CONCLUSIONS: This study provided a non-destructive detection method with Vis-NIR hyperspectral imaging combining with physio-biochemical parameters in Helianthus annuus in response to Orobanche cumana infection that took insights into the monitoring of sunflower weed. Sunflower broomrape (Orobanche cumana Wallr.) is an obligate weed that attaches to the host roots of sunflower (Helianthus annuus L.) leading to a significant reduction in yield worldwide. The emergence of O. cumana shoots after its underground life-cycle causes irreversible damage to the crop. In this study, a fast visual, non-invasive and precise method for monitoring changes in spectral characteristics using visible and near-infrared (Vis-NIR) hyperspectral imaging (HSI) was developed. By combining the bands sensitive to antioxidant enzymes (SOD, GR), non-antioxidant enzymes (GSH, GSH + GSSG), MDA, ROS (O2-, OH-), PAL, and PPO activities obtained from the host leaves, we sought to establish an accurate means of assessing these changes and conducted imaging acquisition using hyperspectral cameras from both infested and non-infested sunflower cultivars, followed by physio-biochemical parameters measurement as well as analyzed the expression of defense related genes. Extreme learning machine (ELM) and convolutional neural network (CNN) models using 3-band images were built to classify infected or non-infected plants in three sunflower cultivars, achieving accuracies of 95.83% and 95.83% for the discrimination of infestation as well as 97.92% and 95.83% of varieties, respectively, indicating the potential of multi-spectral imaging systems for early detection of O. cumana in weed management.

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.

Orobanche coerulescens is a parasitic plant that cannot complete its life cycle without a host and is incapable of photosynthesis. The habitats of O. coerulescens span the coasts of Korea and its volcanic islands, Ulleungdo and Dokdo. Those on the volcanic islands exhibit morphological differences and have distinct hosts compared to those on the peninsula. The family of Orobanchaceae, encompassing both autotrophic and parasitic species, serves as a model for evolutionary studies of parasitic states. However, there are limited genome assemblies for the Orobanche genus. In our study, we produced approximately 100x ONT long reads to construct a chromosome-level genome of O. coerulescens. The resulting assembly has a total size of 3,648 Mb with an N50 value of 195 Mb, and 82.0% of BUSCO genes were identified as complete. Results of the repeat annotation revealed that 86.3% of the genome consisted of repeat elements, and 29,395 protein-coding genes were annotated. This chromosome-level genome will be an important biological resource for conserving biodiversity and further understanding parasitic plants.

In Tunisia, Orobanche foetida Poir. is considered an important agricultural biotic constraint on faba bean (Vicia faba L.) production. An innovative control method for managing this weed in faba bean is induced resistance through inoculation by rhizobia strains. In this study, we explored the biochemical dynamics in V. faba L. minor inoculated by rhizobia in response to O. foetida parasitism. A systemic induced resistant reaction was evaluated through an assay of peroxidase (POX), polyphenol oxidase (PPO) and phenyl alanine ammonialyase (PAL) activity and phenolic compound and hydrogen peroxide (H2O2) accumulation in faba bean plants infested with O. foetida and inoculated with rhizobia. Two rhizobia strains (Mat, Bj1) and a susceptible variety of cultivar Badi were used in a co-culture Petri dish experiment. We found that Mat inoculation significantly decreased O. foetida germination and the number of tubercles on the faba bean roots by 87% and 88%, respectively. Following Bj1 inoculation, significant decreases were only observed in O. foetida germination (62%). In addition, Mat and Bj1 inoculation induced a delay in tubercle formation (two weeks) and necrosis in the attached tubercles (12.50% and 4.16%, respectively) compared to the infested control. The resistance of V. faba to O. foetida following Mat strain inoculation was mainly associated with a relatively more efficient enzymatic antioxidative response. The antioxidant enzyme activity was enhanced following Mat inoculation of the infected faba bean plant. Indeed, increases of 45%, 67% and 86% were recorded in the POX, PPO and PAL activity, respectively. Improvements of 56% and 12% were also observed in the soluble phenolic and H2O2 contents. Regarding inoculation with the Bj1 strain, significant increases were only observed in soluble phenolic and H2O2 contents and PPO activity (especially at 45 days after inoculation) compared to the infested control. These results imply that inoculation with the rhizobia strains (especially Mat) induced resistance and could bio-protect V. faba against O. foetida parasitism by inducing systemic resistance, although complete protectionwas not achieved by rhizobia inoculation. The Mat strain could be used as a potential candidate for the development of an integrated method for controlling O. foetida parasitism in faba bean.

Parasitic weeds in the genera Orobanche, Phelipanche (broomrapes) and Striga (witchweeds) have a devastating impact on food security across much of Africa, Asia and the Mediterranean Basin. Yet, how climatic factors might affect the range expansion of these weeds in the context of global environmental change remains unexplored. We examined satellite-based environmental variables such as surface temperature, root zone soil moisture, and elevation, in relation to parasitic weed distribution and environmental conditions over time, in combination with observational data from the Global Biodiversity Information Facility (GBIF). Our analysis reveals contrasting environmental and altitude preferences in the genera Striga and Orobanche. Asiatic witchweed (Striga asiatica), which infests corn, rice, sorghum, and sugar cane crops, appears to be expanding its range in high elevation habitats. It also shows a significant association with heat-moisture coupling events, the frequency of which is rising in such environments. These results point to geographical shifts in distribution and abundance in parasitic weeds due to climate change.

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.

BACKGROUND: Orobanche is an obligate parasite on faba bean in the Mediterranean region, causes considerable yield losses. Breeding tolerant faba bean genotypes to Orobanche is pivotal to sustain production and ensuring global food security, particularly considering the challenges posed by population growth. In the present study, seven faba bean lines and four testers were used in a line×tester mating design during 2020-2021 and 2021-2022 growing seasons. The eleven parents and their 28 F1 crosses were evaluated under Orobanche free and naturally infested soils.
RESULTS: The results demonstrated considerable variations among the evaluated genotypes, wide diversity among the parental materials, and heterotic effects for all studied agronomic traits under Orobanche-free and infested soils. Orbanche infestation displayed a significant adverse impact on all the studied agronomic traits. The genotypes Line1, Line2, Line3, and Line5 displayed superior performance under Orobanche-infested conditions and recorded the highest values of all studied agronomic traits. Additionally, Line1, Line2, Line3, Line5, and Line7 exhibited desirable significant GCA for most evaluated traits under the two infestation conditions. The obtained crosses displayed significant negative or positive heterosis for studied agronomic characters such as plant height, number of branches per plant, number of pods per plant, number of seeds per plant, and seed weight per plant were observed. Furthermore, specific cross combinations such as Line2×Sakha3, Line3×Nubaria5, Line7 × Nubaria5, Line6×Nubaria1, Line5×Sakha3, Line1×Sakha3, and Line1 × Nubaria5 exhibited superior performance in seed yield and contributing traits under Orobanche-infested conditions. Moreover, these specific crosses showed superior efficacy in reducing dry weight of Orobanche spikes. The results obtained from GGE biplot analysis closely aligned with those from the line×tester procedure, affirming the significance of GGE biplot as a valuable statistical tool for assessing genotype combining ability in line× tester data. Both additive and non-additive gene actions were reported to be predominantly involved in the inheritance of the studied agronomic traits in faba bean.
CONCLUSIONS: The detected genetic diversity within the evaluated faba bean genotypes and their developed crosses exhibits substantial potential for improving faba bean productivity under Orobanche-infested conditions. The parental genotypes, Line1, Line2, Line3, Line5, and Line7, were identified as effective and promising combiners. Moreover, the developed crosses Line2×Sakha3, Line3×Nubaria5, Line7×Nubaria5, Line6×Nubaria1, Line5×Sakha3, Line1×Sakha3, and Line1×Nubaria5 could be considered valuable candidates for developing high-yielding and tolerant faba bean genotypes to Orobanche.

Orobanche foetida Poiret is the main constraint facing faba bean crop in Tunisia. Indeed, in heavily infested fields with this parasitic plant, yield losses may reach 90%, and the recent estimation of the infested area is around 80,000 ha. Identifying genes involved in the Vicia faba/O. foetida interaction is crucial for the development of effective faba bean breeding programs. However, there is currently no available information on the transcriptome of faba bean responding to O. foetida parasitism. In this study, we employed RNA sequencing to explore the global gene expression changes associated with compatible and incompatible V. faba/O. foetida interactions. In this perspective, two faba bean varieties (susceptible and resistant) were examined at the root level across three stages of O. foetida development (Before Germination (BG), After Germination (AG) and Tubercule Stage (TS)). Our analyses presented an exploration of the transcriptomic profile, including comprehensive assessments of differential gene expression and Gene Ontology (GO) enrichment analyses. Specifically, we investigated key pathways revealing the complexity of molecular responses to O. foetida attack. In this study, we detected differential gene expression of pathways associated with secondary metabolites: flavonoids, auxin, thiamine, and jasmonic acid. To enhance our understanding of the global changes in V. faba response to O. foetida, we specifically examined WRKY genes known to play a role in plant host-parasitic plant interactions. Furthermore, considering the pivotal role of parasitic plant seed germination in this interaction, we investigated genes involved in the orobanchol biosynthesis pathway. Interestingly, we detected the gene expression of VuCYP722C homolog, coding for a key enzyme involved in orobanchol biosynthesis, exclusively in the susceptible host. Clearly, this study enriches our understanding of the V. faba/O. foetida interaction, shedding light on the main differences between susceptible and resistant faba bean varieties during O. foetida infestation at the gene expression level.

CONCLUSIONS: The HaOr5 resistance gene is located in a large genomic insertion containing putative resistance genes and provides resistance to O. cumana, preventing successful connection to the sunflower root vascular system. Orobanche cumana (sunflower broomrape) is a parasitic plant that is part of the Orobanchaceae family and specifically infests sunflower crops. This weed is an obligate parasitic plant that does not carry out photosynthetic activity or develop roots and is fully dependent on its host for its development. It produces thousands of dust-like seeds per plant. It possesses a high spreading ability and has been shown to quickly overcome resistance genes successively introduced by selection in cultivated sunflower varieties. The first part of its life cycle occurs underground. The connection to the sunflower vascular system is essential for parasitic plant survival and development. The HaOr5 gene provides resistance to sunflower broomrape race E by preventing the connection of O. cumana to the root vascular system. We mapped a single position of the HaOr5 gene by quantitative trait locus mapping using two segregating populations. The same location of the HaOr5 gene was identified by genome-wide association. Using a large population of thousands of F2 plants, we restricted the location of the HaOr5 gene to a genomic region of 193 kb. By sequencing the whole genome of the resistant line harboring the major resistance gene HaOr5, we identified a large insertion of a complex genomic region containing a cluster of putative resistance genes.

BACKGROUND: As a holoparasitic weed, broomrape has seriously threatened the production of economically important crops, such as melon, watermelon, processed tomato, and sunflower, in Xinjiang in recent years. However, the distribution and genetic diversity of broomrape populations in Xinjiang are not clear at present, which hinders their prevention and control. The purpose of this study was to identify the main species and the genetic differentiation structure of the broomrape population in Xinjiang.
RESULTS: In the present study, 93 samples from different geographic regions of Xinjiang were collected to identify the species based on ITS and plastid rps2 regions, and the samples were also used to analyze the genetic diversity based on ISSR markers. The results showed that broomrape is not monophyletic in Xinjiang and consists of two major clades (Orobanche cf. aegyptiaca and O. cernua) and three subclades (O. cf. aegyptiaca var. tch, O. cf. aegyptiaca var. klz, and O. cernua.var. alt) based on phylogenetic analysis. Furthermore, the results of the genetic diversity analysis indicated that the average polymorphic information content and marker index were high values of 0.58 and 7.38, respectively, showing the efficiency of the ISSR markers in detecting polymorphism among the broomrape population studied. Additionally, the 11 selected primers produced 154 repeatable polymorphic bands, of which 150 were polymorphic. The genetic diversity of the samples was 37.19% within populations and 62.81% among the populations, indicating that the main genetic differentiation occurred among the populations. There was less gene exchange between populations, with a gene flow index (Nm) of 0.2961 (< 1). The UPGMA dendrogram indicated that most populations with similar geographical conditions and hosts were clustered first, and then all samples were separated into two major groups and seven subclusters.
CONCLUSIONS: The broomrapes are mainly O. cf. aegyptiaca and O. cernua in Xinjiang, which were separated into two major groups and seven subclusters based on ISSR markers. Our results provide a theoretical basis for breeding broomrape-resistant varieties.