Serological and electron microscopical investigations of the relationship betweenSorgum red stripe virus and sugar cane mosaic virus

Summary Sorghum red stripe virus (S.R.S.V.) from Italy and sugar cane mosaic virus (S.C.M.V.) from Puerto Rico were investigated at Wageningen serologically and with the electron microscope.By means of the microprecipitation test (van Slogteren, 1955) a qualitative relationship was established between the two viruses (Table 1). Electron microscopical investigations showed that with regard to their length there was no difference between the two viruses (Fig. 1 and 2).Samenvatting Sorghum red stripe virus (S.R.S.V.), afkomstig uit Italië, en suikerrietmozaïekvirus (S.C.M.V.) uit Portorico zijn te Wageningen serologisch en elektronenmicroscopisch onderzocht. Met behulp van de microprecipitatietoets (van Slogteren, 1955) kon een kwalitatieve verwantschap tussen de beide virussen aangetoond worden (tabel 1). Elektronenmicroscopisch onderzoek wees uit, dat er wat betreft de lengte der virusdeeltjes geen verschil bestaat tussen de twee genoemde virussen (fig. 1 en 2).     

The occurrence of inclusion bodies in leaf epidermis cells of sandal affected with spike disease

Round or slightly oval inclusion bodies were found in low numbers in epidermal cells of spiked (expressing spike disease symptoms) leaves. They could not be demonstrated in epidermal tissue of apparently healthy leaves. The intracellular inclusions stained with phloxine and rose bengal. Their relationship to sandal spike virus is discussed.     

Genotyping of Mycoplasma gallisepticum and M. synoviae by Amplified Fragment Length Polymorphism (AFLP) analysis and digitalized Random Amplified Polymorphic DNA (RAPD) analysis

Mycoplasma gallisepticum (MG) and M. synoviae (MS) are the cause of considerable economic losses in the poultry industry. Molecular differentiation of avian Mycoplasma strains may be helpful in tracing infections and in the evaluation of implemented intervention strategies. Amplified Fragment Length Polymorphism (AFLP) has shown to be a powerful typing technique but the application for poultry Mycoplasma strains is very limited. The aim of this study was to evaluate the reproducibility and discriminatory power of AFLP HindIII/HhaI and AFLP BglII/Mfel for the inter- and intraspecies differentiation of avian mycoplasmas and to compare these test characteristics with digitalized Random Amplified Polymorphic DNA (RAPD) analysis. The reproducibility of RAPD, AFLP HindIII/HhaI and AFLP BglII/Mfel was 50-100, 97-98 and 86-99%, respectively. RAPD and both AFLP enzyme combinations were able to differentiate between five avian Mycoplasma species. For AFLP, five MG and four MS clusters could be identified. The phylogenetic tree for both enzyme combinations was comparable. For RAPD, four MG clusters could be identified. For MS, however, due to the poor reproducibility of the RAPD technique, no clear genogroups could be identified. On basis of the results of this study it can be concluded that AFLP is a powerful technique for the genotyping of avian mycoplasmas and that, although AFLP HindIII/HhaI generated patterns with less fragments, the final results showed homologous results.     

Crosses between red clover (Trifolium pratense L.) Varieties to find a suitable combination for reciprocal recurrent selection

Summary As an introduction to a program of reciprocal recurrent selection in red clover crosses of varieties were tested. Five varieties were crossed with Leisi and five with Groninger red clover. Flowering showed that the crosses were successful. Varieties were tested under different conditions. A significant positive difference in dry matter yield between the cross and the better parent of the pair occurred in one of the ten crosses namely Red clover CB × Groninger red clover and under particular conditions. Only a poor comparison was possible in this case because Groninger red clover was attacked by eelworms.It was concluded that none of the tried crosses warranted a program of reciprocal recurrent selection.The data of flowering of the crosses with Leisi showed that in most cases there is intermediate inheritance of the number of flowering heads. In the cross Lembke × Leisi rich flowering was dominant to less rich flowering.     

Technical note: A proposed method to determine the extent of degradation of a feed in the rumen from the degradation profile obtained with the in vitro gas production technique using feces as the inoculum

A method is proposed to determine the extent of degradation in the rumen involving a two-stage mathematical modeling process. In the first stage, a statistical model shifts (or maps) the gas accumulation profile obtained using a fecal inoculum to a ruminal gas profile. Then, a kinetic model determines the extent of degradation in the rumen from the shifted profile. The kinetic model is presented as a generalized mathematical function, allowing any one of a number of alternative equation forms to be selected. This method might allow the gas production technique to become an approach for determining extent of degradation in the rumen, decreasing the need for surgically modified animals while still maintaining the link with the animal. Further research is needed before the proposed methodology can be used as a standard method across a range of feeds.     

Dietary nitrate supplementation reduces methane emission in beef cattle fed sugarcane-based diets

The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P < 0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P < 0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P < 0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH(3)-N()) concentration was significantly greater (P < 0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet.     

Drought and heat stress reduce yield and alter carbon rhizodeposition of different wheat genotypes

Drought and high temperature are major environmental stress factors threatening wheat production during grain filling stage resulting in substantial yield losses. Four wheat genotypes (Suntop, IAW2013, Scout and 249) were planted under two temperature levels (25 and 30°C) and two water levels (15% and 25% soil moisture content). Wheat yield, leaf δ¹³C, plant rhizodeposition, shoot biomass and root traits were examined. Low moisture (drought stress) and high temperature (heat stress) decreased the grain yield of all wheat genotypes, in particular 249, while combined drought and temperature stresses had the most pronounced negative effect on plant biomass and grain yield. Decreasing soil water availability decreased the allocation of plant‐derived C to soil organic carbon (SOC) and to microbial biomass through rhizodeposition. Leaf δ¹³C decreased with increased yield, suggesting that higher yielding genotypes were less water stressed and allocated less C to SOC and microbial biomass through rhizodeposition. Wheat genotypes with lower root/shoot ratios and thinner roots were more efficient at assimilating C to the grain, while genotypes with higher root/shoot ratios and thicker roots allocated more C belowground through rhizodeposition at the expense of producing higher yield. Therefore, improving these traits for enhanced C allocation to wheat grain under variable environmental conditions needs to be considered.