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51.
New Forests - Adventitious rooting (AR) is an obligatory step for vegetative propagation of commercial woody species. Paper industries have interest in Eucalyptus globulus Labill and its hybrids...  相似文献   
52.
Rice production needs to increase in the future in order to meet increasing demands. The development of new improved and higher yielding varieties more quickly will be needed to meet this demand. However, most rice breeding programmes in the world have not changed in several decades. In this article, we revisit the evidence in favour of using rapid generation advance (RGA) as a routine breeding method. We describe preliminary activities at the International Rice Research Institute (IRRI) to re-establish RGA on a large scale as the main breeding method for irrigated rice breeding. We also describe experiences from the early adoption at the Bangladesh Rice Research Institute. Evaluation of RGA breeding lines at IRRI for yield, flowering time and plant height indicated transgressive segregation for all traits. Some RGA lines were also higher yielding than the check varieties. The cost advantages of using RGA compared to the pedigree method were also empirically determined by performing an economic analysis. This indicated that RGA is several times more cost effective and advantages will be realized after 1 year even if facilities need to be built. Based on our experience, and previous independent research empirically testing the RGA method in rice, we recommend that this method should be implemented for routine rice breeding in order to improve breeding efficiency.  相似文献   
53.
Global averages were obtained for amounts of energy, land, water, wildfish, nitrogen, and phosphorus embodied in aquaculture feed ingredients. These data allowed amounts of these embodied resources to be calculated for typical feed formulations for channel catfish, Ictalurus punctatus; hybrid catfish, I. punctatus♀ × I. furcatus♂; Vietnamese catfish, Pangasius spp.; Atlantic salmon, Salmo salar; rainbow trout, Oncorhynchus mykiss; tilapia, Oreochromis spp.; whiteleg shrimp, Litopenaeus vannamei; and black tiger shrimp, Penaeus monodon. Embodied resource use per m.t. of feed varied among species: energy, 4.90–12.48 GJ/m.t.; land, 0.082–0.312 ha/m.t.; water, 502–1227 m3/m.t.; wildfish, 0–2880 kg/m.t.; nitrogen, 3.08–8.63 kg/m.t.; phosphorus, 1.16–5.62 kg/m.t. These calculations did not account for variations in site‐specific factors related to embodied resources and feed composition and use. But they suggest that reducing feed conversion ratio (FCR) by 0.1 unit for the seven species (species groups) could potentially reduce feed use by around 1.1 million tonne (Mt) while conserving 9.8 million GJ of energy, 270,000 ha of agricultural land, 1.4 billion m3 of freshwater, and 1.24 Mt of wildfish. Reduction of the FCR is a powerful means of lessening farm‐level production costs and negative impacts of feed production and use.  相似文献   
54.
乡村振兴人才队伍建设存在的问题与对策研究   总被引:1,自引:1,他引:0  
党的十九大提出了乡村振兴战略,人才振兴是乡村振兴的关键。目前乡村人才队伍存在总体规模偏少、整体素质偏低、后备力量不足等问题。文章结合这些实际问题,提出相应的对策建议,以期助力乡村振兴人才队伍建设。  相似文献   
55.
56.
This study examined the effects of feeding frequency (daily versus every other day [EOD]) on nutrient digestibility/availability of channel catfish, Ictalurus punctatus, reared at optimal (30 C) and suboptimal (24 C) temperatures. A 28% protein practical diet was used as the test diet, and chromic oxide was used at 0.75% of the diet as a maker. Twenty channel catfish of a mean weight of 141 g/fish were stocked into 12 flow‐through aquaria (110 L). Fish were fed daily or EOD to apparent satiation for 7 d before fecal samples were collected by the dissection method. Fish fed EOD to apparent satiation consumed more diet on days fed than those fed daily, and fish reared at 30 C consumed more diet than those reared at 24 C. Neither feeding frequency nor water temperature significantly affected apparent digestibility coefficients for energy and protein and apparent availability coefficients for total amino acids. Results show no advantage by feeding EOD over feeding daily on nutrient digestibility and diet utilization efficiency.  相似文献   
57.
The use of cattle manure (CM) for fertilization presents challenges for optimizing nitrogen (N) use. Our work aimed to assess N efficiencies, in a 6‐year experiment with three biennial rotations of four crops: oat–sorghum (first year) and ryegrass–maize (second year) in a rainfed humid Mediterranean area of Spain. Fertilization treatments included the following: control (no N), 250 kg mineral N ha?1 year?1 (250MN), three CM rates (supplying 170, 250 and 500 kg N ha?1 year?1) and four treatments where the two lowest CM rates were complemented with either 80 or 160 kg mineral N ha?1 year?1. Treatments were distributed randomly in each of three blocks. Maximum dry‐matter yield (~44–49 t ha?1 rotation?1) was achieved in the third rotation, and only the control and the 170CM yielded significantly less. Within the limitations of the EU Nitrate Directive, the N steady state supply of 170CM always requires a complement of mineral N (80 kg N ha?1) to maximize N agronomic efficiency. The maximum N‐fertilizer replacement value (250CM vs. 250MN) was 0·67, without significant differences between the two treatments in other N‐related efficiency indexes, which indicates that plants took advantage of residual‐N effects. Nitrogen losses by leaching in the 250CM treatment were around 5–7% of the N applied. This reinforces the sustainability of manure recycling in long cropping seasons.  相似文献   
58.
Implications of silage hygienic quality for animal production were investigated on forty‐five dairy farms in South West England. Samples of grass and maize silages and of total mixed rations (TMR) were obtained together with information on silage technology, herd size and animal production. Samples were analysed for mycotoxins, bacteria, yeasts, moulds and chemical composition. Thirteen mycotoxins were assayed, but none were detected in the samples of grass silage. However, mycotoxins were found in 0·9 of all maize and other silage samples, with deoxynivalenol and zearalenone predominating. There was no relationship between total mycotoxin concentration and mean lactation milk yield per cow. Enterobacteria counts tended to be higher in maize silage than in grass silage and higher still in TMR – a cause for concern. There were no relationships between mould counts and mycotoxin concentrations in silages, implying that mycotoxins may have been produced in the field pre‐ensiling.  相似文献   
59.
We developed 178 recombinant inbred lines from a southern‐by‐spring oat population designated as “TxH.” These lines were genotyped to generate a high‐quality linkage map that resolved 6,902 markers into 21 linkage groups that matched closely with the latest hexaploid oat consensus map. Three major quantitative trait loci (QTLs) affecting heading date were found in locations that are consistent with known QTLs and candidate genes, and two other QTLs affecting heading date were found in novel locations. Five QTLs affecting plant height were found. Both sets of QTLs are responsible for transgressive segregation observed for these two traits. Four QTLs affecting resistance to crown rust, caused by the pathogen Puccinia coronata f. sp. avenae, were identified. Two of these QTLs are consistent with known clusters of rust resistance genes, while two may represent new locations of novel rust resistance genes. A complete set of SNP sequences suitable for generating markers for molecular selection is provided.  相似文献   
60.
浅谈陆地棉杂种二代利用   总被引:1,自引:0,他引:1  
棉花杂种优势利用是提高棉花产量主要途径之一。研究表明,一些陆地棉F2仍具有明显的产量杂种优势,种子成本低廉的F2具有潜在的应用前景。本文综述了陆地棉F2杂种优势遗传基础、优势表现以及目前生产上出现的问题,并从育种层面提出了有针对性的解决对策。  相似文献   
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