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991.
992.
Multiple Allium accessions (garlic, and wild and ornamental Allium species) were screened for resistance using Penicillium allii and A. sativum (positive control). Single accessions of A. aflatunense, A. atroviolaceum, A. stipitatum, and Allium sp. remained asymptomatic. Single accessions of A. roseum and A. senescens, two accessions each of A. acuminatum and A. ampeloprasum and a single accession of A. moly displayed lesion expansion rates not exceeding 22%, 26%, 46%, 50%, 61%, 67% and 67%, respectively, of positive controls. Single accessions of A. sativum var. ophioscordon and A. scorodoprasum displayed rates not exceeding 68% and 55%, respectively, of positive controls with deep wounding, but did not consistently differ with shallow wounding. Accessions of A. canadense, A. sativum or A. longicuspis did not differ, differed inconsistently, or differed insubstantially from positive controls. Lesion expansion rates for A. acuminatum, A. ponticum and A. scorodoprasum were significantly less than in positive controls, but their small bulbs often rotted completely. Results document publicly available germplasm possessing significant resistance to P. allii. 相似文献
993.
Widespread adoption of genetically modified glyphosate-resistant (GR) crops in the US has dramatically changed the agricultural
landscape to one that selects for establishment and spread of weedy species resistant to glyphosate, a commonly applied herbicide.
Weed species that possess the means to readily spread across the landscape will be contained by weed management strategies
that limit weed establishment and prevent seed set. An empirically-derived simulation model was developed to explore GR Conyza canadensis spread in relation to characteristics of the agricultural landscape. C. canadensis seeds are carried in the wind and move among fields and therefore, access high quality habitat (GR crops) at long distances.
The baseline scenario was the current GR adoption levels in many US agricultural landscapes with corn and soybean rotated
annually. Alternate scenarios examined the interacting effects of management uniformity (GR crop adoption) and increased landscape
richness (three crops: corn, soybean, alfalfa, instead of two), over a 10 year simulation period. When landscape uniformity
increased (increased GR corn adoption), 3× more fields would be infested with the resistant biotype and a specific field would
have up to 24% greater likelihood of being infested compared to the current GR crop adoption levels. Increased landscape richness
(adding alfalfa as a third crop) slightly decreased GR C. canadensis abundance. Reduced GR management uniformity by way of reducing GR soybeans to half their current adoption levels had the
greatest impact on spread and prevented GR C. canadensis from reaching high abundance. Large-scale reliance on glyphosate for weed management has increased high-fitness habitat and
will result in rapid spread of glyphosate-resistant weeds. Without significant reductions of glyphosate use and without spatial
coordination of weed and crop management practices, GR weeds will continue to spread rapidly and impact agricultural practices
in areas reliant on glyphosate. 相似文献
994.
Six inorganic industrial‐waste materials (coal fly ash, bauxite‐processing mud, steel slag, two samples of air‐cooled blast furnace [BF] slag, and one sample of water‐cooled BF slag), along with wollastonite, were evaluated as fertilizer‐Si sources. Evaluation was carried out by analyzing total and extractable Si fractions in the materials, by incubating them at two rates with a Si‐deficient soil and measuring potentially available extractable Si and by measuring yield and Si uptake by two successive rice crops grown in the fertilized soils. Of the waste materials used, fly ash had the highest total Si content (29%) but a negligible quantity was present in extractable forms. Steel slag and bauxite‐processing mud had only 5%–7% Si content while BF slags contained 14%–18% Si. All materials, other than fly ash, increased the amount of extractable Si present in the soil. Additions of steel slag and bauxite‐processing mud caused greater increases in Si extractability than the air‐cooled BF slags while water‐cooled BF slag–treated soils contained notably high acid‐extractable Si. Because of the alkaline nature of the materials, and their reaction products, there was a positive relationship between extractable soil Si and soil pH. However, an equilibration experiment using NaSiO3 as the Si source confirmed that Si solubility in the soil decreased with increasing pH. Dry‐matter yields of rice, at the lower rate of Si addition, were increased by all treatments other than fly ash. The higher rates of steel slag and bauxite‐processing mud caused yield depressions. Total Si uptake by rice was increased by all treatments, other than fly ash, and was greater at the higher rate of Si addition. It was concluded that the BF slags are the most effective waste materials as fertilizer‐Si sources and that, in slag‐amended soils, CaCl2 and NH4 acetate are the most reliable soil‐test extractants. 相似文献
995.
996.
马铃薯Y病毒(PVY)对晚疫病(Phytophthora infestans)的影响 总被引:4,自引:0,他引:4
在温室条件下,以脱毒马铃薯为试材,研究了PVY对晚疫病的影响。结果表明:PVY汁液接种脱毒马铃薯28d后,用晚疫病菌接种,其孢子囊悬浮液浓度为1.0×104个·mL-1时,PVY对晚疫病的抑制作用最明显;马铃薯植株体内PVY的浓度与晚疫病的发病率、病斑大小及病情指数呈负相关。说明马铃薯感染PVY后诱导了植株对晚疫病的抗性,不同因子影响降低了马铃薯感Y病毒叶片对晚疫病菌的感病性。 相似文献
997.
质粒介导的喹诺酮类耐药基因在鸡源大肠杆菌中的流行 总被引:5,自引:0,他引:5
为了解河南省质粒介导的喹诺酮类耐药基因(qnrA、qnrB、qnrS、qepA和aac(6′)-Ib-cr)在产16S rRNA甲基化酶鸡源大肠杆菌中的流行与分布,分别设计特异性引物对2005-2008年在河南省病鸡病料中分离保存的158株16SrRNA甲基化酶阳性鸡大肠杆菌进行PCR扩增。结果显示,在158株产16S rRNA甲基化酶鸡源大肠杆菌中,qnrA、qnrB、qnrS、qepA和aac(6′)-Ib-cr的检出率分别为0.6%,2.5%,13.9%,2.5%和58.2%。提示质粒介导的喹诺酮类耐药基因在河南省产16S rRNA甲基化酶鸡源大肠杆菌中普遍存在,且以qnrS和aac(6′)-Ib-cr为主。 相似文献
998.
油菜品种资源抗(耐)菌核病田间鉴定分析 总被引:1,自引:0,他引:1
对来源于德国、瑞典、日本、中国等15个国家的油菜品种资源田间鉴定抗(耐)菌核病性的结果表明:免疫品种有43份,高抗(耐)品种有194份,中抗(耐)品种有100份,低抗(耐)品种有201份,感病品种有151份,分别占有效鉴定总数689份(次)的6.24%、28.16%、14.51%、29.17%、21.92%。同时文章还介绍了油菜品种资源抗(耐)菌核病性的评价方法。 相似文献
999.
1000.
本文通过梳理抗战时期晋绥边区亩产计量单位及其换算比例,估测边区粮食亩产发现,抗战时期晋绥边区亩产经历了先下降后回升的变化趋势,有的甚至超过战前水平。当然,不同质量土地的亩产差别很大,山地亩产一般不过十几斤,梁地亩产仅30—50斤,水地亩产则可达到200—300斤。显然,仅仅用下降来描述抗战后粮食亩产的变化是较为笼统的。抗战时期边区亩产的回升,缓解了边区的粮食恐慌,不仅使农业支持抗战、支持边区经济成为现实,而且构成近代中国农业经济增长的重要组成部分。 相似文献