首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Common bean (Phaseolus vulgaris L.) is the most important food legume crop in Africa and Latin America where rainfall pattern is unpredictable. The objectives were to identify better yielding common bean lines with good canning quality under drought, and to identify traits that could be used as selection criteria for evaluating drought‐tolerant genotypes. In all, 35 advanced lines were developed through single seed descent and evaluated with a standard check under drought and irrigated conditions at two locations over 2 years in Ethiopia. Grain yield (GY), pod number per m2, seed number per m2 and seed weight decreased by 56%, 47%, 49% and 14%, respectively, under drought stress. Eight genotypes had better yield with good canning quality under drought compared to the check. Moderate to high proportion of genetic effects were observed under drought conditions for GY and yield components compared to genotype × environment effects. Significant positive correlations between GY and pod harvest index (PHI) in drought suggest that PHI could be used as an indirect selection criterion for common bean improvement.  相似文献   

2.
Sharma  R. C.  Duveiller  E.  Gyawali  S.  Shrestha  S. M.  Chaudhary  N. K.  Bhatta  M. R. 《Euphytica》2004,139(1):33-44
Helminthosporium leaf blight (HLB), caused by a complex of Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur and Pyrenophora tritici-repentis Died, is a serious disease of wheat (Triticum aestivum L.) in the warm lowlands of South Asia. Wheat cultivars grown in the area are either susceptible to HLB or possess low levels of resistance to it. A replicated field study was conducted in 1999 and 2000 at two sites in Nepal to determine the level of HLB resistance and other desirable traits in 60 wheat genotypes of diverse origin. The test genotypes were planted in main strips divided into two strips one of which was sprayed four times with Tilt (a.i. propiconazole) @ 125 g of a.i. ha–1. Four readings of HLB were recorded to calculate the area under the disease progress curve (AUDPC). Other traits under investigation included biomass yield (BY), grain yield (GY), 1000-kernel weight (TKW), harvest index (HI), days to heading (DH) and maturity (DM), plant height (PHT), and effective tiller number (ETN). Wheat genotypes differed significantly for all traits. Mean AUDPC values ranged from 45 to 1268. A few exotic genotypes were highly resistant to HLB. Losses in GY due to HLB ranged from 2 to 26%, and TKW was reduced by up to 33%. A few genotypes showed HLB tolerance, i.e., relatively smaller GY and TKW reductions despite high levels of HLB. In general, medium to late maturity and higher levels of HLB resistance and low to high GY and TKW characterized genotypes exotic to South Asia. Biplot analysis identified several genotypes that were HLB-resistant and agronomically superior. Results suggest it is possible to improve HLB resistance of local wheat cultivars based on selective breeding using this pool of germplasm.  相似文献   

3.
Summary Three thousand two hundred and sixty-seven kabuli chickpea (Cicer arietinum L.) germplasm accessions were grown during the spring season of 1980 at Tel Hadya, the main research station of ICARDA, Syria to determine the components of seed yield. Observations were recorded on seed yield and 14 other characters. Correlation and path coefficient analyses were done to find out associations among characters and to assess the direct and indirect contribution of each character to seed yield.Large variation was observed for all the characters studied except days to flowering, days to maturity and protein content. Correlation and path coefficient analyses showed that biological yield and harvest index were the major direct contributors to seed yield. The 100-seed weight, plant height, days to flowering and maturity, canopy width, and protein content contributed to seed yield mainly through indirect effect via biological yield and harvest index. The 100-seed weight and seed yield were major contributors to biological yield. Major contributor to protein content was days to maturity. Results indicated that selection for high biological yield and harvest index would lead to high seed yield; and selection for large seed size would lead to high biological yield. Therefore, these characters should receive the highest priority in selecting high yielding plants in chickpea breeding.  相似文献   

4.
Summary Two hundred genotypes of Coriandrum sativum L. exhibited genetic variation for plant height, primary and effective branches, days to flowering and maturity, umbels and umbellets per plant, grains per umbellet, thousand seed weight, straw yield and grain yield per plant and harvest index. Heritability estimates were high for days to flowering, thousand seed weight and days to maturity; moderate for plant height, straw yield, umbels per plant, umbellets per plant and number of primary branches; and low for harvest index, effective branches, grain yield per plant and grains per umbellet. Phenotypic correlations of grain yield per plant were highly significant and positive with umbellets per plant, umbels per plant, number of effective branches, straw yield per plant, number of primary branches, plant height, number of grains per umbellet and harvest index. Maximum direct contribution to grain yield per plant was made by umbellets per plant, followed by straw yield per plant, umbels per plant and grains per umbellet. Umbellets per plant made sizeable indirect effect via straw yield per plant. Straw yield per plant made sizeable indirect contribution via umbellets per plant.  相似文献   

5.
Summary Groups of 10 barley genotypes were selected for high grain yield under either high yielding (two groups) or low yielding conditions (two groups). The genotypes had a similar average grain yield across a wide range of yielding conditions, but differed in their linear response over environments (environmental sensitivity). The genotypes selected for high grain yield under low yielding conditions were less sensitive to changing environments than genotypes selected for high grain yield under high yielding conditions. The higher stability of genotypes selected under low yielding conditions was shown by both the linear regression analysis and the comparison of coefficients of variation. The use of a safety-first index showed that the probability of a crop failure of genotypes selected for high grain yield under high yielding conditions was between 1.8 and 2.7 times higher than for genotypes selected for high grain yield under low yielding conditions. The development of new cultivars for areas where a large proportion of the crop is grown by subsistence farmers should therefore be based on selection under low yielding conditions.  相似文献   

6.
In order to investigate the agricultural potential of the genus Vicia, and identify traits associated with productivity and responsiveness to environment, 34 undomesticated Mediterranean accessions representing Section Narbonensis (V. johannis, V. narbonensis) and V. sativa were grown in five contrasting environments in northern Syria (growing season rainfall: 76–290 mm).Highly significant genotype × environment interactions were observed for all traits. For most of the components of yield, accession mean performance (productivity)was highly correlated with responsiveness across environments (r = 0.59–0.96), as defined by joint linear regressions. Thus high yielding genotypes tended to be relatively more productive than low yielding genotypes under conditions that favoured high yields. Regression analysis revealed that mean site yields were positively correlated to rainfall (r = 0.85) and its attendant effect on growing season length as measured by cumulative season temperature and phenology (r = 0.59–0.81).In order to examine yield related traits independently of taxonomy, genotypes were grouped into three categories using K-means clustering based on productivity and responsiveness of seed, hay and biological yield. Highly productive/responsive genotypes were tall with high harvest index, large seeds and low fecundity (seeds and pods per plant), whereas unproductive/unresponsive plants tended to be short, highly fecund, with small seeds and low harvest index. Principal components analysis showed that responsiveness, in terms of seed, hay and biological yields, was closely related to phenological plasticity. Thus highly productive/responsive genotypes were able to start flowering earlier than unproductive/unresponsive genotypes in early environments, but significantly later in late, higher rainfall environments. Plant growth habit was also related to yield responsiveness. In environments with little biomass production the proportion of erect plants was high in all three categories. In more favourable, high biomass environments, the proportion of erect plants in unproductive/unresponsive genotypes fell dramatically, but was unchanged among productive/responsive genotypes. We suggest that for unproductive/unresponsive genotypes competition for light is increased under optimal growth conditions. We argue that the optimal combination of fixed and responsive traits in high yielding genotypes results in a `compound interest-type' response to more favourable environments. Highly productive and responsive genotypes can capture resources more effectively than their low yielding counterparts, leading to a positive relationship between performance and responsiveness for most components of yield. Differences in productivity and responsiveness for seed, hay and biological yield reflected Vicia taxonomy, increasing in the following order from low to high: V. johannis, V. sativa, the small seeded V. narbonensis (salmonea, jordanica, affinis) V. n. var. narbonensis, and finally V. n. var.aegyptiaca. V. n. var. aegyptiaca showed the most agricultural potential, since the taxon contained all the properties of productive/responsive genotypes listed above, yielding >1 t/ha under extremely arid conditions (104 mm),and >2.5 t/ha on 290 mm rainfall, confirming its potential for dry environments. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

7.
The availability of a reliable selection criterion for the identification of the most productive genotypes in early generations represents a crucial point in many breeding programs. The findings reported in the literature concerning the effectiveness of early generation testing for grain yield (GY) or harvest index (HI) are contradictory. In this work, we measured the response to selection for GY and HI applied in different generations, from F2 to F6 in nine segregating populations previously screened in F2 by means of visual selection. Genetic variability for HI and GY was found in most of the segregating populations. However, GY of spaced plants in F6 and F3 generations was weakly correlated with yield of F4 and successive generations grown at normal seed density. HI was of limited value as an indicator of yield potential.  相似文献   

8.
Summary The expected improvement in grain yield if selection was made for plant characters measured between flowering and maturity was evaluated in populations of rapeseed (Brassica campestris and B. napus) grown in a droughted environment. Drought was commenced at flowering in each species and measurements were made on plants at the commencement of the drought stress, during the stress treatment and at crop maturity.Substantial genetic and phenotypic variation was observed in yield as well as the different morphophysiological determinants of yield. In B. campestris no single parameter was found to be a suitable alternative selection criterion to yield since the correlated responses in yield if selection was for another character was lower than if selection was for yield alone. By the use of a selection index however, joint selection for yield, as well as harvest index, 1000 seed weight and seeds per pod, was expected to be 20% more effective than direct selection for yield under drought. In the B. napus population direct selection for flowering time or for harvest index was predicted to result in a genetic advance in yield equal to or greater than that obtained by direct selection for yield, whereas joint selection for flowering time and yield should result in a 16% greater yield increase. Selection for increased yield in these populations grown in droughted conditions is discussed.  相似文献   

9.
B. Ehdaie  J. G. Waines 《Euphytica》1989,41(3):183-190
Summary Nine pure lines of bread wheat collected from landraces of southwestern Iran and one local Iranian cultivar from the same area were used to estimate genetic variation and heritability for 12 developmental and yield component characters. Path-analysis was used to partition the genetic correlations between some of the characters into direct and indirect effects. Mean values for these lines were also compared with those of five improved cultivars from Iran and California. The goal of the experiment is to breed improved landraces and/or modern cultivars for areas of low input agriculture in southern California, southwestern Iran, and regions with similar environmental and agronomic conditions.Moderate genetic variation was displayed by the number of effective heads per plant, number of grains per head, and grain weight in the landrace genotypes. The heritability estimates ranged from 43 to 97%. Expected genetic advance with selection of the highest 5%, expressed as percent of the mean, was around 20% for number of heads per plant, number of grains per head, and 1000-grain weight.Days to booting, to heading, and to anthesis were positively correlated but none of them were significantly associated with days to maturity. Plant height had a negative genetic correlation with number of grains per head, 1000-grain weight, grain yield, and harvest index. The genetic correlation between number of heads per plant and number of grains per head, 1000-grain weight, and harvest index was also significantly negative. Harvest index had a negative genetic correlation with days to booting, to maturity, plant height, number of heads per plant, and straw yield and a positive correlation with number of grains per head, 1000-grain weight, and grain yield.Days to maturity, plant height, number of heads per plant, number of grains per head, 1000-grain weight, and harvest index each had a positive direct effect on grain yield. The first two characters exhibited the highest and lowest direct effects, respectively. The positive direct effects of days to maturity, plant height, and number of heads per plant, however, were partially or completely counter-balanced by their strong negative indirect effects through number of grains per head, 1000-grain weight, and harvest index. Pathanalysis indicated that late and tall landrace genotypes tend to produce more heads per plant, but with fewer number of grains per head, smaller grains, and lower harvest index.Comparisons between the local lines and the improved cultivars revealed that, in general, the former were much taller and produced a larger number of non-effective tillers. Mean number of grains per head, grain weight, harvest index, and grain yield of local lines were smaller than those of improved cultivars.Our observations indicate that the landraces could be improved by selecting for shorter genotypes with smaller numbers of tillers per plant, but with larger numbers of grains per head and heavier grains.  相似文献   

10.
高产冬小麦水分利用效率及其组分特征分析   总被引:17,自引:0,他引:17  
贾秀领  蹇家利 《作物学报》1999,25(3):309-314
依据8年田间和盆栽试验,分析了冬小麦基因型、密度和供水对水分利用效率(WUE)的影响。结果表明:当供水量变化范围较大时,总耗水(ET)和WUE呈显著线性负相关,ET对WUE的负效应明显大于产量(GY)对WUE的正效应。GY和ET有正相关趋势。当供水量变化范围较小时,GY和WUE呈显著线性正相关。蒸散效率(ETE)和收获指数(HI )都和WUE有正  相似文献   

11.
Summary Crosses of wild barley (Hordeum vulgare ssp. spontaneum and Hordeum vulgare ssp. agriocrithon) with Hordeum vulgare ssp. vulgare were used to select high yielding grain types under dryland Mediterranean conditions. No special difficulties were faced in making the crosses, in eliminating the brittle rachis genes from the grain types or in selecting 6-rowed types in crosses between 2-rowed wild barley and 6-rowed ssp. vulgare varieties. Brittle rachis genotypes, present in the segregating populations were used in developing self-reseeding permanent pastures for dry areas. The best selections were tested in seven trials during 1989–92 and some of them outyielded their parents and also the best improved check variety by 13–22%. Indications for transgressive segregation were obtained for grain yield, straw yield, total biological yield, harvest index and volume weight. The crude protein content of some of the selections was significantly higher than that of the checks. For breeding programs aiming at large seeds, special ssp. spontaneum lines should be used as parents. High grain yield was positively correlated with high straw yield, total biological yield, earliness in heading date, high harvest index and negatively with volume weight. It was concluded that unexploited useful genes, even when not directly observed in wild barley, could be transfered easily into high yielding genotypes by breeding.  相似文献   

12.
Besides oilseed rape and soybean, sunflower is one of the most important annual oilcrops. Apart from seed yield, which is the most important trait in many crops, oil yield is of utmost interest for sunflower breeders and farmers. Compared to the seed yield of sunflowers, their total biomass is often very high, and it is of great agronomic interest to increase the ratio of both parameters, which is defined as harvest index. With an increase in harvest index, improvements of resource‐use efficiencies can be expected. To generate an adequate seed yield, water and nutrients are key factors and their efficient use becomes increasingly important under conditions of aridity and higher production goals. A pot experiment was conducted in summer 2017 to determine differences in harvest index of various sunflower genotypes which could have an influence on the use efficiencies of water and nutrients (N, P, K). In total, 25 genotypes of different origin and with various morphological traits were investigated under optimal growth conditions. The harvest index varied from 29% to 47% and showed significant differences among some genotypes. The harvest index was less affected by the total biomass of the plants but more by the seed yield. The seed yield itself was mainly determined by the single seed weight rather than by the number of seeds. The experiment also confirmed significant positive correlations between harvest indices and all use efficiencies. Genotypes with high harvest indices were characterized by high oil concentrations in the seeds and particularly by high oil yields. In conclusion, cultivation of sunflower genotypes with high harvest indices most likely results in high water‐use efficiency and high nutrient‐utilization efficiencies as well as in high oil yields.  相似文献   

13.
Genetic improvement of soybean varieties released in India from 1969 to 1993   总被引:11,自引:0,他引:11  
Summary Soybean is an important oilseed crop in India and varieties with high yield potential are being developed since 1969. This study was conducted to assess the impact of breeding on yield and plant characteristics during the last 25 years. A 3-year field experiment was conducted to evaluate forty three soybean varieties belonging to two different selection cycles and representing most of the varieties developed in the domestic breeding programme of India from 1969 to 1993. Varieties resulting from selection cycle 1 showed 4 times higher seed yield and harvest index as compared to the farm traditional variety Kalitur. This yield increase was due to an increase in biomass, pods plant–1, mean seed weight and longer seed filling duration, but a reduced plant height and improved lodging tolerance, less seeds pod–1 and early flowering and maturity dates. The varieties of selection cycle 2 showed 19% higher seed yields and 16% increase in harvest index over selection cycle 1 accompanied by longer seed filling duration, more seeds pod–1 and reduced plant height. The annual genetic gain in seed yield of soybean varieties released in India from 1969 to 1993 was approximately 22 kg ha–1.  相似文献   

14.
Summary Changes in nitrogen (N) economy and N to dry matter (DM) relationships were studied for six cultivars of bread wheat (Triticum aestivum L.) released in Argentina at different times between 1912 and 1980. Experiments were performed on two successive years.N partitioning to reproductive organs was changed both at anthesis and at maturity. Grain N yield (GNY) was associated to both total N accumulated and N partitioning. Most of the changes produced by genetic improvement on N economy at maturity could be explained by parallel changes at anthesis. Neither biological N yield (BNY) at anthesis nor BNY at maturity showed any trend with the year of release of the cultivars.Grain N concentration (GNC) showed a negative trend with the year of release, and was inversely correlated to both grain yield (GY) and harvest index (HI). However, GNC was positively and significantly associated with NHI to HI ratio, indicating that the main reason for its behaviour along this century was the dilution of N on non N compounds.The N utilization efficiencies (NUE) for both GY and grain number were positively affected by breeding. Moreover, modern Argentinian cultivars are as efficient as the best cultivars showed by other authors.It is suggested that to increase GNC together with GY, breeders should improve N accumulation at anthesis maintaining high remobilization of vegetative N.  相似文献   

15.
Seed yield is a major breeding target in tetraploid red clover. We investigated if marker‐assisted parentage analysis can identify progeny plants with two high seed‐yielding parents in tetraploid red clover and if this technique is more advantageous than traditional half‐sib selection. Parentage analysis was successfully performed on the progeny from the 10% highest seed‐yielding genotypes from a second‐cycle family selection trial: 16.0% of progeny were identified with a high seed‐yielding father. However, progeny plants with two high seed‐yielding parents did not produce more seeds than traditionally selected progeny (27.3 g vs. 30.7 g/plant, respectively). The 10% highest seed‐yielding genotypes displayed on average 2% self‐fertilization. Four genotypes were self‐fertile with individual selfing rates up to 20%. Our results discourage the use of marker‐assisted parentage analysis to improve seed yield in tetraploid red clover when the material has been preselected for seed yield. Breeders should be aware that intensive selection for seed yield in tetraploid red clover may inadvertently lead to selection for increased self‐fertility, which may increase inbreeding in the long term.  相似文献   

16.
Successful castor (Ricinus communis L.) cropping in Greece depends on the yielding ability and yield stability of the cultivars (hybrids or inbreds) as well as the reliability of production systems. The adaptation and yielding ability of 19 modern castor oil genotypes were studied for 3 years in two sites of Northern Greece. Genotypes combining high seed and oil yield and desirable morphological characteristics were tested for 2 or 3 years, whereas the rest were tested for 1 year only. The growing period in both locations was long enough for ripening the first raceme and a number of secondary racemes depending on the genotypes. The plant height was dependent mainly on the genotypes but also was affected by the site and the year of the experimentation and ranged from 79 to 278 cm. The seed yield varied between 2.5 and 5.0 Mg ha−1, values that are among the highest reported in the literature. The seed yield was higher in the site where plants produced and ripened more secondary racemes. The seed oil content was dependent mainly on the genotype and ranged from 44.5 to 54.2%. The oil yield followed the changes in seed yield. The variation in seed yield between years was low and in most genotypes less than 20%. Results indicate that the castor oil crop was satisfactorily adapted in the area.  相似文献   

17.
For a better understanding of the inheritance of seed yield traits in Quinoa (Chenopodium quinoa) Willd., a half-diallelic crossing experiment with six diverse but uniform breeding lines was conducted. True hybrid plants were detected by means of differences in panicle colour in 14 out of the 15 crosses performed. The agronomic performance of 14 F2 populations and six parental lines was evaluated in field trials on fertile clay soil. General and specific combining ability of the lines (GCA and SCA) were estimated. Highly significant differences in GCA effects were found between the lines for plant height at maturity, early flowering, early maturity, seed yield and thousand seed weight. Significant SCA effects were only found for plant height at maturity. However, SCA effects were rather small and accounted for 7% of the total variance. The finding of large GCA effects and low SCA effects suggests that best selection results could be expected from crosses between the agronomic best performing genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

18.
There is no information on whether N efficiency in canola at maturity can be reliably determined by screening germplasm in the vegetative stage. Twelve canola genotypes identified in preliminary screening study as having either high or low N efficiency indices were tested for consistency in N efficiency between the vegetative stage and maturity. Plants were grown in a glasshouse under low or adequate N supply and N efficiency was assessed using the following criteria: dry weight at deficient N supply, relative yield at low vs. adequate N supply, and N utilisation efficiency. None of the 12 tested genotypes was classified as efficient or inefficient under all three criteria. One genotype (46C74) was classified as efficient under two criteria, and one genotype (Surpass 300 TT) was inefficient under two criteria. At maturity, three additional efficiency criteria were used: harvest index, N harvest index, and oil and protein concentration in seed. Two genotypes (Wesway and 46C74) (ranked as efficient at vegetative stage) remained efficient at maturity under most of the efficiency criteria used. On the other hand, genotype Surpass 603 CL ranked inefficient during the vegetative stage was ranked as efficient at maturity under two criteria. Overall, there was little consistency in the N efficiency ranking between vegetative stage and maturity in 12 tested genotypes. Screening canola germplasm for N efficiency for breeding purposes would therefore require an assessment at maturity.  相似文献   

19.
Capitalizing on the yield potential in available groundnut germplasm, and high stability of kernel yield are important requirements for groundnut producers in semiarid environments. Forty-seven groundnut genotypes were evaluated from 2003 to 2005 at 4 locations representative of the Guinea and Sudan savanna ecologies in Ghana. The objectives were to assess genotypic differences in reaction to early and late leaf spot infections under natural field conditions, assess the extent of genotype × environment (G × E) interaction for kernel yield, and determine the relationship between yield potential and yield stability. Genotypes differed significantly in their reaction to leaf spot infections indicated by the area under disease progress curve (AUDPC). Genotypic AUDPC was negatively correlated with maturity period (P < 0.01), with kernel yield (P < 0.05) at each of the 3 locations in the Guinea savanna ecology but not in the Sudan savanna ecology and with each of four stability parameters (P < 0.05). High or low yielding genotypes were grouped based on Dunnett’s test at P < 0.10. High yielding groups had significantly low AUDPC, high biomass, high partitioning of dry matter for kernel growth, and were later in maturity compared to low yielding genotypes. Significant G × E interaction effect for kernel yield was dominated mainly by the lack of correlation among environments variance (76–78%) relative to the heterogeneity of genotypic variance component (22–24%). Stability of yield assessed through the among-environment variance, Wricke’s ecovalence, and Finlay-Wilkinson regression coefficient revealed that genotypes in the higher yielding group were relatively unstable compared to the low yielding group. Indicated by the Kataoka’s index of yield reliability, however, relatively unstable genotypes in the high yielding group are expected to be more productive even under assumptions of high risk aversion (P = 0.75–0.95) compared to the more stable, low yielding genotypes. The findings indicate that deploying these recently developed germplasm in semiarid regions in West Africa provides a better match to farmers’ risk-averse strategies compared with the use of existing earlier maturing cultivars.  相似文献   

20.
K. V. Pixley  K. J. Frey 《Euphytica》1992,60(2):149-156
Summary Test weight, seed weight, and groat percentage are three common measures of grain quality for oat (Avena sativa L.). There is considerable disagreement, however, about the utility of each of these traits as measures of grain quality, so it is important to understand the genetic interrelations among them and between them and other agronomic traits. In this study, 50 random F2-derived F3 lines from each of 13 biparental oat crosses were evaluated. Genotypic variances, heritabilities, and genotypic correlations for test weight (TW), seed weight (SW), groat percentage (GP), grain yield (GY), harvest index (HI), plant height (PH), and date of heading (DH) were used to predict and compare direct and indirect gains from single-trait selection. Direct selection was always the most effective method for improving single traits; average predicted improvement of population means was 4% for TW, 10% for SW, 1% for GP, and 14% for GY when 10% selection intensity was applied. Genotypic correlation coefficients, averaged for all crosses, were 0.04 for TW with SW, 0.37 for TW with GP, -0.09 for SW with GP, and 0.29, 0.36, and 0.30 for GY with TW, SW, and GP, respectively. Thus, direct selection for TW, SW, or GP should not greatly affect the other two grain quality indicators. For the seven traits considered, there seemed to be no large advantage or disadvantage, in terms of correlated responses, associated with selection for any of the grain quality indicators.Contribution as Journal Paper No. J-14650 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2447.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号