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21.
Two participatory approaches to varietal selection were compared in February-sown (Chaite) rice and main-season rice in high potential production systems in Nepal. One method, called farmer managed participatory
research (FAMPAR), was researcher intensive, while the other, called informal research and development (IRD), demanded fewer
resources. The trials were conducted in 18 villages in high potential production systems in Chitwan and Nawalparasi districts
of Nepal. Six new varieties of Chaite rice and 16 of main-season rice were tested in over 300 trials of Chaite rice and nearly 1100 trials of main-season rice over two years in 1997 and 1998. Surveys were done in 1997, 1998 and 1999
to record the extent of adoption and spread of the new rice varieties in the study villages. In many cases, farmers tested
varieties for two years before deciding whether to adopt or drop them. Varieties were quite
widely accepted, adopted for niches in a few villages, or rejected. The two participatory approaches identified the same varieties,
but FAMPAR, which used formal survey methods, was more useful for diagnosing reasons for adoption or rejection. However, IRD
used much cheaper anecdotal methods of evaluation, so it was more cost-effective. Moreover,farmer-to-farmer seed dissemination
was higher in IRD villages, probably because farmers in FAMPAR villages felt that the project would re-supply seed if needed.
The benefits from both approaches are considerable, but to adopt them substantial policy changes in varietal testing, release
and extension systems will be required.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
22.
Ram C. Sharma G. Ortiz-Ferrara J. Crossa M. R. Bhatta M. A. Sufian J. Shoran A. K. Joshi R. Chand Gyanendra Singh R. Ortiz 《Euphytica》2007,157(3):457-464
Improving the level and stability of grain yield is the primary objective of wheat breeding programs in the Eastern Gangetic
Plains (EGP) of South Asia. A regional wheat trial, the Eastern Gangetic Plains Yield Trial (EGPYT), was initiated by CIMMYT
in collaboration with national wheat research programs in Bangladesh, Nepal, and India in 1999–2000 to identify wheat genotypes
with high and stable grain yield, disease resistance, and superior agronomic traits for the EGP region. A set of 21 wheat
experimental genotypes selected from a regional wheat screening nursery in South Asia, three improved widely grown cultivars
(Kanchan, PBW343 and Bhrikuti), and one long-term cultivar (Sonalika) were tested at 9–11 sites in six wheat growing seasons
(2000–2005) in the EGP. The 21 experimental genotypes were different in each year, whereas the four check cultivars were common.
In each year, one or more of the experimental genotypes showed high and stable grain yield and acceptable maturity, plant
height, and disease resistance compared to the check cultivars. Three improved cultivars have already been commercially released
in the region through EGPYT and many germplasm lines have been used in the breeding programs as parents. Identification of
wheat genotypes with high-grain yield in individual sites and high and stable yield across the EGP region underlines their
value for regional wheat breeding programs attempting to improve grain yield and agronomic performance. 相似文献
23.
24.
Global wheat (Triticum aestivum L.) production must increase 2% annually until 2020 to meet future demands. Breeding wheat cultivars with increased grain
yield potential, enhanced water-use efficiency, heat tolerance, end-use quality, and durable resistance to important diseases
and pests can contribute to meet at least half of the desired production increases. The remaining half must come through better
agronomic and soil management practices and incentive policies. Analyses of the recent International Yield Trials indicate
that grain yields of the best new entries were usually 10% higher than the local checks globally, as well as within a country
across sites. Variation in yield across sites within a country/region underline the role of genotype × environment (GE) interaction
and provides opportunities to select for stable genotypes, which is not often done. The lack of proper analysis undermines
proper utilization of germplasm with high yield potential and stability in the national wheat breeding programs. Some of the
best performers in irrigated areas were amongst the best in semiarid environments, reinforcing the fact that high yield potential
and drought tolerance can be improved simultaneously. The best performing lines often had genotypic base of widely adapted
genotypes Kauz, Attila, Baviacora, and Pastor, with genetic contributions from other parents including synthetic wheat. We
recommend within country multilocation analysis of trial performance for a crop season to identify lines suiting particular
or different locations within a country. The immediate feedback on GE interaction will also help in breeding lines for countries
having substantial variation across locations and years. 相似文献
25.
Summary An Indian hexaploid wheat var. Pb C591 has been shown to carry gene(s) for chlorophyll synthesis on chromosome 3A (Singh & Joshi, 1979). In the present study cv. Pb.C591, its monosomic 3A and diteocentrics for 3A, 3BL and 3DL of var. Chinese Spring have been used. The F2 segregation involving crosses between Pb.C591 as male, monosomic line 3A of Pb.C591 (female) and ditelocentrics 3A, 3BL and 3DL of cv. Chinese Spring as male and female respectively has been observed. It has been found that there are two dominant genes regulating chlorophyll synthesis in cv. Chinese Spring. These genes are located on chromosomes arms 3A and 3DS respectively.These chlorophyll synthetic genes must be the same which were postulated by Sears (1956, 1957) as the normal alleles of virescent gene v
2 (which was located on 3BS) on chromosomes 3A(v
1) and 3D(V
3). 相似文献
26.
S. R. Joshi 《Water, air, and soil pollution》1988,37(1-2):111-120
The presence of West Valley-derived radionuclides in the densely-populated Niagara River/Lake Ontario region is demonstrated through measurements on water and sediment samples. The 137Cs profile in a 210Pb-dated Lake Ontario sediment core is consistent with the pattern of West Valley discharges to the local aquatic environment in that the observed 137Cs activity maximum corresponds to the 1970 peak discharge and not the 1963 fallout peak activity. Preliminary mass balance estimate, based on a 137Cs/90Sr activity ratio of 1.5 and on the assumption that the dominant regional flow of Lake Erie transports most of the radionuclides to Lake Ontario va the Niagara River, shows that nearly all of the West Valley-delivered 137Cs is deposited in the bottom sediments of Lake Ontario. It is suggested that any accidental releases of radioactivity from the site are likely to provide additional radiation dose to the area residents using municipal water supplies. 相似文献
27.
RP Andres T Bein M Dorogi S Feng JI Henderson CP Kubiak W Mahoney RG Osifchin R Reifenberger 《Science (New York, N.Y.)》1996,272(5266):1323-1325
Double-ended aryl dithiols [alpha,alpha'-xylyldithiol (XYL) and 4,4'-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (approximately18 ± 12 megohms). 相似文献
28.
The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra. 相似文献
29.
Isolated mesophyll cells from leaflets of Arachis hypogaea can be cultured in a simple, defined liquid nutrient medium containing minerals, with an appropriate source of ammonia, sugar, 2,4-dichlorophenoxyacetic acid, and kinetin. The significance of such a simple medium in understanding the problems of cell metabolism, growth, and morphogenesis is discussed. 相似文献
30.
Phosphorylation of ULK1 (hATG1) by AMP-activated protein kinase connects energy sensing to mitophagy
Egan DF Shackelford DB Mihaylova MM Gelino S Kohnz RA Mair W Vasquez DS Joshi A Gwinn DM Taylor R Asara JM Fitzpatrick J Dillin A Viollet B Kundu M Hansen M Shaw RJ 《Science (New York, N.Y.)》2011,331(6016):456-461
Adenosine monophosphate-activated protein kinase (AMPK) is a conserved sensor of intracellular energy activated in response to low nutrient availability and environmental stress. In a screen for conserved substrates of AMPK, we identified ULK1 and ULK2, mammalian orthologs of the yeast protein kinase Atg1, which is required for autophagy. Genetic analysis of AMPK or ULK1 in mammalian liver and Caenorhabditis elegans revealed a requirement for these kinases in autophagy. In mammals, loss of AMPK or ULK1 resulted in aberrant accumulation of the autophagy adaptor p62 and defective mitophagy. Reconstitution of ULK1-deficient cells with a mutant ULK1 that cannot be phosphorylated by AMPK revealed that such phosphorylation is required for mitochondrial homeostasis and cell survival during starvation. These findings uncover a conserved biochemical mechanism coupling nutrient status with autophagy and cell survival. 相似文献