Growth and fitness of triazine-susceptible and triazine-resistant common waterhemp (Amaranthus tuberculatus var. rudis)

Two greenhouse trials were conducted over a 2 year period (2004 and 2005) to compare the relative growth potential and fitness of triazine-susceptible (TS) and triazine-resistant (TR) waterhemp biotypes. Waterhemp plants from each biotype were grown in 6 L pots in the greenhouse in a completely randomized design. There was no difference in leaf number, plant height, plant biomass, time to bud or time to flower between the two biotypes. The TR female waterhemp plants produced 30% less reproductive biomass and 39% less seed than the TS biotype. The fitness penalty associated with triazine resistance was related to reproductive capability, not to vegetative growth.     

Shikimate accumulation in nine weedy species following glyphosate application

Glyphosate is commonly used in a variety of weed control scenarios and plants respond biochemically by continuing to attempt to push carbon through the shikimate pathway. The result is an accumulation of shikimate in sensitive plants in the days immediately after application. This research determined shikimate accumulation dynamics in nine problematic plant species from 0 to 6 days after treatment (DAT). Ambrosia artemisiifolia, Trifolium repens and Conyza canadensis showed rising concentrations through 6 DAT to >4000 mg L^?1. Chenopodium album, Xanthium strumarium and Urochloa platyphylla showed concentrations levelling off to a constant of about 2000 mg L^?1. Ambrosia trifida, Amaranthus palmeri and Polygonum pensylvanicum generally showed lower levels of shikimate accumulation and concentrations were decreasing after 3 DAT. No apparent relationships were evident between shikimate accumulation pattern and plant growth rate or speed of glyphosate activity. There also appeared to be no pattern in the shikimate accumulation trends that would allow for an informed decision as to which of these species would be most likely to develop glyphosate resistance. Shikimate concentrations were in agreement between field and glasshouse conditions for C. canadensis, but did not agree with those from A. palmeri.     

Evaluation of herbicides for selective weed control in grafted watermelons

Grafted watermelon is a combination of two plants, aCucurbita rootstock and a watermelon scion. Therefore, weed control for this crop faces a unique problem: the safety of the selected herbicide has to be tested for both plants that make up the grafted plant. In the current study, we evaluated the usage safety of selected herbicides forCucurbita rootstocks as well as for non-grafted and grafted watermelons, and the control ofAmaranthus retroflexus by the same herbicides. In addition, the residual effect of the herbicides was tested for seeded and transplanted melons representing the next crop following cultivation of the grafted watermelons. The herbicides ethalfluralin, pendimethalin, ethalfluralin, sulfentrazone, oxyfluorfen, chlorsulfuron and clomazone were chosen for their potential to controlA. retroflexus. Pendimethalin and trifluralin were less effective than the other herbicides in controllingA. retroflexus; sulfentrazone, chlorsulfuron and clomazone were not safe for use on the tested cucurbits and thus cannot be recommended for weed control in grafted watermelons. Therefore, by eliminating the herbicides that are toxic to cucurbits and those that are ineffective forA. retroflexus control, it was concluded that the herbicides ethalfluralin and oxyfluorfen can be considered effective and safe for weed control in grafted watermelons. It was shown that trifluralin and oxyfluorfen have the potential to be applied effectively through the drip irrigation system. http://www.phytoparasitica.org posting Jan. 10, 2008.     

棉田反枝苋和马齿苋对草甘膦的抗药性

为明确棉田反枝苋和马齿苋对草甘膦的抗性水平,采用培养皿种子法和整株检测法分别测定了7个省18个采样点反枝苋、马齿苋的抗性水平,并采用紫外分光光度计测定采样点反枝苋、马齿苋体内莽草酸含量变化的差异。结果表明:采样点地区的反枝苋和马齿苋对草甘膦存在不同程度的抗药性,2种监测法的抗性趋势基本一致,其中陕西西安采样点的反枝苋和新疆疏勒采样点的马齿苋处于敏感水平,河北曲周采样点的反枝苋抗性倍数最高。植物体内莽草酸积累变化与植物抗性水平相关,抗性较低的植物体内莽草酸积累量普遍高于抗性较高的植物。     

ITS序列及其SNP位点在外来入侵杂草长芒苋、西部苋和糙果苋物种鉴定中的应用

对于以种子形态为物种主要识别依据的口岸部门,外来入侵杂草长芒苋、西部苋和糙果苋一直是鉴定的难点。本文对34种苋属植物的ITS序列和26SrDNA进行分析,通过SNP变异位点及特异性引物,借助PCR-RFLP方法,对长芒苋、西部苋与糙果苋进行快速、准确的分类鉴定。ITS序列分析表明,长芒苋种内变异小,种间变异显著,可与其他苋属植物明显区分。西部苋与糙果苋之间ITS序列差异小,需依据SNP位点来区别。     

Effects of Nitrogen on the Competitiveness of Echinochloa colona and Amaranthus viridis with Direct-seeded Rice

Information on weed competitiveness responses to added nitrogen （N） is required to assist with the development of appropriate fertilizer management strategies where weed competition is anticipated. A greenhouse study was conducted to examine the effects of four N rates on the competitive ability ofEchinochloa colona and Amaranthus viridis grown together with direct-seeded rice. Rice and each weed species were grown in a replacement series design at added N rates of 0, 50, 100, and 150 kg ha1. Replacement series diagrams for relative yield showed that competitive ability ofE. colona increased with added soil N. Values of weed aggressivity index for E. colona also significantly increased with the addition of N in the soil. In the absence of added N, A. viridis was more competitive than rice but this relationship slightly changed as N was added. However, values of weed aggressivity index of were statistically similar at all N rates. The results suggest that the competitiveness ofE. colona increased with added soil N, and A. viridis unchanged by soil N levels. Both weed species were different in their response to higher N levels. Information gained in this study could be used to demonstrate the importance of effective weed and fertilizer management.     

叉枝鸦不同溶剂萃取物对反枝苋种子萌发及幼苗生长的影响

为了确定沙漠野生植物叉枝鸦葱拟化感物质的有效部位,为分离纯化拟化感先导化合物奠定基础,试验研究了叉枝鸦葱醇提物的四种不同极性溶剂萃取物对反枝苋种子萌发、幼苗生长发育的影响.采用培养皿法,在人工气候箱模拟条件下,测定各萃取物对反枝苋种子萌发、幼苗生长发育的影响.结果表明各萃取物对反枝苋种子萌发、幼苗生长发育均有不同程度的...     

苋菜培养细胞中角鲨烯的提取与含量测定

[目的]建立苋菜培养细胞中角鲨烯提取与含量测定的方法。[方法]以苋菜叶片为外植体诱导愈伤组织,用皂化和不同有机溶剂浸泡的方法提取苋菜愈伤细胞中角鲨烯,并用HLPC测定其含量。[结果]用皂化法提取苋菜愈伤细胞的角鲨烯含量高于用有机溶剂浸泡方法提取的含量。苋菜愈伤细胞提取的角鲨烯在HLPC上与标准品出峰时间一致,而且该峰与其他峰有很好的分离。[结论]皂化法是提取苋菜愈伤细胞中角鲨烯较好的方法。用HLPC测定苋菜愈伤细胞中角鲨烯含量可行。     

氟磺胺草醚对野苋菜和灰绿黎的室内活性测定

在室内条件下,测定了氟磺胺草醚对野苋菜和灰绿黎的杀草活性。结果表明:氟磺胺草醚对野苋菜和灰绿黎的EC50值分为200.282 8 mg/L和233.529 8 mg/L,氟磺胺草醚对野苋菜和灰绿黎具有很好的抑制效果。     

苋菜愈伤组织诱导的研究

以苋菜种子为试材诱导无菌苗,取幼苗期下胚轴、子叶和壮苗期茎段、叶片作为外植体,比较不同组织部位对愈伤组织诱导效果的影响,并探讨不同质量浓度NAA对苋菜愈伤组织诱导的影响。结果表明,以苋菜壮苗期叶片和茎段为外植体的愈伤组织诱导率比幼苗期下胚轴和子叶高,表现为叶片>茎段>下胚轴>子叶;苋菜壮苗期茎段、叶片在MS+6-BA 0.5mg/L+NAA 3.0mg/L培养基上诱导愈伤组织的效果最好,诱导率分别为98.7%和99.3%。