A comparison of soil food webs beneath C<Subscript>3</Subscript>- and C<Subscript>4</Subscript>-dominated grasslands

Soil food webs influence organic matter mineralization and plant nutrient availability, but the potential for plants to capitalize on these processes by altering soil food webs has received little attention. We compared soil food webs beneath C₃- and C₄-grass plantings by measuring bacterial and fungal biomass and protozoan and nematode abundance repeatedly over 2 years. We tested published expectations that C₃ detritus and root chemistry (low lignin/N) favor bacterial-based food webs and root-feeding nematodes, whereas C₄ detritus (high lignin/N) and greater production favor fungal decomposers and predatory nematodes. We also hypothesized that seasonal differences in plant growth between the two grassland types would generate season-specific differences in soil food webs. In contrast to our expectations, bacterial biomass and ciliate abundance were greater beneath C₄ grasses, and we found no differences in fungi, amoebae, flagellates, or nematodes. Soil food webs varied significantly among sample dates, but differences were unrelated to aboveground plant growth. Our findings, in combination with previous work, suggest that preexisting soil properties moderate the effect of plant inputs on soil food webs. We hypothesize that high levels of soil organic matter provide a stable environment and energy source for soil organisms and thus buffer soil food webs from short-term dynamics of plant communities.     

Enrobed Snack Product from Devis’s Anchovy (Stolephorus commersonnii) and its Quality Evaluation during Frozen Storage

Enrobing of fish improves physical as well as consumer acceptance of low value fish. The present work was undertaken to utilize a low value fish with its bones by enrobing with cereal flour based coating. Three combinations of batters were prepared, and the fish was coated and fried; based on the sensory quality, 1:2 batter to water ratio was selected for product preparation. To determine the storage life, frozen par-fried samples were prepared and stored at ?18°C. Quality parameters such as pH, total volatile basic nitrogen, free fatty acids, peroxide value, thiobarbituric acid reactive substances, color, and sensory attributes were evaluated on a monthly basis. It was observed from chemical parameters and sensory scores of the product that the par-fried form can be stored for up to 5 months. This technology will provide a better opportunity for employment of coastal women.     

A CONGENITAL MALFORMATION OF THE MAXILLA OF A HORSE

A 1-month-old male American Paint Horse was evaluated for a hard swelling on the right side of the maxillary region. On radiographs there was a large, expansile outpouching of the right maxillary bone between the second and third premolar teeth. Computed tomography further characterized the expansile lesion to have a soft tissue component and to originate in the region of a caudal maxillary tooth. Surgical reconstruction of the defect was unsuccessful and the animal was euthanetized. Based on failure to find histopathologic evidence of a neoplasm or cyst, the diagnosis was a congenital malformation.     

Decay development in living sapwood of coniferous and deciduous trees inoculated with six wood decay fungi

Development of decay and/or discoloration was assessed in the functional sapwood of one coniferous and three deciduous trees after wounding and artificial inoculation with six wood decay fungi. Living stems of mature Douglas fir, beech, oak, and sycamore trees were wounded in spring 2002 and immediately inoculated with brown, white, and soft rot fungi. Extent of discoloration and decay, wood weight loss, and total phenols in the reaction zone (zone of active response at a dynamic interface between living sapwood and wood colonized by decay fungi) were assessed 16 and 28 months after inoculation.     

Differential Selection on Rhynchosporium secalis During Parasitic and Saprophytic Phases in the Barley Scald Disease Cycle

ABSTRACT Competition among eight Rhynchosporium secalis isolates was assessed during parasitic and saprophytic phases of the disease cycle in field experiments conducted at two locations and over two growing seasons. The eight isolates were inoculated onto six barley populations exhibiting varying degrees of resistance. Microsatellite analysis of 2,866 isolates recovered from the field experiments showed significant, and sometimes opposite, changes in the frequencies of R. secalis genotypes during the growing season (parasitic phase) and between growing seasons (saprophytic phase). Isolates that showed the most complex virulence in greenhouse seedling assays had the lowest fitness in the field experiment. Significant differences in isolate fitness were found on different host populations and in different environments. Selection coefficients were large, indicating that evolution can occur rapidly in field populations. Although inoculated isolates had the lowest overall fitness on the moderately resistant landrace cv. Arabi Aswad, some isolates were more virulent and consistently increased in frequency on this landrace, suggesting a risk of directional selection and possible erosion of the resistance following its widespread deployment in monoculture. These results provide the first direct evidence that R. secalis pathogen genotypes differ in their saprophytic ability and parasitic fitness under field conditions.     

Validation of a feeding strategy to deliver bacterially expressed dsRNA to marine amoeba from the genus Neoparamoeba

RNA interference (RNAi) mediated by double stranded RNA (dsRNA) has emerged as one of the most promising techniques to study gene function of non‐model protozoan parasites. We have previously demonstrated that bacterially expressed dsRNA delivered by immersion elicited successful knockdown in Neoparamoeba pemaquidensis, the non‐infective species closely related to the causative agent of salmonid amoebic gill disease (AGD). However, considering that amoebae naturally feeds on microorganisms, direct ingestion of bacteria designed to express dsRNA could allow rapid and low‐cost analysis of gene function on a large‐scale. Therefore, the main objective of this study was to investigate whether ingestion of bacteria‐expressing dsRNAs would also induce suppression of N. pemaquidensis β‐actin and EF1α. Despite effective bacterial uptake, no significant variation in EF1α relative copy number was triggered by dsRNA ingestion. β‐actin, on the other hand, presented similar silencing efficiency to what was observed in our previous soaking study. However, the observed RNAi response was delayed by at least 72 h. The present work provides evidence that delivery of bacterially expressed dsRNA through feeding can be successfully achieved in N. pemaquidensis, albeit not as efficiently as by soaking. Therefore, further investigation is required to develop more efficient and specific RNAi delivery systems in Neoparamoeba species. To our knowledge, this is the first time that RNAi‐mediated knockdown through ingestion was attempted to manipulate gene function of a marine amoeba.     

Assessment of commercial and recreational fishing effects on trophic interactions in the Cap Roux area (north‐western Mediterranean)

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Molecular characterization of MHC class II region in guinea fowl

1. The MHC class II gene was amplified, cloned and sequenced in guinea fowl. 2. The NumeMHC II sequence of 754 nucleotides included complete exon 1 (91 nt), exon 2 (270 nt), exon 3 (282 nt) and exon 4 (110 nt). 3. The size of β(1) and β(2), domains were 89 and 93 amino acids, respectively in guinea fowl. 4. High amino acid variability (38·2%) was observed within guinea fowl in β(1) domain, while in β(2) domain, amino acid variability (6·3%) was low. 5. Among poultry species, the percent amino acid identity between guinea fowl and chicken, quail, pheasant and duck was 38·8, 42·2, 44·4 and 58·8 in β(1) domain; and 13·8, 17·0, 13·8 and 27·6 in β(2) domain, respectively. 6. Sequence alignment with mammalian and avian MHC showed that many of the conserved features of MHC class II glycoprotein was conserved in guinea fowl. 7. Within-species genetic distances (Poisson correction) based on cumulative amino acid variability in β(1) domain and β(2) domains was 0·141 in guinea fowl. 8. Guinea fowl showed low and similar genetic distances with all the poultry species (0·255-0·268) except duck (0·456). 9. Guinea fowl made separate branch within the major cluster having chicken, quail and pheasant, showing equal distance from these poultry species, whereas duck MHC II clustered separately.