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991.
Mapping QTLs of traits contributing to yield and analysis of genetic effects in tetraploid cotton 总被引:16,自引:0,他引:16
Dao-Hua He Zhong-Xu Lin Xian-Long Zhang Yi-Chun Nie Xiao-Ping Guo Chun-Da Feng James McD. Stewart 《Euphytica》2005,144(1-2):141-149
Fiber yield and yield components – including lint index (LI), seed index (SI), lint yield (LY), seed cotton yield (SCY) and
number of seeds per boll (NSPB) – were investigated on the farm of Huazhong Agricultural University in a population of 69
F2 individuals and corresponding F2:3 families derived from a cross between high-fiber-yield Gossypium hirsutum CV Handan 208 and a low-fiber-yield Gossypium barbadense CV Pima 90. On the basis of the genetic map constructed previously from the same population by Lin et al. (Plant Breed.,
2005), quantitative trait locus (QTL) analysis was performed with the software QTL Cartographer V2.0 using composite interval
mapping method (LOD ≥ 3.0). A total of 21 QTLs were identified, which were located in 15 linkage groups. The number of QTLs
per trait ranged from one to seven. Of these QTLs detected, one affecting LI explained 24.3% of phenotypic variation (PV),
five influencing SI explained 16.15–39.21% of PV, seven controlling LY explained 13.01–28.35% of PV, and two controlling SCY
explained 22.76 and 39.97% of PV, respectively. Simultaneously, the detected six QTLs for NSPB were located on five linkage
groups, which individually explained 28.01–38.32% of the total phenotypic variation. The results would give breeders further
insight into the genetic basis of fiber yield. 相似文献
992.
S. H. Begna R. I. Hamilton L. M. Dwyer D. W. Stewart D. Cloutier L. Assemat K. Foroutan-pour D. L. Smith 《European Journal of Agronomy》2001,14(4):293-302
Recently, corn (Zea mays L.) hybrids accumulating more leaf area above the ear, maturing earlier, yielding better in narrower row spacings and tolerating higher population densities than conventional hybrids have been developed. However, no research has been conducted to assess their ability to compete with weeds. The objective of this study was to quantify morphological and grain yield responses of hybrids with differing canopy architectures to the presence and absence of weeds. Field experiments were conducted in 1996, 1997, and 1998 at Ste. Anne de Bellevue, Quebec and in 1996 at Ottawa, Ontario. Three hybrids, leafy reduced-stature (LRS), late maturing big leaf (LMBL), and conventional Pioneer 3979 (P3979), were evaluated at two population densities (normal and high), row spacings (38 and 76 cm) and weed pressure levels (weed-free and weedy). Weed pressure reduced the plant height of LRS less (only 4 cm) than the tall hybrids (average reduction of 26 cm). The overall grain yield of the LMBL hybrid was much greater (12.7 mg ha−1) than the LRS (9.6 mg ha−1) and P3979 (11.0 mg ha−1) hybrids in the absence, but not in the presence (LRS, 6.5; LMBL, 6.7; and P3979, 6.8 mg ha−1), of weeds. The yield of early-maturing LRS and P3979 (especially LRS) hybrids, were least affected by weed pressure, suggesting better tolerance of, and competition with, weeds. However, further research with more LRS hybrids is needed, as is the development of better yielding LRS hybrids, before they can be recommended over conventional hybrids. 相似文献
993.
Whitefly infestations and parasitism were monitored year-round in overlapping cotton crops sown on three dates in Burkina Faso. The relative abundance of B. tabaci (Gennadius) and its parasitoids, Eretmocerus spp. and Encarsia spp., was recorded in control and insecticide-sprayed plots. Low B. tabaci populations developed during the first half of the rainy season. Pest populations increased when rainfall was ending, and the levels reached were higher in insecticide-treated plots (48 nymphs/leaf) than in control plots (25 nymphs/leaf). Parasitism reached 88.7% in control plots, and 53.7% in insecticide-treated plots. Eretmocerus spp. nymphs were more abundant than Encarsia spp. in both treated and control plots. A positive and significant curvilinear relationship was observed where % parasitism, on a linear scale, rose to a plateau with logarithmic increase in host density. In general % parasitism was correlated with the abundance of pest populations except in March and April where parasitism increased while B. tabaci populations decreased. In a separate experiment, adult Eretmocerus spp. were released into caged cotton plants to study the impact of augmentative releases of the parasites on the population dynamics of the pest. Pest densities increased from 1.47 nymphs/leaf to 39.4 nymphs/leaf in the control, but were reduced to 0.8 and 0.6 nymphs/leaf in the cages where, respectively, 4 and 8 parasitoids were released per plant. It appears that parasitism is an important factor reducing B. tabaci populations during and after the cotton-growing season, and that Eretmocerus spp. are promising biological control candidates against the pest in cotton. 相似文献
994.
Fox GP O'Donnell NH Stewart PN Gleadow RM 《Journal of agricultural and food chemistry》2012,60(24):6183-6187
Hydrogen cyanide (HCN) is a toxic chemical that can potentially cause mild to severe reactions in animals when grazing forage sorghum. Developing technologies to monitor the level of HCN in the growing crop would benefit graziers, so that they can move cattle into paddocks with acceptable levels of HCN. In this study, we developed near-infrared spectroscopy (NIRS) calibrations to estimate HCN in forage sorghum and hay. The full spectral NIRS range (400-2498 nm) was used as well as specific spectral ranges within the full spectral range, i.e., visible (400-750 nm), shortwave (800-1100 nm) and near-infrared (NIR) (1100-2498 nm). Using the full spectrum approach and partial least-squares (PLS), the calibration produced a coefficient of determination (R(2)) = 0.838 and standard error of cross-validation (SECV) = 0.040%, while the validation set had a R(2) = 0.824 with a low standard error of prediction (SEP = 0.047%). When using a multiple linear regression (MLR) approach, the best model (NIR spectra) produced a R(2) = 0.847 and standard error of calibration (SEC) = 0.050% and a R(2) = 0.829 and SEP = 0.057% for the validation set. The MLR models built from these spectral regions all used nine wavelengths. Two specific wavelengths 2034 and 2458 nm were of interest, with the former associated with C═O carbonyl stretch and the latter associated with C-N-C stretching. The most accurate PLS and MLR models produced a ratio of standard error of prediction to standard deviation of 3.4 and 3.0, respectively, suggesting that the calibrations could be used for screening breeding material. The results indicated that it should be feasible to develop calibrations using PLS or MLR models for a number of users, including breeding programs to screen for genotypes with low HCN, as well as graziers to monitor crop status to help with grazing efficiency. 相似文献
995.
Catriona Harrington F. Jerry Reen Marlies J. Mooij Fiona A. Stewart Jean-Baptiste Chabot Antonio F. Guerra Frank O. Gl?ckner Kristian F. Nielsen Lone Gram Alan D. W. Dobson Claire Adams Fergal O’Gara 《Marine drugs》2014,12(12):5960-5978
The search for new antimicrobial compounds has gained added momentum in recent years, paralleled by the exponential rise in resistance to most known classes of current antibiotics. While modifications of existing drugs have brought some limited clinical success, there remains a critical need for new classes of antimicrobial compound to which key clinical pathogens will be naive. This has provided the context and impetus to marine biodiscovery programmes that seek to isolate and characterize new activities from the aquatic ecosystem. One new antibiotic to emerge from these initiatives is the antibacterial compound tropodithietic acid (TDA). The aim of this study was to provide insight into the bioactivity of and the factors governing the production of TDA in marine Pseudovibrio isolates from a collection of marine sponges. The TDA produced by these Pseudovibrio isolates exhibited potent antimicrobial activity against a broad spectrum of clinical pathogens, while TDA tolerance was frequent in non-TDA producing marine isolates. Comparative genomics analysis suggested a high degree of conservation among the tda biosynthetic clusters while expression studies revealed coordinated regulation of TDA synthesis upon transition from log to stationary phase growth, which was not induced by TDA itself or by the presence of the C10-acyl homoserine lactone quorum sensing signal molecule. 相似文献
996.
Pollack JB Ragent B Boese R Tomasko MG Blamont J Knollenberg RG Esposito LW Stewart AI Travis L 《Science (New York, N.Y.)》1979,205(4401):76-79
Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small ( approximately 1 micrometer) or large ( approximately 10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising. 相似文献
997.
The forest frog Eleutherodactylus coqui defends specific sites for retreats and nests in the Luquillo Forest, Puerto Rico. The hypothesis that shortages of nest and retreat sites limit population size was tested by placing 100 bamboo frog houses in plots measuring 100 square meters in areas of high frog density. These new sites were readily adopted by adult frogs. After one year, experimental plots had significantly more nests and frogs of all sizes than did control plots. 相似文献
998.
Jie Li Yuanliang Shi Jiafa Luo David Houlbrooke Stewart Ledgard Anwar Ghani Stuart Lindsey 《Journal of Soils and Sediments》2014,14(8):1341-1349
Purpose
With land application of farm effluents from cows during housing or milking as an accepted practice, there are increasing concerns over its effect on nitrogen (N) loss through ammonia (NH3) volatilization. Understanding the relative extent and seasonal variation of NH3 volatilization from dairy effluent is important for the development of management practices for reducing NH3 losses. The objectives of this study were to determine potential NH3 losses from application of different types of dairy effluent (including both liquid farm dairy effluent (FDE) and semi-solid dairy farm manure) to a pasture soil during several contrasting seasons and to evaluate the potential of the urease inhibitor (UI)—N-(n-butyl) thiophosphoric triamide (NBTPT, commercially named Agrotain®) to reduce gaseous NH3 losses.Material and methods
Field plot trials were conducted in New Zealand on an established grazed pasture consisting of a mixed perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) sward. An enclosure method, with continuous air flow, was used to compare the effects of treatments on potential NH3 volatilization losses from plots on a free-draining volcanic parent material soil which received either 0 (control) or 100 kg N ha?1 as FDE or manure (about 2 and 15 % of dry matter (DM) contents in FDE or manure, respectively) with or without NBTPT (0.25 g NBTPT kg?1 effluent N). The experiment was conducted in the spring of 2012 and summer and autumn of 2013.Results and discussion
Results showed that application of manure and FDE, both in fresh and stored forms, potentially led to NH3 volatilization, ranging from 0.6 to 19 % of applied N. Difference in NH3 losses depended on the season and effluent type. Higher NH3 volatilization was observed from both fresh and stored manure, compared to fresh and stored FDE. The difference was mainly due to solid contents. The losses of NH3 were closely related to NH4 +-N content in the two types of manure. However, there was no relationship between NH3 losses and NH4 +-N content in either type of FDE. There was no consistent seasonal pattern, although lower NH3 losses from fresh FDE and stored FDE applied in spring compared to summer were observed. Potential NH3 losses from application of fresh FDE or manure were significantly (P?<?0.05) reduced by 27 to 58 % when NBTPT was added, but the UI did not significantly reduce potential NH3 volatilization from stored FDE or manure.Conclusions
This study demonstrated that NH3 losses from application of FDE were lower than from manure and that UIs can be effective in mitigating NH3 emissions from land application of fresh FDE and manure. Additionally, reducing the application of FDE in summer can also potentially reduce NH3 volatilization from pasture soil. 相似文献999.
DR Stewart D Sprinzak CM Marcus CI Duruoz JS Harris 《Science (New York, N.Y.)》1997,278(5344):1784-1788
The ground and excited state spectra of a semiconductor quantum dot with successive electron occupancy were studied with linear and nonlinear magnetoconductance measurements. A direct correlation was observed between the mth excited state of the N-electron system and the ground state of the (N + m)-electron system for m up to 4. The results are consistent with a single-particle picture in which a fixed spectrum of energy levels is successively filled, except for a notable absence of spin degeneracy. Further departures from the single-particle picture due to electron-electron interaction were also observed. Magnetoconductance fluctuations of ground states show anticrossings where wave function characteristics are exchanged between adjacent levels. 相似文献
1000.
The set of viable design elements available for animals to use in building skeletons has been fully exploited. Analysis of animal skeletons in relation to the multivariate, theoretical "Skeleton Space" has shown that a large proportion of these options are used in each phylum. Here, we show that structural elements deployed in the skeletons of Burgess Shale animals (Middle Cambrian) incorporate 146 of 182 character pairs defined in this morphospace. Within 15 million years of the appearance of crown groups of phyla with substantial hard parts, at least 80 percent of skeletal design elements recognized among living and extinct marine metazoans were exploited. 相似文献