Response of Russet Burbank and Shepody potatoes to nitrogen fertilizer in two cropping systems

Russet Burbank and Shepody potatoes were grown with at-planting N fertilizer rates ranging from 0 to 270 kg ha^?1 during 1986 through 1989. Experiments were conducted each year following small grains and red clover. Total yields and tuber size were strongly increased by N on most sites where potatoes followed small grains. Specific gravities declined with increasing N rate. Total yields of Russet Burbank and Shepody were optimized at an average of 196 and 211 kg ha^?1 of N, respectively, following small grains. The effect of N fertilizer on yields was much less dramatic following red clover. Total yields averaged 88% of maximum with only 45 kg ha^?1 of N applied, compared to 77% of maximum for this N rate following small grains. Total yields for the two varieties were optimized at 126 and 136 kg ha^?1, respectively. U.S. #1 yields were generally not increased at N rates above 45 to 90 kg ha^?1 following red clover and tuber size was not increased at rates above 90 to 135 kg ha^?1. Based on these studies, the N fertilizer credit for red clover grown prior to potatoes can be up to 75 kg ha^?1. Maintenance of tuber quality necessitates conservative use of N fertilizer when potatoes are grown following legumes. The highest N rates tested suppressed total yields of Russet Burbank, a late-season, indeterminate variety, by approximately 9% averaged over cropping systems.     

A note on the melting point of α-solanine

A discussion of the problems involved in the determination of the melting point of α-solanine is combined with an estimation of the reliability of this physical property for establishing the purity of a preparation.     

Reconciling alternative models of phenological development in winter wheat

Simulation of the timing of anthesis in wheat crops is achieved using two very different approaches. The older of these simulates progress to flowering by calculating the duration of phases between significant events on the shoot apex. The alternative method tracks development through leaf appearance, using the prediction of final mainstem leaf number to control the duration of the phase from emergence to flowering. Although these methods appear to differ substantially, we show in this paper that the number of leaves on the mainstem when the stage of terminal spikelet occurs is extremely tightly coupled to final mainstem leaf number. We conclude that accurate prediction of the terminal spikelet stage or similar prediction of mainstem leaf number amount to the same thing, so reconciling the methods.     

Chemical composition of potatoes. VIII. Effect of variety,location, and year of growth on the content of nitrogen compounds

Free amino acid content, total nitrogen, extractable nitrogen, ratio of extractable to total nitrogen, solids content, and specific gravity in Cobbler, Katahdin, Kennebec, Red Pontiac, and Russet Burbank potatoes was studied. Each variety was grown in six different locations (Idaho, Maine, Pennsylvania, Wisconsin, Long Island, and the Red River Valley) during the years 1961 through 1963. The mean values for each factor, with significant differences indicated, are listed along with the high and low range, the coefficient of variation and the overall mean. The percent of total variance contributed by each of the variables and their interactions also are listed. Long Island potatoes had the highest nitrogen and amino acid content. Varietal differences were less significant. Proline was the most variable of the constituents measured. Aspartic and glutamic acids had the highest variability with respect to years grown. The effect of each variable varies from one constituent to another.     

Factors that impact on the ability of biofumigants to suppress fungal pathogens and weeds of strawberry

This research aimed at identifying factors that improve the efficacy of biofumigants for soil disinfestation against strawberry (Fragaria×ananassa) pathogens and weeds. In laboratory bioassays, volatiles released from the macerated roots of a Brassica rapa/Brassica napus biofumigant crop were six times more effective at suppressing the growth of the strawberry pathogen Rhizoctonia fragariae than shoots. Furthermore, the toxicity of the volatiles from the biofumigant crop to R. fragariae increased as plant developmental stage progressed. These results related to the release of higher quantities and greater diversity of isothiocyanates (ITCs) from the roots of mature biofumigant plants than from their shoots. Separate bioassays showed that volatiles from the biofumigant crop suppressed the growth of six different soil-borne pathogens (Alternaria alternata, Colletotrichum dematium, Cylindrocarpon destructans, Fusarium oxysporum, Pythium ultimum, Phytophthora cactorum, and R. fragariae) of strawberry and seven Trifolium spp. (clover) weeds. The suppression of Trifolium spp. by biofumigant volatiles did not relate to their seed size, but might relate to their hard-seededness or genotype. In the field, rotary incorporation of the biofumigant crop did not produce detectable levels of ITCs in soil; reduce the survival of the strawberry pathogens, P. cactorum and C. destructans; or affect populations of culturable soil microflora. Yet, it suppressed the growth of emerging weeds by 40% and the growth of P. cactorum by 20%. We hypothesise that allelochemicals other than ITCs, such as nitriles, or other biological mechanisms might also play a role in biofumigation. A key to improving the efficacy of biofumigation in the field seems to lie in the development of application technologies that can macerate and incorporate biofumigants evenly in soils, in addition to incorporating biofumigants under optimal edaphic conditions for release of ITCs.     

Environmental influences on melatonin secretion in Atlantic cod (Gadus morhua L.) and their relevance to commercial culture

This study investigated the effects of photoperiod and temperature on plasma melatonin secretion in Atlantic cod (Gadus morhua L.). Initial work confirmed the presence of a diel profile of melatonin synthesis, with elevated levels during the dark phase. Unusually for fish, the peak in plasma melatonin occurred towards the end of the dark phase, which is indicative of a type `A' melatonin profile. When exposed to 60 hours of continuous darkness a clear endogenous rhythm of melatonin synthesis was observed, which continued for 4 cycles with a periodicity which, approximated to 24 h. When acclimated to varying temperatures (4, 8, 12 or 16 °C) no variation in melatonin production was seen, however, body size appeared to be an important influence, with the smallest fish exhibiting significantly higher levels of dark phase melatonin. Finally, the application of additional night-time illumination to cod maintained in sea cages i.e. without blackout, did not significantly reduce dark phase plasma melatonin, suggesting that cod are less sensitive to photoperiod manipulation in cages than salmonids.     

Radiometric pooled faecal culture for the detection of Mycobacterium avium subsp paratuberculosis in low-shedder cattle

OBJECTIVE: To identify the optimum pooling rate for pooled faecal culture (PFC) as a diagnostic tool in bovine Johne's disease control, for detection of cattle shedding low concentrations of Mycobacterium avium subsp paratuberculosis (Map). METHOD: Thirteen target animals were selected by delayed growth of Map from initial individual radiometric faecal cultures (first growth index at 5 weeks or later). A procedure based on radiometric culture and IS900 polymerase chain reaction and restriction endonuclease analysis confirmation was then used for PFC. RESULTS: Eight samples (stored for up to 17 months at -80 degrees C) yielded Map on subsequent culture, either from undiluted faeces or those mixed with normal cattle faeces at dilution rates from 1 in 5 to 1 in 50. From a regression equation, culture-positive animals were considered to be shedding relatively low levels of Map (< 6 x 10(4)/g of faeces). Pooling dilutions of more than 1 in 5 reduced PFC sensitivity. A minimum incubation period of 10 weeks at a dilution of 1 in 5 is recommended to detect such infected cattle. This pooling rate in radiometric culture is probably capable of detecting cattle shedding < or = 5 x 10(3) Map organisms/g of faeces, representing an estimated inoculum per culture vial of fewer than 20 viable organisms. CONCLUSION: Map was detected in more than 50% of the stored faecal samples from cattle shedding low concentrations of the organism. A pooling rate of 5 samples per pool is required to reliably detect infected low-shedder cattle using PFC based on radiometric culture.     

Epidemiology of necrotizing meningoencephalitis in Pug dogs

BACKGROUND: Although the histopathologic features of necrotizing meningoencephalitis (NME) have been described previously, little information is available concerning the signalment, geographic distribution, seasonal onset, treatment, and survival of affected dogs. ANIMALS: Sixty Pugs with NME and 14 contemporaneous control Pugs with other intracranial diseases (non-NME group). METHODS: Pugs that were euthanized or died because of intracranial disease were prospectively obtained. All dogs had necropsy, histopathology, and testing for various infectious diseases and were subsequently divided into NME and non-NME groups. Signalment, geographic distribution, seasonal onset, treatment, and survival were compared between groups. RESULTS: In Pugs with NME, median age at onset of clinical signs was 18 months (range, 4-113 months). A greater proportion of female dogs were present in the NME group (40/60) compared with the control group (6/14). Pugs with NME had a significantly lower mean weight (7.81 kg) than control Pugs (9.79 kg) (P= .012). Mean survival in Pugs with NME was 93 days (range, 1-680 days), with dogs receiving any form of treatment living significantly longer than those that were not treated (P= .003). Anticonvulsive drugs were the only treatment significantly associated with longer survival (P= .003). CONCLUSIONS AND CLINICAL IMPORTANCE: NME appears to be a common cause of intracranial signs in Pugs, based on the high proportion of NME dogs reported in this population. Pugs with NME are most commonly young adult female dogs. Although further investigation is needed to determine the optimal treatment of NME, anticonvulsive drugs appear to beneficially affect duration of survival.     

Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein

We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.