Striga Seeds Research Articles

The arbuscular mycorrhizal host status of plants can not be linked with the Striga seed-germination-activity of plant root exudates

Root exudates from sorghum, a Striga and arbuscular mycorrhizal fungal (AMF) host plant, and a number of Striga non-host plants which are AM host or AM non-host plants were collected and their effect on seed germination of Striga hermonthica was tested. Striga seeds germinate exclusively in presence of strigolactones, thus, Striga seeds germination is an indicator for the presence of strigolactones. Strigolactones are also thought to be essential signals (branching of AMF) for a successful root colonization by AMF. Root exudates of AM host plants stimulated Striga seed germination or showed no effect, whereas root exudates of AM non-host plants never showed an effect on Striga seed germination. This means that Striga seed germination stimulation by compounds in root exudates can not necessarily be linked with the host and nonhost status of plants to AMF. This absence of an effect on Striga seed germination of root exudates of AM host plants can be linked i) either with different levels of strigolactones in the root exudates of different AM host plants or ii) with the fact that not the same compounds are involved in Striga seed germination and in signaling during the establishment of the AM symbiosis.

Efficacy of Pesta granular formulation of Striga-mycoherbicide Fusarium oxysporum f. s p. strigae Foxy 2 after 5-year of storage

An important goal for mycoherbicide research and development is to produce a viable and consistently efficacious product with a long shelf life. The efficacy of 5-year-old Pesta granules of Fusarium oxysporum Foxy 2 in comparison to freshly prepared Pesta granules in controlling the root parasitic weed Striga hermonthica was studied. Pesta granules were made by encapsulating fresh chlamydospores of Foxy 2 in a matrix composed of durum wheat-flour, kaolin, and sucrose. Samples of Pesta granules were stored at 4°C over a period of 5 years. Two g per pot (4 kg soil) of each granular preparation were incorporated pre-planting to sorghum together with Striga seeds. The application of the 5-year-old Pesta granules (2.4 × 105 Cfu g–1) as well as the freshly prepared Pesta granules (1.5 × 106 Cfu g–1) of Foxy 2 sharply reduced the total number of healthy emerged S. hermonthica shoots and/or caused severe disease on the emerged Striga plants compared to the control. None of the emerged plants reached flowering stage in Foxy 2-treated pots, whereas in the control treatment 19.2% of the Striga plants flowered. Maximum efficacy (i.e., 100% reduction in healthy emerged Striga shoots compared to the control treatment) of both Pesta preparations in controlling Striga was achieved, indicating similar potential of both old and fresh formulations. The result revealed that encapsulation of Foxy 2 into “Pesta” formulation did not adversely affect its virulence and efficacy even after 5 years of storage under cold conditions. This represents an important attribute to support wide-scale deployment, storage, handling and delivery of Striga-mycoherbicides Pesta technology in Africa.

Germination of witchweed (<i>Striga hermonthica</i>) (del.) Benth. seeds in response to stimulation by root exudates of groundnut <i>Arachis hypogaea</i> l.)

Seventeen varieties of groundnut were screened in the laboratory at 10 DAP, 15DAP and 20 DAP for the stimulation of germination of Striga seeds. The varieties were UGA-3, MDR8-15, FPEUR-II, ICGV-SM-87123, icgv-sm-86021 and UGA-4. Others were M412-801, 48-115B, EX DAKAR, RRB and M554-76. Included also were UGA-13, UGA-10, UGA-1, ICGV-90127 and NEGTM88-801. A sorghum variety SDSP (OD) 8900C3 was used as control. Results showed that the sorghum control caused higher germination of seeds than the groundnut varieties. Among the groundnut varieties UGA-13, UGA-10, UGA-4, UGA-3, UGA-1, EX DAKAR, MDR8-15, M422-801 and RRB stimulated the highest levels of Striga seed germination. The age of the groundnut plants apparently had no influence on activity of root exudates accepts for UGA-1, which exhibited an increase in germination stimulation from 10 DAP to 20, DAP. It is therefore recommended that any of these promising groundnut varieties may be introduced into rotation systems in the field for the management of S. hermonthica infestation.Journal of Applied Chemistry and Agricultural Research Vol. 7 2000-2001: pp. 87-94

Relationships Between Sources and Levels of Nitrogen Fertilization and the Control of Striga hermonthica in Sorghum

Striga hermonthica has been identified as an economic parasitic weed affecting high grain yield production of sorghum in Africa particularly Nigeria. Seven sorghum varieties were evaluated for three years (1998-2000) in soil treated with Striga seeds using two sources of nitrogen fertilizer and at five levels of nitrogen to study their association in the control of Striga. The experiment was split-split plot with three replication having sorghum varieties as main plot, source of fertilizer as sub-plot and levels of N as sub-sub plot treatments. There were no significant differences among sources of fertilizer and their interactions. Levels of N and varieties were significant for all the traits (p<0.001). There was positive and significant association between levels of N applied and plant vigour, dry matter yield (shoot and root) p<0.01 and Striga count (p<0.05). The significant linear relationship obtained, recognized plant vigour, dry matter yield and Striga count as beneficial Striga resistance indicator. Between 50 to 100 ppm (when converted 110 to 170 kg of N ha-1) is significant in the control of Striga. SK-5912, KSV-4, KSV-8 and NR71150 are potential sources of Striga resistance.

Behaviour and biology of Chilo partellus (Swinhoe) on Striga hermonthica (Del.) Benth. infested and uninfested maize plants

Stemborers and Striga hermonthica co-exist in cereal fields in sub-Saharan Africa where together they cause crop damage that sometimes results in total crop loss. Striga alters both the chemistry and morphology of cereals and this may influence behaviour and performance of stemborers on the host plants. Studies were undertaken to compare the effects of various levels of Striga infestation of maize on oviposition preference and survival of Chilo partellus. Potted maize plants were exposed to different densities of Striga seeds (0, 1000, 2000 and 3000/pot) and subsequent effects on C. partellus oviposition evaluated in no-choice and choice-tests. In addition, larval arrestment, settlement, feeding, growth and development were assessed. Results showed that Striga infestation and plant height had non-significant influence on oviposition preference of C. partellus, except in 2-choice assays involving uninfested maize and one under high Striga infestation, in which case they preferred to oviposit on the latter. Similarly, Striga infestation had no influence on larval arrest and settlement. The larvae, however, consumed significantly more of the leaves and stems from uninfested than infested maize plants, with a progressive decline in the consumed proportions with increasing level of Striga infestation. Larval food assimilation was not influenced by Striga infestation, but larval period, percentage of pupation and growth rate were significantly higher on uninfested plants as compared to medium and high Striga infested plants. Possible reasons underlying these observations and their implications are discussed.

Effect of Intra- and inter-row mixing of sorghum with two varieties of cowpea on host crop yield in a Striga hermonthica infested field

A trial was conducted in the International Institute of Tropical Agriculture (IITA) research farm in Kano, Nigeria during the 2002/2003 cropping season to evaluate the effect of intrarow and interrow mixing of sorghum with two varieties of cowpea on host crop yield in a Striga hermonthica infested field. Significantly (P≤0.05) highest number of Striga per sorghum plant were obtained with sorghum only, which also have the lowest yield (2370 kg/ha). A significantly (P≤0.05) higher yield (3709 kg/ha) was obtained with intra-row mixture of sorghum and densely planted cowpea variety, IT96D-452-1. This treatment also had the least number of Striga per net plot and per plant, which may be attributed to the effectiveness of the cowpea trap crop in stimulating the suicidal germination of the Striga seeds which would have otherwise attacked and reduced the productivity of the host plant. It may also be attributed to the effectiveness of the cropping method, with a ratio of sorghum : cowpea plants of 1:13, which improves the productivity of the system and at the same time suppresses the germination of Striga seeds. Keywords: Sorghum, yield, Intra-row, inter-row, cowpea, mixed-cropping

The most widespread symbiosis on Earth.

The most widespread symbiosis on Earth.

Plant–fungal symbiosis en gros and en détail

Plant–fungal symbiosis <i>en gros</i> and <i>en détail</i>

Seed treatment technology: An attractive delivery system for controlling root parasitic weed Striga with mycoherbicide

Coating sorghum seeds with Fusarium oxysporum (Foxy 2) for control of the root parasitic weed Striga, appears to be an attractive option for minimizing the inoculum amount, establishing the biocontrol agent in the potential infection zone of the host plants, and offering a simple, easy and economical delivery system. Our investigations resulted in the selection of appropriate seed coating materials and a suitable type and form of fungal inoculum. The coating materials tested were arabic gum (AG10%, 20%, 40%), carboxymethylcellulose (CMC1%, 2%) and pectin (LS 440, LM-5 CS) 1%, while the fungal inoculum included microconidia and fresh and dried chlamydospores produced using different substrates. Foxy 2 survived the seed treatment processing and showed excellent viability on seeds for at least 8 months of storage after coating. In general, the performance of 40% arabic gum in combination with dried chlamydospores was the best among the other types of inoculum and coating material tested. Regardless of the type and form of inoculum and coating materials tested, Foxy 2 was able to colonize all roots, even root tips and hairs of the host (sorghum), thereby meeting important criteria of a promising candidate for controlling Striga when applied as a seed treatment. The efficacy of treated sorghum seed with Foxy 2 using different coating materials in reducing S. hermonthica infestation was evaluated in pot and root chamber trials. Foxy 2 markedly reduced Striga emergence and dry weight and increased the percentage of the diseased emerged Striga shoots. However, the efficacy of seed coating varied according to the type and form of fungal inoculum as well as coating material. Coating sorghum seed with dried chlamydospore inoculum homogenized into 20% arabic gum (as adhesive) showed the highest efficacy of 81 and 77% (i.e., percent reduction in healthy emerged Striga shoots compared to the control treatment) against Striga using either sterilized or non-sterilized soil, respectively. In root chamber bioassays, the application of Foxy 2 in combination with AG40% significantly caused disease in 77% of the germinated Striga seeds and in all tubercles after 25 days of sowing. These findings provide an optimized coating protocol as an attractive delivery system for bioherbicides for root parasitic weeds.

Effect of growth medium, Striga seed burial distance and depth on efficacy of Fusarium isolates to control Striga hermonthica in Burkina Faso

Summary Striga hermonthica is a destructive parasite of cereal crops in the semi‐arid tropical zone. Two greenhouse experiments were conducted at Kamboinsé, Burkina Faso, to investigate the effect of inoculum substrate and location of Striga seeds on the ability of 14 indigenous Fusarium isolates to control the parasite. In Expt 1, Fusarium isolates reduced emerged Striga number, Striga vigour and dry biomass. As a result, sorghum dry biomass and grain yield were enhanced. Inoculum substrate did not influence the ability of Fusarium isolates to control Striga. In Expt 2, Fusarium isolates, substrate and their interaction significantly influenced germination of Striga seeds at both 35 and 50 days after sowing. Isolates grown on compost were more effective at reducing germination of Striga seeds than those grown on chopped sorghum straw. The per cent germination of seeds 50 days after sowing, buried at 5 cm depth, was significantly lower than that of seeds buried at 10 cm. At 10 cm depth, Fusarium isolates still reduced Striga seed germination with respect to the control; horizontal planting distance, 5 or 10 cm from sorghum hills, had no effect.

“Striga”, Economic Loss To Crops And The Control Measures In Africa With Particular Reference To Mubi North Local Government Area Of Adamawa State

Over many years striga has become a pest of crops in the sudano-sahelian regions and Eastern Africa. This parasitic plant sustains itself while damaging cultivated plants. It causes considerable yield losses of up to 100% in some major field crops. The minute seeds of striga germinate in a few days and cause remarkable losses. An estimated striga infestation of 150 – 150,000 plants was recorded in some farms around Vimtim, Mubi North Local Government Area on 19-22 Dec. 2003. Control measures such as herbicides application, use of resistant varieties, hand pulling of striga, etc are being practised by farmers with little success. KEY WORDS:- Striga hermonthica, Fireweed, Witch weed, Losses control measures, Mubi, Africa, Vimtim, Africa. Global Journal of Pure and Applied Sciences Vol.11(2) 2005: 175-178

The potential of planted shrub fallows to combat Striga infestation on maize

Two experiments were conducted on farms infested by the witch weed Striga hermonthica in western Kenya from 1997 to 1999 with the aim of testing whether short-duration planted shrub fallows that have potential to replenish soil fertility can reduce Striga on maize in rotation. In experiment 1, 1-year fallows of nine different species were compared with natural weed fallow and continuous maize for their effects on Striga on subsequent maize. In experiment 2, we tested whether Striga reduction by shrub fallows is associated with their in situ growing (i.e. root – soil interaction) or foliar biomass or combination of these two, using three fallow species. On a moderately Striga-infected field, fallows of Desmodium distortum, Sesbania sesban, Sesbania cinerascens, Crotalaria grahamiana and Tephrosia vogelii reduced Striga by 40 – 72% and increased maize yields by 224 – 316% compared with continuous maize. These species reduced Striga probably due to the combined effects of suicidal germination of Striga seed and increasing inorganic nitrogen (N) availability in the soil, which has a negative effect on Striga. Although Senna didymobotrya reduced Striga, it did not increase maize yield because of low quantity of N added to the soil through its foliar biomass. Senna occidentalis, Cajanus cajan and natural fallow did not affect Striga and maize yields. Although Tithonia diversifolia did not reduce Striga, it increased maize yield because of efficient nutrient recycling. On a highly Striga-infested field, planted fallows of C. grahamiana, S. spectabilis and S. sesban did not reduce Striga infection similar to natural fallow. Only in situ growing of shrub species, combined with incorporation of foliar biomass, significantly increased maize yields compared with continuous maize without inorganic fertilizer or green manuring of maize with only foliage of the fallow species. On moderately Striga-infected and N-depleted fields, planted fallows using species that germinate Striga seeds and produce high amounts of biomass such as S. sesban, C. grahamiana and T. vogelii can reduce Striga, but on severely Striga-infected fields perhaps longer-term testing may be needed to realize their positive effects.

Utility of indirect and direct selection traits for improving Striga resistance in two sorghum recombinant inbred populations

Breeding of sorghum ( Sorghum bicolor L. Moench) for resistance to the parasitic weed Striga hermonthica (Del.) Benth. has been hampered by the difficulty of evaluating host resistance in the field and lack of reliable screening techniques. Therefore, we investigated the value of various indirect and direct measures of Striga resistance as selection traits. Two sorghum recombinant inbred populations of 226 F 3:5 lines each were developed from the crosses (1) IS 9830×E 36-1 and (2) N 13×E 36-1. Striga-resistant line IS 9830 is characterized by low stimulation of Striga seed germination, whereas Striga-susceptible line E 36-1 produces germination stimulants in abundance. Line N 13 possesses “mechanical” resistance and probably also an antibiosis mechanism. Resistance was assessed in 1997 and 1998 using in vitro agar-gel assays with Striga seeds from Kenya, Mali, and Niger, pot trials in the respective three countries, and field experiments in Kenya and Mali. The agar-gel assay proved to be a useful, precise and fast indirect selection method to screen for sorghum entries with the low-stimulant character. However, correlation analysis showed that this resistance mechanism was ineffective in some environments, especially in Kenya, pointing to the necessity of field evaluation. Because of low heritability estimates and moderate to low correlations to Striga resistance under field conditions, pot screening appeared to be of limited use in breeding programs. The field trials confirmed the effectiveness of several direct measures of Striga resistance in sorghum: emerged Striga counts, Striga severity index, and area under the Striga number or severity progress curves. A two-row plot field layout with an empty row between plots, coupled with artificial infestation of test rows, lattice design and six replications offered an improved screening procedure that achieved high heritability. Significant genotype×environment interactions in the field experiments stress the importance of multi-locational trials to achieve stable Striga resistance.

FARMERS' PERCEPTION OF THE STRIGA PROBLEM AND ITS CONTROL IN NORTHERN NIGERIA

The parasitic angiosperms, Striga hermonthica and S. gesnerioides, obligate root parasites endemic in sub-Saharan Africa, constitute severe constraints to cereal and legume production in West and Central Africa. Over the years, a range of effective component technologies has been identified for Striga control in Africa. The potential of these technologies has been demonstrated under researcher-managed conditions. To promote farmer testing of the technologies, community workshops were conducted in 42 rural communities in Kaduna State, northern Nigeria. These revealed that agriculture was the main source of livelihood for most households. The three most important crops, maize, sorghum and pearl millet are attacked by S. hermonthica, regarded as the major constraint to crop production, often causing 70–100% crop loss. Farmers recognised two types of Striga damage (underground and aboveground), with greater damage being caused by underground Striga. Farmers attributed increasing incidence and severity of Striga damage to lack of capital, poor soil fertility, infestation of previously uninfested land by Striga seeds, and continuous cropping of host crops. The most widely used among the 15 existing Striga control techniques identified by the farmers were hoe weeding and hand pulling, application of inorganic fertilizer and manure, crop rotations, fallowing, and early planting. In assessing possible control measures farmers considered increased crop yield, reduced Striga reproduction and Striga emergence, greater crop vigour, and increased soil fertility as positive attributes. Negative attributes comprised increased labour requirement, higher costs, increased risk of crop damage or yield reduction, and lower quantity and quality of produce. Overall, a legume-cereal rotation was the most highly rated control option for S. hermonthica management evaluated by the farmers. The implications of these results are examined with respect to farmers' adoption and adaptation of Striga control options beyond the experimental plots.

Bioherbicidal effect of fumonisin B1, a phytotoxic metabolite naturally produced by Fusarium nygamai, on parasitic weeds of the genus Striga

Fusarium nygamai has been isolated and identified from diseased Striga hermonthica plants collected from sorghum fields in the Sudan. Fumonisin B1, produced by this fungus, was isolated and purified. In in vitro experiments, the bioherbicidal potential of this mycotoxin was evaluated against S. hermonthica and S. asiatica. Different concentrations (250, 500 and 1000 μg L−1 of water) of fumonisin B1, applied during the conditioning phase of the Striga seeds significantly reduced the germination of both species in a range of 19.8–32.2 and 34.5–47.6%, respectively. In addition, the length of the germ tubes was reduced and the germ tubes became brownish. Fumonisin B1 slightly delayed the emergence of Striga when 250 mg fumonisin B1 dissolved in 1 L of water were applied into the soil per pot before sowing sorghum. By the way of contrast, fumonisin B1 was very phytotoxic when Striga seedlings (leaves and stems) of different heights and ages were sprayed with a concentration series of 250, 500 and 1000 μg fumonisin B1 mL−1 until run-off, or when plants were injured with a scalpel before fumonisin B1 was applied into the injury at concentrations of 250 and 500 μg mL−1. One day after application, the plants showed symptoms of wilting, first at the top and then moving downwards. Leaves turned black and stems desiccated at the point of injuries. Within 4 days after the application, 55% of the plants tested were completely destroyed. In total, at the end of the experiment, 40 days after the treatment, 85% of the treated plants were killed by fumonisin B1, regardless of the concentration applied and the application technique used.

Organic amendments mitigate heterotrophic weed infestation in savannah agriculture

The relationship between soil fertility and Striga infestation was studied in 17 lightly infested compound and 17 highly infested bush fields in 15 villages of the Tolon/Kumbungu district of north Ghana. Thirty percent of the compound fields contained Striga seeds (on average 0.4 seeds in 100 g dried soil) but emergence of the parasite was rare (0.1–6% of the planting holes). The bush fields were contaminated with 11 Striga seeds/100 g soil on average and Striga plants were observed at 45.5% (10–81%) of the planting holes. Maize in the compound fields is continuously monocropped whereas mixed cropping is common in the bush fields (e.g. maize/sorghum, maize/groundnut). Fallow periods lasted 2 years on average in bush fields and the introduction of fallow was rather exceptional and linked to local practice in compound fields. Two-year fallows were too short to maintain soil productivity in the bush fields. In the compound fields organic manure (e.g. cattle dung, in addition to continuously dispersed human faeces and compound waste) was applied in 8 out of 10 years on average. The bush fields received organic manure or mineral fertilizer in 4 out of 10 years. Due to long-term application of organic manure the contents of phosphorus, nitrogen and organic carbon were significantly higher in compound field soils. The availability of nutrients (NH 4, NO 3, P bray 1 , K, Ca, Mg), the microbial biomass and the microbial activity benefited significantly from the manure treatment compared to bush fields. The results indicated that the Striga infestation is negatively related to the total nitrogen content and microbial biomass.

Changes in soil fertility and Striga hermonthica prevalence associated with legume and cereal cultivation in the Sudan savannah zone of Ghana

AbstractIn the Sudano–Sahelian zones of West Africa, cultivated land is degraded due to reduced fallow periods and Striga hermonthica (Del.) Benth. infestation, and poses a serious threat to sustainable food production. To provide options for addressing these problems, we investigated the possibility of replacing the short fallow periods with food legume cultivation. We tested this in two farming communities within the Sudan savannah zone of Ghana. In the 1997 and 1998 cropping seasons, selected farmers within each community planted soybean [Glycine max. (L.) Merr.] or bambara groundnuts [Vigna subterranea (L.) Verdc.] on continuously cropped, Striga‐infested farmlands, whereas lands that were maintained under two or three years of bush fallowing were planted to millet [Pennisetum glaucum (L.) R. Br.] or sorghum [Sorghum bicolor (L.) Moench]. Analysis of soil sampled from 0–15 cm (plough layer) revealed that contents of major plant nutrients were inadequate to support long‐term crop production. Within each farming community, total nitrogen content at initial sampling showed significant negative correlation with the number of Striga seeds in the plough layer. Under legume cultivation, soil organic carbon content increased and the number of Striga seeds per square metre decreased in both communities from a mean value of 28 183 seeds m−2 to 8185 seeds m−2. Under cereal cultivation Striga seed density increased from 9383 seeds m−2 to 16 696 seeds m−2. The study provides evidence that introduction of food legume cultivation on farmlands with high S. hermonthica infestation as an alternative to bush fallow system could help achieve sustainable crop production in the Sudan savannah zones of sub‐Saharan Africa. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Synthesis and bioactivity of labelled germination stimulants for the isolation and identification of the strigolactone receptor.

Strigolactones are highly potent germination stimulants for seeds of the parasitic weeds Striga and Orobanche spp. The induction of seed germination is thought to proceed via a receptor-mediated mechanism. Isolation and purification of the strigolactone receptor by affinity chromatography using immobilized avidin or streptavidin requires a biotin labelled strigolactone analogue. For this purpose biotin has been attached, directly as well as indirectly, via a hydrophilic linker to the amino function of optically active amino-GR24. Using the same amino substituted synthetic stimulant GR24, labelled stimulants have been prepared which may be suitable for the identification of the receptor by means of fluorescence correlation spectroscopy, scanning force microscopy or photoaffinity techniques. Bioassays of the labelled stimulants reveal that the germination activity on seeds of Striga hermonthica is retained. Crystal data for the diastereoisomer (+)-8 are reported.

In Vitro Germination of Striga hermonthica and Striga aspera Seeds by 1-Aminocyclopropane-1-Carboxylic Acid

Treatment of conditioned seeds of four isolates of Striga hermonthica and one isolate of Striga aspera with various concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), caused complex stimulation of germination patterns. GR 24, the strigol analogue served as a positive control and its stimulatory activity was comparable to that of ACC. When conditioned Striga seeds were treated with negative control that did not contain ACC, the stimulatory effect was lost. Overall, the germination data suggested a hormonal mode of action by ACC, which involves indirect stimulation of biosynthesis of ethylene that then triggers seed germination. The various mechanisms that have been proposed for the chemical and biological oxidation of ACC to generate ethylene are discussed.

Ability of excised root and stem pieces of maize, cowpea and soybean to cause germination of Striga hermonthica seeds

High variation in results from Striga hermonthica experiments is common. The cut-root assay for in vitro screening of host and non-host plant cultivars for germination of S. hermonthica is particularly insensitive. In this study, some factors of the cut-root technique that could effect significant variation in germination percentage of a population of S. hermonthica seeds induced by the same crop cultivar were studied. It was found that excised pieces of both root and stem of maize (hybrid var 8338-1), cowpea (var IT81D-994) and soybean (var TGx 1448-2E) stimulated the germination of S. hermonthica seeds. Germination percentages obtained with maize and cowpea stem pieces were significantly higher than those produced by root pieces. Moistening filter paper on which conditioned Striga seeds were subjected to germination stimulants with 5ml of distilled water resulted in significantly higher germination of the parasite's seeds induced by stimulants from both maize and soybean, than adding 3ml of water, regardless of the plant part tested. Starting germination stimulant extraction immediately after cutting plant parts gave significantly higher germination percentage of S. hermonthica seeds than starting 3h later, regardless of crop species and plant part tested. Conditioning S. hermonthica seeds and subsequent extraction of germination stimulant with non-sterile water generally resulted in higher germination percentage of S. hermonthica seeds than with sterile distilled water. These results are discussed and suggestions made about how to reduce variability of results of the cut-root method of in vitro assaying of germination stimulant production by hosts and trap crops of S. hermonthica.