Stimulation Of Germination Research Articles

Bacteria as potential biocontrol agents for managing purple witchweed (Striga hermonthica) in grain sorghum

Abstract Purple witchweed [Striga hermonthica (Delile) Benth.], a highly destructive parasitic weed, poses a significant threat to sorghum [Sorghum bicolor (L.) Moench] cultivation. This hemiparasitic plant intrudes its root system into the host plant, leading to substantial yield losses, particularly in susceptible genotypes. In the pursuit of eco-friendly solutions, the biocontrol approach has gained attention as a potential management strategy for Striga. In this study, 13 bacterial strains belonging to the genera Bacillus, Gluconobacter, Pseudomonas, and Streptomyces were investigated in vitro for their efficiency in controlling the early-stage development of Striga. Among the tested strains, Streptomyces morookaensis NRRL B-12429 demonstrated significant inhibition of Striga seed germination and radicle elongation at 54.36% and 61.84%, respectively, when applied to preconditioned seeds with a synthetic germination stimulant. The effect of S. morookaensis on the inhibition of Striga seed germination was more pronounced in the presence of the host plant, sorghum, at 62.35%. However, biopriming of sorghum seeds with S. morookaensis did not enhance the inhibitory effects on Striga seed germination but resulted in a greater reduction in radicle elongation at 74.64% compared with non-primed seeds. Additionally, the biopriming with S. morookaensis promoted the growth of shoots and roots of germinating sorghum, regardless of the presence of Striga seeds. These findings highlight the potential of S. morookaensis strain NRRL B-12429 as a viable candidate for biocontrol agent applications in sorghum cultivation. Further exploration and investigation of its biocontrol capabilities can provide valuable insights for sustainable management practices against Striga infestations.

A powerful molecular marker to detect mutations at sorghum LOW GERMINATION STIMULANT 1.

The parasitic weed Striga (Striga hermonthica) limits productivity of sorghum (Sorghum bicolor) and other cereals in sub-Saharan Africa and elsewhere. Improved host plant genetics is an effective control method but verified loci contributing to Striga resistance are limited. LOW GERMINATION STIMULANT 1 remains the only known sorghum locus affecting resistance to Striga. Functional loss (lgs1) alleles at this locus result in low Striga germination stimulant activity. We developed a robust polymerase chain reaction (PCR)-based LGS1 marker that detects all known natural lgs1 alleles. We have successfully used this marker to improve Striga resistance in our sorghum breeding program. To check its utility among diverse sets of germplasm, we genotyped 406 lines of the sorghum association panel (SAP) with the marker and phenotyped them for Striga germination stimulant activity. The SAP contains 23 lines (6%) with lgs1 mutations that involve a complete loss of this gene. Three previously described deletion alleles (lgs1-1, lgs1-2, and lgs1-3) ranging from 28.5 to 34kbp are present among SAP members with a new one, lgs1-6, missing nearly 50kbp relative to the reference genome. All 23 members of the SAP carrying lgs1 alleles had low Striga germination stimulant activity. The smaller previously described intragenic deletion mutations lgs1-4 and lgs1-5 are not present in the SAP. The LGS1 marker is useful for both detecting sources of lgs1 and introgressing Striga resistance into new genetic backgrounds.

Naturally Occurring Dehydrocostus Lactone Covalently Binds to KARRIKIN INSENSITIVE 2 by Dual Serine Modifications in Orobanche cumana and Arabidopsis.

Parasitic weeds, such as Orobanche and Striga, threaten crops globally. Contiguous efforts on the discovery and development of structurally novel seed germination stimulants targeting HYPOSENSITIVE TO LIGHT/KARRIKIN INSENSITIVE 2 (HTL/KAI2) have been made with the goal of weed control. Here, we demonstrate that a natural compound dehydrocostus lactone (DCL) exhibits effective "suicide germination" activity against Orobanche cumana and covalently binds to OcKAI2d2 on two catalytic serine sites with the second modification dependent on the first one. The same interactions and covalent modifications of DCL are also confirmed in AtKAI2. Further in-depth evolution analysis indicates that the proposed two catalytic sites are present throughout the streptophyte algae, hornworts, lycophytes, and seed plants. This discovery is particularly noteworthy as it signifies the first confirmation of a plant endogenous molecule directly binding to KAI2, which is valuable for unraveling the elusive identity of the KAI2 ligand and for targeting KAI2 paralogues for the development of novel germination stimulants.

The Evaluation of Debranone Series Strigolactone Agonists for Germination Stimulants in Orobanche Species.

Strigolactones (SLs) are plant hormones that regulate shoot branching. In addition, SLs act as compounds that stimulate the germination of root parasitic weeds, such as Striga spp. and Orobanche spp., which cause significant damage to agriculture worldwide. Thus, SL agonists have the potential to induce suicidal germination, thereby reducing the seed banks of root parasitic weeds in the soil. Particularly, phenoxyfuranone-type SL agonists, known as debranones, exhibit SL-like activity in rice and Striga hermonthica. However, little is known about their effects on Orobanche spp. In this study, we evaluated the germination-inducing activity of debranones against Orobanche minor. Analysis of structure-activity relationships revealed that debranones with electron-withdrawing substituents at the 2,4- or 2,6-position strongly induced the germination of Orobanche minor. Lastly, biological assays indicated that 5-(2-fluoro-4-nitrophenoxy)-3-methylfuran-2(5H)-one (test compound 61) induced germination to a comparable or even stronger extent than GR24, a well-known synthetic SL. Altogether, our data allowed us to infer that this enhanced activity was due to the recognition of compound 61 by the SLs receptor, KAI 2d, in Orobanche minor.

Sulfuric acid as a germination stimulator in forage soybean seeds (Neonotonia wightii)

Forage soybean (Neonotonia wightii) is a legume frequently used as a cover crop in field crops. However, as a species of the Phaseoloideae subfamily, it is characterized by the physical latency of the seed, which makes it difficult to obtain a high, homogeneous, and rapid germination. The aim of the present study was to determine which method of scarification stimulates the germination process to a greater extent. The following immersion times were evaluated: 5 to 20 minutes in 98% sulfuric acid, 24 hours in 5.4% sodium hypochlorite, water, and gibberellic acid [100 ppm], 15 minutes of treatment with sandpaper and the combination of these last two. They were distributed in a completely randomized experimental design, where eight treatments and a control were evaluated, with three replicates each and 200 seeds as experimental units, subjected to controlled conditions (germination chambers at constant temperatures and a relative humidity of 27 °C and 70%, respectively) during the spring of 2022. The results were favorable, a high germination percentage was obtained from seeds subjected to a 20-minute immersion time in sulfuric acid (90% germination and an average of six germinated seeds per day) and this was significantly higher than the rest, making it an effective method to break the physical latency of the seeds, as it removes the impermeable cover allowing inhibition and consequently the activation of the seed’s metabolism.

The role of strigolactone structural diversity in the host specificity and control of Striga, a major constraint to sub‐Saharan agriculture

Social Impact StatementThe parasitic weed Striga affects crops such as sorghum, maize, millet, and rice in over 40 countries on the African continent and negatively impacts the livelihood of over 300 million small‐holder farmers. Striga seeds can remain dormant in the soil for many years until they are triggered to germinate by germination stimulants, called strigolactones, exuded from the roots of their host. Here, the current knowledge on the biosynthesis of the strigolactones, their structural diversity, and biological relevance are reviewed. This knowledge could improve Striga control and thus improve the livelihood of small‐holder farmers.SummaryThe parasitic plant genus Striga causes major yield losses to several crops such as sorghum, millet, and rice in arid and semi‐arid regions of the tropics. For Striga to successfully parasitize its host plant, two conditions should be fulfilled: suitable germination conditions and the presence of a host plant that exudes so‐called germination stimulants, strigolactones, that are also as a signal to attract beneficial micro‐organisms such as arbuscular mycorrhizal (AM) fungi. Different plant species exude qualitatively and quantitatively different blends of strigolactones, and this plays a key role in determining Striga host specificity. Sorghum lgs1 genotypes with a mutation in a sulfotransferase (SbSOT4A), for example, exude orobanchol and are resistant to Striga, while 5‐deoxystrigol is the major strigolactone exuded by susceptible cultivars with wild type SbSOT4A. In this review, we discuss the current knowledge on the biosynthesis of the large diversity of strigolactones, how SbSOT4A may be involved in this, and how strigolactone diversity may contribute to microbiome recruitment. Finally, we discuss how knowledge on the importance of strigolactone diversity can contribute to Striga control.

Smoke-water treatment of seeds, an ancient technique for increasing seed vigor.

Germination is an essential phenomenon in the life cycle of plants, and a variety of external and internal factors influence it. Fire and the produced smoke have been vital environmental stimulants for the germination of seeds in many plant species, like Leucospermum cordifolium and Serruria florida. These plants do not germinate at all if fire and smoke are not present. This phenomenon of germination in plant species has existed in the ecosystem since ancient times. Various studies to study the response of seeds to smoke and its extracts have been undertaken for stimulation of germination by burning various plant materials and bubbling the smoke produced through water. The application of plant-derived smoke and smoke water is well known for promoting germination, breaking dormancy, and checking abiotic stress. This significantly indicates that plant-derived smoke contains some bioactive metabolites responsible for the physiological metabolism of seed germination and is involved in enhancing seed vigor. The present review deals with the ancient use of smoke and smoke extracts for seed priming, the cost-efficient method of its preparation, the mode of action of karrikins relating to its perception by plants, and its significant effects on various crops, including its ability to check biotic and abiotic stresses.

Enhanced astaxanthin production in Haematococcus lacustris by electrochemical stimulation of cyst germination

This study investigated the technical feasibility of using electrogermination to activate dormant cysts as an inoculum for subsequent 14-d photosynthetic astaxanthin production in Haematococcus lacustris. Electrotreatment affected the cell viability, surface charge, and morphology of H. lacustris cysts. At an optimal voltage of 2 V for 60 min, the cyst germination rate peaked at 44.6 % after 1 d, representing a 2.2-fold increase compared with that of the untreated control. Notably, electrogermination significantly enhanced both the astaxanthin content (44.9 mg/g cell) and productivity (13.2 mg/L/d) after 14 d of photobioreactor cultivation, corresponding to 1.7- and 1.5-fold increases compared with those in control, respectively. However, excessive electrotreatment, particularly at voltages exceeding 2 V or for durations beyond 60 min, did not enhance the astaxanthin production capability of H. lacustris. Proper optimization of renewable electrogermination can enable sustainable algal biorefinery to produce multiple bioactive products without compromising cell viability and astaxanthin productivity.

Spectroscopic Investigation of Tomato Seed Germination Stimulated by Trichoderma spp.

Seed germination is a complex process that can be negatively affected by numerous stresses. Trichoderma spp. are known as effective biocontrol agents as well as plant growth and germination stimulators. However, understanding of the early interactions between seeds and Trichoderma spp. remains limited. In the present paper, Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to reveal the nature of tomato seed germination as stimulated by Trichoderma. A rapid response of tomato seeds to Trichoderma spp. was observed within 48 h on Murashige and Skoog medium (MS) substrate, preceding any physical contact. Raman analysis indicated that both Trichoderma species stimulated phenolic compound synthesis by triggering plant-specific responses in seed radicles. The impact of T. harzianum and T. brevicompactum on two tomato cultivars resulted in alterations to the middle lamella pectin, cellulose, and xyloglucan in the primary cell wall. The Raman spectra indicated increased xylan content in NA with T9 treatment as well as increased hemicelluloses in GZ with T4 treatment. Moreover, T4 treatment resulted in elevated conjugated aldehydes in lignin in GZ, whereas the trend was reversed in NA. Additionally, FTIR analysis revealed significant changes in total protein levels in Trichoderma spp.-treated tomato seed radicles, with simultaneous decreases in pectin and/or xyloglucan. Our results indicate that two complementary spectroscopic methods, FTIR and Raman spectroscopy, can give valuable information on rapid changes in the plant cell wall structure of tomato radicles during germination stimulated by Trichoderma spp.

Evaluation of granular formulated strigolactone analogs for Striga suicidal germination.

Striga hermonthica, an obligate root parasitic weed, poses a significant threat to cereal production in sub-Saharan Africa. Lowering Striga seed bank in infested soils is a promising strategy to mitigate infestation levels. The dependency of Striga seed germination on strigolactones opens up the possibility of a 'suicidal germination' approach, where synthetic germination stimulants induce lethal germination in the absence of a host. Implementing this approach requires active germination stimulants with a suitable formulation for field application. Here, we describe the development of slow-releasing granular formulation of two potent germination stimulants 'Methyl Phenlactonoate 3' and 'Nijmegen-1' and the assessment of their activity under Laboratory, greenhouse, mini-field, and field conditions. Under laboratory conditions, the granular formulation of either of the two germination stimulants (1.25 mg per plate, corresponding to 0.09 mg a.i.) induced Striga seed germination at a rate of up to 43%. With 10 mg granular product (0.75 mg a.i.) per pot, we observed 77-83% reduction in Striga emergence under greenhouse pot conditions. Application of the formulated stimulants under artificially or naturally infested fields resulted in approximately 56%, 60%, and 72% reduction in Striga emergence in maize, sorghum, and millet fields in Kenya and Burkina Faso, respectively. Our findings on the newly designed granular formulation of Methyl Phenlactonoate 3 and Nijmegen-1 reveal encouraging prospects for addressing the Striga problem in Africa. These findings underscore several significant advantages of the formulated stimulants, including suitability for the African agricultural context, and, most importantly, their effectiveness in reducing Striga infection. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Non-Thermal Plasma (NTP) Treatment of Alfalfa Seeds in Different Voltage Conditions Leads to Both Positive and Inhibitory Outcomes Related to Sprout Growth and Nutraceutical Properties.

Non-thermal plasma (NTP) has proven to be a green method in the agricultural field for the stimulation of germination, growth, and production of nutraceutical compounds in some cases. However, the process is far from being fully understood and depends on the targeted plant species and the NTP used. In this work, we focus on the production of alfalfa sprouts from NTP-treated seeds under different voltage conditions. A flexible electrode configuration was used to produce the NTP, which can also be placed on packages for in-package treatments. The surface of the seeds was analyzed, indicating that the microstructure was strongly affected by NTP treatment. Biometric measurements evidenced the possibility of stimulating the sprout growth in some conditions by up to 50% compared to the sprouts obtained from untreated seeds. Biochemical traits for the sprouts obtained in different processing conditions were also studied, such as the concentrations of chlorophyll pigments, flavonoids and polyphenols, and antioxidant activity. Most NTP treatments led to inhibitory effects, proving the strong dependence between NTP treatment and targeted plant species.

Selective Influence of Chromolaena odorata Extracts on the Germination and Growth of Vegetable Crops: A Comparative Study of Aqueous and Methanolic Solutions

This study conducted a thorough assessment of how germination and growth of shoots and roots in eight vegetable crops are influenced by aqueous and methanolic extracts from Chromolaena odorata. Findings reveal a broad spectrum of germination responses to leaf extracts (13.3% to 86.7%), signaling the intricate dynamics at play between the plant's chemical compounds and the germination mechanism. Notably, Cucumis sativus (70% at AQE 5%) and Phaseolus vulgaris (56.70% at AQE 10%), displayed remarkable resilience and even stimulation of germination under specific extract concentrations, suggesting a potential selective stimulatory effect. For root extracts, the introduction of AQE and MTE decreased germination percentages across crops. A. esculentus had the highest germination rate at AQE 20%, significantly lower than the control (60%). Solanum. melongena tolerated AQE 5% best, while MTE 20% was most inhibitory. Conversely, Solanum lycopersicum experienced complete germination inhibition in both AQE and MTE of leaf and root extracts, indicating species-specific vulnerability to the allelopathic compounds within the extracts. Shoot growth mostly declined with higher extract concentrations, except in Solanum melongena, Capsicum annuum, and Zea mays, which saw increased shoot lengths under certain conditions. Root growth responses were mixed; Abelmoschus esculentus and Zea mays showed growth increases at some concentrations, in contrast to Cucumis sativus and Solanum melongena, which had limited growth. Methanolic extracts had a stronger inhibitory effect, likely due to their potent bioactive compounds. These findings highlight the importance of extract type, concentration, and crop species in weed management, providing insights for sustainable agricultural practices.

MicroRNA‐encoded peptides inhibit seed germination of the root parasitic plant Orobanche cumana

Societal Impact StatementThe root parasitic plant Orobanche cumana (sunflower broomrape) is one of the major pests of sunflower crops. Despite intense efforts to develop effective agricultural practices and breeding programs, selective control of broomrapes is still rare and ineffective in terms of sustainability. It is thus essential to develop new specific control methods against those pests. miRNA‐encoded peptides (miPEPs) are a new class of peptides regulating the expression of miRNAs and their corresponding target genes. This study demonstrates that certain miPEPs strongly inhibit the germination of broomrape seeds by regulating their miR gene, making them good candidates for use as biocontrol agents against this pathogen.Summary Root parasitic plants of the Orobanchaceae family are a constant and growing threat to agriculture worldwide. Among them, the parasitic weed Orobanche cumana, the sunflower broomrape, causes significant losses to sunflower production in European‐Asian and North African countries. Despite the use of several conventional control methods against this pathogen, none has proved effective or durable, underlining the need to develop innovative strategies. miRNA‐encoded peptides (miPEPs) are regulatory peptides stimulating the expression of their own primary transcript of miRNA, and plant watering with those molecules leads to down‐regulating specifically miRNA target genes and altering plant physiology. Through seed germination assays and qRT‐PCR analysis, we investigated the impact of exogenous treatments of synthetic miPEPs on broomrape seed germination. First, we report that the conserved miRNA repertoire of O. cumana consists of 39 members. Thirty‐nine miPEPs were designed, synthetized, and assayed, 11 of which strongly inhibited O. cumana seed germination. Interestingly, miPEP319a showed the strongest inhibiting effect while miPEP319b did not. Three out of the four corresponding miR319 target genes showed upregulation after treatment with a germination stimulant, which was impaired by treatment with miPEP319a. This downregulation of expression is associated with an increase in the expression of the corresponding pri‐miR319a. We reveal thus that the use of miPEPs can increase our knowledge of key molecular mechanisms underlying a complex parasite interaction and should provide a new phytosanitary method to control broomrape parasitism with highly specific and biodegradable natural substances.

Development of a Standardized Soybean Cyst Nematode Screening Assay in Pennycress and Identification of Resistant Germplasm.

The prospect of incorporating pennycress as an oilseed cover crop in the Midwest's corn-soybean rotation system has drawn researcher and farmer attention. The inclusion of pennycress will be beneficial as it provides an excellent soil cover to reduce soil erosion and nutrient leaching while serving as an additional source for oilseed production and income. However, pennycress is an alternative host for soybean cyst nematode (SCN), which is a major biological threat to soybean that needs to be addressed for sustainable pennycress adoption into our current production systems. To develop a standardized SCN resistance screening strategy in pennycress, we tested and optimized five parameters: (i) germination stimulants, (ii) inoculation timing, (iii) inoculation rate, (iv) experimental incubation time, and (v) susceptible checks. The standardized SCN resistance screening protocol includes the following: (i) treating pennycress seeds with gibberellic acid for 24 h, (ii) transplanting seedlings 12 to 15 days after initiating germination and inoculating 10 to 12 days after transplantation, (iii) inoculating at a rate of 1,500 eggs/100 cc soil (1,500 eggs per plant), (iv) processing roots at 30 days after inoculation, and (v) using susceptible pennycress accession Ames 32869 to calculate the female index. The standardized protocol was used to quantify the response of a diverse set of pennycress accessions for response against SCN HG type 1.2.5.7 and HG type 7. While there were no highly resistant pennycress lines identified, 15 were rated as moderately resistant to HG type 1.2.5.7, and eight were rated moderately resistant to HG type 7. The resistant lines identified in this study could be utilized to develop SCN-resistant pennycress cultivars. The study also opens a new avenue for research to understand SCN-pennycress interactions through molecular and genomic studies. This knowledge could aid in the successful inclusion of pennycress as a beneficial cover/oilseed crop in the United States Midwest.[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Encapsulation of garlic oil and diallyl disulfide with β-cyclodextrin for white rot control in Allium crops

White rot, caused by Sclerotium cepivorum, is a devastating disease of onion, garlic, and other Allium crops. The pathogen reproduces and survives by forming sclerotia, which can survive in field soils for decades. The pathogen is host-specific to Allium spp., and sclerotia germinate in response to sulfur compounds produced by Allium roots. Sulfur-containing compounds such as diallyl disulfide (DADS) and garlic oil can stimulate sclerotia germination and effectively reduce pathogen populations before planting an Allium crop; however, these compounds are often highly volatile and difficult to handle and apply. Therefore, a study was conducted to encapsulate DADS and garlic oil with β-cyclodextrin (β-CD) to protect sulfur volatiles from interactions with soil and against oxidation, degradation, and evaporation. Microcapsule extract analysis showed that garlic oil and DADS were successfully encapsulated with greater than 90% recovery of the starting product. In addition, the micro-encapsulation process did not change the chemical compounds, but their proportions were altered. Furthermore, lab and growth chamber incubation experiments revealed that DADS and DAS could be slowly released into the soil from microcapsules and worked effectively for white rot sclerotia germination. Compared to the non-treated control, liquid DADS, microcapsules of DADS, and microcapsules of garlic oil reduced sclerotia populations by between 73.7 and 82.3%, depending on the treatment. When compared to liquid DADS and garlic oil, the encapsulated formulations DADS and garlic oil are equally effective but easier to handle, which can provide more flexibility in terms of timing, placement, and method of sclerotia germination stimulant applications.

Contribution of Signaling Partner Association to Strigolactone Receptor Selectivity.

The parasitic plant witchweed, Striga hermonthica, results in agricultural losses of billions of dollars per year. It perceives its host via plant hormones called strigolactones, which act as germination stimulants for witchweed. Strigolactone signaling involves substrate binding to the strigolactone receptor, followed by substrate hydrolysis and a conformational change from an inactive, or open state, to an active, or closed state. In the active state, the receptor associates with a signaling partner, MAX2. Recently, it was shown that this MAX2 association process acts as a strong contributor to the uniquely high signaling activity observed in ShHTL7; however, it is unknown why ShHTL7 has enhanced MAX2 association affinity. Using an umbrella sampling molecular dynamics approach, we characterized the association processes of AtD14, ShHTL7, a mutant of ShHTL7, and ShHTL6 with MAX2 homologue OsD3. From these results, we show that ShHTL7 has an enhanced standard binding free energy of OsD3 compared to those of the other receptors. Additionally, our results suggest that the overall topology of the T2/T3 helix region is likely an important modulator of MAX2 binding. Thus, differences in MAX2 association, modulated by differences in the T2/T3 helix region, are a contributor to differences in signaling activity between different strigolactone receptors.

Evaluation of Different Geographic Provenances of Silver Fir (Abies alba) as Seed Sources, Based on Seed Traits and Germination

The evaluation of the diversity of silver fir (Abies alba Mill.) populations and the reproductive traits of the trees are of great importance for the conservation of genetic resources and forest management. Therefore, important reproductive characteristics of A. alba from seven Romanian provenances, considered as different geographical populations, were evaluated. Significant differences between the provenances were observed for the female cones, seed morphology, and germination. Due to the relatively low germination of silver fir seeds, germination tests were conducted to identify treatments that can stimulate the germination capacity. Thus, the seed germination capacity was determined using four different stimulation treatments and the data were compared with those of untreated seeds, designed as the control. Considerable differences were recorded not only depending on the seed provenances, but also regarding the treatments applied to stimulate germination (Atonik biostimulator, scarification, acetone, H2SO4). The biostimulator seed treatment gave the highest germination percentage, while sulfuric acid caused the lowest germination. The research also revealed that not all the forest seed sources provide high-quality reproductive material. Furthermore, for some of the seed resources, even the germination stimulation treatments did not result in adequate germination. The findings are pertinent and valuable for identifying suitable forest populations as seed sources, as well as for their use in silver fir reforestation programs.

Effect of Algicide Based on Metabolites, Allelochemicals of Aquatic Plants on Seed Germination and the Development of Seedlings of Three Species of Helophytes

For the first time, the effect of a patented alcoholic solution of algicide on seed germination and the development of seedlings of three species of helophytes Sparganium emersum, S. glomeratum and Schoenoplectus lacustris was studied based on gallic, tetradecanoic, heptane and octane organic acids. Significant differences were found in the effect of different algicide concentrations (0.1, 1.0 and 10.0 mg/L) on seed germination and the initial stages of seedling development of three species of helophytes. We observed the stimulation of germination of Sparganium emersum seeds at a concentration of 10.0 mg/L and inhibition of this process in S. glomeratum at concentrations of 1.0 and 0.1 mg/L. No significant effect of algicide on the germination of Schoenoplectus lacustris seeds was found. According to the degree of increase in the resistance of morphological parameters of plants to the effect of different algicide concentrations, seedlings of three species of helophytes are arranged in the following series: Schoenoplectus lacustris Sparganium glomeratum S. emersum.

Strigolactone biosynthesis lgs1 mutant alleles mined from the sorghum accession panel are a promising resource of resistance to witchweed (Striga) parasitism

Societal Impact StatementStriga is a parasitic plant that greatly limits the production of Africa's most staple cereals, including sorghum. Infection occurs when the parasite germinates in response to biomolecules emitted into the soil from the host's roots. Some sorghum genotypes harbor a mutation that makes them ineffective in stimulating Striga seed germination. This resistance is of great importance because of its possible application in Striga management. Here, additional resistant sorghum genotypes with varying levels of Striga resistance are discussed in the context of their candidacy for integration in breeding programs and their possible role in alleviating food insecurity in sub‐Saharan Africa by reducing crop losses because of Striga infestation.Summary Sorghum is a food staple for millions of people in sub‐Saharan Africa, but its production is greatly diminished by Striga, a parasitic weed. An efficient and cost‐effective way of managing Striga in smallholder farms in Africa is to deploy resistant varieties of sorghum. Here, we leverage genomics and the vast genetic diversity of sorghum—evolutionarily adapted to cope with Striga parasitism in Africa—to identify new Striga‐resistant sorghum genotypes by exploiting a resistance mechanism hinged on communication molecules called strigolactones (SLs), exuded by hosts to trigger parasite seed germination. We achieved this by mining for mutant alleles of the LOW GERMINATION STIMULANT 1 (LGS1) that are ineffective in stimulating Striga germination from the sorghum accession panel (SAP). Our analysis identified lgs1 sorghum genotypes, which we named SAP‐lgs1. SAP‐lgs1 had the SL exudation profile of known lgs1 sorghum, whose hallmark is the production of the low inducer of germination, orobanchol. Laboratory and field resistance screens showed that the SAP‐lgs1 genotypes also exhibited remarkable resistance against Striga. Our findings have the potential to reduce crop losses because of Striga parasitism and therefore have far‐reaching implications for improving food security in Africa.

Essential plant nutrients impair post‐germination development of Striga in sorghum

Societal Impact StatementInfestation by the parasitic weed Striga is a major cause of cereal crop production losses on smallholder farms in Africa. Essential plant nutrients play an important indirect role in parasite seed germination, the first prerequisite for successful parasitism. Here, we demonstrate that increasing the nutrient availability for the host plant can also impede Striga development beyond its germination, independent of the resistance levels of the sorghum host. This insight provides additional support for crop protection recommendations to Striga‐affected farmers. Growing a resistant crop variety combined with adequate levels of fertilisers should be the backbone of defence against this parasitic weed.Summary Striga hermonthica is a widespread parasitic weed in sub‐Saharan Africa and an important biotic constraint to sorghum production. Resistant varieties and fertilisers are crucial components of integrated Striga management. N and P fertilisers reduce the production of host‐plant strigolactones, known as Striga germination stimulants, and thereby reduce infection. Whether essential plant nutrients affect the parasite–host interaction beyond Striga germination is unknown. We conducted mini‐rhizotron assays to investigate the effects of macronutrient and micronutrient availability on post‐germination Striga development. Four sorghum genotypes (Framida, IS10978, N13, IS9830) covering the complete array of known mechanisms of post‐attachment resistance were compared with susceptible genotype Ochuti. Plants were infected with pre‐germinated Striga seeds and subjected to four nutrient treatment levels: (1) 25% of the optimal concentration of Long Ashton solution for cereals; (2) 25% macronutrient and optimal micronutrient concentration; (3) optimal macronutrient and 25% micronutrient concentration; and (4) optimal macronutrient and micronutrient concentrations. Compared with the 25% base nutrient level, treatments supplemented with macronutrients reduced the number of viable vascular connections established by pre‐germinated Striga seedlings as well as the total parasite biomass on the sorghum root system. Macronutrient treatment effects were observed across sorghum genotypes, independent of the presence and type of post‐attachment resistance, but appeared to specifically improve mechanical resistance, hypersensitive and incompatibility responses before Striga reaches the host‐root xylem. This study demonstrates, for the first time, that nutrient availability drives Striga parasitism beyond the germination stages. Increased availability of nutrients, in particular macronutrients, enhances host‐plant resistance in post‐attachment stages, reinforcing the importance of current fertiliser recommendations.