Elongation and insolubilisation of α-glucans by the action of Neisseria polysaccharea amylosucrase

Amylosucrase (E.C. 2.4.1.4) from Neisseria polysaccharea catalyses a transglycosylation reaction using sucrose as a glucose donor to synthesise an insoluble (1→4)-α-glucan, releasing fructose in the solution. If glycogen is used as a glucosyl unit acceptor, amylosucrase elongates polymer branches from their non-reducing ends. Testing of a large series of acceptors with various molar masses, glycosidic linkages, branching degrees and solubilities showed that chain elongation occurred only on polymers with (1→4)-α- or (1→4)-α- and (1→6)-α- linkages. Synthesis yields were better for completely soluble polymers (1.45 glucosyl units grafted per glucosyl unit for polymers with (1→4)-α- and (1→6)-α- linkages), than for partially soluble polymers (0.27–0.97 glucosyl units grafted per glucosyl unit for polymers with either (1→4)-α- linkages or (1→4)-α- and (1→6)-α- linkages). Elongation occurred randomly at the non-reducing ends of some external chains. Elongation of soluble branched molecules led to rapid gel formation favourable to gelation control inside suspensions and solutions. These polymers showed resistant starch contents (22% (w/w) to 57%) after elongation with amylosucrase.     

Influence of Energy and Protein Supplementation on Growth Rate,Empty Body Composition and Ruminal and Blood Metabolites of Goat Kids Fed Hay Diets

A comparative slaughter experiment was conducted with 28 Spanish kids (BW = 20.6 kg) fed a hay-based diet to determine the effects of supplemental energy and protein on growth rate, body composition, and ruminal and blood metabolites. After 84 d, kids were harvested, digesta contents removed and empty body weighed and ground. Samples were freeze-dried and analyzed for DM, CP, ether extract, ash, and gross energy. All kids had increased BW gains. However, unsupplemented kids lost empty BW and weight of all body components except ash. Kids supplemented with energy or protein increased (P<0.05) empty BW, body water, protein, fat, ash, and gross energy when compared with unsupplemented kids. The percentages of body water and ash decreased (P<0.05) when supplemental energy or protein was fed. The percentage of body protein was reduced (P<0.05) by supplemental energy and unaffected (P=0.81) by supplemental protein. Supplemental energy reduced (P<0.05) ruminal acetate and increased (P<0.05) propionate and butyrate. Supplemental protein increased (P<0.05) concentrations of ruminal ammonia N, plasma urea N, and all ruminal volatile fatty acids. Regression equations suggest that intake of 144 kcal of ME and 6.0 g of CP per kilogram of empty BW^0.75 are necessary to maintain empty BW.     

Bioaccumulation of ivermectin from natural and artificial sediments in the benthic organism <Emphasis Type="Italic">Lumbriculus variegatus</Emphasis>

Purpose  

Although ivermectin is a widely used lipophilic parasiticide, data on its potential bioaccumulation in aquatic invertebrates are scarce. In this study, bioaccumulation patterns of radiolabeled ³H-ivermectin from sediments into tissues of the sediment-dwelling worm Lumbriculus variegatus were investigated and assessed.     

Ralstonia solanacearum virulence in tomato seedlings inoculated by leaf clipping

Ralstonia solanacearum is a phytopathogenic bacterium that colonizes the xylem vessels of host plants leading to a lethal wilt disease. Although several studies have investigated the virulence of R. solanacearum on adult host plants, infection studies of this pathogen on the seedling stages of hosts are less common. In a preliminary observation, inoculation of R. solanacearum F1C1 on 6‐ to 7‐day‐old tomato seedlings by a simple leaf‐clip strategy resulted in a lethal pathogenic condition in seedlings that eventually killed these seedlings within a week post‐inoculation. This prompted testing of the effect of this inoculation technique in seedlings from different cultivars of tomato and similar results were obtained. Colonization and spread of the bacteria throughout the infected seedlings was demonstrated using gus‐tagged R. solanacearum F1C1. The same method of inoculating tomato seedlings was used with R. solanacearum GMI1000 and independent mutants of R. solanacearum GMI1000, deficient in the virulence genes hrpB, hrpG, phcA and gspD. Wildtype R. solanacearum GMI1000 was found to be virulent on tomato seedlings, whereas the mutants were found to be non‐virulent. This leaf‐clip technique, for inoculation of tomato seedlings, has the potential to be a valuable approach, saving time, space, labour and costs.     

Leaf epidermis characters of Iranian <Emphasis Type="Italic">Pyrus</Emphasis> L. (Rosaceae) and their taxonomic implications

Pyrus L. is a taxonomically difficult genus mainly because of interspecific and intergeneric hybridization. A majority of the wild species of Pyrus occurs in Iran, making this region very important for any study of the systematics of the genus. In this investigation, seven quantitative and seven qualitative characters of leaf epidermis, particularly epidermal cells shape, anticlinal walls patterns, type and size of stomata, and cuticular ornamentation of 22 taxa of Pyrus plus Malus orientalis are studied for assessment of their taxonomical value at different levels. Scanning electron microscopy and light microscopy were used for evaluation of epidermis features of these taxa. Some characters such as shape and anticlinal wall pattern of epidermal cells, presence of adaxial stomata, pattern of cuticular ornamentation and epicuticular wax types are useful in separation of some Pyrus taxa. Moreover, Malus orientalis is recognized easily from all Pyrus species via the density of stomata. According to ANOVA analysis, all quantitative variables show high level of between-group differentiation. Also, based on the hierarchical clustering results gained by multiple correspondence analysis and factor analysis of mixed data analyses of the current study, micromorphological characters of epidermal cells reflect the ecological conditions of pear taxa, so most of the mesophyte and xerophyte taxa can be separated from each other in accordance with epidermal cells characters, specially the anticlinal wall pattern. Totally, the application of some other biological markers, particularly suitable molecular data are needed to present well-resolved relationships among these taxa.     

Chronic toxicity of fenoxycarb to the midge Chironomus riparius after exposure in sediments of different composition

Background, aim, and scope  

Fenoxycarb is an insect growth regulator widely used to control a variety of pests. As a juvenile hormone analogue, it interacts with the natural hormones involved in insect development, inhibiting metamorphosis to the adult stage. Adverse effects of fenoxycarb on non-target organisms have been repeatedly observed and its rapid dissipation from water to the organic fraction of the sediment is known. The aim of this work was to investigate the impact of fenoxycarb on the development of sediment-dwelling larvae of the midge Chironomus riparius after exposure to spiked sediment.     

A review on crop losses, epidemiology and disease management of rice brown spot to identify research priorities and knowledge gaps

Rice brown spot (BS) is a chronic disease that affects millions of hectares of rice every growing season, grown by some of the most resource-poor farmers. Despite its widespread occurrence and impact, much still needs to be understood about BS. Reported yield losses in relative terms vary widely from 4 to 52 %. However, accurate, systematic estimates are lacking. BS is conventionally perceived as a secondary problem that reflects rice crops that experience physiological stresses, e.g. drought and poor soil fertility, rather than a true infectious disease. Much remains to be understood about the mechanisms leading to epidemics and crop losses. Quantitative and qualitative knowledge gaps exist in our understanding of the epidemiological processes, sources of resistance and biocontrol methods. In this review we identify several of these gaps, which if filled, could lead to a strong impact on the management of brown spot. We also use the architecture of a simulation model to position and prioritize these knowledge gaps, assess the epidemiological consequences of disease management options on BS monocyclic processes and explore the impact changing production situations on this important disease.     

Effects of field and landscape variables on crop colonization and biological control of the cabbage root fly Delia radicum

Agriculture intensification has deeply modified agroecosystems from field to landscape scales. To achieve successful pest control using natural enemies, understanding species interactions over all scales remains a challenge. Using the cabbage root fly as a model, we studied whether field and landscape characteristics influenced colonization and infestation of broccoli fields by the pest and its control by natural enemies. We also determined whether species of different trophic level or host specialization would respond to environmental characteristics at the same spatial extent. During a multiple-species and multiple-spatial extent study in northwestern France, we recorded pest colonization and infestation in 68 fields, collected associated natural enemies and assessed crop damages. In each field, we considered management practices and characterized the surrounding landscape in 50–500 m-wide buffers. Our main findings are that Delia radicum and its main natural enemies respond to both field and landscape characteristics. Semi-natural areas supported both crop colonization by pests and natural enemy action. The pest and its enemies differed in their responses to field or landscape variables. Landscape elements such as field banks favored the movement of the pest while impeding the movement of some natural enemies. Pest pressure did not increase with the neighboring density of Brassica crops. The presence of natural enemies did not reduce crop damage but reduced pest emerging rates. Finally, specialist parasitoids responded to the landscape at larger spatial extents than generalists. These results outline the complexity of improving pest control through landscape management.