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1.
Crop rotation showed a pronounced effect on incidence of tomato damping-off and onion (Fusarium) basal rot as well as on the soil population of the two disease incitants. Out of nine rotation systems, wheat/sorghum and wheat/maize preceding tomato diminished damping-off while clover/maize, lentil/sorghum, wheat/sorghum and wheat/maize preceding tomato diminished damping-off while clover/maize, lentil/sorghum, wheat/sorghum and wheat/maize preceding onions increased basal rot incidence. First crops of the rotation system as well as the second crop were of noticeable effect onRhizoctonia solani andFusarium oxysporum f. sp.cepae as onBacillus subtilis (antagonistic to both fungi) population in soil. Almost all rotations increased population ofF. oxysporum f. sp.cepae andB. subtilis in soil while response ofR. solani was variable. The results show thatBac. subtilis did not correlate with tomato damping-off or onion basal rot. There must be some other factors found in the soil that play a role in effect of crop rotation on disease incidence.  相似文献   

2.
Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.  相似文献   

3.
Summary Tests with Bromophos applied to stored grain in Yugoslavia Tests were made with Bromophos for controlling beetles infesting stored grain and for protecting non infested grain. Bromophos-emulsion (1g/qm) sprayed in empty stores always effected 100% mortality in beetles of generaTribolium, Oryzaephilus andCalandra. Bromophos proved to be more durable than Malathion, Lindan and DDVP, By using Bromophos-powder (1,2%; 100g/100kg = 12 ppm) wheat and maize were protected against grain pests. At the end of two months the mortality of beetles in wheat (in laboratory) amounted to 97–99%. In maize the effect lasted only two months.

Institut za Zaštitu Bilja, Yu 11 081 Beograd-Zemun, Nemanjina 6, P. O. Box 127, Jugoslawien.  相似文献   

4.
A normal variety of rice (Oryza sativa L.cv. Taichung 65, T65c), its isogenic dwarf line (T65d 1), and a semidwarf variety of a different line (Oryza sativa L.cv. IR8, IR8) were studied. The results were compared with those of an isogenic dwarf line (Rh i) of wheat straw, which was previously reported. Expression of the dwarf gene,d 1, on the chemical composition and the structural features of lignin present in rice internodes differs from that in an isogenic dwarf line of wheat. The differences include the lignin content, total yield of alkaline nitrobenzene oxidation products, and distribution of wall-bound hydroxycinnamic acids. There was, however, no difference in the syringyl/ guaiacyl nuclei (S/V) molar ratio and neutral sugar composition. The lignin composition of rice straw cell walls, particularly that of the dwarf variety, contained more of the condensed structure and fewer syringyl nuclei than lignin in wheat straw cell walls. It is suggested that crosslinking between lignin and polysaccharides by ester-ether bridges via ferulic acid contributes to the mechanical properties of the cell walls of rice straw. Thus the chemical and structural characteristics of lignin in rice straw differ to some extent from those of other temperate grasses, such as wheat (Triticum aestivum) and phalaris (Phalaris aquatica), as reported previously. This can probably be attributed to the water environment of rapidly growing rice seedlings, but it also depends on the genetic variety of the rice plant.  相似文献   

5.
The effect of perennial mulches on moisture status, soil characteristics and on crop yields (maize-wheat rotation) was evaluated from 1986 through 1989 in a silty loam acidic soil (pH 5.6, PWP 11.4 & FC 25.6%) at the Research Farm of the Central Soil & Water Conservation Research & Training Institute, Dahra Dun. Mulch materials, comprised of leaves of Leucaena leucocephala, Eucalyptus hybrid, Shorea robusta, Broussonatia paprifera or Puerarua hirsuta (chopped) @ 4 t/ha were applied just after sowing of wheat and the residual effect of applied mulch was seen in kharif maize each year.The distribution of profile moisture revealed that at the time of sowing of wheat the soil water content did not differ with depth (0–90 cm). With the advancement of time, the magnitude of moisture distribution changed. At various crop growth stages the highest amount of water was found in the plots mulched with S. robusta followed by E. hybrid. All the mulch materials, except B. paprifera, lowered the soil pH, the maximum effect was noted with E. hybrid (pH reduced from 5.6 to 5.0). After three years, N and K content of soil were found to be greatest with the application of L. leucocephala whereas the highest P content was observed in B. paprifera mulched plots.The highest wheat grain yield (2.46 t/ha) was recorded with L. leucocephala and minimum under control (2.11 t/ha) which represents a gain of 11.7 per cent. Maximum maize grain yield (0.73 t/ha) was found in S. robusta mulched plots followed by L. leucocephala (0.63 t/ha) and the minimum in the control (0.51 t/ha).  相似文献   

6.
Striga hermonthica is a major constraint to smallholder subsistence agriculture production in the sub-Saharan African region. Low soil fertility and overall environmental degradation has contributed to the build-up of the parasitic weed infestation. Improved cropping systems have to be introduced to address the interrelated problems of S. hermonthica and soil fertility decline. Thus, the effects of improved fallow with leguminous shrub Sesbania sesban on maize yields and levels of S. hermonthica infestation on farm land in the bimodal highlands of western Kenya were investigated. The experimental treatments were arranged in a phased entry, and randomized complete block scheme were six months Sesbania fallow, 18 months Sesbania fallow, six months natural fallow consisting of regrowth of natural vegetation without cultivation, 18 months natural fallow, continuous maize cropping without fertilizer application, and continuous maize cropping with P and N fertilization. Results show that Sesbania fallows significantly (p<0.05) increase maize yield relative to continuous unfertilized maize. S. hermonthica plant populations decrease in continuous maize between the first season (mean = 428 000 ± 63 000 ha−1) and second season (mean=51 000 ± 15 000 ha−1), presumably in response to good weed management. S. hermonthica seed populations in the soil decrease throughout the duration of the experiment in the continuous maize treatments. Short-duration Sesbania fallows can provide modest yield improvements relative to continuous unfertilized maize, but short-duration weedy fallows are ineffective. Continuous maize cultivation with good weed control may provide more effective S. hermonthica control than fallowing.  相似文献   

7.
Yin  Wandong  Xue  Qi  Su  Lei  Feng  Xiaopei  Feng  Xinlei  Zheng  Yanghui  Hoffmann  Ary A. 《Journal of pest science》2021,94(3):795-804

Niche separation between competing species is a central issue in ecology. As two of the most important pests worldwide of cereal production, Rhopalosiphum padi primarily dominates stems and basal leaves of wheat plants, whereas Sitobion avenae is common on the upper leaves and ears. Here, we investigated this microniche separation by considering effects of food resources and microclimates on the behavior and performance of R. padi and S. avenae on tissues from individual wheat seedlings. Wheat leaves provided favorable food for both aphid species and this tissue had high free amino acid and low soluble sugar compared with wheat stems. Both species preferred microclimates in the lower area of the seedlings where humidity was relatively higher and temperatures were relatively lower. In terms of performance, R. padi was more sensitive to microclimate effects than S. avenae, while the latter species was relatively more sensitive to limiting food resources. These factors may help explain why R. padi is relatively more common on lower microhabitats of seedlings, in contrast to S. avenae, contributing to the microspatial distribution of these species more generally. This information contributes to a better understanding of the relationship between these aphids and their host plants, which may assist in control strategies targeting these aphids.

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8.
The study investigated diversity and frequency of occurrence of glomale (Arbuscular- or Vesicular Arbuscular-) mycorrhizal fungi on three farming systems in a drought prone and nitrogen deficiency site in southern Malawi. The farming systems comprised of two agroforestry systems of Sesbania sesban (L) Merr intercropped with maize and Sesbania macrantha E Phillips & Hutch. intercropped with maize and a maize monocrop systems without fertilizer, with nitrogen, phosphorus and a combination of nitrogen and phosphorus. Species diversity and species frequency of occurrence were examined in soil samples obtained in the dry and wet seasons. Twelve glomale mycorrhizal species were recorded, four species being in the genus Acaulospora, four in Glomus, two in Gigaspora and two in Scutellospora. Species diversity in the two agroforestry systems were not significantly (p ≤ 0.05) different but had lower species diversity than maize monocrop with only Sesbania macrantha intercropped with maize significantly (p ≤ 0.05) lower. Species diversity was significantly increased by the inorganic nitrogen fertilizer. Inorganic phosphorus fertilizer had no effect. The study shows that the occurrence and persistence of glomale species are influenced by agroforestry combinations, and that the spores of most species are tolerant to dry conditions. Only four species responded to fertilizer application with the occurrence of spores of some species high and some low. Management practices have great implication in the persistence of spore propagules of glomale species. The order Glomale was revised in 2001 and upgraded to a phylum Glomeromycota.  相似文献   

9.
Three multipurpose tree species (MPTS)-leucaena (Leucaena leucocephala), sesbania (Sesbania sesban var. nubica) and pigeonpea (Cajanus cajan) were pruned at a height of 60 cm above the ground every two months, and resulting plant biomass was incorporated into the soil as green manure. For comparison, maize (Zea mays) stover was also incorporated into some plots, while some other plots were left fallow. Varying quantities of plant biomass which were incorporated into the soil over a period of 12 months caused large changes in major soil plant nutrients, and it substantially improved soil fertility. To test for improved soil fertility, test crops of maize and beans (Phaseolus vulgaris) were grown on the plots after six biomass incorporations of 4806, 13603, 16659 and 7793 kg. ha–1yr–1 for pigeonpea, sesbania leucaena and maize, respectively. Responses of the test crops indicated that sesbania and leucaena green manures improved maize stover, cobs and grain yields; and bean haulms and grain yields by 77.6% when compared to fallow plots. Residual effects of green manures still resulted in significant (P < 0.05) yield differences in the test cropin the third testing season. Economic significance of green manures in increasing food crop yields to small scale farmers is discussed.  相似文献   

10.
Phosphorus (P) in soil exists both in organic and inorganic forms and their relative abundance could determine P supplying capacity of soil. Differential input of exogenous and plant-mediated phosphorus and carbon in soil under different land-uses could influence P availability and fertilizer P management. While the effect of land-use on soil organic carbon (SOC) is fairly well-documented, its effect on soil P fractions is relatively less known. We investigated the effect of different land-uses including rice–wheat, maize–wheat, cotton–wheat cropping systems and poplar-based agroforestry systems on soil P fractions and organic carbon accrual in soils. Total P concentration was the highest under agroforestry (569 mg P kg?1) and the lowest under maize–wheat (449 mg P kg?1) cropping systems. On the contrary, soils under rice–wheat had significantly higher available P concentration than the agroforestry systems, probably because of higher fertilizer P application in rice–wheat and prevailing wetland conditions during rice growth. In soils under sole cropping systems viz. rice–wheat, maize–wheat and cotton–wheat, inorganic P was the dominant fraction and accounted for 92.2–94.6% of total P. However, the soils under agroforestry had smaller proportion (73%) of total P existing as inorganic P. Among soil P fractions, water soluble inorganic P (0.13–0.26%) represented the smallest proportion inorganic P in soils under different land-uses. Agroforestry showed significantly (p < 0.05) higher concentrations of SOC than the other land-uses. Soil organic C was significantly correlated with soil P fractions. It was concluded that poplar-based agroforestry systems besides leading to C accrual in soil result in build-up of organic P and the P supplying capacity of soil.  相似文献   

11.
Host plant preference of the Russian wheat aphid Diuraphis noxia (Kurdj.) was studied on 11 cultivars of 9 plant species: winter barley, spring barley, winter wheat, spring wheat, rye, oat, Triticale, canary grass, red millet yellow millet and maize. Seeds of the host plants were sown in a circle near the edge of pots. The host plant choice was evaluated 24 hours after releasing 55 Diuraphis noxia female adults in the middle of each pot. The suitability of different hosts for aphid development was evaluated 2, 7 and 14 days after infestation based on the mean number of Russian wheat aphid individuals per plant. Red millet, yellow millet and maize were chosen by significantly fewer aphids than grain crops. Winter and spring barley were chosen as hosts most frequently, and the progeny production was also the highest on these plants. The growth rate of D. noxia was significantly affected by the host plants and the date of assessment and their interaction.  相似文献   

12.
The potential of allye cropping systems to sustain a high productivity with low external inputs and the reduction of maize/weed competition through weed suppression in different alley cropping and sole-cropped mulched systems was studied in Costa Rica at CATIE. Data were recorded eight years after establishment of the experiment. Plant residues ofErythrina poeppigiana trees (10 t/ha dry matter) planted at 6 by 3 m reduced weed biomass by 52%, whileGliricidia sepium trees (12 t/ha dry matter) planted at 6 by 0.5 m reduced weed biomass by 28%, in comparison to controls.Erythrina had a considerable impact on grass weeds, whileGliricidia reduced the incidence of some dicot weeds. Weed competition significantly reduced maize yield in all systems. Nevertheless weed suppression contributed to the higher maize grain yield underErythrina andGliricidia alley cropping of 3.8 t per hectare as opposed to the unmulched control yield of 2.0 t per hectare.  相似文献   

13.
The first record of a “field” infestation of stored lettuce seeds (Lactuca sativa) byTineola bisselliella (TB) is reported. The pest is able to consume almost the whole kernel ofL. sativa including the shell. The ability od TB to damage selected stored cereal, pulse and oil seeds under laboratory condition was evaluated. In maize and wheat, germ area was damaged preferably and the germination decreased considerably. TB was unable to infest and damage sound seeds of rape and beans ofPhaseolus vulgaris and soya. These findings enabled the development of a vegetarian diet for laboratory rearing of TB. The pest status and hazards resulting from cross-infestation is discassed.  相似文献   

14.
Zusammenfassung In Baden-Württemberg treten Sch?den an Mais durch das Stengel?lchen(Ditylenchus dipsaci), Wiesen?lchenPratylenchus spp.) und das Getreidezysten?lchen(Heterodera avenae) auf. Es wird über das Stengel?lchen berichtet. Der Mais lagert bei einer H?he von 20 bis 40 cm (Umfallkrankheit; in Frankreich: verse précoce). Vergleiche gesunder und kranker Pflanzen haben ergeben: geringer Befall der Pflanzen mitD. dipsaci = schwacher oder kein Schaden; starker Befall der Pflanzen mitD. dipsaci = schwerer Schaden. Schon eine verh?ltnism? ?ig schwache Bodenversenchung kann bei nassem und kaltem Wetter nach der Saat des Maises schwere Sch?den verursachen. Andererseits bleiben trotz starker Bodenverseuchung Sch?den aus, wenn das Wetter nach der Saat trocken und warm ist. Je ungeeigneter das Klima eines Gebietes für den Mais ist, um so h?ufiger sind die Sch?den. Die Bodenart hat keinen Einflu?. Die Populationen, die die Umfallkrankheit beim Mais verursachen, k?nnen keiner bestimmten.D. dipsaci-Rasse zugeordnet werden. Die Krankheit ist keine Folge eines zu h?ufigen Maisanbaues. Sie kann auch schon beim erstmaligen Anbau von Mais auf einem Acker auftreten. Der Sch?dling vermehrt sich in den anderen Kulturen der Fruchtfolge. Gute Wirte sind:Beta-Rüben, Leguminosen, Hafer, Roggen, Weizen. Ein schlechter Wirt ist die Gerste. Aus den Ergebnissen zahlreicher Bodenuntersuchungen ist keine Beziehung zwischen den Vorfrüchten der letzten 3 bis 6 Jahre und der Verseuchung des Bodens mitD. dipsaci abzuleiten. Es bestehen Unterschiede in der Anf?lligkeit verschiedener Maissorten.
Summary Injurios nematodes in maize in Baden-Württemberg I. The lay of maize by Ditylenchus dipsaci In Baden-Württemberg there are damages in maize by the stem nematode(Ditylenchus dipsaci), lesion nematodes (Pratylenchus spp.) and the cereal cyst nematode(Heterodera avenae). In this paperD. dipsaci is discussed. Maize at the hight of 20 to 40 cm lays byD. dipsaci (Umfallkrankheit; in France: verse précoce). Comparisons of healthy plants with infested ones have shown: a weak population ofD. dipsaci in the plants = weak or no damages; a strong population ofD. dipsaci in the plants = heavy damages. A relatively low population ofD. dipsaci in the soil can cause heavy damages if the weather is cold and moist after the sowing of the maize. On the other hand, even high populations in the soil cause no harms, if the weather is warm and dry after sowing. The less favourable the climate of a province for the cultivation of maize is, the more frequent are losses. The kind of soil has no influence on the disease. The population, causing the lay of maize, cannot be classified to a certain race ofD. dipsaci. The disease is not the result of a frequent culture of maize on a field. It can occur at the first culture of maize on a field. The pest develops in other crops during the rotation. Good hosts are beets, legumes, oats, rye, wheat. A bad host is barley. The results of many soil extractions did not show any relation between the crops cultivated during the last 3 to 6 years and the population inD. dipsaci, in the soil. There are differences in the susceptibility of different maize-varieties.
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15.
Phytotoxic effects ofGliricidia prunings were tested on maize seedlings in the laboratory and on maize and cowpea seedlings in the field. In the laboratory test, growth of maize seedlings was significantly depressed by addition of leachate ofGliricidia prunings. In the field, leaf, chlorosis of maize and cowpea seedlings occurred when mulched withGliricidia prunings; number of affected leaves increased with increasing mulch rate. Maize was more susceptible than cowpea. This phytotoxic effect, however, did not reduce growth of maize and cowpea seedlings in the field. ApplyingGliricidia mulch one week before planting eliminated the phytotoxic effects on maize.  相似文献   

16.
In Ireland, the grey field slug (Deroceras reticulatum) is the predominant slug pest species in arable crops. It can cause enormous damage, but the knowledge about its feeding biology is limited. Adult species were reared under laboratory conditions, and the survival, feeding activity, and weight change of slugs when feed on maize, peas, or wheat seeds were investigated. An especially high mortality was experienced in the wheat treatment. It was hypothesised that the high mortality was due to a Fusarium species, however, a Fusarium infection of the wheat seeds was not confirmed. The weight change of the slugs was very variable due to a high egg production of some slugs. A second experiment examined the food choice and feeding activity of D. reticulatum when offered a choice of the three seed types. Most of the slugs preferred to feed on a mixture of seeds, but the highest feeding activity was recorded on the pea seeds.  相似文献   

17.
A field study was carried out on a six-year-old on-farm field trial during long-rains season (April–August) 2003 to investigate the effect of improved fallow systems and phosphorus application on arbuscular mycorrhiza fungi (AMF) symbiosis in maize. The trial comprised of maize rotated with a fast growing leguminous Crotalaria grahamiana fallow and a non-leguminous Tithonia diversifolia fallow for 3 years followed by continuous maize. The experiment was randomized complete block design with three cropping (continuous maize, Crotalaria fallow and Tithonia fallow) systems and two phosphorus levels (0 and 50 kg P/ha). AMF colonization in maize roots, maize yield and macro-nutrients uptake were recorded. Phosphorus applications improved (P < 0.05) early (<8 weeks old maize) AMF colonization, nutrient uptake and maize yield in improved fallow systems. Greater differences due to phosphorus application were noted in maize in Tithonia fallow than in Crotalaria fallow. Following phosphorus application, a positive relationship existed between early AMF colonization and maize yield (r = 0.38), and phosphorus and nitrogen uptake (r = 0.40 and r = 0.43, respectively), demonstrating the importance of phosphorus fertilization in enhancing low-input technologies (improved fallows systems) in phosphorus deficient and acidic soils of western Kenya.  相似文献   

18.
In the Central Highlands on Kenya, Grevillearobusta (A. Cunn.) trees are commonly planted on maize (Zeamays L.) fields. This type of production system covers about 750 000ha in the highland area around Mt Kenya. Knowing the influence oftrees on maize yield would help to regulate the density and size distribution ofthe tree cover. The spatial distribution of trees varies from rather uniform toextremely aggregated patterns, calling for a spatial modelling approach. Thisstudy employed three different spatial competition index types to model theeffect of trees on the maize yield at a given location. The maize yield wasexpressed as a function of competition index, which was calculated from thediameters and distances of trees. The data were collected from 14 maize fields,and included measurements on 857 trees and 2514 one-m2 maize plots. The models indicated that high competition by treesdecreases maize yields considerably, but at the field level the decrease issmall with normal tree stockings (about 200 trees per hectare). Characteristicto the models was low degree of explained variance, which was partly due to highsampling error in maize yield measurement and low variation in competition(places with high competition by trees were seldom planted with maize). One ofthe maize yield models was combined with an earlier simulation program forG. robusta. The simulator allows one to predict thetemporal development of any G. robusta – maize fieldin Central Kenya. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

19.
Modelling population dynamics of the maize pest Diabrotica virgifera virgifera LeConte (western corn rootworm; Coleoptera: Chrysomelidae) requires knowledge on the growth rate (=net reproductive rate) of the species. We investigated the generational (=annual) growth rate of D. v. virgifera in isolated maize fields in southern Hungary and eastern Croatia over several years. The population densities of D. v. virgifera were assessed by absolute counts of emerging adults in 90 gauze cages per study field. Emergence ranged from 1.3 to 30.7 adults per m2 in continuous maize field sections, and from 0.3 to 5.1 adults per m2 in adjacent first-year maize sections. The annual growth rates of D. v. virgifera ranged from 0.5 to 13, and averaged in close to 4. These experimentally assessed growth rates could complement growth estimates in population dynamic models, particularly those for forecasting the population growth to economic thresholds or for estimating population build-ups after new introductions of this alien species in Europe. As an example, the determined growth rate was used to estimate that the first documented successful introduction of this species into Europe occurred between 1979 and 1984, which is 8–13 years before the detection of this species and its larval damage in maize fields near Belgrade, Serbia, in 1992.  相似文献   

20.
Improved fallows have been used to reduce time required for soil fertility regeneration after cropping in low input agricultural systems. In semi-arid areas of Southern Africa, Acacia angustissima and Sesbania sesban are among some of the more widely used improved fallow species. However the residual effects of improved fallows on soil hydraulic properties during the cropping phase is not known. The aim of this study was to quantify the residual effects of fallows and tillage imposed at fallow termination on soil hydraulic properties (infiltration rates, hydraulic conductivity and soil porosity) during the cropping phase. Treatments evaluated were planted fallows of Acacia angustissima, Sesbania sesban and natural fallow (NF) and continuous maize as a control. Steady state infiltration rates were measured using a double ring infiltrometer and porosity was calculated as the difference between saturated infiltration rates and tension infiltration measurements on an initially saturated soil. Unsaturated hydraulic conductivity (Ko) and mean pore sizes of water conducting pores were measured using tension infiltrometer at tensions of 5 and 10 cm of water on an initially dry soil. While there was no significant difference in steady state infiltration rates from double ring infiltrometer measurements among the fallow treatments, these were significantly higher than the control. The steady state infiltration rates were 36, 67, 59 and 68 mm h-1 for continuous maize, A. angustissima, S. sesban and NF respectively. Tillage had no significant effect on steady state infiltration rate. Pore density at 5 cm tension was significantly higher in the three fallows than in maize and varied from 285–443 m−2 in fallows, while in continuous maize the pore density was less than 256 m−2. At 10 cm tension pore density remained significantly higher in fallows and ranged from 4,521–8,911 m−2 compared to 2,689–3,938 m−2 in continuous maize. Unsaturated hydraulic conductivities at 5 cm tension were significantly higher in fallows than in continuous maize and were 0.9, 0.7, 0.8 cm and 0.5 cm h−1 for A. angustissima, S. sesban, NF and continuous maize, respectively. However there were no significant treatment differences at 10 cm tension. Fallows improved infiltration rates, hydraulic conductivity and soil porosity relative to continuous maize cropping. Through fallowing farmers can improve the soils hydraulic properties and porosity, this is important as it affects soil water recharge, and availability for plant growth  相似文献   

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