Equine Culicoides hypersensitivity in Florida: biting midges collected in light traps near horses

Twenty-three species of Culicoides were trapped near pruritic horses during a 2-year survey in Florida. Nearly 99% of the biting midges collected were represented by Culicoides insignis Lutz, C. edeni Wirth and Blandon, C. stellifer (Coquillett), C. niger Root and Hoffman, C. haematopotus Malloch and C. venustus Hoffman. The relative contribution to the total catch by each of these species varied among collection sites. Seasonally, different species attain their largest population sizes at different times. Association of species collected in light traps with the seasonality of lesion development on the horses suggests that more than one species must be involved in causing Culicoides hypersensitivity in horses from Florida. Nulliparous females were present in most months that females of the same species were active; in some cases, species were trapped in each month of the year, particularly at the more southerly sites. The species of biting midge most likely to be involved in Culicoides hypersensitivity in horses in Florida are C. insignis, C. stellifer and C. venustus based upon their mammalophilic behaviour and seasonality.     

The effects of time of sowing and harvest on carrot biochemistry and the resistance of carrots to carrot fly

Two carrot cultivars which represented contrasting levels of resistance to carrot fly, Psila rosae, were grown in a replicated field experiment at Wellesbourne in 1984–85. Seed was sown on five occasions between April and August 1984 and the crop harvested after a minimum growth in the field of 16 wk on seven occasions between August 1984 and February 1985. A highly significant correlation (r = -0.78; P > 0.001) between the levels of carrot fly damage and the concentration of chlorogenic acid in the roots enabled a model to be formulated to predict the relative predisposition to carrot fly larval damage; high levels of chlorogenic acid early in the season predisposed roots to severe attack when they were older.     

Differences in the relative resistance of two carrot cultivars to carrot fly attack over five seasons

A comparison was made over five seasons of carrot fly (Psila rosae) damage on two carrot cultivars, Sytan and Danvers, which represented the extremes of resistance discovered in screening trials at Wellesbourne. Plants were harvested regularly during the seasons and at each harvest the number and weight of roots was recorded and carrot fly damage was assessed using various techniques; in 1979-80 the numbers of carrot fly larvae and pupae in and around root samples were counted. The experiments confirmed repeatedly the relative resistance of cv. Sytan compared with Danvers. The estimated reduction in carrot fly larvae on Sytan relative to Danvers in early November in four seasons ranged from 40% to 67%. When tested against first generation carrot fly attack the reduction in larvae on Sytan was 54%. There were 45% fewer mines per root on Sytan resulting in less damage at each harvest in all seasons. Larvae took longer to develop on Sytan than Danvers and 18% more plants of Sytan survived carrot fly attack. Differences in seedstock, season, sowing time, generation of carrot fly, plant size and density did not account for observed differences in damage between the two cultivars. The studies indicated satisfactory practical techniques for assessing carrot fly damage in cultivar screening trials.     

Evaluation of enteric methane prediction equations for dairy cows used in whole farm models

The importance of evaluating greenhouse gas (GHG) emissions from dairy cows within the whole farm setting is being realized as more important than evaluating these emissions in isolation. Current whole farm models aimed at evaluating GHG emissions make use of simple regression equations to predict enteric methane (CH₄) production. The objective of the current paper is to evaluate the performance of nine CH₄ prediction equations that are currently being used in whole farm GHG models. Data used to evaluate the prediction equations came from a collection of individual (IND) and treatment averaged (TRT) data. Equations were compared based on mean square prediction error (MSPE) and concordance correlation coefficient (CCC) analysis. In general, predictions were poor, with root MSPE (as a percentage of observed mean) values ranging from 20.2 to 52.5 for the IND database and from 24.0 to 38.2 for the TRT database and CCC values ranging from 0.009 to 0.493 for the IND database and from 0.000 to 0.271 for the TRT database. Overall, the equations of Moe & Tyrrell and IPCC Tier II performed best on the IND dataset, and the equations of Moe & Tyrrell and Kirchgeßner et al., performed best on the TRT dataset. Results show that the simple more generalized equations performed worse than those that attempted to represent important aspects of diet composition, but in general significant amounts of bias and deviation of the regression slope from unity existed for all equations. The low prediction accuracy of CH₄ equations in whole farm models may introduce substantial error into inventories of GHG emissions and lead to incorrect mitigation recommendations.     

The relationships among eucalypt forest,grassland and rainforest in a highland area in north-eastern Tasmania

Changes in the vegetation of a highland area of north-eastern Tasmania are described and related to a change 150 years ago from Aboriginal to settled land use. Expansion of rainforest dominated by Nothofagus into areas previously dominated by Eucalyptus, and of Eucalyptus forest on to grassland that occupied former rain - forest areas is accounted for by local differences in frequency and severity of fires since about 1835. Successional relationships amongst 12 vegetation types are defined, and discussed in relation to three models of vegetational succession.     

Environmental Control of Flowering in Barley (Hordeum vulgare L.). I. Photoperiod Limits to Long-day Responses, Photoperiod-insensitive Phases and Effects of Low-temperature and Short-day Vernalization

Barley plants were grown at a mean diurnal temperature of 15°C and reciprocally transferred between different photoperiods(from 16 h d^–1 to 8, 10 or 13 h d^–1 or vice versaat 4, 8, 16 or 32 d after germination). Ten contrasting genotypeswere examined, including seven spring-sown types-Mona, BGS T16-2,Athenais, Emir, Funza, USDA-016525 and S-37, and three autumn-sowntypes-Gerbel B, Arabi Abiad and Ager. In the latter two alltreatments were repeated on plants grown from seeds which hadbeen vernalized at 2 °C for 42 d. The results suggest that, between the critical photoperiod (belowwhich there is a delay in flowering) and the ceiling photoperiod(below which there is no further delay), there is a linear relationbetween photoperiod and the reciprocal of the time taken toflower (awn emergence). In all genotypes the ceiling photoperiodwas     

Structural Differentiation of the Nucellar Epidermis in the Caryopsis of Rice (Oryza sativa)

In the developing caryopsis of rice (Oryza sativa L.) the nucellarepidermis forms a uniseriate layer through which assimilatesare transported to the endosperm. An anatomical study demonstratedthat the nucellar epidermal cells are fusiform in shape andare hexagonally packed. The anticlinal walls of the nucellarepidermis are characterized by ribs of wall-thickening whichare orientated radially with respect to the caryopsis. The wall-thickeningsappear to be cellulosic primary walls, as indicated by theirstaining with Calcofluor and periodic acid-Schiff's reagent.It is proposed that the geometry of the nucellar cells and theribs of wall-thickening are structural adaptations to resistthe compressional force which is placed on the nucellar epidermisduring the latter stages of grain filling. Oryza sativa, rice, caryopsis, grain filling, nucellar epidermis, wall-thickening