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DB ADAMS JJ LYNCH† BH ANDERSON LR FELL‡ GN HINCH§ RK MUNRO¶ 《Australian veterinary journal》1990,67(12):443-445
Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted. 相似文献
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PE Bennemann GN Diehl E Milbradt RM Vidor HCC Fries I Wentz ML Bernardi FP Bortolozzo 《Reproduction in domestic animals》2005,40(6):507-510
This study evaluated the reproductive performance of gilts inseminated at three intervals before ovulation (0-12, 13-23, 24-30 h) with sperm doses (SD) stored for 0-48 and 96-120 h. A total of 218 PIC Camborough 22 gilts were inseminated once with SD of 1.5 x 10(9) sperms. Pregnant gilts (n = 166) were slaughtered 30.8 +/- 3.7 days after artificial insemination. The number of corpora lutea (CL) and total embryos (TE) was counted. Pregnancy rates (PR) were analysed by chi-square test. TE and embryonic survival (ES), obtained as the ratio between viable embryos and CL, were analysed by GLM procedure (SAS) and mean values were compared by Tukey's test. Pregnancy rate was similar among artificial insemination-ovulation (AIOV) intervals when semen was stored for 0-48 h. However, the lowest PR was observed in the 24-30 h AIOV interval with storage time (ST) of 96-120 h (p < 0.05). There was a significant effect of the interaction between ST and AIOV (p < 0.05) on TE and ES variables. Total embryos and ES did not differ (p > 0.05) among AIOV intervals in ST of 0-48 h. However, gilts inseminated at 24-30 h AIOV interval with ST of 96-120 h showed a reduction of 6.7 embryos (p < 0.05) compared with gilts in the same interval inseminated with semen stored for 0-48 h. ES for the 24-30 h AIOV interval and ST of 96-120 h was lower than that observed in the other groups (p < 0.05). 相似文献
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L. Krishnamurthy Rachid Serraj C. Tom Hash Abdullah J. Dakheel Belum V. S. Reddy 《Euphytica》2007,156(1-2):15-24
Genetic improvement of salt tolerance is of high importance due to the extent and the constant increase in salt affected areas.
Sorghum [Sorghum bicolor (L.) Moench] has been considered relatively more salt tolerant than maize and has the potential as a grain and fodder crop
for salt affected areas. One hundred sorghum genotypes were screened for salinity tolerance in pots containing Alfisol and
initially irrigated with a 250-mM NaCl solution in a randomized block design with three replications. Subsequently 46 selected
genotypes were assessed in a second trial to confirm their responses to salinity. Substantial variation in shoot biomass ratio
was identified among the genotypes. The performance of genotypes was consistent across experiments. Seven salinity tolerant
and ten salinity sensitive genotypes are reported. Relative shoot lengths of seedlings were genetically correlated to the
shoot biomass ratios at all stages of sampling though the relationships were not close enough to use the trait as a selection
criterion. In general, the whole-plant tolerance to salinity resulted in reduced shoot Na+ concentration. The K+/Na+ and Ca2+/Na+ ratios were also positively related to tolerance but with a lesser r
2. Therefore, it is concluded that genotypic diversity exists for salt tolerance biomass production and that Na+ exclusion from the shoot may be a major mechanism involved in that tolerance. 相似文献
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Dinitrogen fixation and legume productivity are greatly influenced through the interactions of legume host, Rhizobium, and the above- and below-ground environment. The benefits of improving legume N2 fixation include reduced reliance on soil N, leading to more sustainable agricultural systems and reduced requirements for fertilizer N, enhanced residual benefits to subsequent crops, and increased legume crop yields. Most of the gains in N2 fixation to date have been derived from management of legume cropping systems and through inoculation of legume seed with competitive and symbiotically effective rhizobia. Further gains are possible by developing plant cultivars with tolerance to soil abiotic factors, increased plant yield, and a broader and more effective matching of plant host and rhizobia. Techniques for screening material for superior N2 fixation and examples of programs to increase fixed N, with attention to the major abiotic stresses, are discussed. 相似文献
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Relationship between Carbon Isotope Discrimination, Ash Content and Grain Yield in Wheat in the Peninsular Zone of India 总被引：3，自引：0，他引：3
S. C. Misra R. Randive V. S. Rao M. S. Sheshshayee R. Serraj P. Monneveux 《Journal of Agronomy and Crop Science》2006,192(5):352-362
Carbon isotope discrimination (Δ) and ash content (ma) have been proposed as indirect selection criteria for grain yield in wheat. The associations between Δ, ma and grain yield were found, however, to depend highly on the environmental conditions, the organ sampled and the time of sampling. In this study, carried out in the warm conditions of the Peninsular Zone of India, the relationship between Δ, ma and yield was studied in 30 bread and durum wheat cultivars under residual soil moisture stress (RSMS), post‐anthesis water stress (PAWS) and well‐watered (WW) conditions. Both Δ and ma were analysed in young seedlings (four‐leaf stage), leaves at anthesis and grain at maturity. Ash content was also evaluated in leaves at booting stage and maturity. Grain Δ was lower under PAWS and RSMS than under WW, while seedling and leaf Δ did not significantly differ among water regimes. Grain yield was positively correlated to grain Δ under PAWS and negatively correlated to grain ma under RSMS. A significant positive correlation was noted under RSMS and WW treatments between maLm and grain yield. Ash content in leaf at maturity consequently appears to be a useful indirect selection criterion in environments where Δ does not show any correlation with yield. The results highlight the potential of Δ and ma as indirect selection criteria for wheat yield in the conditions of the Peninsular Zone of India. 相似文献
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Genetic variability of drought-avoidance root traits in the mini-core germplasm collection of chickpea (Cicer arietinum L.). 总被引：2，自引：0，他引：2
Junichi?KashiwagiEmail author L.?Krishnamurthy Hari?D.?Upadhyaya Hari?Krishna S.?Chandra Vincent?Vadez Rachid?Serraj 《Euphytica》2005,146(3):213-222
Extensive and deep root systems have been recognized as one of the most important traits for improving chickpea (Cicer arietinum L.) productivity under progressively receding soil moisture conditions. However, available information on the range of variation
for root traits is still limited. Genetic variability for the root traits was investigated using a cylinder culture system
during two consecutive growth seasons in the mini-core germplasm collection of ICRISAT plus several wild relatives of chickpea.
The largest genetic variability was observed at 35 days after sowing for root length density (RLD) (heritability, h
2 = 0.51 and 0.54) across seasons, and followed by the ratio of plant dry weight to root length density with h
2 of 0.37 and 0.50 for first and second season, respectively. The root growth of chickpea wild relatives was relatively poor
compared to C. arietinum, except in case of C. reticulatum. An outstanding genotype, ICC 8261, which had the largest RLD and one of the deepest root system, was identified in chickpea
mini-core germplasm collection. The accession ICC 4958 which was previously characterized as a source for drought avoidance
in chickpea was confirmed as one with the most prolific and deep root system, although many superior accessions were also
identified. The chickpea landraces collected from the Mediterranean and the west Asian region showed a significantly larger
RLD than those from the south Asian region. In addition, the landraces originating from central Asia (former Soviet Union),
characterized by arid agro-climatic conditions, also showed relatively larger RLD. As these regions are under-represented
in the chickpea collection, they might be interesting areas for further germplasm exploration to identify new landraces with
large RLD. The information on the genetic variability of chickpea root traits provides valuable baseline knowledge for further
progress on the selection and breeding for drought avoidance root traits in chickpea. 相似文献
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Soybean ( Glycine max L.) nitrogen nutrition is ensured by both symbiotic nitrogen fixation and mineral nitrogen assimilation. The relationship between these two modes of N nutrition was analysed in 3 growth types (determinate, semi-determinate and undeterminate) of soybean. The nitrate reductase activity and nitrogenase activity (acetylene reduction) of plants grown in the field and greenhouse showed that these enzymatic activity acted simultaneously or successively during the growth cycle, depending on the availability of inorganic nitrogen in the growing medium. Undeterminate soybean types had a higher potential nitrate reductase activities than determinate types.
The proportion of N2 fixed as measured by 15 N labelling or stem ureide content indicated that determinate soybeans derived a higher proportion of their N from N2 fixation than the undeterminates. 相似文献
The proportion of N