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Despite the phenomenon of heterosis having been used to improve crop productivity for almost a century, there is little understanding of the molecular mechanisms involved. Heterosis has been described recently in the widely used plant model Arabidopsis thaliana. To assess the opportunity afforded by this system, we have developed, through pollination to a male sterile female parent (Ler ms1), a range of hybrids of A. thaliana accessions. We tested this method of hybrid production in A. thaliana by comparing seed produced by natural pollination and hand pollination of emasculated plants. Our results demonstrate that using male sterile lines, which more closely represent methods used for hybrid crop production, circumvents the problems associated with the analysis of hybrids produced from emasculated plants. We identified hybrid combinations exhibiting mid-parent heterosis for vegetative fresh weight ranging from −9 to 103% and characterised heterosis in the reciprocal hybrids of one strongly heterotic combination. We found no evidence of a relationship between the extent of genetic relatedness of A. thaliana accessions and the strength of heterosis exhibited by their hybrids. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
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Composted sewage sludge (biosolids) supply plant available Fe and may represent a sustainable alternative to more costly chelated Fe fertilizers currently used to supplement nutrition in hybrid poplar test plots of elevated soil pH. To test the response of poplars, field plots were amended with composted biosolids at two agricultural rates: 22.75 and 44.5 Mg ha−1. Iron EDDHA served as a fertilizer check and control plots received no amendment. The hybrid poplar OP-367 (Populus deltoides × P. nigra) was planted on a 3.6 m grid spacing. Significant amounts of P and Fe originating from the sewage treatment process were detected in soils 13 months after amending. Chlorosis evaluated with a SPAD-502 meter, showed that poplars amended with biosolids remained the least chlorotic and had greater tree growth when compared to Fe EDDHA and control plots during two growing seasons. Biosolids show promise as a cost effective alternative for the remediation of Fe chlorosis in hybrid poplar agroforestry plantations and present new opportunities in northwestern New Mexico for municipalities seeking solid waste land disposal options.  相似文献   
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Samples of wheat grain and straw have been analysed from trials with the wild oat herbicide benzoylprop-ethyl ( I ) in several countries. Following recommended commercial treatments (application of 1.0–1.6 kg ha?1 at Feekes growth stage G-J), total residues of I and its hydrolysis product N-benzoyl-N-(3,4-dichlorophenyl)-DL - alanine (free and conjugated) were low and in the majority of instances they were < 0.01 mg kg?1 in samples of grain from the UK, although rather higher residues were detected in some grain samples from other countries. Residues in straw were higher, but normally did not exceed 2 mg kg?1, and were rather variable, possibly as a result of differences in agricultural practice.  相似文献   
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Five calves from tuberculosis free herds were each inoculated intranasally with 10(6) viable organisms of a field isolate of Mycobacterium bovis. Four of the calves developed acute tuberculosis. ELISAs employing protein and phosphatide extracts of M bovis as antigens were used to monitor the humoral response of the infected calves. Fourteen days after infection there was a dramatic increase in the level of antibodies demonstrated by the phosphatide antigen. This increase coincided with the first appearance of signs of the disease. The results suggest that the phosphatide antigen may be of potential value in detecting a humoral response, if present, in cattle infected with M bovis. The tests employing the protein antigen demonstrated a humoral response in only one of the infected calves and emphasises the importance of antigen selection to detect antibodies in tuberculous animals.  相似文献   
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