Biological activity and characterization of nucleopolyhedrovirus isolates ofSpodoptera litura

Geographical isolates ofSpodoptera litura (Fabricius) (Noctuidae: Lepidoptera) nucleopolyhedrovirus (SpltNPV), collected from different parts of India and maintained at Tamil Nadu Agricultural University, were compared for their biological activity and subjected to Restriction Endonuclease (REN) analysis. Neonate and second instar bioassay studies revealed similarity in biological activity as shown by the overlapping fiducial limits of LC₅₀ values. However, there were differences in yield among isolates: significantly higher yields were obtained from isolates UAS and CBE than from the BARC isolate. REN analysis of the four isolates withPst I,Hind III,Bam HI andEco RI enzymes indicated genotypic variation among the isolates. Based on the commonality of the bands, the isolates could be broadly divided into two groups: isolates AU and CBE formed one group, and the other group comprised UAS and BARC based on genetic relatedness. http://www.phytoparasitica.org posting Nov. 21, 2005.     

Comparative sensitivity of barley (Hordeum vulgare L.) to insecticide and fungicide on different stages of cell cycle

In this study, the comparison of cytogenetic effects of insecticide and fungicide in different phases of cell cycle was investigated in the root tip cells of barley (Hordeum vulgare L.). The seeds of H. vulgare L. Var. Karan 16 were treated with different concentrations (0.05%, 0.1% and 0.5%) of insecticide Profenophos (PF) and fungicide Mancozeb (MZ) for 6 h after presoaking durations of 7, 17 and 27 h.The different presoaking durations were used to bring the cells in various phases of cell cycle. Negative control was run parallel in distilled water. Cytogenetic examinations of root meristems exposed to the PF and MZ showed significant inhibition of mitotic index (MI) as well as significant increase in chromosomal aberrations (CAs). These parameters were dependent on the concentrations of insecticide and fungicide. The present study shows that PF and MZ both caused more damage in S phase of cell cycle which indicates that S phase is more sensitive in comparison to other phases.     

Association of double-stranded RNA with whitefly-mediated silvering in squash

A disorder of unknown aetiology appearing as silvering on squash (Cucurbita pepo) leaves has become prevalent in south Florida. Typical symptoms, observed after 2 weeks of exposure to adults of Bemisia tabaci , the sweet potato whitefly (SPWF) include vein clearing followed by silvering of whole leaves. Fruits from affected plants are blanched or streaked longitudinally. The silverleaf syndrome was not mechanically transmissible when crude extracts of symptomatic leaves were used as inoculum. Two sizes of double-stranded RNA (dsRNA) of c. 4.6 and 4.2 kilobase pairs (kbp) were consistently observed in leaf extracts of caged, whitefly-infested, symptomatic plants. In contrast, caged plants not exposed to whiteflies showed no symptoms and contained no detectable dsRN A. In addition, squash plants exposed to SPWF colonies from California neither developed silverleaf symptoms nor contained any dsRNA. Double-stranded RNA could also be readily detected in whitefly-infested yellow summer squash and zucchini from the field. However, asymptomatic eggplant and watermelon infested with SPWF from nearby fields did not contain detectable dsRNA. Dot-spot hybridization assays using an RNA-specific probe detected homologous sequences in both adults and nymphs of SPWF that induced silverleaf symptoms but not in adults and nymphs of SPWF that could not induce silverleaf symptoms. These results, along with the non-endogenous nature of the detected dsRNA suggest that the dsRNA is or is associated with the causal agent of whitefly-mediated leaf silvering in squash.     

Contingency nature of Helicobacter bizzozeronii oxygen-insensitive NAD(P)H-nitroreductase (HBZC1_00960) and its role in metronidazole resistance

Genomic analysis of a metronidazole resistant H. bizzozeronii strain revealed a frame length extension of the oxygen-insensitive NAD(P)H-nitroreductase HBZC1_00960 (RdxA), associated with the disruption of the C-terminal cysteine-containing conserved region (IACLXALGK). This was the result of the extension (from C₈ to C₉) of a simple sequence cytosine repeat (SSCR) located in the 3’ of the gene. A 3'' SSCR is also present in the rdxA homolog of H. heilmannii sensu stricto, but not in H. pylori. We showed that in the majority of in vitro spontaneous H. bizzozeronii metronidazole resistant mutants, the extension of the 3′ SSCR of rdxA was the only mutation observed. In addition, we observed that H. bizzozeronii ΔrdxA mutant strain showed the same MIC value of metronidazole observed in the spontaneous mutants. These data indicate that loss of function mutations in rdxA and in particular the disruption of the conserved region IACLXALGK is associated with reduced susceptibility to metronidazole in H. bizzozeronii. Slipped-strand mispairing of the SSCR located in the 3′ of the H. bizzozeronii rdxA appears to be the main mechanism. We also observed that H. bizzozeronii acquires resistance to metronidazole at high mutation rate, and that serial passages in vitro without selection induced an increased level of susceptibility. In conclusion, contrary to what was previously described in H. pylori, the H. bizzozeronii rdxA appears to be a contingency gene which undergoes phase variation. The contingency nature of rdxA should be carefully considered when metronidazole is used in the treatment of H. heilmannii-associated gastritis.     

Yield and yield-attributing traits of rice (Oryza sativa L.) under lowland drought and suitability of early vigor as a selection criterion

Fifteen experiments testing seven sets of genotypes under irrigated non-stress and drought stress situations were conducted from 2004 to 2006 with the objective to study the effect of different severity levels of drought on tolerant and susceptible advanced breeding lines, current varieties, and traditional and improved donors, and to study the effect of selection for high early vigor on yield. With the onset of drought, a yield reduction due to a decrease in biomass was observed in both susceptible and tolerant lines. However, after an initial reduction in yield, tolerant lines were able to sustain a yield loss more effectively than susceptible lines by better maintenance of biomass and higher harvest index. Under intermittent drought stress, genotypes with the ability to maintain higher biomass, reflected in terms of high early vigor recorded 3 wk after transplanting, recorded higher grain yield than genotypes with low early vigor. Lines with high early vigor yielded higher under both irrigated non-stress and intermittent drought stress situations. Under intermittent stress, plants with high vigor, low vigor, or random plants with high or low vigor coming from tolerant × susceptible crosses yielded higher than did the plants with the same vigor coming from susceptible × susceptible crosses. Under both irrigated non-stress and intermittent drought stress situations, early vigor showed significant genetic correlation with grain yield and could be included as an efficient selection criterion to improve yield in the lowlands.     

Effect of a Previous Washing Step with Tannic Acid on the Quality of Minced Horse Mackerel (Trachurus trachurus) During Frozen Storage

Fatty fish have been recognized as potential raw material for production of minced meat; however, they are prone to oxidation and further deterioration. In the present study, the effect of washing and antioxidant (tannic acid) treatment on the quality of minced meat of Trachurus trachurus (horse mackerel) during frozen storage was observed. Minced meat of Trachurus trachurus was divided into three lots (T0, T1, and T2). T1 was washed with cold water, T2 with cold water containing tannic acid (100 mg/kg), and T0 was not washed. All the lots were frozen at ?40°C and stored at ?20 ± 2°C for 125 days and were subjected to biochemical, microbiological, and sensory evaluation at regular intervals of 25 days. The antioxidant treatment with tannic acid at the dosage used was found effective in minimizing the rancidity problems of minced meat (T2), compared to T0 and T1. During the whole period of storage, samples from T2 showed good quality in terms of microbiological, biochemical, and sensory analysis compared to T1 and T0.     

Effect of practical diets with different protein levels on the performance of Farfantepenaeus paulensis juveniles nursed in a zero exchange suspended microbial flocs intensive system

Farfantepenaeus paulensis juveniles (72 ± 24 mg), were reared in a suspended microbial flocs system and fed practical diets containing increasing amounts of crude protein (250, 300, 350, 400 and 450 g kg^?1 CP). Development of microbial flocs was promoted by high aeration rates and fertilization with wheat bran and molasses. Flocs were composed of detritus in the form of flocculated matter colonized by heterotrophic bacteria, cocoid and filamentous cyanobacteria, flagellate and ciliate protozoa and rotifers. Proximate composition analysis of the suspended microbial floc showed CP levels of 304 g kg^?1. After 45 days, mean shrimp survival were above 89%, with no significant differences between treatments. Shrimp fed diets with 350 g kg^?1 or higher CP content achieved significant higher (P < 0.05) final weight (0.66–0.68 g), weight gain (0.58–0.61 g) and instantaneous growth rate (0.049–0.050), with feed conversion rates (2.17–2.30) significantly lower (P < 0.05). Results show that, when rearing is carried out in a suspended microbial flocs system, dietary CP levels can be kept at 350 g kg^?1. Furthermore, results confirm that microbial‐based systems allow shrimp culture without compromising the surrounding environment and shows the possible reduction of production costs and fish meal dependence.     

Optimization of the stocking parameters for mud spiny lobster Panulirus polyphagus (Herbst, 1793) capture‐based aquaculture in tropical open sea floating net cages

Mud spiny lobsters, Panulirus polyphagus (Herbst, 1793), were reared at four different stocking sizes and stocking densities in open sea cages to evaluate their effects on growth performance. To evaluate the effect of stocking size on the growth performance, the lobsters were segregated into four different treatment groups according to size and were stocked at a density of 300 animals per cage. To evaluate the effect of stocking density on the growth performance, lobsters of 81–100 g were stocked in four different stocking densities, i.e. 16/m², 24/m², 32/m² and 40/m². The results showed that the growth rate of (60–80 g) size group, was significantly higher compared to the size groups, i.e. 101–120 g and 121–140 g comprising of larger individuals. The final body weight, though significantly higher in 81–100 g as compared to 60–80 g, the growth performance (i.e. weight gain percentage (WG %) and specific growth rate (SGR)) were not significantly different. The density‐dependent influence on growth performance was evident in this study. The WG % and SGR during 90 days’ culture period was significantly higher in 24/m² compared to other groups. This study provides crucial information about the appropriate stocking density and stocking size of lobsters at the field level, which would help to promote sustainable lobster cage farming by maximizing the production potential of the system.     

Assessment of perceived farming risks,communication of risk management practices,and evaluation of their efficiency in Pacific white shrimp (Penaeus vannamei) farming—a survey-based cross-sectional study

Aquaculture International - Pacific white shrimp (Penaeus vannamei) farming is an important commercial aquaculture production system contributing substantially to the economic and societal...