1. The effect of gradual acclimation to high ambient temperatures on egg‐shell quality was studied in the Sinai fowl, the commercial White Leghorn, and their reciprocal crossbreds.
2. The Leghorn egg was characterised by a thinner and weaker shell compared with the Sinai and the crossbreds, at all the experimental temperatures.
3. In contrast to other reports, high ambient temperatures for a long period had only mild effects on egg‐shell quality.
4. The results suggest that gradual acclimation to high ambient temperatures might improve the efficiency of the physiological mechanisms involved in the hen's response to heat. Consequently, the reproductive process adapts to the hot environmental conditions.
5. The results indicate that the Sinai breed might be used for future selection of a breed, highly resistant to extreme environmental conditions and with an improved shell quality. 相似文献
The Pi‐ta gene in rice confers resistance to strains of the blast pathogen Magnaporthe grisea (Herbert) Borr. (anamorph Pyricularia oryza Cav.) containing the corresponding avirulence gene AVR‐Pita in a gene‐for‐gene fashion. The Pi‐ta gene is a typical nucleotide‐binding site type resistance gene. Nucleotide sequences distinguishing the resistant Pi‐ta and susceptible pi‐ta alleles were previously identified and used for developing DNA markers for a resistant Pi‐ta haplotype and three susceptible pi‐ta haplotypes. In the present study, the existence of the Pi‐ta gene in 141 rice germplasm accessions was rapidly determined using these markers, and the results were confirmed by inoculating rice germplasm with an M. grisea strain containing AVR‐Pita. The Pi‐ta gene was found in accessions from several major rice producing countries, including China, Colombia, Japan, Vietnam, the Philippines, Iran and the United States. The usefulness of DNA markers for rapid determination of the genotype of rice germplasm was thus demonstrated. The Pi‐ta gene also was found in rice cultivar known to contain the Pi‐ta2 gene, although the allelic relationship of these genes remains to be determined. The presence of the Pi‐ta gene in landrace cultivars in several different geographical locations, the Philippines and Vietnam, other indica rice cultivars in China and Colombia suggest that the Pi‐ta gene may have spontaneously originated in indica rice cultivars. These results are useful for incorporating the Pi‐ta gene into advanced breeding lines by marker‐assisted selection for rice breeding programmes worldwide. 相似文献
Poor compatibility was found between exploded wood fiber strand (WFS) and cement due to the excessive presence of water-soluble degraded polysaccharides in extractives of exploded WFS obtained from weathered wood waste treated by the water-vapor explosion process (WVEP). This study presents some comparative results from a continuing investigation on the compressive strengths of exploded WFS–cement mixtures. Based on results previously obtained with the hydration test, the relation between hydration behavior and compressive strength of the mixture was explored. In addition, the effect of the curing age on compressive strength development of the mixture with selected additive chemicals was examined. The results supported the results of early studies with hydration tests indicating that adding MgCl2 to the mixtures of exploded WFS mixed with quick-curing cement or ordinary Portland cement and a composite of MgCl2 + CaO added to the mixture of exploded WFS and furnace-slag cement effectively improved the hydration behaviors; it greatly enhanced the compressive strengths of mixtures as well. Compressive strengths were strongly correlated to maximum hydration temperatures (Tmax) of wood–cement mixtures influenced by the cement type, wood wastes (treated or not with WVEP), additive chemicals, and their content levels. The results also indicated that adding selected chemicals had no significant effect on compressive strength among the mixtures of exploded WFS mixed, respectively, with three types of cement at a curing age of 180 days. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to identify the hydration products and to probe the element distribution of the mixture in the wood–cement interface zone from a fractured surface.Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002 相似文献