abnormalities in erythrocytes, and specific growth rate). In contrast, the trend towards a higher GSH-Px post-stress in Se supplemented diets over the basal diet, particularly in Se-yeast fed fish, indicates that Se requirements may not be met by the un-supplemented practical diet in stressed fish. Seven days of chronic physical stress decreased whole body Se and increased GSH-Px activity signifying an increased Se utilisation. During stress Se status was more effectively maintained by Se-yeast than selenite. Increased hepatic lipid peroxidation in stressed fish fed 8 mg kg^− 1 selenite indicates a possible pro-oxidant effect of selenite. A positive interaction was observed between dietary selenite and whole body copper, but no such interaction was observed with Se-yeast. This study concludes that physical stressors can result in an elevated Se utilisation and consequently supplementation of commercial diets may be necessary such that Se reserves are available as a contingency for stress.     

Length–weight relationship and growth performance of different life stages of hatchery‐produced magur,Clarias magur (Hamilton, 1822)

Length–weight relationship (LWR) of 661 numbers of hatchery‐produced magur, Clarias magur of all the life stages such as hatchlings, fry, fingerlings, juveniles and adults, was studied. The LWR of all the life stages of magur was estimated and the equations are as follows, hatchlings W = 0.0052*L^1.282 (r² = 0.8784), fry W = 0.0088*L^3.028 (r² = 0.8113), fingerlings W = 0.0065*L^3.226 (r² = 0.8906), juveniles W = 0.0028*L^3.420 (r² = 0.8175) and adults W = 0.0017*L^3.491 (r² = 0.8310). A positive allometric growth (b > 3) was observed in all the life stages except hatchlings. The annual growth rate of magur was observed with the body length and weight of 24 ± 1 cm and 115 ± 17 g, respectively, under the commercial production system. This is the first kind of study that describes about the LWR and growth performance of all the life stages of hatchery‐produced C. magur catfish from hatchlings to adults under commercial production system. This study will be more useful to the hatchery managers and fish growers to optimize the resources and husbandry practices to improve the growth, survival, and biomass production.