Host influence on germination and reproduction of the facultative hemi‐parasitic weed Rhamphicarpa fistulosa

Rice Vampireweed, Rhamphicarpa fistulosa, was a minor parasitic weed until recently when rice cultivation in sub‐Saharan Africa was expanded into marginal wetlands, that are the parasite's natural habitat. Unlike most of the parasitic weeds, R. fistulosa is facultative, meaning that the parasite is able to complete its life cycle without a host. However, when not connected to a host plant, its biomass and seed production is lower. Because very little is known regarding the germination ecology of the parasite, the main objective of our study was to identify the cues that favour germination. We hypothesised that, first, being a wetland species, germination of R. fistulosa is stimulated by light and high soil moisture. Second, we hypothesised that if host plant presence increases its reproductive output then a germination stimulatory effect from host presence is likely to have developed. A Petri‐dish and pot experiment showed that light and completely saturated soils were a requirement for germination, demonstrating that germination requirements of R. fistulosa are typical of species that grow in environments with fluctuating water levels. A pot experiment in which five infestation levels of R. fistulosa were installed in the absence and presence of a rice plant, showed that host plant presence resulted in a 3.7 times higher seed production rate and a 15% larger average seed size. Despite this reproductive advantage, a pot experiment with three rice cultivars, selected because of their difference in strigolactone production, showed that host plant presence, regardless of the development stage, did not influence the emergence rate of R. fistulosa. In a follow‐up study, the germination stimulation effect of root exudates collected from the same three rice cultivars and a treatment consisting of an artificial germination stimulant (GR24) was compared with a treatment consisting of plain water. In these treatments, seeds of R. fistulosa were compared with seeds of the obligate parasite Striga hermonthica. Germination of S. hermonthica was strongly advanced by the presence of root exudates and GR24 but was completely absent in water, whereas germination of R. fistulosa in all treatments was similar to that in plain water. The absence of a host recognition mechanism at the germination stage suggests that the regulation of germination through light and soil moisture is near optimal. Our finding might also indicate that for this facultative parasitic plant species, a more opportunistic germination strategy is superior. Implications of the findings for management of R. fistulosa in rice cultivation are discussed.     

Slavery in plants: how the facultative hemi‐parasitic plant Rhamphicarpa fistulosa can completely dominate its host

The rain‐fed lowland rice weed Rhamphicarpa fistulosa (Rice Vampireweed) is a facultative root parasitic plant. Growth and reproduction of R. fistulosa benefit considerably from parasitism, but how this affects the host plant is not well established. We determined accumulation and partitioning of rice–parasite biomass in two pot experiments. First, rice (cv. IR64) was grown under eight R. fistulosa densities (15–1000 seeds per pot) with two sampling times. Next, 2 parasite densities (6 and 13 plants per pot) were combined with 9 destructive samplings. Infection increased host root: shoot ratios and decreased host plant height, leaf area and tiller number. Reductions in light interception were followed by reductions in light use efficiency, causing 22–71% losses in host plant biomass and 78–100% losses in host kernel production. Parasitism eventually caused a complete standstill of host plant growth, while the parasite managed to gradually increase its share in total host plant–parasite biomass up to 50–82%. This implies that ultimately the host plant was producing solely for the sake of the parasite. Due to its facultative nature, R. fistulosa may incorrectly be perceived as relatively harmless. Upon infection this Rice Vampireweed, however, turns into a genuine slave master, whereby it completely dominates its host.     

长期稻鸭共作对稻田杂草群落组成及物种多样性的影响

2000~2003年连续4年研究了稻鸭共作条件下田间杂草群落的特征及其动态变化规律。结果表明,在长期稻鸭共作条件下,田间杂草密度逐年降低,下降趋势符合阻滞模型y=k+a·e^bx,模型参数b反映了杂草种群的下降速率。在稻田6种主要杂草中,水虱草(Fimbristylis miliaceae)、陌上菜(Lindernia procumbens)、丁香蓼(Ludwigia prostrata)种群数量降低较快,鸭舌草(Monochoria vaginalis)、异型莎草(Cyperus difformis)次之,稗(Echinochloa crusgalli)最慢。稻鸭共作使稻田杂草群落的物种多样性持续降低,群落均匀度提高,群落相似性与稻鸭共作前相比逐年降低。说明稻鸭共作改变了田间杂草的群落结构,有利于限制杂草的发生危害。随着稻鸭共作的连年进行,对田间杂草的控制效果逐渐上升,4年后达99%以上。稻鸭共作是稻田替代化学除草的一种非常有效的生物、生态控草措施,具有显著的经济和生态效益。     

不同稻作方式对稻田杂草群落的影响

运用半试验与调查相结合的方法,以贵州省从江县传统农业区的糯稻和杂交稻为例,研究了在水稻单作（R）、稻-鱼（R-F）和稻-鱼-鸭（R-F-D）3种不同稻作方式下稻田杂草群落的特征.结果表明：糯稻在3种稻作方式下的抑制杂草能力均优于杂交稻;R-F-D显著降低了田间杂草的发生密度,对鸭舌草、节节菜等的抑制效果达到100%,总体抑制杂草效果显著优于其他稻作方式,杂草的物种丰富度及Shannon多样性指数显著降低,Pielou均匀度指数提高,表明群落物种组成发生了很大的改变,降低了原来优势杂草的发生, 是一种较好的可达到抑制杂草效果的稻作方式.     

江苏南部麦田杂草群落发生分布规律的数量分析

利用七级目测法对江苏省南部麦田81个样点796块田地共计82,7hm^2草害进行调查,采集数据,经转化后,对其进行主成分(PCA)和系统聚类分析,并赋予生态学意义的解释,研究表明,决定江苏省南部麦田杂草的发生、危害和分布的主要因素是种植制度导致的田间土壤饱和水分持续时间和土壤酸碱度,生境相似,杂草群落具有趋同性,并就杂草发生的特点提出杂草综合治理的建议。     

Age-stage,two-sex life table and food utilization efficiencies of Galerucella placida Baly (Coleoptera: Chrysomelidae) on two Polygonaceae weeds

Rumex dentatus L. and Polygonum glabrum Willd. (Polygonaceae) are important weeds of wheat and rice fields, respectively, in India and Pakistan. Adults and larvae of Galerucella placida Baly (Coleoptera: Chrysomelidae) feed both weeds. Therefore, we studied the biology of G. placida on two weed leaves using age-stage, two-sex life table at 21 °C, 65 ± 5% r.h. and 12L: 12D. We also studied food utilization indices of G. placida on these leaves. Further, we investigated the quantities of nutrients (total carbohydrates, proteins, lipids, amino acids and nitrogen) and antinutrients (total phenols, flavonols and tannins) of the leaves. Correlation analysis suggested that fecundity and the intrinsic rate of increase (r_m) of G. placida were positively correlated with nutrients of leaves, while negatively correlated with antinutrients. Faster larval development, higher longevity of adults and greater fecundity of G. placida were recorded on R. dentatus than P. glabrum. The r_m was higher on R. dentatus than P. glabrum. The nutrients were greater in R. dentatus than P. glabrum, while antinutrients were lower in R. dentatus than P. glabrum. The growth rate and consumption index were greater on R. dentatus than P. glabrum. The above results suggested that better nutritional quality of R. dentatus than P. glabrum influenced faster larval development, higher longevity of adults and greater fecundity of G. placida on R. dentatus. This study concluded that R. dentatus could be used for mass rearing of G. placida in biocontol program prior to release in fields for control of both these weeds.     

Evidence of sibling species between two host-associated populations of brown planthopper, N. lugens (stål) (Homoptera: Delphacidea) complex based on morphology and host–plant relationship studies

Morphological and host–plant relationship studies were conducted to differentiate two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice (Oryza sativa) and the other from Leersia hexandra, a weed grass. In morphometric studies based on esterase activities, an UPGMA dendrogram using 17 quantitative morphological characters, including stridulatory organs (courtship signal-producing organs) between two sympatric populations of N. lugens, one from rice and the other from L. hexandra, a weed grass revealed that both populations were separated from each other. An out-group, N. bakeri, was found to be completely different from the two sympatric populations of N. lugens. Rice plants were best suited for the establishment of the rice-infesting population, and L. hexandra was a favourable host for the Leersia-infesting population. The individuals derived from one host did not thrive on the other host, as shown by a significant reduction in survival and nymphal development, ovipositional preferences, ovipositional response, and egg hatchability. Therefore, morphological and host–plant relationship studies indicate that rice-associated population with high esterase activities and L. heaxandra-associated population with low esterase activities are two closely related sibling species.     

Performance of different fish species for controlling weeds in rainfed lowland rice field

A field experiment was conducted during wet season to evaluate the performance of different fish species for biocontrol of weeds in rainfed waterlogged rice fields with fingerlings of three exotic carps – grass carp, Ctenopharyngodon idella (Val.) (Cyprinidae, Cypriniformes), silver barb, Puntius gonionotus (Bleeker) (Cyprinidae, Cypriniformes) and common carp, Cyprinus carpio (L.) (Cyprinidae, Cypriniformes) – and three Indian major carps – rohu, Labeo rohita (Ham.) (Cyprinidae, Cypriniformes), catla, Catla catla (Ham.) (Cyprinidae, Cypriniformes), mrigal, Cirrhinus mrigala (Ham.) (Cyprinidae, Cypriniformes). A total of 13 major weeds under the categories of grassy, sedges, broadleaf and aquatic weeds were observed in the rice fields. Grass carp reduced maximum weed biomass (weed control efficiency [WCE] 63% at 60 days after transplanting [DAT] and 62% at 100 DAT) followed by silver barb and common carp. Among the Indian carps, only rohu was effective in control of weeds (WCE, 23% at 60 DAT). The grain yield of rice (variety Varshadhan) slightly increased (4.2–4.5 t/ha), but straw yield was significantly higher (10.2–10.7 t/ha) under rice-fish farming. Fish yield was significantly higher in exotic carps (270–288 kg/ha/90days) due to higher specific growth rates (1.8–2% body weight/day). The study indicated that exotic carps (grass carp, silver barb and common carp in order) were more effective than Indian carps for control of weed in rainfed lowland rice fields and among the Indian carps, rohu showed potential for weed control.     

Indirect effects of weeds on rice plants via shared heteropteran herbivores

In agricultural ecosystems, weeds indirectly affect crops via phytophagous insects that feed on both weeds and crops. In paddy fields, heteropteran insects are among the most serious pests of rice plants. In some heteropterans, the proboscis is used to suck rice ears, inducing black spots on the grains (i.e., pecky rice). Even a low proportion of pecky rice (>0.1%) significantly decreases the market price of rice; in Japan, this problem has led to severe economic losses. Because heteropterans feed on the reproductive organs of weeds as well as rice plants, various weeds that grow around paddy fields may increase the populations of heteropterans that cause pecky rice. To clarify which types of weeds can be used by heteropterans causing pecky rice, we investigated the interactions between plants (including rice plants) and heteropterans in an agricultural landscape in Hyogo, Japan. We observed 833 individuals of 27 heteropteran species (13 families) feeding on the reproductive organs of 35 plant species (Poales: three families) including rice plants from June to October 2019. All heteropteran species were native, whereas six of 35 plant species were non-native. We found 12 heteropteran species on rice plants; nine of the 12 heteropteran species fed on weeds (a total of 32 species) as well as rice plants, whereas the other three species fed exclusively on rice plants. Heteropterans fed on native weeds throughout the growing seasons (June–October), but on non-native weeds only before rice plants bloomed (June–July). Therefore, diverse weed species that grow around paddy fields are food resources for heteropteran insects and they might indirectly increase the incidence of pecky rice.     

Interference of allelopathic rice with paddy weeds at the root level

• Despite increasing knowledge of the involvement of allelopathy in negative interactions among plants, relatively little is known about its action at the root level. This study aims to enhance understanding of interactions of roots between a crop and associated weeds via allelopathy.
• Based on a series of experiments with window rhizoboxes and root segregation methods, we examined root placement patterns and root interactions between allelopathic rice and major paddy weeds Cyperus difformis, Echinochloa crus‐galli, Eclipta prostrata, Leptochloa chinensis and Oryza sativa (weedy rice).
• Allelopathic rice inhibited growth of paddy weed roots more than shoots regardless of species. Furthermore, allelopathic rice significantly reduced total root length, total root area, maximum root width and maximum root depth of paddy weeds, while the weeds adjusted horizontal and vertical placement of their roots in response to the presence of allelopathic rice. With the exception of O. sativa (weedy rice), root growth of weeds avoided expanding towards allelopathic rice. Compared with root contact, root segregation significantly increased inhibition of E. crus‐galli, E. prostrata and L. chinensis through an increase in rice allelochemicals. In particular, their root exudates induced production of rice allelochemicals. However, similar results were not observed in C. difformis and O. sativa (weedy rice) with either root segregation or root exudate application.
• The results demonstrate that allelopathic rice interferes with paddy weeds by altering root placement patterns and root interactions. This is the first case of a root behavioural strategy in crop–weed allelopathic interaction.

     

轻型栽培技术对稻田潜杂草群落多样性的影响

为明确轻型栽培技术对稻田潜杂草群落多样性的影响,研究了旱直播、水直播、抛秧、机插秧、麦套稻5种轻型栽培稻作模式及传统手插秧模式下稻田杂草种子库的数量特征.结果表明：旱直播稻田种子库密度显著高于其他模式,达228416粒·m^-2,麦套稻模式其次.另外,旱直播稻田莎草类杂草与麦套稻稻田阔叶类杂草种子密度显著高于其他模式的各类杂草种子.传统手插秧稻田具有最高的物种丰富度,Margalef指数达1.86; 麦套稻与水直播模式中,Shannon-Wiener指数、Gini指数、Pielou群落均匀度指数明显高于旱直播和机插秧等模式.与传统手插秧相比,各轻型栽培稻作模式具有不同的潜杂草群落优势种.为防治稻田杂草的持续危害,应轮流实施不同轻型栽培稻作模式.     

种植制度对江苏省棉田杂草群落影响的研究

 经连续5年对江苏省主棉区水旱轮作及旱连作两种种植制度下的棉田杂草种群密度及草害优势度级数进行定田调查,通过时间和空间上的比较统计分析,研究了棉田杂草群落演替趋势及草害发生规律。研究结果表明,种植制度与江苏省棉田杂草群落的组成和草害发生程度紧密相关。在水旱轮作棉田中,随着棉花(Gossypium hirsutum)种植年数的增加,喜湿性杂草稗草(Echinochloa crusgalli)等优势度值逐渐减少,喜旱性杂草马唐(Digitaria sanguinalis)等优势度值逐渐提高,它们之间存在显著的线性关系。旱连作棉田以喜旱性杂草为主,发生量较大,草害较重,年际间杂草群落变化较小。另外,水旱轮作和旱连作棉田之间的杂草群落结构和种群数量差异显著。而地理区域差异的影响明显小于轮作制度差异导致的影响。     

Interference of horse purslane (Trianthema portulacastrum L.) and other weeds affect yield of autumn planted maize (Zea mays L.)

To assess comparative losses of Trianthema portulacastrum (HP) relative to other weeds, the experiment was set during consecutive summer seasons 2018 and 2019 at the Research Farm MNS-University of Agriculture, Multan, Pakistan. Experiment consisted three replications which were laid out under randomized complete block design. Experiment consisted of ten treatments viz: weeds free (whole season), HP free till 20 Days after emergence (DAE), HP free till 40 DAE, HP free till 60 DAE, all weeds free 20 DAE, all weeds free 40 DAE, all weeds free 60 DAE, weedy check (all weeds), weedy check except HP and weedy check containing only HP. During 2018 in all weeds weedy check, maximum HP relative density (33.33%) was observed while in 2019, plot where weeds were controlled from growing till 20 DAE showed (80%) relative density at 30 DAE. HP maximum frequency (66.67%, 77.78%) and relative frequency (66%, 100%) was recorded at 45 DAE in plots where HP was kept controlled till 20 DAE and all weeds kept controlled till 20 DAE, respectively. Maximum number of grains per cob (738, 700.68), 1000 grain weight (306.66, 271.51 g) and grain yield (6150, 8015 kg hec^-1) were recorded in plots which were kept all weed free till 60 DAE. As the competition period of weeds increased over 40 DAE, it substantially reduced yield of maize. Keeping the plots HP free till 40 DAE in the maize fields with HP as the major dominating weed, likely increase in maize grain yield is up to 30% compared to the fields where HP left un attended throughout the growing season. However, if maize field is infested with a mix of weeds with more than one dominating weeds including HP, compared to weedy situation the whole season, 30% higher grain yield can be obtained if all weeds are kept controlled till 40 DAE. Hence it can be concluded that whether the farmers face heavy HP infestation only or the mix of weeds as dominating weeds, in either case farmer should control weeds within first 40 days in maize field for better grain yield.     

Direct and Indirect Effects of a Shoot-Base Boring Weevil and Plant Competition on the Performance of Creeping Thistle, Cirsium arvense

Creeping thistle or Canada thistle, Cirsium arvense (L.) Scop., is considered one of the world's worst weeds and the third most important weed in Europe. Biological control of this indigenous weed in Europe by use of native agents may provide a low-cost alternative to use of chemical or mechanical control measures and contribute to a more sustainable weed management. We investigated the potential of a shoot-base boring weevil, Apion onopordi Kirby (Coleoptera: Apionidae), for biological weed control, in the presence or absence of plant competition by three grass species. Infestation of thistle shoots by A. onopordi at natural infestation levels reduced above- and belowground plant performance after 2 years. Plant competition at natural levels had an overall greater effect than that of herbivory, significantly reducing both above- and belowground thistle performance in both years, thereby slowing the propagation of the weed. Weevil infestation and grass competition had a synergistic effect on C. arvense growth; the combined effects of the two factors was greater than the sum of both single-factor effects. The experiment revealed that A. onopordi promotes systemic infections of the rust fungus Puccinia punctiformis (Str.) Röhl in the year following weevil infestation. Systemically infected thistle shoots died before the end of the growing season. Although the direct effect of A. onopordi may not be sufficient to control creeping thistle, the synergistic interaction with plant competition and the indirect effect via promotion of systemic rust infections makes A. onopordi a promising agent for the biological control of this weed.     

不同除草方式对浙西南柑橘园杂草群落及其多样性的影响

于2005年6月—2008年5月在浙江衢州市柑橘主产区,运用群落生态学方法研究了化学除草、人工除草和化学除草+人工除草3种方式对果园杂草群落及其多样性的影响.结果表明:化学除草试验区杂草为17科46种,人工除草试验区杂草为20科59种,化学除草+人工除草试验区杂草为18科51种,对照区杂草为25科75种.化学除草处理的杂草物种丰富度指数、Shannon多样性指数和Shannon均匀度指数最低,人工除草处理最高,表明化学除草对果园杂草多样性的影响最大.在浙西南柑橘园既要防除杂草,又要维持果园杂草的多样性,建议采取化学除草+人工除草的方式.     

Recovery of native grass biodiversity by sowing on former croplands: Is weed suppression a feasible goal for grassland restoration?

Grassland restoration on former croplands offers good opportunity to mitigate the loss of grassland biodiversity. Weed suppression can be another benefit, which becomes increasingly important because of the high recent rate of abandonment of arable lands in Central and Eastern Europe. Our aim was to evaluate the usefulness of sowing two low-diversity seed mixtures followed by annual mowing, a frequently used restoration technique, in weed suppression. We found that rapidly forming cover of sown grasses effectively suppressed short-lived weeds and their germination except in the first year. The detected dense seed bank of short-lived weeds points out the possibility and threat of later weed infestation. In the short run perennial weeds cannot be suppressed easily by sowing and annual mowing. We found that the effectiveness of seed sowing followed by mowing in weed suppression can be different on sites with different history or seed mixture. Rapidly establishing perennial weeds, such as Agropyron species were only detected in former alfalfa fields; Cirsium arvense was found in former cereal and sunflower fields but not in former alfalfa fields. We found that the rate of weed suppression and success was influenced by the seed mixtures used. In several alkali restorations the high proportion of perennial weeds was detected in year 3. In loess restorations, much lower scores were typical. This was likely caused by the different seed mixture used. The loess seed mixture contained seeds of a clonally spreading tall-grass, Bromus inermis, which could compete more effectively with clonally spreading weeds, than could short grass species with or without tussock forming. Our findings indicate that post-restoration management require carefully designed actions that are fine-tuned addressing specific threats at the site level.     

All roads lead to weediness: Patterns of genomic divergence reveal extensive recurrent weedy rice origins from South Asian Oryza

Weedy rice (Oryza spp.), a weedy relative of cultivated rice (O. sativa), infests and persists in cultivated rice fields worldwide. Many weedy rice populations have evolved similar adaptive traits, considered part of the ‘agricultural weed syndrome’, making this an ideal model to study the genetic basis of parallel evolution. Understanding parallel evolution hinges on accurate knowledge of the genetic background and origins of existing weedy rice groups. Using population structure analyses of South Asian and US weedy rice, we show that weeds in South Asia have highly heterogeneous genetic backgrounds, with ancestry contributions both from cultivated varieties (aus and indica) and wild rice. Moreover, the two main groups of weedy rice in the USA, which are also related to aus and indica cultivars, constitute a separate origin from that of Asian weeds. Weedy rice populations in South Asia largely converge on presence of red pericarps and awns and on ease of shattering. Genomewide divergence scans between weed groups from the USA and South Asia, and their crop relatives are enriched for loci involved in metabolic processes. Some candidate genes related to iconic weedy traits and competitiveness are highly divergent between some weed‐crop pairs, but are not shared among all weed‐crop comparisons. Our results show that weedy rice is an extreme example of recurrent evolution, and suggest that most populations are evolving their weedy traits through different genetic mechanisms.     

Effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on associated soil bacterial communities: A field‐based experiment

Loss of plant biodiversity can result in reduced abundance and diversity of associated species with implications for ecosystem functioning. In ecosystems low in plant species diversity, such as Neotropical mangrove forests, it is thought that genetic diversity within the dominant plant species could play an important role in shaping associated communities. Here, we used a manipulative field experiment to study the effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on the composition and richness of associated soil bacterial communities. Using terminal restriction fragment length polymorphism (T‐RFLP) community fingerprinting, we found that bacterial community composition differed among R. mangle maternal genotypes but not with genetic diversity. Bacterial taxa richness, total soil nitrogen, and total soil carbon were not significantly affected by maternal genotypic identity or genetic diversity of R. mangle. Our findings show that genotype selection in reforestation projects could influence soil bacterial community composition. Further research is needed to determine what impact these bacterial community differences might have on ecosystem processes, such as carbon and nitrogen cycling.     

Seed-Mediated Gene Flow Promotes Genetic Diversity of Weedy Rice within Populations: Implications for Weed Management

Increased infestation of weedy rice—a noxious agricultural pest has caused significant reduction of grain yield of cultivated rice (Oryza sativa) worldwide. Knowledge on genetic diversity and structure of weedy rice populations will facilitate the design of effective methods to control this weed by tracing its origins and dispersal patterns in a given region. To generate such knowledge, we studied genetic diversity and structure of 21 weedy rice populations from Sri Lanka based on 23 selected microsatellite (SSR) loci. Results indicated an exceptionally high level of within-population genetic diversity (H_e = 0.62) and limited among-population differentiation (F_st = 0.17) for this predominantly self-pollinating weed. UPGMA analysis showed a loose genetic affinity of the weedy rice populations in relation to their geographical locations, and no obvious genetic structure among populations across the country. This phenomenon was associated with the considerable amount of gene flow between populations. Limited admixture from STRUCTURE analyses suggested a very low level of hybridization (pollen-mediated gene flow) between populations. The abundant within-population genetic diversity coupled with limited population genetic structure and differentiation is likely caused by the considerable seed-mediated gene flow of weedy rice along with the long-distance exchange of farmer-saved rice seeds between weedy-rice contaminated regions in Sri Lanka. In addition to other effective weed management strategies, promoting the application of certified rice seeds with no weedy rice contamination should be the immediate action to significantly reduce the proliferation and infestation of this weed in rice ecosystems in countries with similar rice farming styles as in Sri Lanka.     

Weed species within cereal crop rotations can serve as alternative hosts for Fusarium graminearum causing Fusarium head blight of wheat

Fusarium graminearum is the main causal agent of Fusarium head blight (FHB) of small grain cereals, but the importance of weeds in the FHB disease cycle and the establishment of F. graminearum in agroecosystems are still not fully understood. The objective of this study was to determine the potential role of weeds present within cereal crop rotations as alternative hosts. F. graminearum was isolated from different organs of asymptomatic weeds sampled from six fields with cereal-crop rotations in Lithuania for two consecutive years (2015 and 2016). The fungi were identified using morphological and molecular methods. Out of 57 weed species that were investigated, 41 (71.9%) harboured F. graminearum isolates. Twenty five weed species were identified as new, previously undocumented, hosts. The majority (73.3%) of the isolates of F. graminearum from this study belonged to the 15ADON genotype while a smaller proportion (23.4%) belonged to the 3ADON genotype. All F. graminearum isolates that were assessed induced FHB symptoms on artificially inoculated spring wheat tested in the field.