Parasitic plants in the Scrophulariaceae invade the roots of neighboring plants in order to rob them of water and nutrients. A distinctive feature of these parasites is their ability to cue their development to small molecules released by host-plant roots. Evidence is continuing to emerge that parasite perception of host factors occurs via a redox-associated mechanism. Genes predicted to function during the early stages of parasite–host interactions have been cloned from both plant partners, and their characterization is providing a genetic framework on which to model subterranean plant–plant interactions.

Abstract Root parasites of the genus Orobanche are serious weeds in agriculture. An aseptic infection system of host roots using calli of three Orobanche species was developed for the study of host-parasite interaction. The response of calli to various hormonal combinations was studied, because a requirement for infection is the differentiation of root-like protrusions, which are capable of producing haustorial connections to the host. Infectious root-like protrusions develop under the influence of 0.5-1.0 mg l(-1) IAA, and under the combination of 0.2 mg l(-1) NAA with 5.0 mg l(-1) kinetin. These protocols produced root protrusions with pad-like structures that resembled attachment organs of Orobanche seedlings, and proved effective in parasitizing host roots. Direct contact with the medium inhibited haustorium development and prevented infection. To overcome this problem, certain root portions were isolated from the medium by inserting thin glass plates underneath. Calli were then placed on the raised root portions and successfully infected the roots and developed young Orobanche tubercles with vascular system that directly connected to the host.

In order to study the effect of different resistant sunflower root exudates on the germination of Cl.The dichloromethane extracts were then separated with silica gel column.The result showed that:(1)In a certain range of concentration,low concentration of sunflower root exudates promoted O.cumana seeds to germination,but high concentration inhibited it.(2)The germination rate was the highest when treated with 0.1 mg/mL dichloromethane extracts,O.cumana seeds germination rate under the ‘Xinghuodabaibian’ and ‘Baikuiza NO.9’ root exudates were 46.92% and 43.88%,immune variety ‘MGS’ was lower than the formers,germination rate was 27.81%.(3)The hexane-ethyl acetate(1∶1) fractions had the higher germination activity than other four fractions,O.cumana seeds germination rate under this fraction of ‘Xinghuodabaibian’,‘Baikuiza NO.9’ and ‘MGS’ were 49.90%,45.66% and 30.00%,respectively.(4)When added GR24 or dehydrocostus lactone to the root exudates of ‘MGS’,O.cumana seeds germination rate was decreased compare to GR24 or dehydrocostus lactone only,this indicated that the immune sunflower variety ‘MGS’ root exudates had the negative effect on the germination of O.cumana seed and there were some chemicals in its root exudates that inhibited the O.cumana seeds germination.

Broomrapes ( Orobanche spp. and Phelipanche spp.) are weedy root parasites that represent a major constraint for faba bean ( Vicia faba) cultivation in the Mediterranean area. Control methods are being developed that comprise techniques ranging from agronomical practices to precision farming, including chemical and biological control, genetic and induced resistance, modelling, and probably nanotechnology in a nearby future. However, the main concern is that to date, no single method of control provides complete protection against these parasites. For that reason, an integrated approach is needed in which a variety of such techniques are combined, in order to maintain parasite populations below threshold levels of damage.

通过2年盆栽接种鉴定试验,研究向日葵资源对列当的抗性,并对资源抗性规律进行分析.结果表明:对41份向日葵资源进行抗性分析,其中免疫材料25份,高抗材料2份,抗性材料7份,易感材料6份,高感材料1份；抗源在外源材料、油用材料、杂交种中广泛存在,本地资源中没有免疫材料.

研究证明化感作用需要满足如下4个方面:1)供体植物释放化感物质使得受体植物受到连续和定量的影响;2)能从供体植物中分离、鉴定得到化感物质,而且这些化感物质无论是在室内还是在田间,都能对在自然生态系统中邻近的伴生植物产生效应;3)供体植物产生和释放的化感物质在自然条件下能以足够的浓度到达邻近受体植物;4)以足够生物活性到达受体植物的化感物质能够被吸收并能够影响受体植物的生理生化过程,而且这种影响必须排除受体植物的生长发育不是由于竞争、动物侵害、病菌感染以及物理环境等非化感因素产生的影响。列当是列当科(Orobanchaceae)列当属(Orobanche)的根寄生植物,是一种寄生于其他植物根部的全寄生植物。全世界已发现100种列当属根寄生植物,在我国危害较为严重的是向日葵列当(O.cumana)和瓜列当(O.aegyptiace)。向日葵列当主要分布在陕西北部、河北、新疆、山西、内蒙古及东北三省,主要危害向日葵。瓜列当主要分布在新疆,危害瓜类、番茄、马铃薯。列当杂草的种子体积小、重量轻(3~6μg),而且每株植物可以生产大量种子。这些种子数量巨大且在土壤中可以保持生存力长达15~20年以上。成熟后的列当种子需要经过一段时间的后熟过程,完成后熟的列当种子在发芽之前需要1~2周时间在一定的温度和湿度条件下进行预培养,预培养后的列当种子还必须从寄主那里获得一个化学物质才能发芽,在自然条件下这种发芽刺激物质是由寄主或非寄主植物的幼根分泌提供的。获得该物质后,列当种子的"发芽管"可在数日内长出种皮,之后在吸器诱导物质的作用下很快形成吸器,与寄主根吸附并穿入根内后与寄主根的木质部形成联结,从寄主植物那里竞争性地夺取水分、养分及生长激素。由于列当属植物是根寄生杂草,在没有长出地面之前,它已经给作物造成严重的伤害,所以不易控制,有效的途径是尽量减少土壤中的列当种子含量。诱捕作物是指该作物的根系能够分泌列当属植物种子发芽的刺激物质,但是又不会被列当正常寄生,诱捕作物本身可以进行正常收获。由于列当属植物种子的生命只有一次,发芽后不能寄生就会死亡,这种发芽又称之为"自杀发芽",如此可以在列当找不到寄主之前死亡,从而大大降低土壤中列当的种子库。本文介绍了作者项目组从事采用化感作用与诱捕作物(小麦、玉米、棉花、大豆等)消除列当土壤种子库最新研究进展。

种植模式显著影响土壤理化生物学性质,并与作物土传真菌病害的发生密切相关。试验选择云南省具有代表性的红壤,设置烤烟-休闲-玉米(T-B-M)、烤烟-油菜-玉米(T-C-M)、烤烟-油菜-水稻(T-C-R)和烤烟-苕子-水稻(T-V-R)等4种轮作模式,利用化学、酶学分析及454高通量测序技术,研究了土壤养分、酶活性及真菌群落结构,旨在为烤烟的合理轮作提供科学依据。经16a的不同轮作种植后,土壤pH变化于5.6-6.4之间,仍然适合种植水稻、玉米、油菜和烤烟等多种作物。在T-V-R处理的土壤中,烤烟产量、烟叶产值和上中等烟比例最高,有机质比原初提高45.11%,碱解氮、有效磷和微生物量碳氮显著增加,蔗糖酶、脱氢酶、脲酶、磷酸酶和过氧化氢酶活性也显著高于其它轮作模式,说明T-V-R改善了土壤生态环境,促进了微生物繁衍,数量增加,活性增强。土壤真菌的18S rDNA读数依次为13097(T-B-M)、11345(T-C-M)、12939(T-C-R)和13763(T-V-R),分别代表530、378、395和581种(类)的真菌,由子囊菌门、担子菌门、接合菌门、壶菌门和尚待鉴定的真菌等构成,其中尚待鉴定的真菌属种和子囊菌门占绝大部分。在不同轮作处理的土壤中,前15种优势真菌的丰富度变化于29.46%-62.86%之间,优势菌株的相似性极低,说明土壤真菌的种群结构因轮作模式不同而异。T-V-R处理土壤中的真菌多样性指数最高,优势度指数最低,说明T-V-R轮作的土壤适合多种真菌的繁殖生长,种群数量增加。多种真菌共同存在,互相制约,可防止病原真菌过度繁殖,降低作物发生真菌病害几率。从作物产量和产值、土壤有机质、养分和真菌种群结构看,T-V-R优于其它3种轮作模式,值得推广应用。

水旱轮作是一种解决水稻连作障碍的重要种植模式,该技术方法简单,实用性强,目前已成为我国广泛采用的稻田耕作方式不过各地因为气候等因素的影响,其具体栽培措施存在着一定的差异本研究利用文献检索、内容归类的方法将稻田水旱轮作对作物生长、土壤特性的影响及目前常见的稻田水旱轮作方式进行了阐述,同时对稻田水旱轮作中存在的问题进行了分析,并提出建议,希望能为克服水稻连作障碍提供参考.

以宁夏回族自治区固原市当地种植的大麻为材料,采用盆栽试验探索大麻在不同生育期(苗期、快速生长期、开花期)的根际土、根、茎及叶的甲醇和水提取液对瓜列当和向日葵列当种子萌发的刺激效果。结果表明:根际土提取液刺激瓜列当种子的发芽率大于向日葵列当。大麻植株的甲醇和水提取液刺激瓜列当种子发芽率高低顺序为根>茎>叶,其中甲醇提取液刺激列当种子萌发率高于水提取液。根与茎的甲醇提取液刺激瓜列当和向日葵列当种子发芽率均显著相关(R2=0.833 6,P<0.001和R2=0.544 4,P<0.05)。植株的甲醇提取液对瓜列当种子的萌发诱导作用在快速生长期最强(45.2%),而向日葵列当种子的萌发诱导作用则在苗期最强(41.5%),水提取液对瓜列当及向日葵列当种子萌发诱导作用均在苗期表现为最强,发芽率分别为53.6%和23.7%。本研究结果表明,大麻在苗期和快速生长期可以作为列当的"捕获"作物,结论可为生物防除寄生杂草列当提供科学依据。

Sunflower broomrape is a noxious parasitic weed which has caused severe damage to crop ecosystems. Trap crops can release a mixture of allelochemicals to induce the germination of sunflower broomrape. We studied the allelopathic effects of soybean on sunflower broomrape. Fourteen common soybean cultivars were grown in pots. Samples were collected from soybean plants and rhizosphere soil at five growth stages (V1, V3, V5, R2, and R4). The allelopathic effects of soybean reached highest at the V3 stage. Methanolic extracts of soybean roots induced higher broomrape germination than methanolic extracts of stems or leaves. The germination rates induced by root extracts (10-fold dilution) were positively correlated with germination rates induced by stem (10-fold dilution) and leaf extracts (10-fold dilution). The broomrape germination rates induced by root extracts were also positively correlated with soybean nodule diameter and dry weight. The results indicated that soybeans could induce sunflower broomrape germination. We conclude that soybean has the potential to be used as a trap crop for sunflower broomrape.

通过盆栽试验和水培试验的方法在不同地区分别种植小麦、蚕豆和油菜3种作物,研究这3种作物的甲醇浸提液以及根系分泌物对向日葵列当种子萌发的影响。结果显示,小麦和蚕豆植株的根部甲醇浸提液以及根系分泌物对向日葵列当种子的萌发有较强的刺激作用,其中小麦甲醇浸提液处理的向日葵列当种子萌发率最高（41.5%）。蚕豆植株的甲醇浸提液和根系分泌物也对向日葵列当种子萌发有较强的影响,其中蚕豆根系分泌物处理向日葵列当种子的萌发率高达41.1%。综合得出,小麦和蚕豆的根部可能含有刺激向日葵列当发芽的物质,具有作为向日葵列当诱捕作物的可能性。

Orobanche cumanaWallr. (sunflower broomrape) is a devastating root parasitic weed, causing enormous crop losses worldwide. The question was whether or not switchgrass has the potential to be a rap crop forO. cumanacontrol. To answer this question, the field experiments, pot experiments, and laboratory experiments were conducted in this study. The ability of nine switchgrass (Panicum virgatumL.) cultivars to induceO. cumanaseeds germination was tested. Results indicated that root extracts shoot extracts, rhizosphere soil, and root exudates from switchgrass inducedO. cumanagermination. Ability to induce germination varied significantly among growing stages, with the earlier part of growing season (grown for 2 weeks) generally inducing the highestO. cumanagermination rates. The methanol was a more suitable solvent than distilled water for extracting germination stimulants from switchgrass plants. Ten-fold dilutions of the extracts generally induced higher germination rates than either undiluted or 100-fold dilutions. The germination rates ofO. cumanaseeds in shoot extracts treatments were positively correlated with those in the root extracts (R2= 0.6397;p< 0.01) and negatively correlated with those in the rhizosphere soil treatments (R2= 0.4433;p< 0.05). In conclusion, it is believed that switchgrass is a potential trap crop for the control of root parasitic weedO. cumana.

Orobanche cumana Wallr. (sunflower broomrape) is a devastating root parasitic weed, causing enormous crop losses throughout the world. Maize (Zea mays L.) is able to induce germination of at least two Orobanche species. Our question was whether or not maize has potential to be used as a "trap crop" for O. cumana. To answer this question, we screened four maize hybrids and their parental lines for their ability to induce O. cumana germination. The results indicated that rhizosphere soil, rhizosphere soil extracts, root extracts, and shoot extracts from three of the four maize hybrids and their parental lines induced significant O. cumana germination. Root extracts generally induced higher germination rates than shoot extracts. Ten-fold dilutions of the extracts generally induced higher germination rates than either undiluted extracts or 100-fold dilutions. The ability to induce germination varied significantly among maize hybrid and inbred lines, with the hybrid 3255 x 335 and its parental lines generally inducing the highest O. cumana germination rates. The genetic mechanism for the production of the chemical stimulant that induces O. cumana germination needs to be analyzed further; however, we propose that there is potential for a breeding program to be developed to produce maize lines with greater ability to induce O. cumana germination. These lines could be used as trap crops for the control of this devastating root parasitic weed.

Orobanche cernua Loefl. is a serious problem in tobacco growing in India. Including a trap crop in the rotation may help to reduce the problem. Two field experiments at die Agricultural Research Station, Nipani were conducted during 1993 94 and 1994 95 to identify potential trap crops for utilization in a cropping system with bidi tobacco. Trip crops reduced the population of broomrape; especially sunhemp and greengram proved to be effective. Broomrape reduced economic yield of tobacco by 42 % in the fallow treatment but was much less detrimental in the treatments with a trap crop. There was a close negative correlation between above-ground crop yield and the broomrape yield; broomrapes reduced the yields of their hosts much more than they invested in their own above-pound pans. Trap crops also had a positive effect on tobacco yield by other mechanisms than above-ground broomrape control, because yield increases were also observed on apparently non-infested plants. There was no systematic difference between the leguminous trap crops and the non-leguminous ones. Sunhemp and greengram are promising trap crops in a cropping system containing bidi tobacco in the areas where tobacco is grown in a long growing season during the late kharif/rabi seasons.

Growing trap and catch crops to decrease infestation of Egyptian broomrape ( Orobanche aegyptiaca Pers.) was tested in a 2-year field experiment supported by two pot experiments. Growing flax ( Linum usitatissimum L.) in two successive winter seasons or one summer cropping with mung beans (Phaseolus aureus Roxbg.) reduced early infestation of the parasite and significantly increased tomato ( Lycopersicum esculentum Mill.) vigour and production. However, the efficacy of using trap and catch crops for broomrape control in a heavily infested field was limited. Orobanche aegyptiaca attacked clover ( Trifolium alexandrinum L.), flax and mung bean and developed inflorescences. Various sources of the parasite showed different degrees of virulence to flax, from heavy attack and severe damage, to sparse attachment with no production of flowering shoots. The virulent subspecies attacked flax all year round, causing severe damage. Vetch (Vicia saliva L.) var. Sadot was not parasitized by O. aegyptiaca . Effets du lin (Linum usitatissimum L .) et d'autres plantes cultivées comme plantes pièges et h00tes pour lutter contre l'orobanche égyptienne (Orobanche aegyptiaca Pers .) L'utilisation de plantes cultivées comme pièges et h00tes pour diminuer l'infestation par l'orobanche égyptienne ( Orobanche aegyptiaca Pers.) a fait l'objet d'une expérimentation au champ sur deux ans ainsi que de deux expériences en pots. Si du lin ( Linum usitatissimum L.) était cultivé sur deux saisons hivernales successives ou lors d'une saison estivale avec de l'ambérique (Phaseolus aureus Roxbg.), l'infestation précoce de la tomate ( Lycopersicum esculentum Mill.) par le parasite était réduite, et sa vigueur ainsi que sa production étaient significativement augmentées. Cependant, l'efficacité des plantes cultivées pièges et h00tes pour lutter contre l'orobanche égyptienne dans des champs fortement infestés était limitée. Orobanche aegyptiaca attaquait le trèfle ( Trifolium alexandrinum L.), le lin et l'ambérique, et développait des inflorescences. Différentes sources du parasite montraient des degrés variés de virulence à l'égard du lin, allant d'attaques importantes qui occasionnaient de sévères dommages, jusqu'à des infestations éparses qui ne produisaient pas de tiges florales. Les espèces virulentes attaquaient le lin tout au long de l'année et causaient des dommages importants. La vesce (Vicia sauva L.) variété Sadot n'était pas parasitée par O. aegyptiaca . Saat-Lein (Linum usitatissimum L.) und andere Kulturen als Fangpflanzen und Zwischenfrüchte zur Bek01mpfung von Orobanche aegyptica Pers. In einem 2 01hrigen Freiland- und 2 Gef0108versuchen wurden Fangpflanzen und Zwischenfrüchte zur Minderung der Verunkrautung mit Orobanche aegyptica untersucht. Nach dem Anbau von Saat-Lein ( Linum usitatissimum L.) in 2 aufeinanderfolgenden Wintern oder einer Sommerkultur der Mungo-Bohne ( Phaseolus aureus Roxbg.) war bei der Tomate ( Lycopersicum esculentum Mill.) der frühe Befall durch den Parasiten herabgesetzt und Wachstum und Ertrag signifikant erh02ht. Die Wirksamkeit des Anbaus von Fangpflanzen und Zwischenfrüchten zur Bek01mpfung der Sommerwurz war jedoch auf stark verseuchten Feldern begrenzt. Orobanche aegyptica befiel Trifolium alexandrinum L., Saat-Lein und Mungo-Bohne und entwickelte Blüten. Die Virulenz verschiedener Herkünfte des Parasiten variierte von schwerem Befall und starkem Schaden bis schwachem Befall ohne Blütenbildung. Die virulente Unterart befiel den Lein das ganze Jahr über und führte zu schwerem Schaden. Die Sorte 'Sadot' der Saat-Wicke ( Vicia sativa L.) wurde von O. aegyptica nicht befallen.

Crop rotations with crops that are non-hosts of Striga were evaluated to reduce the Striga seed bank in the soil and increase farm productivity. Field experiments were conducted at two sites in western Kenya from 1996 to 1998 to study the effect of eight different crop rotations on Striga populations, Striga seed bank in the soil, maize yields and overall productivity of these cropping systems under low-input rainfed field conditions. A variety of crops, such as peanut, soybean, sunflower, pigeon pea showed greater economic potential than maize. The productivity of the best rotation under low soil fertility conditions was five times greater than maize mono-cropping. All crop rotation treatments reduced Striga seed numbers in the soil. Less Striga emerged if maize was planted after a two- season rotation that included pigeon pea. Crop rotation is probably one of the most effective ways to reduce Striga infestations and increase maize yields and income considering the limited resource base of small-scale subsistence farmers in sub-Saharan Africa.

We investigated the parasitism rate,dry weight of shoot and root,plant height of different Helianthus annuus varieties in seedling stage,measured the content of malondialdehyde (MDA) and the activities of enzyme PAL,SOD,POD and CAT in leaves after sowing 30,50 and 70 days,respectively.The seeds were sown in plastic pots and the soil was collected from continuous H.annuus cropping yield where the Orobanche cumana infection was severe.The results indicated that different H.annuus varieties in seedling stage exhibited obviously different resistance to O.cumana.Oil H.annuus varieties ‘T012244’ and ‘MGS’ were immune to O.cumana in seedling stage,‘S31’ and ‘Baiza 9’ showed a strong resistance to O.cumana.However,‘Xinghuodabaibian’ and ‘Baiza 6’ were sensitive to O.cumana in their seedling stage.Parasitization of O.cumana could restrain the growth of sensitive H.annuus varieties but hardly impact the growth of resistant H.annuus varieties.After parasitization of O.cumana,the MDA content and the PAL activity in leaves of ‘Xinghuodabaibian’ seedling increased significantly,which indicated an aggravated damage on H.annuus seedings.However,the MDA content in leaves of varieties‘T012244’and‘S31’ decreased and the activity of PAL did not significantly changed.The enzyme activities of SOD,POD and CAT in different H.annuus varieties all decreased after an initial increase.The change ranges of protective enzyme activities in immune varieties are bigger than that in sensitive varieties.The parasitization of O.cumana put the sensitive H.annuus varieties under environmental stress in seedling stage,defense reactions based on protective enzyme system were induced in seedling leaves.

向日葵列当(Orobanche cumana Wallr)是专寄生向日葵、烟草和番茄的寄生性杂草。由于近年内蒙古的向日葵种子大量无序从国外和区外调入,以及种植高感向日葵列当的食用向日葵品种,导致列当在自治区大范围扩展蔓延,特别是向日葵主产区巴彦淖尔市,造成严重的经济损失。文章通过查阅大量资料和田间调查,详述了列当的种类、分布、发生危害规律以及防控措施,为指导向日葵列当杂草的科学防除提供参考。

The parasitic weed Striga hermonthica is a major yield-reducing factor for cereal crops in savannah regions in Africa. This applies in particular to agro-ecosystems where a high human population density imposes a strong pressure on arable land. In these areas rotation with a leguminous trap crop is an attractive control method. Effectiveness of root exudates from varieties of cowpea (Vigna unguiculata), groundnut (Arachis hypogea) and soybean (Glycine max), on germination of S. hermonthica seeds were assessed in vitro. In addition, a 2-year study on effectiveness in situ was conducted with cowpea variety IT 90k-56 identified in vitro as a potential trap crop. Furthermore, cowpea variety TVX 1850-01F also identified in vitro as a potential trap crop, was tested on-farm. Results indicated that effectiveness of root exudates depends on Striga seed population and it is recommended that geographical origin and host crop of S. hermonthica, period of the year, as well as age of seeds be taken into consideration for identification of potential trap crops. There was no significant difference in Striga infestation of maize in 1995 if sowing of cowpea variety IT 90k-56 had been carried out on June 3 (early sowing), June 20 (intermediate sowing) or July 5 (late sowing) in 1994. However, plots where maize was grown in 1995 after they had been maintained as weed-free-fallow in 1994 showed significantly higher Striga infestation than plots where during previous year early sowing of trap crop had been undertaken. Maize grain yields in 1995 were significantly higher after trap cropping in 1994, regardless of sowing date, compared to weed free fallow plots. On-farm evaluation of cowpea variety TVX 1850-01F showed good results, reducing incidence of S. hermonthica on maize to nearly undetectable level after one season rotation.

We report the effects of the root hemiparasite Striga hermonthica (Del.) Benth. on the growth and photosynthesis of two cultivars of sorghum: CSH-1, a susceptible variety, and Ochuti, which shows some tolerance to S. hermonthica in the field. Within 4 d of parasite attachment to the host roots, infected plants of both cultivars were significantly shorter than uninfected controls. At 55 d, infected plants of both cultivars had significantly less shoot and root biomass, and significantly smaller leaf areas than uninfected controls. The dry weight of S. hermonthica attached to host roots was insufficient at this stage to explain the decreased growth in terms of a competing sink for carbon and nitrogen. Leaf chlorophyll and nitrogen per unit area were greater in infected plants of both cultivars compared with control plants. However, whereas photosynthesis and transpiration in young leaves of infected CSH-1 plants declined with time when compared with controls, the rates in infected Ochuti plants were similar to those in uninfected controls throughout the time course of observation. In both cultivars, a strong correlation was observed between the rate of photosynthesis and stomatal conductance during photosynthetic induction, but infection resulted in a much slower induction than in controls. In CSH-1 plants, both steady-state photosynthesis and stomatal conductance were lower than in controls, whereas in leaves of Ochuti steady-state photosynthesis and stomatal conductance eventually reached the same values as in the control leaves. Results from AlC i analysis and also from determination of 13 C isotope discrimination were consistent with a stomatal limitation to photosynthesis in the leaves of Striga -infected plants. The concentration of the plant growth regulator abscisic acid (ABA) was measured in the xylem sap of infected CSH-1 plants only, and was found to be twice that of uninfected plants. A possible role of ABA in determining host response to infection by S. hermonthica is discussed.

为探究地膜覆盖对旱作农田土壤水热状况、向日葵产量及减轻土壤风蚀效果的影响,通过大区试验对不同覆膜方式和覆膜时间处理的土壤温度、水分,向日葵生长状况、产量及土壤风蚀量进行了监测。结果表明,土壤温度表现为春季全覆膜>秋季半覆膜>春季半覆膜、全覆膜处理>半覆膜处理、垄上覆膜测定点>垄沟覆膜测定点;与春季半覆膜相比,春季全覆膜和秋季半覆膜全生育期累积地温分别增加了71.70℃和55.42℃,出苗时间分别提前了3d和1d,开花时间分别提前2d和1d,花期分别延长3d和1d,子实空秕率分别降低8.44和7.05个百分点,增产率分别为19.82%和9.84%,作物耗水量分别降低了5.82%和8.11%,水分利用效率分别提高2.70和0.73kg/(hm~2·mm);秋季半覆膜可降低土壤风蚀量,与大面积裸露农田相比可以降低土壤风蚀量73.87%左右,而且有利于增加冬春雨雪的储集,减少地表蒸发。试验认为春季全覆膜和秋季半覆膜具有提高土壤温度、增加土壤贮水量、促进向日葵提前出苗和开花并延长花期、增加向日葵产量和水分利用效率等作用,秋季半覆膜还具有减轻土壤风蚀的良好效果。

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The co-evolution of Orobanche spp.and their hosts within the same environment has resulted in a high degree of adaptation and effective parasitism whereby the host releases parasite germination stimulants,which are likely to be unstable in the soil.Our objective was to investigate whether extracts from non-host plants,specifically,Chinese medicinal plants,could stimulate germination of Orobanche spp.Samples of 606 Chinese medicinal herb species were extracted with deionized water and methanol.The extracts were used to induce germination of three Orobanche species;Orobanche minor,Orobanche cumana,and Orobanche aegyptiaca.O.minor exhibited a wide range of germination responses to the various herbal extracts.O.cumana and O.aegyptiaca exhibited an intermediate germination response to the herbal extracts.O.minor,which has a narrow host spectrum,showed higher germination rates in response to different herbal extracts compared with those of O.cumana and O.aegyptiaca,which have a broader host spectrum.Methanolic extracts of many Chinese herbal species effectively stimulated seed germination among the Orobanche spp.,even though they were not the typical hosts.The effective herbs represent interesting examples of potential trap crops.Different countries can also screen extracts from indigenous herbaceous plants for their ability to induce germination of Orobanche spp.seeds.The use of such species as trap plants could diminish the global soil seed bank of Orobanche.

As a devastating holoparasitic weed,Orobanche aegyptiacaPersoon. (Egyptian broomrape) causes serious damage to agricultural production and threatens economic development, which has raised widespread concern. The present study was conducted to determine whether lilies have the potential to be used as ‘trap crops’ for controllingO.aegyptiacaPersoon. In the experiments, the ability of three popular lily cultivars (LiliumOriental hybrids ‘Sorbonne’,LiliumLA (Longiflorum hybrids x Asiatic hybrids) hybrids ‘Ceb Dazzle’, andLiliumLongiflorum hybrids (L.formosanumxL.longiflorum) ‘L.formolongo’) to induceO.aegyptiacaPersoon. seed germination was assessed. Parts of the three lily cultivars, including the rhizosphere soil and underground and above-ground organs, all induced “suicidal germination” of parasiticO.aegyptiacaPersoon. seed at four growth stages. Specifically, Sorbonne and Ceb Dazzle behaved with similar allelopathy, and the bulb, scale leaf and aerial stem exhibited stronger allelopathic effects onO.aegyptiacaPers. germination compared to other organs. Aqueous L.formolongoleaf extracts may contain more stable, effective stimulants given that they induced the highest germination rate at 76.7% even though the extracts were serially diluted. We speculate that these organs may be advantageous in further isolating and purifying economical active substances that can be substitutes for GR24. These results indicate that lilies have the potential to be used as a trap crops or can be processed into green herbicide formulations that can be applied in agriculture production to rapidly deplete the seed bank ofO.aegyptiacaPersoon. parasitic weeds in soil.