Seed pretreatment with brassinosteroids stimulates sunflower immunity against parasitic weed (Orobanche cumana) infection.

Broomrape (Orobanche cumana) negatively affects sunflower, causing severe yield losses, and thus, there is a need to control O. cumana infestation. Brassinosteroids (BRs) play key roles in plant growth and provide resilience to weed infection. This study aims to evaluate the mechanisms by which BRs ameliorate O. cumana infection in sunflower (Helianthus annuus). Seeds were pretreated with BRs (1, 10, and 100 nM) and O. cumana inoculation for 4 weeks under soil conditions. O. cumana infection significantly reduced plant growth traits, photosynthesis, endogenous BRs and regulated the plant defence (POX, GST), BRs signalling (BAK1, BSK1 to BSK4) and synthesis (BRI1, BR6OX2) genes. O. cumana also elevated the levels of malondialdehyde (MDA), hydroxyl radical (OH-), hydrogen peroxide (H2O2) and superoxide (O2 •-) in leaves/roots by 77/112, 63/103, 56/97 and 54/89%, as well as caused ultrastructural cellular damages in both leaves and roots. In response, plants activated a few enzymes, superoxide dismutase (SOD), peroxidase (POD) and reduced glutathione but were unable to stimulate the activity of ascorbate peroxidase (APX) and catalase (CAT) enzymes. The addition of BRs (especially at 10 nM) notably recovered the ultrastructural cellular damages, lowered the production of oxidative stress, activated the key enzymatic antioxidants and induced the phenolic and lignin contents. The downregulation in the particular genes by BRs is attributed to the increased resilience of sunflower via a susceptible reaction. In a nutshell, BRs notably enhanced the sunflower resistance to O. cumana infection by escalating the plant immunity responses, inducing systemic acquired resistance, reducing oxidative or cellular damages, and modulating the expression of BR synthesis or signalling genes.

Are root parasitic broomrapes still a good target for bioherbicide control?

Root parasitic weeds of the genera Orobanche and Phelipanche (commonly named broomrapes) are responsible for enormous yield losses of several crops all around the world. Traditional weed management methods, including among others the use of herbicides, soil fumigation and solarization, and mechanical, agronomic or physical methods, may have limits of use or can provide a modicum of control. Difficulties in controlling parasitic weeds are due to both the enormous number of seeds produced by each plant that can remain viable for many years, even in the absence of a host, and to the unique physiological and biological properties of the parasite. Although long considered a suitable and promising approach, biological control, in particular the use of microbial organisms or compounds stimulating or inhibiting seed germination, has had no commercial success and no products have reached the market. This article provides a quick overview of the bioherbicide approaches attempted until now, briefly discussing the causes of the failures and the possibility to improve biocontrol agents' effectiveness. Indeed, despite the failures, the 'bioherbicide' approach deserves renewed interest in light of the enormous scientific and technological progress made in past years, which offers new chances of success. © 2023 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Inhibition of broomrape germination by 2,4-diacetylphloroglucinol produced by environmental Pseudomonas.

Parasitic weeds such as broomrapes (Phelipanche ramosa and Orobanche cumana) cause severe damage to crops and their development must be controlled. Given that phloroglucinol compounds (PGCs) produced by environmental Pseudomonas could be toxic towards certain plants, we assessed the potential herbicidal effect of the bacterial model Pseudomonas ogarae F113, a PGCs-producing bacterium, on parasitic weed. By combining the use of a mutagenesis approach and of pure PGCs, we evaluated the in vitro effect of PGC-produced by P. ogarae F113 on broomrape germination and assessed the protective activity of a PGC-producing bacteria on oilseed rape (Brassica napus) against P. ramosa in non-sterile soils. We showed that the inhibition of the germination depends on the PGCs molecular structure and their concentrations as well as the broomrape species and pathovars. This inhibition caused by the PGCs is irreversible, causing a brown coloration of the broomrape seeds. The inoculation of PGCs-producing bacteria limited the broomrape infection of P. ramosa, without affecting the host growth. Moreover, elemental profiling analysis of oilseed rape revealed that neither F113 nor applied PGCs affected the nutrition capacity of the oilseed rape host. Our study expands the knowledge on plant-beneficial Pseudomonas as weed biocontrol agents and opens new avenues for the development of natural bioherbicides to enhance crop yield.

Screening for potential mycoherbicides within the endophyte community of Phelipanche ramosa parasitizing tobacco.

Branched broomrape (Phelipanche ramosa (L.) Pomel) is an achlorophyllous root parasitic plant with a wide host range. Its complex management is leading to the abandonment of tobacco or oilseed rape cultivation in the most affected regions in France. Among broomrape regulation factors, soil microorganisms such as fungi seem to be a relevant biocontrol lever. The aim of this work was to detect potential mycoherbicides among fungal endophytic colonizers of P. ramosa parasitizing tobacco. Our hypothesis was that both the inhibitory of broomrape seed germination and the necrotic activities are characteristic of the fungal isolates whatever their taxonomic position. To test this hypothesis, we analysed the taxonomic and functional diversity of fungal isolates of symptomatic P. ramosa collected from infested tobacco-growing regions in France in order to identify one or more fungal strains for future biocontrol. The fungal isolates were characterized using morphological and molecular identification tools and tested for their ability to inhibit the germination of P. ramosa seeds, their necrotic activity on the stems of the pest and their non-pathogenicity to the host plant. We highlighted the specific richness of fungal colonizers associated with symptomatic P. ramosa. Among the 374 collected isolates, nearly 80% belonged to 19 Fusarium species. Eighty-seven isolates representative of this diversity also showed functional diversity by inhibiting seed germination of the parasite. The 20 best-performing isolates showed differences in germination inhibition of P. ramosa at the intraspecific level. Among these 20 fungal isolates, a set of 15 randomly selected isolates was tested for their necrotic activity on the parasite stems. Fusarium venenatum isolates showed dual competence, i.e. germination inhibition and necrotic activity, and were non-pathogenic to tobacco. This led us to discuss the potential mycoherbicidal effect of this fungal species on P. ramosa.

Genome-wide investigation of bHLH genes and expression analysis under different biotic and abiotic stresses in Helianthus annuus L.

The basic helix-loop-helix (bHLH) transcription factors play important roles in many processes such as plant growth, metabolism and response to biotic/abiotic stresses. Sunflower (Helianthus annuus) is a major oil crop, cultivated throughout the world. However, no systematic characterization of bHLH gene members in sunflower (HabHLH) and their functions involved in drought, cadmium tolerance and Orobanche cumana resistance has been reported yet. In this study, 183 HabHLH genes were identified and named according to their chromosomal locations. We classified these proteins into 21 subfamilies by phylogenetic tree analysis. Subsequently, DNA-binding patterns, sequence analysis, duplication analysis and gene structures were analyzed. All of the HabHLH genes were randomly distributed on 17 chromosomes, and 10 pairs of tandem duplicated genes and one pair of segmental duplicated genes were detected in the HabHLH family. Among the duplicated gene pairs, eight pairs of HabHLH genes suffer from positive selection. Moreover, qRT-PCR results revealed significant up-regulated expression of HabHLH024 gene in response to both abiotic (cadmium, drought) and biotic (Orobanche cumana) stresses, suggesting its important functions in response to different stresses. Therefore, HabHLH024 would be the potential candidate gene for the sunflower tolerance breeding.

Host sunflower-induced silencing of parasitism-related genes confers resistance to invading Orobanche cumana.

Orobanche cumana is a holoparasitic plant that attaches to host-plant roots and seriously reduces the yield of sunflower (Helianthus annuus L.). Effective control methods are lacking with only a few known sources of genetic resistance. In this study, a seed-soak agroinoculation (SSA) method was established, and recombinant tobacco rattle virus vectors were constructed to express RNA interference (RNAi) inducers to cause virus-induced gene silencing (VIGS) in sunflower. A host target gene HaTubulin was systemically silenced in both leaf and root tissues by the SSA-VIGS approach. Trans-species silencing of O. cumana genes were confirmed for 10 out of 11 target genes with silencing efficiency of 23.43%-92.67%. Knockdown of target OcQR1, OcCKX5, and OcWRI1 genes reduced the haustoria number, and silencing of OcEXPA6 caused further phenotypic abnormalities such as shorter tubercles and necrosis. Overexpression of OcEXPA6 caused retarded root growth in alfalfa (Medicago sativa). The results demonstrate that these genes play an important role in the processes of O. cumana parasitism. High-throughput small RNA (sRNA) sequencing and bioinformatics analyses unveiled the distinct features of target gene-derived siRNAs in O. cumana such as siRNA transitivity, strand polarity, hotspot region, and 21/22-nt siRNA predominance, the latter of which was confirmed by Northern blot experiments. The possible RNAi mechanism is also discussed by analyzing RNAi machinery genes in O. cumana. Taken together, we established an efficient host-induced gene silencing technology for both functional genetics studies and potential control of O. cumana. The ease and effectiveness of this strategy could potentially be useful for other species provided they are amenable to SSA.

Hormonal seed-priming improves tomato resistance against broomrape infection.

Although it is well known that parasitic weeds such as Orobanche (broomrape) significantly reduce the yield of economically important crops, their infection-induced oxidative changes need more exploration in their host plants. Moreover, applying an eco-friendly approach to minimize the infection is not yet available. This study was conducted to understand the effect of Orobanche ramosa infection on oxidative and redox status of tomato plants and the impact of hormonal (indole acetic acid (IAA); 0.09 mM and salicylic acid (SA); 1.0 mM) seed-priming upon mitigating the infection threats. Although Orobanche invades tomato roots, its inhibitory effects on shoot biomass were also indicted. Orobanche infection usually induces oxidative damage i.e., high lipid peroxidation, lipoxygenase activity and H2O2 levels, particularly for roots. Interestingly, hormonal seed-priming significantly enhanced tomato shoots and roots growth under both healthy and infected conditions. Also, IAA and SA treatment significantly reduced Orobanche infection-induced oxidative damage. The protective effect of seed-priming was explained by increasing the antioxidant defense markers including the antioxidant metabolites (i.e., total antioxidant capacity, carotenoids, phenolics, flavonoids, ASC, GSH, tocopherols) and enzymes (CAT, POX, GPX, SOD, GR, APX, MDHAR, DHAR), particularly in infected tomato seedlings. Additionally, cluster analysis indicated the differential impact of IAA- and SA-seed-priming, whereas lower oxidative damage and higher antioxidant enzymes' activities in tomato root were particularly reported for IAA treatment. The principal component analysis (PCA) also proclaimed an organ specificity depending on their response to Orobanche infection. Collectively, here and for the first time, we shed the light on the potential of seed-priming with either IAA or SA to mitigate the adverse effect of O. ramosa stress in tomato plants, especially at oxidative stress levels.

Genetic and Genomic Tools in Sunflower Breeding for Broomrape Resistance.

Broomrape is a root parasitic plant causing yield losses in sunflower production. Since sunflower is an important oil crop, the development of broomrape-resistant hybrids is the prime breeding objective. Using conventional plant breeding methods, breeders have identified resistant genes and developed a number of hybrids resistant to broomrape, adapted to different growing regions worldwide. However, the spread of broomrape into new countries and the development of new and more virulent races have been noted intensively. Recent advances in sunflower genomics provide additional tools for plant breeders to improve resistance and find durable solutions for broomrape spread and virulence. This review describes the structure and distribution of new, virulent physiological broomrape races, sources of resistance for introduction into susceptible cultivated sunflower, qualitative and quantitative resistance genes along with gene pyramiding and marker assisted selection (MAS) strategies applied in the process of increasing sunflower resistance. In addition, it presents an overview of underutilized biotechnological tools, such as phenotyping, -omics, and genome editing techniques, which need to be introduced in the study of sunflower resistance to broomrape in order to achieve durable resistance.

Salicylic acid confers resistance against broomrape in tomato through modulation of C and N metabolism.

It is well known that parasitic weeds such as Orobanche (broomrape) significantly decrease crop growth and yield. Although hormonal priming is a well-known inducer of plant resistance against broomrapes (Orobanche spp.), the metabolic events associated with such resistance are poorly understood. Therefore, the current work was undertaken to elucidate the role of SA in inducing tomato resistance against Orobanche, considering its impact on carbon and nitrogen metabolism of the host. Total carbon and nitrogen and levels of carbon (sugars, organic acids and fatty acids) and nitrogen (amino acids and polyamines)-containing metabolites as well as the activities of some key enzymes involved in their metabolic pathways were evaluated. Broomrape infection significantly disrupted C/N ratio in the host roots. On contrary, SA treatment markedly induced accumulation of sugars, organic acids, fatty acids, amino acids as well as polyamines in healthy plants. Under broomrape challenge, SA mitigated the infection-induced growth inhibition by improving the level of nitrogen-containing osmoprotectants (proline, arginine and some polyamines). However, a decrease was observed in some C and N assimilates which are well known to be potentially transferred to the parasite, such as sucrose, asparagine, alanine, serine and glutamate. Interestingly, SA treatment induced the catapolism of polyamines and fatty acids in the host root. Accordingly, our study suggests that SA-induced resistance against broomrape relies on the rational utilization of C and N assimilates in a manner that disturbs the sink strength of the parasite and/or activates the defense pool of the host.

Inheritance of faba bean resistance to Broomrape, genetic diversity and QTL mapping analysis.

Six faba bean parents and their F1 and F2 generations were used in this investigation to study the genetic system controlling resistance of faba bean (Vicia faba L.) to broomrape (Orobanche crenata). Most of the F1 hybrids were tolerant to broomrape. In the F2 generation, the population P5 × P6 (Assiut 125 × Romy 12) gave the highest value of relative yield and tolerance index. Heterosis and inbreeding depression were only positive in number of tillers/plant and seed yield/plant characters. The results indicated that the additive effect was more important than the dominance one (D > H1) only for No. of pods/plant in the F1 generation. Moreover, the narrow-sense heritability was low for most of the studied traits. Three molecular marker systems, namely RAPD, ISSR and SRAP were used for identification and estimation of the genetic diversity among the six faba bean genotypes. The three molecular markers generated DNA unique bands for all genotypes. Only, eight DNA fragments were related to Orobanche tolerance. Clearly and reproducible polymorphic markers were subjected to QTL analysis. The linkage analysis showed that, out of 34 marker loci segregated in the F2 population, 29 (85.29%) were mapped on three linkage groups. QTL analysis using SIM method performed for the 29 markers assigned to LG-1, LG-2 and LG-3 with the eight traits, number of tillers/plant, plant height, number of pods/plant, seed yield/plant, number of broomrape spikes per plant, height of broomrape spikes, relative yield and tolerance index, showing 12 putative QTLs for all traits except number of tillers/plant. From this study, it is clear that P5 × P6 (Assiut 125 × Romy12) population could be considered promising for selection for resistance to broomrape infestation.

Hybrid-type strigolactone analogues derived from auxins.

BACKGROUND: Strigolactones (SLs) have a vast number of ecological implications because of the broad spectrum of their biological activities. Unfortunately, the limited availability of SLs restricts their applicability for the benefit of humanity and renders synthesis the only option for their production. However, the structural complexity of SLs impedes their economical synthesis, which is unfeasible on a large scale. Synthesis of SL analogues and mimics with a simpler structure, but with retention of bioactivity, is the solution to this problem. RESULTS: Here, we present eight new hybrid-type SL analogues derived from auxin, synthesized via coupling of auxin ester [ethyl 2-(1H-indol-3-yl)acetate] and of ethyl 2-phenylacetate with four D-rings (mono-, two di- and trimethylated). The new hybrid-type SL analogues were bioassayed to assess the germination activity of seeds of the parasitic weeds Striga hermonthica, Orobanche minor and Phelipanche ramosa using the classical method of counting germinated seeds and a colorimetric method. The bioassays revealed that analogues with a natural monomethylated D-ring had appreciable to good activity towards the three species and were the most active derivatives. By contrast, derivatives with the trimethylated D-ring showed no activity. The dimethylated derivatives (2,4-dimethyl and 3,4-dimethyl) were slightly active, especially towards P. ramosa. CONCLUSIONS: New hybrid-type analogues derived from auxins have been prepared. These analogues may be attractive as potential suicidal germination agents for parasitic weed control because of their ease of preparation and relevant bioactivity. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Assessment of the yield loss imparted by Orobanche aegyptiaca in tomato in Pakistan.

Broomrapes (Orobanche sp.) are root holoparasitic plants causing severe damage to various families of horticultural crops. A Preliminary survey was carried in tomato fields infested with orobanche in Potohar plateau of Pakistan. Results indicated that each planting bed comprising10-12 tomato plants contained 7-8 parasitic weeds. Overall survey indicated the 65-70% plants suffered partial or complete yield loss. Further, it was estimated that the number of weeds inhabiting plant-1 was ranged from 2-4. Yield loss was estimated at 57.17 tons/ha while in terms of financial loss, it was 2579.87 $/ha. Hence total estimated loss on the total surveyed area of 16 hectares was 41395.85 $. The high potential of tomato cultivation in Pakistan reinforces the urgent protection measures to resolve this emerging issue.

Low Infection of Phelipanche aegyptiaca in Micro-Tom Mutants Deficient in CAROTENOIDCLEAVAGE DIOXYGENASE 8.

Strigolactones (SLs), a group of plant hormones, induce germination of root-parasitic plants and inhibit shoot branching in many plants. Shoot branching is an important trait that affects the number and quality of flowers and fruits. Root-parasitic plants, such as Phelipanche spp., infect tomato roots and cause economic damage in Europe and North Africa-hence why resistant tomato cultivars are needed. In this study, we found carotenoid cleavage dioxygenase 8-defective mutants of Micro-Tom tomato (slccd8) by the "targeting induced local lesions in genomes" (TILLING) method. The mutants showed excess branching, which was suppressed by exogenously applied SL. Grafting shoot scions of the slccd8 mutants onto wild-type (WT) rootstocks restored normal branching in the scions. The levels of endogenous orobanchol and solanacol in WT were enough detectable, whereas that in the slccd8 mutants were below the detection limit of quantification analysis. Accordingly, root exudates of the slccd8 mutants hardly stimulated seed germination of root parasitic plants. In addition, SL deficiency did not critically affect the fruit traits of Micro-Tom. Using a rhizotron system, we also found that Phelipanche aegyptiaca infection was lower in the slccd8 mutants than in wild-type Micro-Tom because of the low germination. We propose that the slccd8 mutants might be useful as new tomato lines resistant to P. aegyptiaca.

Orobanche foetida resistance in two new faba bean genotypes produced by radiation mutagenesis.

PURPOSE: Broomrape produces serious damage to many legume crops and, particularly, becomes a limiting factor for faba bean (Vicia faba L.) production in the Mediterranean basin. Currently, several traditional methods of control have been developed, but none has proved to be effective for this parasite. However, breeding for resistance to this pest remains as one of the most feasible and environment-friendly methods for managing broomrape, but the mechanisms governing the interaction between the parasite and the host are not yet well understood. Therefore, we studied the behavior and molecular and enzymatic changes associated with the resistance to Orobanche foetida in faba bean mutants, which were obtained through radiation mutagenesis. MATERIALS AND METHODS: Three faba bean genotypes were used in this study, the variety 'Badï', characterized by high productivity in Orobanche-free soils and susceptibility to O. foetida, and two mutant lines P2M3 and P7M3 (derived from radio mutagenesis program), selected for their higher resistance to O. foetida in a field evaluation. The infection progress and the relative changes in the co-culture response, the enzymatic activities changes and the efficiency of the root extract stimulants from the host plant were followed and evaluated in all the genotypes. RESULTS: Experiments showed that low induction of seed germination is a major component of resistance in these lines against O. foetida. This is confirmed by the in vitro experiments with root exudates. The parallel reduction in infection was accompanied by the continuous enhancement of the peroxidase activity, the polyphenol oxidase activity and the phenylalanine ammonia lyase activity in faba bean roots. CONCLUSION: These data suggest the contribution of these enzymes in faba bean resistance to O. foetida broomrape induced by the use of gamma rays. Management of Orobanche by way of crop selection, based on these enzyme systems is a possible option.

Expansion of a holoparasitic plant, Orobanche lutea (Orobanchaceae), in post-industrial areas - a possible Zn effect.

Industrial waste sites, although extremely difficult to revegetate, may be suitable for rare plants such as Orobanche lutea that are condemned to extinction due to their low ability to compete in their natural habitats. The presence of potentially toxic metals seems to facilitate the expansion of O. lutea (parasitizing Medicago falcata) and was found in hundreds of exemplars per m2 in south Poland and potentially could spread to other localities, causing yield loss in agricultural plants. The main aim of this research was to characterize the interaction between the host, the parasitic plant and symbiotic microbes under different metal concentration in the substratum. The parasite was more common on more polluted soil and when the parasite was connected to the host, potentially toxic metals (Zn, Cd and Pb) were shared by both plants; thus, the content and concentration of these potentially toxic metals in the host were lower than those in plants without parasites. While the performance index (PIABS) of photosynthesis was lower in parasitized plants on control soil, on metal-rich industrial waste soil, PIABS was higher in the parasitized plants than in cases where M. falcata grew alone. This result suggests a role of this parasite in toxicity attenuation, although the biomass of parasitized plants and those growing on polluted sites was lower than that in control sites. In the described case, mycorrhizal colonization and arbuscular richness in M. falcata were even more highly developed on polluted sites than in control ones. The data presented support the hypothesis that the expansion of O. lutea is most likely supported by the increased concentrations of Zn and Cd in areas connected with industrial waste. Although, on industrial wastes the host yield was decreased in the parasite presence, its photosynthetic capacity was even increased.

Control of Egyptian Broomrape in Processing Tomato: A Summary of 20 Years of Research and Successful Implementation.

The obligate root parasitic weeds commonly known as broomrape (Orobanche and Phelipanche spp.) cause severe damage to vegetable and field crops worldwide. Efficient control of these parasites is difficult due to their development and attachment to the host plant (via a specialized organ, the haustorium) under the soil surface and to their unique biological traits of massive seed production, facile seed dispersal, germination only under specific conditions, and seed longevity. The major damage inflicted by the parasites takes place underground, making control extremely challenging. Egyptian broomrape (Phelipanche aegyptiaca) is a devastating pest in the Mediterranean basin, parasitizing a wide host crop range, including tomato, sunflower, legumes, and carrot, resulting in severe crop losses. Twenty years of research have led to the development of integrated smart management strategies for combating this parasite in processing tomato fields. In particular, an explicit decision support system (DSS) designated PICKIT has been developed; this DSS is based on predicting parasitism dynamics and employing a range of selective targeted chemical applications (preplanting incorporation, foliar application, and herbigation). In this feature article, we describe the evolution of this research from the laboratory, through greenhouse and experimental field trials, to large scale commercial fields and the successful assimilation of PICKIT into agricultural practice. The use of PICKIT in fields of processing tomatoes in northern Israel has led to effective control of Egyptian broomrape, even in fields with high infestation levels, resulting in a tomato yield increase of an average of 40 tons ha-1 compared with nontreated plots. In 2016, PICKIT was commercially implemented in 33 fields, totaling 400 ha, giving 95% Egyptian broomrape control and tomato yields of 115 to 145 tons ha-1. The outcome of this research is now enabling farmers to grow tomatoes in Egyptian broomrape-infested fields with assured increased yields and hence high profits.

Haustorium initiation in the obligate parasitic plant Phelipanche ramosa involves a host-exudated cytokinin signal.

The heterotrophic lifestyle of parasitic plants relies on the development of the haustorium, a specific infectious organ required for attachment to host roots. While haustorium development is initiated upon chemodetection of host-derived molecules in hemiparasitic plants, the induction of haustorium formation remains largely unknown in holoparasitic species such as Phelipanche ramosa. This work demonstrates that the root exudates of the host plant Brassica napus contain allelochemicals displaying haustorium-inducing activity on P. ramosa germinating seeds, which increases the parasite aggressiveness. A de novo assembled transcriptome and microarray approach with P. ramosa during early haustorium formation upon treatment with B. napus root exudates allowed the identification of differentially expressed genes involved in hormone signaling. Bioassays using exogenous cytokinins and the specific cytokinin receptor inhibitor PI-55 showed that cytokinins induced haustorium formation and increased parasite aggressiveness. Root exudates triggered the expression of cytokinin-responsive genes during early haustorium development in germinated seeds, and bio-guided UPLC-ESI(+)-/MS/MS analysis showed that these exudates contain a cytokinin with dihydrozeatin characteristics. These results suggest that cytokinins constitutively exudated from host roots play a major role in haustorium formation and aggressiveness in P. ramosa.

iTRAQ-based proteomics of sunflower cultivars differing in resistance to parasitic weed Orobanche cumana.

Orobanche cumana is an obligate root parasite causing severe damage to many economically important crops, including sunflowers worldwide. For efficient control measures, it is necessary to understand the resistant mechanism during interaction at molecular level. The present study emphasizes on comparative proteomics to investigate the mechanistic basis of compatible and incompatible interaction of O. cumana with resistant (JY207) and susceptible (TK0409) sunflowers. More than 3500 proteins were identified from two cultivars by iTRAQ analysis. Identified proteins associated with general functions, posttranslational modification, energy production and conversion, carbohydrate transport and metabolism, and signal transduction mechanisms were the most represented category of induced proteins in both cultivars. The resistant interaction was characterized by alteration of defense-related proteins involved in recognition of parasites, accumulation of pathogenesis-related proteins, biosynthesis of lignin, and detoxification of toxic metabolites in JY207 after inoculation. The susceptible interaction was characterized by decreased abundance of proteins involved in biosynthesis and signaling of plant growth regulators including auxin, gibberellin, brassinosteroid, and ethylene in TK0409 after inoculation. The present study provides comprehensive details of proteins and differential modulation of pathways regulated under compatible and incompatible interaction, allowing the identification of important molecular components for development of sustainable resistance against this parasite.

Host differentiation and variability of Orobanche crenata populations from legume species in Morocco as revealed by cross-infestation and molecular analysis.

BACKGROUND: Orobanche crenata represents a major biotic constraint to production of faba bean and lentil in Morocco. While this parasitic plant attacks both of these crops, the extent to which Orobanche biotypes specialise in parasitising specific crops is unknown. To address this question, we studied O. crenata that grew on different hosts and quantified their host specificity to faba bean and lentil. The virulence of O. crenata populations on each host was investigated through field trials, pot and Petri dishes assays. Genetic diversity of the parasite populations was also assessed through molecular analyses. RESULTS: The two legume species showed distinct patterns of specificity. Faba bean was more susceptible to both O. crenata populations, while the specificity for lentil by lentil-grown O. crenata was evident at the final stage of the parasite life cycle as shown by correspondence factorial analyses. Considerable internal variation (81%) within O. crenata populations parasitising both legume species was observed by molecular analyses, but significant divergence (19%; Ø = 0.189; P = 0.010) among the populations was detected. CONCLUSION: These results indicate that O. crenata can adapt to specific host species, which is important knowledge when developing integrated pest management practices for parasitic weed control. © 2017 Society of Chemical Industry.