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1.
ALI M GOLMIRZAIE JORGE TENORIO FELIX SERQUÉN RODOMIRO ORTIZ 《The Annals of applied biology》2003,143(2):231-234
Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non‐sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid‐derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y‐245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid‐derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non‐cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato. 相似文献
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Raw count data are often used to estimate bird population densities. However, such data do not consider detection probability. As an alternative, methods that model detection probability such as distance-sampling have been proposed. However, standard distance-sampling provides reliable estimates for absolute density only when the underlying assumptions are met. One of the most critical of these assumptions is that animals on a transect line or at an observation point have to be detected with certainty (the g (0) = 1 assumption). We radiotagged nine Orphean Warblers Sylvia hortensis and estimated their short-distance detection probability. Birds were radio-located in 264 cases in single bushes or trees. Their visual detection probability after a 5-min search was only 0.58 (sd = ±0.14, range = 0.38–0.80), although the observer knew the bird's location. Furthermore, we carried out a literature review to assess how the g (0) = 1 assumption is handled in practice. None of the 28 standard distance-sampling papers reviewed contained an estimation of g (0). In 57% of the papers, the g (0) = 1 assumption was not even mentioned. Nevertheless, none of the authors declared their estimates as being relative. Our empirical data show that the g (0) = 1 assumption would be severely violated for a foliage-gleaning bird species at a desert stopover site outside the breeding season. The literature review revealed that the testing of the g (0) = 1 assumption is largely ignored in practice. We strongly suggest that more attention should be paid to the testing of this key assumption, because results may not be reliable when it is violated. If it is not possible to test the g (0) = 1 assumption or g (0) is less than 1, alternative methods should be used. Another possibility is to estimate detection probability by the means of radiotagged individuals. 相似文献
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HEIKO SCHMALJOHANN† FELIX LIECHTI ERICH BÄCHLER THOMAS STEURI & BRUNO BRUDERER 《Ibis》2008,150(2):342-355
Besides the scientific interest in the quantification of bird migration, there is an increasing need to quantify bird movements for the assessment of bird collision risk with artificial structures. In many environmental impact studies, the radar method is used in an inappropriate manner. The processing of echoes consists often of counting blips within defined screen fields, and the surveyed volume is estimated without reference to the detection probabilities of different 'target sizes' (radar cross-sections). The aim of this paper is to present a procedure to quantify bird migration reliably using radar by stating the theoretical requirements of every single step of this procedure and presenting methodological solutions using our own radar data from extensive field studies. Our methodological solutions can be applied to various radar systems, including widely used ship radar. The procedure presented involves discriminating the echoes of birds and insects and estimating the different detection probabilities of differently 'sized' birds (radar cross-sections). By ignoring the different detection probabilities, density estimations may be wrong by as much as 400%. We fear that quantification of bird migration and predicted bird numbers affected by collisions with artificial structures are in many cases based on unreliable estimates. 相似文献