列当(Orobanche spp. and Phelipanche spp.)种子的采集与预处理方法

列当(Orobanche spp.and Phelipanche spp.)是一种在世界范围内危害严重的根寄生杂草,防除列当的研究也越来越多。正确地采集和预培养列当种子是获得正确防除列当研究结果的前提。列出了大田正确采集列当种子的方法,以及对采集到的种子进行过筛提纯、加洗洁精和吐温20清洗后,再表面消毒和预培养,并通过发芽试验检验此方法的可行性。结果表明,经过处理的向日葵列当、瓜列当种子的发芽率最高分别为54.4%、59.1%。此方法可以应用于列当的采集和预处理过程中,可为列当研究和防除提供参考。     

我国新疆焉耆垦区作物轮作种植模式防除列当的有效性研究

本研究以新疆地区危害最严重的向日葵列当和瓜列当为研究对象,通过室内水培试验和室外盆栽模拟轮作试验来探究焉耆垦区轮作模式对两种列当的防除效果。结果表明,室内水培试验中各轮作作物的根系分泌物及萃取相刺激瓜列当种子的萌发率均在20.0%以下,但刺激向日葵列当种子产生的萌发率达到了50.0%以上;室外盆栽模拟轮作试验中,甜菜、小麦、辣椒与加工番茄轮作后,瓜列当的寄生数量未显著降低;但与向日葵轮作后,向日葵列当的寄生数量显著减少了60.0%以上。不同品种甜菜、辣椒和小麦地上部甲醇提取液刺激瓜列当种子的萌发率均低于10.0%,但是刺激向日葵列当种子的萌发率均达70.0%以上。本研究表明新疆焉耆垦区轮作种植模式不能有效防除瓜列当,但模式中的轮作作物均能够有效防除向日葵列当。本研究结果为防除新疆焉耆垦区向日葵列当和瓜列当提供理论依据。     

烟草及向日葵上列当Orobanche cumana的发生及其生物防治

 近年,在河北省部分烟草和向日葵种植地发现大量寄生性杂草列当发生并造成严重为害。经鉴定为向日葵列当Orobanche cumana Wallr.。向日葵、烟草、番茄和黄瓜等作物的根分泌物能够刺激向日葵列当O. cumana种子萌发,而油葵根的分泌物则不能刺激向日葵列当种子萌发。利用列当致病镰刀菌L2菌株进行田间生物防治,防治效果达到92.4%。L2菌株对小麦、玉米、棉花、烟草和向日葵等作物生长无影响,L2菌株粗毒素能够抑制列当种子萌发,并造成列当种子萌芽管损伤。     

农田草害的综合防除(续)

4.肥料与杂草防除肥料与杂草防除的关系表现在两个方面:一是没有腐熟的有机肥,往往给农田带来了大量的杂草种子。因为很多杂草种子具有休眠特性和高发芽势、耐高温、耐冰冻的特性,这些杂草种子随肥料进入农田造成危害。此外用草塘泥、河泥也往往把很多水生杂草的繁殖体种子带进了农田。另一方面使用无机肥的目的是促进农作物生长发育,如果作物种群一开始处于劣势的情况下施用化肥,由于杂草夺取肥料的能力比作物要强得多,反而助长了杂草。所以在这种情况下应该首先消灭杂草,再使用无机肥料。如若作物种群苗期生长正常,那么     

新疆列当种类、危害与防治现状

列当是一种根部全寄生恶性杂草,影响作物生长,对农业生产造成了巨大破坏。目前,列当防治措施主要包括轮作、种植诱捕作物、化学防治等,但尚无适用于大部分地区及作物的有效防治措施。本文综述了新疆列当种类、寄生特点、危害和目前采取的防治措施,并对列当的萌发刺激物、防治机理和化学除草剂在大田应用提出展望,以期为新疆相关防治工作提供参考。     

检疫性寄生杂草列当及其防除与检疫

检疫性寄生杂草列当及其防除与检疫黄建中，李扬汉（南京农业大学杂草研究室２１００９５）列当属（Ｏｒｏｂａｎｃｈｅ）属于列当科（Ｏｒｏｂａｎｃｈａｃｅａｅ），全世界约有１００种。分布中心在地中海（如埃及、叙利亚等）和亚洲西部地区，东欧和原苏联南部、高加索...     

检疫性全寄生杂草种子萌芽的诱导

五角菟丝子和向日葵列当,分属于菟丝子属 Cuscuta 和列当属 Orobanche。菟丝子属植物的叶绿体片层少,RUBP 化酶(光合酶)活性小,几乎全靠从寄主植物(如大豆、花生、柳等)的茎、叶中吸收水分和养分,称为茎、叶全寄生植物;列当属植物不含叶绿素,全靠从寄主植物(如向日葵、烟草、西瓜、哈密瓜等)根中吸收养分和水分,称为根全寄生植物。由于全靠寄主而生活,全寄生植物为害重,防除困难,引起了科学工作者广泛重视和研究。要对这些全寄生杂草进行研究,关键一步就是要对这些杂草种子进行萌芽的诱     

根寄生杂草种子萌发剂概述

独脚金属（Striga spp.）及列当属（Orobanche spp.和Phelipanchce spp.）杂草是世界范围内对农业生产危害严重的根寄生杂草,主要依靠寄生茄科、豆科、谷类等作物获得水分和营养。根寄生杂草种子只有在合适的萌发诱导物（如独脚金内酯）刺激下才能萌发。文章从根寄生杂草的分类、分布及危害,种子萌发剂类型及适用范围,种子萌发剂独脚金内酯的生物合成及分离鉴定,根寄生杂草种子萌发诱导剂的作用机制以及种子萌发过程中激素间协同调控作用等方面进行了综述,并展望了种子萌发剂设计筛选及其在根寄生杂草化学防控中的潜在应用前景。     

土壤中寄生性杂草弯管列当种子检测体系的建立及应用

弯管列当是一种根寄生性杂草,其种子微小,在土壤中极难检测。为了建立土壤中弯管列当种子定量检测体系,本研究扩增了弯管列当的ITS基因,以含ITS基因的阳性质粒为参考构建了标准曲线,并对该标准曲线进行验证。结果表明该方法具有高效、灵敏的特点,为弯管列当的检测检疫提供高效方法。同时我们从不同地块采集了土壤,通过该方法检测了土壤中弯管列当的种子数量,为弯管列当的发生预测预报提供了依据。     

用荧光显微镜检测和鉴定列当属种子

列当属Orobanche L.植物是危害极大的寄生性杂草,能侵害多种大田作物,如番茄、大豆、向日葵等的根部,导致减产甚至绝收。许多国家将其列为恶性杂草或检疫对象。为避免在已受列当侵染的大田中种植可能的寄主作物,以及防止列当随     

Seed viability determination in parasitic broomrapes (Orobanche and Phelipanche) using fluorescein diacetate staining

Fluorescein diacetate (FDA) was investigated as a potential viability stain for seeds of holoparasitic broomrapes Orobanche and Phelipanche (Orobanchaceae), using four weedy and two non-weedy taxa. FDA viabilities were compared with the currently used 2,3,5-triphenyl tetrazolium chloride (TTC) test, and in vitro germination induced by the strigolactone analogue GR-24. Viable FDA-stained seeds were characterised by bright yellow–green fluorescence under 450–490 nm blue light. These viable seeds could be discriminated from non-viable seeds, in which low levels of fluorescence, similar to non-stained control seeds were observed. FDA viabilities were not significantly different from those obtained using the TTC stain; however, viability values for both stains were consistently higher than levels of artificially induced germination. Positive TTC-staining showed continuous variation that was difficult to interpret. Nevertheless, the TTC test does not involve grinding seeds, and therefore probably remains a practical alternative to FDA for screening soil samples contaminated with Orobanche and Phelipanche seeds, which indicates different applications for the two viability tests. Interestingly, the strigolactone analogue GR-24 only induced germination in O. crenata , P. ramosa and O. minor , suggesting a high specificity towards this germination inducer among the species investigated. We suggest that FDA-staining provides a potential alternative to the currently used TTC test for seed viability assays for Orobanche and Phelipanche , and other parasitic weeds which are an obstacle to crop cultivation.     

In vitro culture of Orobanche ramosa

Orobanche spp. (broomrapes) are holoparasites that subsist on the roots of many important crops and can considerably reduce yield. The control of Orobanche spp. includes physical, chemical and biological methods. Interactions between parasitic angiosperms and their hosts first occur at the level of parasite seed germination. The seeds of all Orobanchaceae germinate in soil under natural conditions only in response to specific chemical exudates from the host plant. This study describes the influence of different plant growth regulators and host plant root exudates on germination and development of calli from Orobanche seeds in vitro . The effect of indole-3-acetic acid, gibberellic acid and kinetin on the germination of Orobanche seeds varied with concentration. These plant growth regulators also affected the period of germination and the structure of calli and protrusions. An in vitro system for the collection of tobacco root exudates was established. Compounds released from the host roots of three different tobacco cultivars were found to provoke high levels of germination of the Orobanche seeds without any period of pre-conditioning. This study developed methods for the investigation of host–parasite interactions and the effect of germination stimulants in Orobanche spp.     

Fenugreek root exudates show species-specific stimulation of Orobanche seed germination

Various Orobanche species are weedy and cause severe reduction in the yields of many important crops. The seeds of these parasitic weeds may remain dormant in the soil for many years until germination is stimulated by the release of a chemical signal from a host plant. In order to determine the effects of fenugreek root exudate on the induction of Orobanche crenata, Orobanche ramosa and Orobanche foetida seed germination, root exudate was collected from hydroponically grown fenugreek seedlings. Fractionation patterns obtained from column and thin layer chromatography of the fenugreek root exudate showed a set of metabolites differing in their polarity with stimulatory activity on Orobanche seed germination. The crude root exudate stimulated both O. ramosa and O. crenata seed germination to the same level caused by the synthetic germination stimulant GR24 at 10 mg L^?1. It also stimulated O. foetida seed germination which did not respond to GR24. Active fractions of root exudate stimulated the germination of Orobanche species differentially.     

Germination response of Orobanche seeds subjected to conditioning temperature, water potential and growth regulator treatments

Broomrapes (Orobanche spp.) are parasitic weeds that cause significant losses of crop yield. Experiments were conducted to investigate the seed response to the artificial germination stimulant GR₂₄ in three species of Orobanche subjected to preconditioning under various temperatures, water potentials and with plant growth regulators. The highest germination percentages were observed in Orobanche ramosa, Orobanche aegyptiaca and Orobanche minor seeds conditioned at 18°C for 7 days followed by germination stimulation at 18°C. With the increase of the conditioning period (7, 14, 21 and 28 days), the germination percentage of O. ramosa and O. aegyptiaca progressively decreased. When conditioned at −2 MPa, the germination percentage was lower than at 0 and −1 MPa, especially at 13 and 28°C. Orobanche minor seeds could retain relatively high germination if conditioned at 18, 23 or 28°C, even after significantly extended conditioning periods (up to 84 days). GA₃ (30–100 mg L⁻¹), norflurazon and fluridone (10–100 mg L⁻¹), and brassinolide (0.5–1.0 mg L⁻¹) increased seed germination, while 0.01 mg L⁻¹ uniconazole significantly reduced germination rates of all three Orobanche spp. The promotional effects of GA₃ and norflurazon and the inhibitory effect of uniconazole were evident, even when they were treated for 3 days. Germination of Orobanche seeds was much lower when the unconditioned seeds were directly exposed to GR₂₄ at 10⁻⁶ m . This early GR₂₄-induced inhibition was however alleviated or even eliminated by the inclusion of GA₃ or norflurazon (10–50 mg L⁻¹) in the conditioning medium. On the contrary, the inclusion of uniconazole increased the inhibitory effect of GR₂₄, particularly in the case of O. ramosa.     

Strigolactone deficiency confers resistance in tomato line SL-ORT1 to the parasitic weeds Phelipanche and Orobanche spp

The parasitic flowering plants of the genera Orobanche and Phelipanche (broomrape species) are obligatory chlorophyll-lacking root-parasitic weeds that infect dicotyledonous plants and cause heavy economic losses in a wide variety of plant species in warm-temperate and subtropical regions. One of the most effective strategies for broomrape control is crop breeding for broomrape resistance. Previous efforts to find natural broomrape-resistant tomato (Solanum lycopersicon) genotypes were unsuccessful, and no broomrape resistance was found in any wild tomato species. Recently, however, the fast-neutron-mutagenized tomato mutant SL-ORT1 was found to be highly resistant to various Phelipanche and Orobanche spp. Nevertheless, SL-ORT1 plants were parasitized by Phelipanche aegyptiaca if grown in pots together with the susceptible tomato cv. M-82. In the present study, no toxic activity or inhibition of Phelipanche seed germination could be detected in the SL-ORT1 root extracts. SL-ORT1 roots did not induce Phelipanche seed germination in pots but they were parasitized, at the same level as M-82, after application of the synthetic germination stimulant GR24 to the rhizosphere. Whereas liquid chromatography coupled to tandem mass spectrometry analysis of root exudates of M-82 revealed the presence of the strigolactones orobanchol, solanacol, and didehydro-orobanchol isomer, these compounds were not found in the exudates of SL-ORT1. It can be concluded that SL-ORT1 resistance results from its inability to produce and secrete natural germination stimulants to the rhizosphere.     

Germination stimulatory activity of bacterial butenolide hormones from Streptomyces albus J1074 on seeds of the root parasitic weed Orobanche minor

Damage caused by Orobanchaceae root parasitic weeds is a substantial agricultural problem for global food security. Many studies have been conducted to establish practical methods of control, but efforts are still required for successful management. Seed germination of root parasitic weeds requires host-derived germination stimulants including strigolactones (SLs). Studies on SLs have revealed that a butenolide ring is the essential moiety for SL activity as a germination stimulant. Interestingly, recent studies have revealed that butenolide hormones regulate the biosynthesis of secondary metabolites and mediate communication in actinomycete bacteria. Because of the structural similarity between SLs and the bacterial butenolides, we evaluated the germination stimulatory activity of butenolides isolated from Streptomyces albus J1074 on root parasitic weeds. These butenolides were found to specifically induce seed germination of Orobanche minor. Our findings contribute to understanding the molecular mechanisms of germination stimulant perception and to the development of a method for their biological control.     

The implication of stubble tillage for weed population dynamics in organic farming

In practical farming, early and shallow stubble tillage is carried out post‐harvest to stimulate germination of freshly ripened crop and weed seeds, to kill the resulting seedlings and hence to reduce the input into the soil seedbank. Additionally, it aims at reducing perennial weeds by mechanical damage. In this paper, field experiments and laboratory studies are presented which show that stubble tillage can reduce perennial weeds. However, it had a variable effect on annual weeds. After 5 years of experimentation, no effect of stubble tillage was seen on the aboveground vegetation. In contrast, the soil seedbank of the control was roughly doubled where the stubble had been left uncultivated until autumn ploughing. These results indicate that practical experience which assumes that stubble tillage reduces annual weed populations may be correct, despite the fact that in other published studies stubble tillage exerted no control on annual weeds or had a variable effect. This will have practical application in organic arable production systems.     

Possible involvement of gibberellins and ethylene in Orobanche ramosa germination

Summary Six inhibitors acting at different stages of gibberellin biosynthesis, applied during conditioning of Orobanche ramosa seeds, reduced subsequent germination in the presence of GR₂₄ (a strigol analogue). Ethylene seems to be involved in the induction of germination of conditioned seeds by GR₂₄, as inhibitors of its synthesis or action, applied to conditioned seeds, also strongly reduced induction of germination by GR₂₄. Exogenous ethylene did not induce germination of conditioned seeds, but 2-chloroethylphosphonic acid was able to do so. When inhibitors of gibberellin biosynthesis were applied to conditioned seeds in the presence of GR₂₄, they inhibited germination. These same inhibitors also strongly inhibited germination of conditioned Striga hermonthica seeds in response to GR₂₄; this inhibitory effect was reversed by the addition of 2-chloroethylphosphonic acid. The effect of these inhibitors on S. hermonthica , in which ethylene is a necessary mediator of germination induction by GR₂₄, strongly suggests that ethylene synthesis is also required for the induction of O. ramosa seed germination by GR₂₄. These growth regulators, which inhibit the two steps of germination in O. ramosa , could be useful for the development of methods for early season control of this parasite.