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61.
Frost resistance of interspecific and varietal potato crosses was evaluated at Bogotá, Colombia using intact plants in a programmed low temperature growth cabinet. Plants were exposed to a 2 hour frost during the dark period and the minimum test temperature was successively lowered 1 C on subsequent nights. The foliage was visually scored for damage 10–12 hours after each frost. While most commercial varieties were killed at—2 to—3 C (28 to 26 F), 101 of 121 clones which have been bred specifically for frost resistance survived to at least—5 C (23 F) and some crosses resisted—9 C (16 F) without observable foliar damage. This suggests the possibility of obtaining cultivated varieties from varietal parents of cultivated species such as G. Andigena, G. Phureja, G. Stenotomum,S. ajanhuiri, and others, which are reasonably frost resistant. 相似文献
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Volume Contents
Contents Volume 126 2002 相似文献63.
Douglas Tave R. Oneal Smitherman V. Jayaprakas Daryl L. Kuhlers 《Journal of the World Aquaculture Society》1990,21(4):263-270
Lengths and weights of Auburn University-Egypt and Auburn University-Ivory Coast strains of Tilapia nilotica and their F1 F2 , and backcross hybrids were analyzed by multiple regression to estimate strain additive genetic effects, strain maternal genetic effects, individual heterosis (specific combining ability), maternal heterosis, and strain egg cytoplasmic effects for growth to determine why heterosis of the F2 and backcross hybrids was greater than that of the FI hybrids. Individual heterosis and maternal heterosis made the greatest contributions to growth. The F2 and backcross hybrids were larger than the F1 hybrids because of maternal heterosis. Regression coefficients were used to predict growth for any possible hybrid combination. Egypt ♀× Ivory Coast ♂ FI hybrid females backcrossed to Egypt males and Egypt ♀× Ivory Coast ♂ F2 hybrids were the largest groups evaluated in this study and were also predicted to have faster growth rates than any other possible Egypt-Ivory Coast hybrid. 相似文献
64.
Kefyalew Girma Kyle W. Freeman Roger Teal Daryl B. Arnall Brenda Tubana Starr Holtz 《Archives of Agronomy and Soil Science》2013,59(4):435-442
Abstract Field average based recommendations have been a common practice for recommending the major crop nutrients nitrogen (N) and phosphorus (P). The problem is yield will not be the same from year to year with application of the same amount of recommended rate of fertilizer. The objectives of this study were to demonstrate how recommendations generated using nutrient response experiments were dynamic; and to assess the relative contribution of temporal variability, N and P fertilizers on winter wheat grain yield and N concentration. Twelve factorial combinations of four N (0, 56, 112, and 168 kg ha?1) and three P (0, 14.5, and 29 kg P ha?1) rates were evaluated in a randomized complete block design with three replications at Perkins, Oklahoma. To address the first objective, ANOVA and orthogonal polynomial contrasts were used. To address the second objective, a ten predictor variable multiple linear regression model with two quantitative variables and their interaction (N, P and N×P) and seven-year variables was evaluated and a reduced model containing seven variables was generated. Wheat grain yield showed three distinct responses to N rates: Linear, quadratic and no response. These individual year data show that it is not always appropriate to use results of nutrient response experiments to estimate next year's N fertilizer requirement due to apparent temporal variability in the results. Wheat only responded to P during the first two years of the study. The reduced model from the regression analysis revealed that most of the variability in grain yield was accounted for by five individual indicator years and N only. High variability across years in grain yield and fertilizer (N and P) response, even between years of similar grain yield, is an indication of a given season's production dependence on factors other than N and P. 相似文献
65.
Adriana Ressurreição James Gibbons Michel Kaiser Tomaz Ponce Dentinho Tomasz Zarzycki Charlotte Bentley Melanie Austen Daryl Burdon Jonathan Atkins Ricardo S. Santos Gareth Edwards-Jones 《Biological conservation》2012,145(1):148-159
Understanding the cultural variation in public preference for marine species is a necessary pre-requisite if conservation objectives are to include societal preferences in addition to scientific considerations. We report the results of a contingent study undertaken at three case-study sites: Azores islands (Portugal), Gulf of Gdansk (Poland) and Isles of Scilly (UK). The study considered species richness of five specific marine taxa (mammals, birds, fish, invertebrates and algae) as proxies of marine biodiversity and the aim of analysis was to estimate from a multi-site perspective public’s willingness to pay (WTP) to avoid increased levels of species loss (reduction of species richness) for different marine taxa. Results, based on 1502 face-to-face interviews, showed that income, education and environmental awareness of the respondents were significant predictors of WTP for marine species conservation. Results also indicated that respondents in each of the European locations had different preferences for marine taxa. In the Azores, although mammals and fish were valued highly, small differences occurred in the WTP among different taxa. Respondents in the Isles of Scilly put a relatively low value on fish while algae and marine mammals were highly valued. In Gdansk, respondents defined a clear order of preference for marine mammals > fish > birds > invertebrates and algae. These findings suggested that cultural differences may be important drivers of valuation and undermines the commonly held premise that charismatic/likeable taxa consistently have a disproportionately strong influence on WTP for biodiversity conservation. We conclude that conservation policy must take account of cultural diversity alongside biological diversity. 相似文献
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Nydam DV Lindergard G Santucci F Schaaf SL Wade SE Mohammed HO 《American journal of veterinary research》2005,66(3):413-417
OBJECTIVE: To determine the risk posed by Cryptosporidium parvum and Cryptosporidium hominis from dairy cattle in the New York City watershed (NYCW). SAMPLE POPULATION: Samples from cattle at risk for shedding Cryptosporidium organisms on randomly selected dairy farms in the NYCW. PROCEDURE: Feces were collected for 4 years from calves at risk for infection on 37 dairies. Oocysts were detected by use of centrifugation concentration-flotation microscopy. The DNA was directly isolated from fecal samples and used to amplify fragments of the small subunit ribosomal RNA and thrombospondin-related adhesion protein C-2 genes by use of nested polymerase chain reaction assays. Small subunit ribosomal RNA fragments were restriction digested by the enzyme Vspl and thrombospondin-related adhesion protein C-2 fragments were digested by Eco91l to distinguish between C hominis (formerly known as genotype 1) and C parvum (formerly known as genotype 2). RESULTS: Of 437 fecal samples examined, 214 contained oocysts. Amplicons were generated for 200 samples. We can be certain, with 95% confidence, that cattle in the NYCW did not harbor C hominis. CONCLUSIONS AND CLINICAL RELEVANCE: Cryptosporidium infections in cattle are under examination because of the potential contamination of public waters by manure. Although cattle may be the source of zoonotic infection via C parvum, they pose little risk for C hominis (the strain commonly isolated from humans in waterborne outbreaks of disease). Other sources of oocysts should be considered when investigating outbreaks attributable to contaminated urban drinking water because cattle pose only a small risk via shedding of C hominis. 相似文献
68.
Trotz-Williams LA Martin SW Martin D Duffield T Leslie KE Nydam DV Jamieson F Peregrine AS 《Veterinary parasitology》2005,134(1-2):15-23
There is a need for simple and inexpensive diagnostic and screening tests for the detection of Cryptosporidium parvum infection in calves. A sucrose wet mount test and a lateral immunochromatography test were evaluated for epidemiological sensitivity and specificity, cost per test, simplicity, test time and ease of batching. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the Cryptosporidium oocyst wall protein (COWP) gene locus, with gel electrophoresis, was used as a gold standard. Cohen's kappa statistic of agreement (kappa) between the Ontario Veterinary College (OVC) sucrose wet mount test and COWP PCR-RFLP was 0.82, and the sensitivity and specificity of the OVC sucrose wet mount test were 88.6% and 93.8%, respectively. The sensitivity and specificity of the lateral immunochromatography test were 78.3% and 93.3%, respectively, and agreement between this test and PCR-RFLP was good (kappa=0.73). There was substantial agreement between the OVC sucrose wet mount test and the lateral immunochromatography test (kappa=0.84). Both tests were inexpensive and easy to use; however, the lateral immunochromatography test was faster and simpler to perform than the sucrose wet mount test, and was generally more user-friendly. These tests provide practitioners and researchers with cheap, quick and accurate methods of detecting C. parvum infection in young calves. 相似文献
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70.
Carnivore stable carbon isotope niches reflect predator–prey size relationships in African savannas 下载免费PDF全文
Jacqueline CODRON Nico L AVENANT Corli WIGLEY‐COETSEE Daryl CODRON 《Integrative zoology》2018,13(2):166-179
Predator–prey size relationships are among the most important patterns underlying the structure and function of ecological communities. Indeed, these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil record. Stable isotope analysis (SIA) is a powerful remote approach to examining animal diets and paleodiets. The approach is based on the principle that isotope compositions of consumer tissues reflect those of their prey. In systems where resource isotope compositions are distributed along a body size gradient, SIA could be used to reconstruct predator–prey size relationships. We analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio–Pleistocene African savanna assemblages, and show that the range of δ13C values among mammalian prey species (herbivores and rodents) increases with body mass (BM), because C4 plant feeding (essentially grazing) is more common among larger taxa. Consequently, δ13C values of mammalian carnivores in these systems are related to species' BM, reflecting a higher average C4 prey component in the diets of larger‐bodied carnivores. This pattern likely emerges because only the largest carnivores in these systems have regular access to the C4 prey base, whereas smaller carnivores do not. The δ13C–BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator–prey size relationships in contemporary and fossil savanna assemblages, and for interpreting how various behavioral, ecological and environmental factors influence prey size selection. 相似文献