The metabolism of R-20458 [(E)-6,7-epoxy-1-(4-ethylphenoxy)-3,7-dimethyl-2-octene] in rat hepatocyte suspensions

The metabolism of R-20458 [(E)-6,7-epoxy-1-(4-ethylphenoxy)-3,7-dimethyl-2-octene] by rat hepatocytes has been analyzed and compared with that of juvenile hormone I [methyl-(E,E)-cis-10,11-epoxy-7-ethyl-3,11-dimethyl-2,6-tridecadienoate] under identical conditions. The metabolism of R-20458 is characterized by the predominance of NADPH-dependent cytochrome P-450 and epoxide hydrolase reactions; whereas, JH I is metabolized mainly by carboxylesterase, epoxide hydrolase, and glutathione S-transferases. The metabolites of R-20458 have been shown to correspond to (E)-6,7-epoxy-1-(4-hydroxyethylphenoxy)-3,7-dimethyl-2-octene; (E)-6,7-epoxy-1-(4-acetylphenoxy)-3,7-dimethyl-2-octene; (E)-6,7-dihydroxy-1-(4-ethylphenoxy)-3,7-dimethyl-2-octene; and, (E)-6,7-dihydroxy-1-(4-acetylphenoxy)-3,7-dimethyl-2-octene. The production of the α-hydroxyethyl, p-acetylphenoxy, and acetylphenoxy-6,7-diol metabolites is markedly inhibited by SKF 525-A. No dramatic effects are produced by diethylmaleate and 1,2-epoxy-3,3,3-trichloropropane.     

Toxigenic Fusarium species and Mycotoxins Associated with Head Blight in Small-Grain Cereals in Europe

The Fusarium species predominantly found associated with Fusarium head blight (FHB) in wheat and other small-grain cereals all over Europe are F. graminearum, F. avenaceum and F. culmorum. Among the less frequently encountered species are several others which are less pathogenic or opportunistic, but also toxigenic. These include F. poae, F. cerealis F. equiseti F. sporotrichioides F. tricinctum and, to a lesser extent, F. acuminatum F. subglutinans F. solani F. oxysporum F. verticillioides F. semitectum and F. proliferatum. The species profile of FHB is due to several factors, primarily climatic conditions, particularly rain and the temperature at flowering stage, but also agronomic factors, such as soil cultivation, nitrogen fertilization, fungicides, crop rotation, and host genotype. The most frequently encountered Fusarium mycotoxins in FHB in Europe has proved to be deoxynivalenol and zearalenone produced by F. graminearum and F. culmorum with the former more common in southern (warmer) and the latter in northern (colder) European areas. Nivalenol was usually found associated with deoxynivalenol and its derivatives (mono-acetyldeoxynivalenols), together with fusarenone-X, formed by F. graminearum F. cerealis F. culmorum and, in northern areas, by F. poae. Moreover, from central to northern European countries, moniliformin has been consistently reported, as a consequence of the widespread distribution of F. avenaceum whereas the occurrence of T-2 toxin derivatives, such as T-2 toxin and HT-2 toxin, and diacetoxyscirpenol have been recorded in conjunction with sporadic epidemics of F. sporotrichioides and F. poae. Finally, beauvericin and various enniatins have recently been found in Finnish wheat colonized by F.avenaceum and F. poae.     

Effects of protein-energetic supplementation frequency on growth performance and nutritional characteristics of grazing beef cattle

Two experiments were conducted to evaluate reduced supplementation frequencies for grazing beef cattle in rainy season. In experiment 1, evaluating the nutritional parameters, four rumen-cannulated Nellore bulls (BW = 410 kg) were used. In experiment 2, evaluating animal performance, 48 Nellore bulls (BW = 358 kg) were used. The treatments were as follows: mineral supplement (MS) alone and MS plus protein-energy supplement provided 3×, 5× and 7×/week. Supplementation frequency did not affect (P > 0.05) intake and digestibility. Average daily gain was greater (P < 0.001) to supplementation compared with MS. The supplementation 5×/week resulted in greater weight gain per hectare (9.24) and higher economic returns during the study period (1.64%) compared to other supplementations. Supplementation 5×/week increased animal performance and positively influenced economic returns.     

Heritability of the resistance to pepper huasteco yellow vein virus in wild genotypes of <Emphasis Type="Italic">Capsicum annuum</Emphasis>

Pepper huasteco yellow vein virus (PHYVV) is the main virus of pepper crop in Mexico. No resistant cultivars are available and resistance breeding is hampered by the lack of knowledge of heritability (h ²) of PHYVV resistance. This is a continuation of previous studies and the objectives were to analyze the h ² and the behavior of the resistant trait to PHYVV. Four resistant assays were done with three resistant wild lines (UAS12, UAS13 and UAS10) of Capsicum annuum in the S4, S5, S6 and S7 generation under greenhouse conditions. Plants from all tests were inoculated with PHYVV through Bemisia tabaci. Line UAS12 was the most resistant showing a significantly proportion of resistant plants, less disease symptoms and longer incubation time, followed by the lines UAS13 and UAS10 in all assays. Distribution of symptoms showed a bimodal tendency in all the trials, suggesting that two groups of genes are involved in this resistance trait. The lines UAS12, UAS13 and UAS10 showed the same pattern of response to selection with an average of h ² of 0.17, 0.06, 0.02 and 0.00 in the S4, S5, S6 and S7, respectively. These results indicate that all lines responded positively to the selection in the S4, S5 and S6, whereas in the S7 there was no response by the possible exhaustion of variation. Line UAS12 is the most promising genotype and the lines UAS13 and UAS10 are genetic resources that can be supplemented to breed the resistance of PHYVV. These results provides basic information for resistance breeding.     

Pedotransfer functions to assess adsorbed phosphate using iron oxide content and magnetic susceptibility in an Oxisol

Adsorbed phosphate in soils can be chemically extracted; however, this process is both time‐consuming and not cost‐effective if large numbers of samples have to be analysed. Indirect assessment of adsorbed phosphate by pedotransfer functions (PTFs) can help optimize fertilizer strategies. This study aimed to evaluate the spatial variability of adsorbed phosphate (P_ads), iron oxides and magnetic susceptibility (MS) in oxisols and to calibrate PTFs to predict P_ads. A total of 308 soil samples were collected from Hapludox and Eutrudox soils formed from sandstone in Brazil. The contents of clay (196–607 g/kg), iron oxides (40–165 g/kg), MS (1.2–29 × 10^?6 m³/kg) and P_ads (327–842 mg/kg) were in the range of typical values for these highly weathered soils. This study showed that the attributes studied were spatially dependent. Geomorphic surfaces enabled understanding of spatial variability and helped to develop a more efficient sampling scheme to calibrate PTFs. Moreover, the adsorbed phosphate in these oxisols could be predicted by a PTF using iron oxides and MS as predictors. The MS attribute enabled the most accurate prediction (concordance coefficient = 0.95, root‐mean‐square error = 46 mg/kg and relative improvement in root‐mean‐square error = ?4.12) of spatial variability through PTF compared to other predictors.     

Shading effects on canopy and tillering characteristics of continuously stocked palisadegrass in a silvopastoral system in the Amazon biome

In silvopastoral (SP) systems, forage responses depend on the microenvironment in which the plants develop. Our objective was to evaluate canopy and tillering characteristics of shaded 'Marandu' palisadegrass [Brachiaria brizantha (Hochst A Rich) Stapf, syn. Urochloa brizantha] under continuous stocking in a SP system. Treatments were one full sun (FS) and three shaded systems (silvopasture, SP) corresponding to distances from tree groves: 7.5 m north (SP1), and 15 m (SP2) and 7.5 m south (SP3) studied during two rainy seasons (Year 1 and Year 2). The tree in the SP system was Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla S. T. Blake). The photosynthetic active radiation was greater in FS (923 μmol m^-2 s^-1), followed by SP2 (811 μmol m^-2 s^-1), SP1 (727 μmol m^-2 s^-1) and SP3 (673 μmol m^-2 s^-1). Forage accumulation in FS was 15% greater than the mean of SP1, SP2 and SP3 (10,663 kg DM/ha). There was no difference in net accumulation of leaf, stem and dead material, averaging 3,302, 3,420 and 4,063 kg DM/ha respectively. Leaf accumulation and accumulation rate were greater in Year 2, and leaf accumulation rate was similar among treatments (19 kg DM ha⁻¹ day⁻¹). Leaf proportion increased 14% from Year 1 to Year 2. Specific leaf area was greater for treatments SP1 and SP3 (193 cm²/g). Tiller population density was similar across treatments in Year 1. Shaded palisadegrass maintains leaf productivity similar to FS under continuous stocking in an SP system.