枝顶孢霉对毒光盖伞子实体形成的影响

报道枝顶孢霉Acremonium strictum对毒光盖伞Psilocybe venenata子实体形成的影响。拮抗试验结果表明它们之间存在着较弱的干扰竞争作用;人工培养时,毒光盖伞混合菌株产生大型、小型和畸形3种类型的子实体,推测毒光盖伞畸形子实体的形成可能是枝顶孢霉寄生的结果,为毒光盖伞的人工栽培和进一步合理利用、野生蕈菌的驯化提供了理论依据。     

分离自蜻蜒虫草的拟青霉属一新种

本文描述了拟青霉属(Paecilomyces)一新种—蜻蜓拟青霉(P. odonatae),该菌分离自蜻蜓虫草(Cordyceps odonatae),与其它种的典型区别特征是它具有拟青霉型产孢结构,产椭圆形链状排列的分生孢子和枝顶孢霉型产孢结构,产柱状粘成团排列的分生孢子.     

捕食真菌及其相关丝孢菌中国的新记录

本文报道了来自我国云南及长白山地区的捕食真菌及其相关丝孢菌的8个新记录种,即纺锤孢指隔孢(Dactylella atractoides),狭长孢指隔孢(D. stenomeces)、顶毛孢单顶孢(Monacrosporium acrochaeturn),泡环单顶孢(M. aphrobrochum),异孢单顶孢(M. heterobrochum),瘤捕单顶孢(M. phymatopagum),三叉霉(Tridentaria sp.)及龟头轮枝孢(Verticillium balanoides).     

拮抗烟草疫霉的枝穗霉菌株筛选

【背景】烟草疫霉(Phytophthora nicotianae)引起的烟草黑胫病(tobacco black shank)是烤烟生产上重要的土传根茎病害之一,生产上防治困难。【目的】筛选对病原菌具有强拮抗能力的有益微生物菌株是开展生物防治的基础。【方法】采用平板对峙法筛选对烟草疫霉具有拮抗作用的枝穗霉菌株。根据枝穗霉在烟草疫霉菌落上的覆盖程度和产孢量,以及对烟草疫霉菌丝、孢囊梗和孢子囊的缠绕情况,将枝穗霉的拮抗能力划分为强、中等、弱和无4个等级。【结果】供试8种65株枝穗霉中,6株具有强拮抗能力、27株具有中等拮抗能力、22株具有弱拮抗能力、10株无拮抗能力;不同枝穗霉菌株对烟草疫霉的抑制率大小为20.0%-86.7%。【结论】粉红枝穗霉(Clonostachys rosea)菌株7901、11361和亚麻生枝穗霉(C. byssicola)5072、6729、7507及条孢枝穗霉(C. grammicospora)6730对烟草疫霉具有强拮抗能力,这为后续盆栽试验及作用机理研究等提供了种质资源。     

葡萄生单轴霉菌围可培养微生物多样性及潜在生防菌研究

【目的】揭示葡萄生单轴霉(Plasmoparaviticola)菌围可培养细菌和真菌的多样性特征,筛选对葡萄霜霉病有较强稳定防治效果的生防菌。【方法】连续两年从我国南北方具有代表性的7个葡萄产区采集葡萄霜霉病叶,镊子夹取经保湿培养获得的新鲜霉层并配制孢子囊悬浮液,采用传统分离培养法,结合形态分类、BOX-PCR指纹图谱分析以及分子鉴定结果,对葡萄生单轴霉菌围的可培养细菌和真菌进行聚类分析;采用菌株及其发酵液与病原菌孢子囊悬浮液等体积混合培养测定其对孢子囊的抑制作用,离体叶片接种法检测该菌株及其发酵液对霜霉病的防治效果。【结果】分离获得了90株细菌和110株真菌,分别归属于8个细菌属和14个真菌属,且相同地区不同葡萄品种葡萄生单轴霉菌围的细菌和真菌在同年处于同一分支。假单胞菌属(Pseudomonas)和枝孢属(Cladosporium)稳定存在于各地区不同品种葡萄霜霉病叶上葡萄生单轴霉菌围;在两年间稳定存在的菌株占比多数在80.0%以上且均具有较高的生防作用;其中,广泛分布的6株枝顶孢属(Acremonium)真菌对葡萄霜霉病的防治效果均较好,最高可达100.0%;防治效果较高的11个菌株的无菌发酵液中,黑曲霉(Aspergillusniger) NX2F、苋楔孢黑粉菌(Thecaphora amaranthi) BJ1G和匍枝根霉(Rhizopus stolonifer) BM1L的无菌发酵液防治效果均为100.0%。【结论】葡萄生单轴霉菌围的可培养细菌和真菌群落主要受地区因素影响,有较高的稳定性和生防作用,揭示了枝顶孢属真菌在我国葡萄主要产区葡萄生单轴霉菌围附生的普遍性,为葡萄霜霉病的防治提供了丰富和宝贵的资源。     

甘肃河西走廊土壤中的暗色丝孢菌

从甘肃河西走廊的25份土样中分离出39个暗色丝孢菌分离物,经鉴定分别属于16个属的27个种。其中厚垣链格孢Alternaria chlamydospora、黑小枝顶孢Acremoniella atra和疣小枝顶孢Acremoniella verrucosa为中国新记录种:士栖葡萄穗霉Stachybotrys terrestris为新种。研究过的标本(干制培养物)与活菌种均保存在山东农业大学植物病理学标本室(HSAUP)。     

中国的被孢霉种类

被孢霉属(Mortierella Coemans)是接合菌纲(Zygomycetes)、毛霉目(Mucorales)、被孢霉科(Mortierellaceae)中的一个大属,目前已知约有90种;主要存在于土壤、植物残体、动物粪便等基物中。我国过去对被孢霉的研究不多,在《中国真菌总汇》(1979)中记录了8个种。本研究从全国22个省、市、自治区采集的2000多号样品中,分离到约220个被孢霉菌株。本研究主要采用Gams (1970, 1977)的分类系统进行分类鉴定,并对该系统进行了修改。在属下分3个亚属(Micromucor, Mortierella和Gamsiella), 8个组(Actinomortierella, Alpina,Hygrophila, Mortierella, Schmuckii, Simplex, Spinosa和Stylospora),单囊霉(Haplosporangium)被承认为独立的一个属。本研究鉴定出22个种和3个变种,包括一个新种(武夷山被孢霉Mortierella wuyishanensis sp. nov.)和一个新变种(极细无色被孢霉Mortierella hyalina(Harz) W. Gams var. subtilissima var. nov.), 14个中国新纪录。这14个新纪录为:产芽胞被孢霉(Mortierella. gemmifera M. Ellis)、园圃被孢霉(M. horticola Linnem.)、矮小被孢霉(M. humilis Linnem.)、无色被孢霉(M. hyalina(Harz) W. Gams)、印度被孢霉(M. indica B.S. Mehrotra)、英杜被孢霉(M. indohii C.Y. Chien),詹金氏被孢霉(M. jenkinii (A.L. Sm.) Naumov)、可疑极小被孢霉(M. minutissima Tiegh. var. dubia Linnem.)、易变被孢霉(M. mutabilis Linnem.)、微孢被孢霉(M. parvispora Linnem.)、角胞拉曼被孢霉(M. ramanniana(Moller) Linnem. var. angulispora (Naumov) Linnem.)、网孢被孢霉(M. reticulata Tiegh.& G. Le Monn.)、多疣被孢霉(M. verrucosa Linnem.)、轮枝被孢霉(M. verticillata Linnem.)。文中讨论和评价了一些分类性状,还列出分亚属、分组、分种和变种的检索表.每个分类单元都有描述和讨论以及线条图、并列出分布地区。     

刺孢小克银汉霉原变种和轮生刺孢小克银汉霉变种(新组合)

刺孢小克银汉霉[Cunninghamella echinulata(Thaxt.) Thaxt. ex Blakeslce]是小克银汉霉属的模式种,多年来因不同作者是否将贝尼尔小克银汉霉(C. bainieri Naum.)包含在内而对此种持广义(sensu lato)或狭义(scnsu stricto)的不同理解。我们在国内分离到51株刺孢小克银汉霉(广义)菌种,经与获自css的7株菌(包括刺孢小克银汉霉的模式菌种在内)和IMI的1株菌(原定名称均为刺孢小克银汉霉)一起研究后,根据它们的无性型形态特征有明显不同但在配合试验中又可互相配合形成可育的接合孢子的结果,认为将它们处理为同一个种的两个不同变种较为合理.其中,13株中国的菌和3株CBS及IMI的菌被鉴定为刺孢小克银汉霉原变种(C. echinulata var. echinulata);其余的38株中国的菌和5株CBS的菌被鉴定为轮生刺孢小克银汉霉变种(新组合)[C. echinulata var. verticillata (F. S. Paine.) comb. nov.j.以‘轮生(verticillata)’作为新组合变种的加词是根据与贝尼尔小克银汉霉同物异名的‘轮生布拉小克银汉霉(C. blakesleeana var. verticillata (F. S. Paine) Baijal & B. S. Mchrotra)’而来的.在前人的工作中,对刺孢小克银汉霉持狭义理解的作者往往根据孢子枝的分枝方式、巨型暗色孢子的有无、以及40℃能否生长来区分这两个分类群.对刺孢小克银汉霉持广义理解的作者则认为这些特性毫无意义.我们同意后面两个特性意义不大,因为二者的许多菌系都能形成巨型暗色袍子并在40℃生长,但认为孢子枝分枝方式确实是区别这两个分类群的重要依据.此外,根据产孢构造的种类、孢子枝主枝的直径、孢子枝第一次分枝的数目、分枝长度、孢子枝主枝的顶生泡囊形状以及其直径等性状综合考虑,这两个分类群是不难明确区分的,对12株刺孢小克银汉霉原变种和13株轮生刺孢小克银汉霉相互之间所进行的配合试验结果表明,在具一定性亲和力的(+)、(一)菌系同时存在时,两个变种内和变种之间均可形成可育的接合孢子。对上述三种配合的各六对菌所形成的有性型形态的研究结果则表明,除轮生刺孢小克银汉霉变种内形成的接合孢子的壁往往较厚外,各种配合形成的有性型形态基本上是一致的.我们研究组的其他成员最近曾对小克银汉霉的22株菌进行了rDNA的ITS区的PCR产物长度测定,其中包括了刺孢小克银汉霉原变种和轮生刺孢小克银汉霉变种的各3株菌,它们的平均长度(bp)分别为890±7.5和915±7.6.这个结果也支持了我们在这两个分类群可以互相配合的情况下仍将它们作为两个不同变种的处理.这两个分类群虽然已被发表多次,但它们的描述和绘图均过于简单而未能充分显示出它们的区别性特征,因此我们在本文中再次作了描述并再次提供了详尽的线条图和显微照相.     

山西省不同地区柴胡根部可培养内生真菌的多样性分析

为研究柴胡（Bupleurum chinense DC.）根部可培养内生真菌的多样性，分析山西省不同地区柴胡根部可培养内生真菌多样性的差异性，建立柴胡根部内生真菌库。本文以山西省不同产地的柴胡根为材料，采用传统植物组织平板分离法对柴胡根部可培养内生真菌进行分离培养和分子鉴定。从25个不同产地的柴胡样品根部中共分离培养得到705株真菌，经分子生物学鉴定，其中695株真菌归属为4门14纲23目32科55属119种。晋南地区的优势菌属为镰刀菌属（Fusarium, 32.18%）、亚隔孢壳属（Didymella, 15.96%）、曲霉属（Aspergillus, 8.24%）、异茎点霉属（Paraphoma, 6.91%）、茎点球属（Phoma, 5.32%）、链格孢属（Alternaria, 5.05%），晋北地区的优势菌属为镰刀菌属（31.66%）、曲霉属（15.36%）、链格孢属（9.09%）、亚隔孢壳属（8.15%）、异茎点霉属（7.52%），亚隔孢壳属、曲霉属、链格孢属等优势属的相对丰度差异较大；晋南地区的优势物种为Didymella bellidis（11.44%）、三线镰刀菌（Fusarium tricinctum, 7.98%）、腐皮镰刀菌（Fusarium solani, 7.45%）、锐顶镰孢菌（Fusarium acuminatum, 5.85%）、烟曲霉（Aspergillus fumigatus, 5.85%），晋北地区的优势物种为锐顶镰孢菌（14.11%）、烟曲霉（11.91%）、三线镰刀菌（9.40%）、菊异茎点霉（Paraphoma chrysanthemicola, 5.64%）、D. bellidis（5.64%）、链格孢菌（Alternaria alternata, 5.64%），D. bellidis、锐顶镰孢菌、烟曲霉等优势种的相对丰度差异较大。差异性分析表明晋南地区的生物多样性显著高于晋北地区，D. bellidis、锐顶镰孢菌、烟曲霉等优势种的相对丰度差异较大，为进一步研究柴胡根内生真菌相对丰度差异较大的物种及其不同菌株对柴胡皂苷积累的影响提供参考。     

中国叶围煤污菌初探II．毛白杨叶围煤污菌的研究

对毛白杨(Populus tomentosa Carr.)叶围煤污菌(sooty moulds)群落组成及演替进行了探罚,分析了叶面营养物及其变化。 结果表明,叶面真菌的分离物密度随叶片的衰老而增加。对毛白杨叶面真菌分离鉴定,属于煤污菌有8种真菌：链格孢(Alternaria alternata),芽枝状枝孢(Cladosporium cladosporioides),球孢枝孢(Coladosporium sphaerospermum),尖孢枝孢(Cladosporium oxysporum),出芽短梗霉(Aurecobasidium pullulans),棕黑腐质霉(Humtco'a tuscoatra),伏克盾壳霉(Coniothyrixm fuckelii)和直立枝顶孢(Acremoniumstrictum)。不同生长期叶面真菌群落组成及优势种不同,叶面出现黑霉层后,以3种煤污菌为优势种即出芽短梗霉、链格孢和芽枝状枝孢。不同的菌表现一定的演替模式,定殖及达到峰值的时间不同。毛白杨叶面含有多种营养物,其含量及组分随生长期不同而异．与叶面真菌分离物密度呈显著性相关。此外,对蚜虫的发生、叶面营养物含量、煤污菌三者的关系进行了讨论。     

Interactions between Psilocybe fasciata and its companion fungus Acremonium strictum

Interactions between Psilocybe fasciata and its companion fungus Acremonium strictum were analysed. The conidia of A. strictum were observed on stipe, flesh and gill of P. fasciata, which suggested that A. strictum is the fungicolous fungi or mycophilic fungi of P. fasciata. The microscopic observations of the interacting hyphae of P. fasciata and A. strictum in dual culture and the negligible activities of chitinase and β-1,3-glucanase in inducing or non-inducing media of the pure and mixed cultures of the two fungi indicated that A. strictum is not the mycoparasite of P. fasciata. In addition, the co-existence, no pigmentation and dew formation in dual culture of both fungi were observed, which implied that the interference competition between the two fungi is weak. The activities of cellobiase, filter paper enzyme, endoglucanase and xylanase of pure and mixed cultures of P. fasciata and A. strictum were the same or similar, which may allow the co-existence of the two fungi. As a consequence of coevolution, the relationship between P. fasciata and A. strictum is commensalism: A. strictum showed no clear benefit to P. fasciata; however, P. fasciata may shelter A. strictum by its psychoactive tryptamines and may be helpful to conidium dispersal of A. strictum. The relationship between P. fasciata and A. strictum is different from that of A. strictum and other fungi.     

春兰菌根真菌CL-3菌株的鉴定及共生体系的构建

采用分离自野生春兰(Cymbidium goeringii)根部的真菌CL-3菌株, 进行了春兰内生菌根真菌的人工接种、再分离及其共生培养研究。通过对CL-3菌株形态学观察和ITS序列同源性分析, 发现该菌株ITS序列与Acremonium strictum的亲缘关系最为接近, 序列同源性为100%。用CL-3菌株接种春兰组培苗, 接种后2个月可从组培苗中再分离获得该菌株, 且CL-3菌株处理苗的鲜重增长率达80.5%, 经方差分析, 与对照相比有显著差异。通过石蜡切片和染色, 在已接种的组培苗的根部组织中可观察到CL-3菌株存在。表明CL-3菌株能与组培幼苗成功建立共生培养体系。     

不同水分条件下混种密度对芦苇和反枝苋种间竞争的影响

与本地植物的种间竞争是影响外来植物能否成功入侵的关键因素之一,该研究通过受控模拟试验研究了本地植物芦苇(Phragmites australis)和外来入侵植物反枝苋(Amaranthus retroflexus)在淹水和干旱两种水分条件下混种密度(6∶2、4∶4和2∶6)对其种间竞争的影响。结果表明:(1)芦苇和反枝苋的相对产量与相对产量总和均小于1,即两种植物存在种间竞争。(2)种间竞争使芦苇和反枝苋的生长均受到了不同程度的抑制,表现在两者的株高和生物量均随着竞争者密度的增加而降低。(3)植株地上部分和地下部分的氮浓度表现出与株高和生物量相同的趋势,且在不同水分条件下存在差异。(4)芦苇和反枝苋分别在淹水和干旱环境下具有较强竞争力,但在各自较高混种密度下亦具有较强竞争力。可见,芦苇和反枝苋的种间竞争受到了水分和混种密度的影响。因此,在有反枝苋分布的湿地中,植物生长初期可通过增加土壤水分和/或增加芦苇等本地植物的种群密度以降低反枝苋的种群密度来限制其竞争能力,防止反枝苋在湿地中生长建群和扩散入侵。     

Fungal endophyte negative effects on herbivory are enhanced on intact plants and maintained in a subsequent generation

1. Fungal endophytes are ubiquitous associates of virtually all plant species. Although many studies have focused on the role of these microorganisms as mediators of plant–herbivore interactions, these studies have usually been conducted using short‐term experiments. 2. Truly effective defences against herbivores may require normal functioning of the plant, as excised leaves may be less resistant as compared with those still attached to the plant. Yet, most studies investigating possible effects of endophytes in conferring host resistance to herbivores have been conducted with plant parts rather than intact plants. 3. Using the root endophytic fungus (Acremonium strictum)—broad bean (Vicia faba)—generalist herbivore (Helicoverpa armigera) model, we conducted experiments to examine whether endophyte effects on herbivory would depend on the experimental setting used in the investigation and whether they would translate into a subsequent generation of the herbivore. 4. Acremonium strictum negative effects on the fitness of H. armigera first generation were more evident when the larvae foraged freely on inoculated intact whole plants than when offered leaf discs of inoculated plants. Furthermore, these effects were carried over into H. armigera second generation reared on an artificial diet. 5. Acremonium strictum could not be re‐isolated from V. faba leaves; hence direct contact between the endophyte and the insect could be excluded. Alternatively, loss of volatiles or inhibitory effects of compounds that were stronger in situ might have caused changes in larval feeding and performance on leaf discs as compared with intact plants, regardless of infection status. 6. We suggest that the reduction in fitness parameters of H. armigera across two generations is caused indirectly via an endophyte‐triggered reduction in plant quality.     

Influence of an endophytic fungus on host plant selection by a polyphagous moth via volatile spectrum changes

Recently the role of micro-organisms as mediators of plant-herbivore interactions has been increasingly acknowledged in ecological research. We investigated the interaction between an unspecialized root fungal endophyte (Acremonium strictum) and the polyphagous moth Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), in greenhouse and laboratory bioassays. Specifically we examined in tomato (Lycopersicon esculentum Mill.) the systemic effects of the endophytic fungus on the host selection behaviour of female moths for oviposition and the volatile profiles of host plants to understand the mechanisms acting in this multi-trophic model system. Both laboratory and field strains of H. armigera moths oviposited more on leaves of A. strictum inoculated plants as compared to endophyte-free plants, both in free flight cages and in tethered moth laboratory experiments; the moth’s preferences were significant between 10 and 18 days after inoculation. The analysis of volatile profiles showed strong quantitative differences between treatments. Endophyte inoculated plants emitted diverse terpenes and sesquiterpenes at significantly lower amounts as compared to endophyte free-plants, except for α-terpinene, which did not differ between the treatments, and trans-β-caryophyllene, which was emitted in significantly higher amounts on inoculated plants. β-Thujene and α-phellandrene accounted for 73.3 and 12.0% of total amounts of volatiles emitted from endophyte-free and inoculated plants, respectively. Our findings demonstrate that A. strictum is able to systemically influence the host selection of H. armigera moths for oviposition; conceivably mediated by the induced changes in volatile emissions (and probably additional biochemical parameters of the host plants, which have not been analysed so far). We argue for a more detailed assessment of micro-organisms invisibly colonizing plants, when studying plant-herbivore or multitrophic interactions.     

麻疯树种子发育过程中JcOle14.3和JcOle16.6基因的表达模式研究

油质蛋白基因对种子中油体的形成至关重要,该研究通过实时荧光定量PCR,对麻疯树的两个油质蛋白基因JcOle14.3和JcOle16.6在种子不同发育时期的表达模式进行了分析。结果表明:两个基因在种子发育初期(10~30 d)表达量逐渐升高,但表达水平均较低;40 d时表达量急剧增加并达到最高,而种子发育后期(50~55 d)两个基因表达水平均逐渐降低。由此可初步推测,JcOle14.3和JcOle16.6基因的表达量可能与种子油脂积累量存在正相关。该研究结果为麻疯树油体形成机理和油质蛋白的深入研究提供了理论基础。     

外来红树植物拉关木对乡土种桐花树和正红树的化感作用研究

为了探究外来红树植物拉关木对乡土红树植物的化感作用,该研究观察了不同浓度(0.1、0.3、0.5g·mL~(-1))的拉关木根、叶水浸提液对乡土红树植物桐花树和正红树的胚轴(种子)萌发、幼苗生长及叶片抗氧化酶活性的影响。结果表明:(1)拉关木水浸提液对桐花树种子的成苗率、萌发指数和根长均存在抑制作用,其中对根长的抑制作用随水浸提液浓度的提高而增强。(2)根水浸提液对桐花树幼苗的根长、苗高、生物量等生长指标的影响总体上均表现为低浓度促进,高浓度抑制。(3)拉关木水浸提液对正红树胚轴的萌发率、萌发指数、生长指标均表现为促进作用,且根水浸提液0.1、0.3 g·mL~(-1)处理组的芽长以及根、叶水浸提液0.1、0.3 g·mL~(-1)处理组的生物量显著大于对照组;拉关木水浸提液对正红树幼苗的生物量也表现为促进作用。(4)抗性生理方面,随着拉关木水浸提液浓度的升高,桐花树和正红树幼苗SOD活性降低,正红树幼苗POD活性在根水浸提液0.3 g·mL~(-1)和叶水浸提液0.1 g·mL~(-1)处理组显著高于对照组。以上结果表明,不同乡土植物对拉关木化感作用的敏感性不同,拉关木水浸提液抑制了桐花树的生长,而对正红树的生长则表现出一定程度的促进作用。     

滴水珠珠芽发育过程研究

珠芽是滴水珠(Pinellia cordata)的营养繁殖结构,为揭示滴水珠珠芽发育过程中的特征,该研究以野外采集材料进行盆栽观察试验,通过形态观察法和石蜡切片方法,探索滴水珠叶片和叶柄处珠芽发育过程中的形态学和解剖学结构特征。结果表明:滴水珠珠芽发育过程在形态上分为叶柄无现象时期、早期珠芽结构分化和珠芽膨大成熟时期三个时期;相应的解剖学发育时期为珠芽原基启动期和形成期、原基分化期和膨大成熟期四个阶段。叶片和叶柄珠芽起始细胞均由叶柄腹面表皮下层薄壁细胞组织脱分化形成,起始细胞不断分裂形成细胞团最后发育成珠芽原基;在原基分化期的特征是生长点形成,最终分化形成芽原基和鳞片叶;膨大成熟期的特征是珠芽结构不断生长,生长点侧生分化鳞片叶增多。叶片和叶柄处珠芽成熟脱落时期为灰色椭圆形结构,测得平均直径分别为(2.79±0.40)mm和(2.69±0.36)mm,外部有鳞片包裹,内部含大量营养物质。在环境适宜条件下,珠芽遇土萌发,萌发率达75%。这表明滴水珠珠芽与同属植物半夏珠芽发育过程差别不大,都是无性克隆营养繁殖体结构。     

Modeling the impact of a biocontrol agent, Puccinia lagenophorae, on interactions between a crop, Daucus carota, and a weed, Senecio vulgaris

The impact of a biocontrol agent spreading from a point source on crop–weed interactions was modeled. The model encompassed: (i) severity of crop–weed competition as affected by a rust pathogen, (ii) velocity of spread of the rust pathogen, and (iii) density of infected plants introduced in the weed population as starting points (inoculum sources) for an epidemic. The model was parameterized for a study system encompassing the crop Daucus carota (carrot), the weed Senecio vulgaris (common groundsel), and its antagonist Puccinia lagenophorae. The parameters of (i) were estimated in a greenhouse study using a response-surface design. Estimates of the parameter of (ii) were obtained from the literature. The density of infected plants (iii) was varied to simulate crop loss as function of density. Simulations were run for various densities of the weed and various velocities of rust pathogen spread. The results of the simulations indicated a crop-loss ranging from 5 to 10% at levels of relatively weak D. carota–S. vulgaris competition. Density of inoculum sources and velocity of P. lagenophorae spread had only minor effects on crop loss. In contrast, density of inoculum sources and velocity of spread had major effects on crop loss at levels of intermediate (range of 10–35% loss) and severe competition (range of 30–70% loss). The results are discussed both with respect to biological control of S. vulgaris using P. lagenophorae as biocontrol agent and as a general model describing the impact of the spatial dynamics of a pathogen (natural enemy) on plant competition.