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Crenate broomrape (Orobanche crenata Forsk.) is a serious long-standing parasitic weed problem in Algeria, mainly affecting legumes but also vegetable crops. Unresolved questions for parasitic weeds revolve around the extent to which these plants undergo local adaptation, especially with respect to host specialization, which would be expected to be a strong selective factor for obligate parasitic plants. In the present study, the genotyping-by-sequencing (GBS) approach was used to analyze genetic diversity and population structure of 10 Northern Algerian O. crenata populations with different geographical origins and host species (faba bean, pea, chickpea, carrot, and tomato). In total, 8004 high-quality single-nucleotide polymorphisms (5% missingness) were obtained and used across the study. Genetic diversity and relationships of 95 individuals from 10 populations were studied using model-based ancestry analysis, principal components analysis, discriminant analysis of principal components, and phylogeny approaches. The genetic differentiation (F-ST) between pairs of populations was lower between adjacent populations and higher between geographically separated ones, but no support was found for isolation by distance. Further analyses identified four genetic clusters and revealed evidence of structuring among populations and, although confounded with location, among hosts. In the clearest example, O. crenata growing on pea had a SNP profile that was distinct from other host/location combinations. These results illustrate the importance and potential of GBS to reveal the dynamics of parasitic weed dispersal and population structure. National Institute of Food and Agriculture [VA-160055, VA-160111]; National Science Foundation [IOS-1238057] Published version National Institute of Food and Agriculture, Grant/Award Number: VA-160055 and VA-160111; National Science Foundation, Grant/Award Number: IOS-1238057

Crenate broomrape (

Crenate broomrape (Orobanche crenata Forsk.) is a serious long-standing parasitic weed problem in Algeria, mainly affecting legumes but also vegetable crops. Unresolved questions for parasitic weeds revolve around the extent to which these plants undergo local adaptation, especially with respect to host specialization, which would be expected to be a strong selective factor for obligate parasitic plants. In the present study, the Genotyping-By-Sequencing (GBS) approach was used to analyze genetic diversity and population structure of 10 Algerian O. crenata populations with different geographical origins and host species (faba bean, pea, chickpea, carrot and tomato). In total, 8,004 high-quality single-nucleotide polymorphisms were obtained and used across the study. Genetic diversity and relationships of 95 individuals from 10 populations were studied using model-based ancestry analysis, principal components analysis, discriminant analysis of principal components, and phylogeny approaches. The genetic differentiation (FST) between pairs of populations was lower between adjacent populations and higher between geographically separated ones, but no support was found for isolation by distance. Further analyses identified four genetic clusters and revealed evidence of structuring among populations and hosts with more evident structuring among hosts than strictly along a geographic gradient. In the most striking example, O. crenata growing on pea had a distinct SNP profile from those growing on faba bean or other crops. These results illustrate the potential of GBS to reveal the dynamics of parasitic weed dispersal and adaptation.

International audience; Alternaria leaf spot caused by Alternaria alternata (Fries.) Kiessler was found on sow thistle (Sonchus oleraceus L.) and field bindweed (Convolvulus arvensis L.) in the experimental station of ENSA (Ecole Nationale Superieure d'Agronomie) in Algiers, Algeria, during the winter of 2016. Necrotic spots in the form of concentric circles were observed on the leaves of both weeds with disease incidence of approximately 70% and disease severity ranging from 50% to 70%. Fungi were isolated from the infected leaves and identified as A. alternata, based on morphological and molecular analyses (using genetic marker internal transcribed spacer, ITS of rDNA). Pathogenicity tests confirmed that A. alternata is the causing agent of leaf spot disease of sow thistle and field bindweed in accordance with the original symptoms. To the best of our knowledge, this is the first report of sow thistle and field bindweed naturally infected by A. alternata in Algeria.

The aim of the present study was the evaluation of the phytotoxic effect of essential oils (EOs) from two Labiatae species, namely Thymus fontanesii Boiss. et Reut. and Satureja calamintha subsp. n...

From the organic extract of

From the organic extract of Lavandula stoechas, a Mediterranean native plant species, two new phytotoxic copaane sesquiterpenoids were isolated and named stoechanones A and B (1 and 2). They were obtained together with the methyl esters of caffeic and p-coumaric acids and the flavonoid apigenin (3-5, respectively). The structures of stoechanones A and B were determined by spectroscopic (essentially 1D and 2D 1H and 13C NMR and HRESIMS) and chemical methods, and they were characterized as 9,10-dihydroxy-8-isopropyl-1,5-dimethyltricyclo[4.4.0.02.7]dec-4-en-3-one and its 9-O-acetyl derivative. Their relative configurations were assigned by NOESY experiments, and the absolute configurations by comparison of the experimental and DFT-computed ECD spectra. When assayed through Petri dish bioassays, both stoechanones A and B showed phytotoxic effects against seed germination and seedling growth of Amaranthus retroflexus, strongly inhibiting seed germination percentage and radicle and hypocotyl lengths of seedlings. Owing to the herbicidal activity toward A. retroflexus, these two new tricyclic sesquiterpenoids could be proposed and developed as natural bioherbicides in order to increase the control of this problematic weed in the future.

This study evaluated the mycoherbicidal potential of Alternaria alternata (Fries.) Kiessler on cocklebur (Xanthium strumarium L.), a noxious weed in Algeria. Conidial suspension, a rapeseed-oil-based liquid formulation and a sodium-alginate-based solid formulation, all with 106 conidia/ml, as well as the herbicide (Mustang®) at a reduced dose (0.45 L/ha) were compared. Inoculum was applied on detached leaves of cocklebur under laboratory conditions and on 4–5 leaf stage cocklebur seedlings in pots in a greenhouse and in the field. Disease severity was highest following application of the liquid formulation in the detached leaf assay (95.5%) as well as in the pot (80%) and field (43%) experiments. Similarly, the oil-based liquid formulation reduced cocklebur height, root length and dry weight by up to 50%, 27% and 58%, respectively in pot trial and 40%, 51% and 45%, respectively in the field experiment. The conidial suspension ranked second in efficacy, followed by the solid formulation. Mustang® showed the highest herbicidal effect. None of the crops tested for host specificity including tomato, wheat, faba bean and zucchini was susceptible to the fungus. Our findings suggest that A. alternata has potential as biocontrol agent of cocklebur especially when applied in an oil-emulsion-based formulation.

The efficacy of four bi- and tri-cyclic sesquiterpenes, namely inuloxins A, B and C and alpha-costic acid, extracted from aerial parts of Dittrichia viscosa collected in Algeria was assessed against the cowpea seed beetle Callosobruchus maculatus. The compounds were evaluated for their effect on adult mortality, oviposition and adult emergence. Three concentrations (100, 50 and 25 mu g/ml) of each compound were tested with chickpea being used as the test plant. Complete adult mortality (100%) was achieved at only 1 day after exposure to inuloxins B and C and alpha-costic acid with LC50s less than 36 mu g/ml. Lethal concentration values (LC50) were determined as 30.4, 35.2, 31.6 and 29.4 mu g/ml, respectively, for inuloxins A, B and C and alpha-costic acid. Oviposition and F1 progeny emergence were significantly reduced (27% and 73%, respectively) after treatment with D. viscosa compounds. Our results also revealed that oviposition, adult emergence and sex ratio varied with the sex of the treated mating partner suggesting that the test compounds may have acted as male (or indirect female) chemosterilants resulting in reduced fecundity and fertility of untreated females that mated with treated males.

A karyological study of eight populations of Plantago albicans L. (Plantaginaceae) collected from the central high-plain steppe in the province of Djelfa in Algeria was undertaken for the first time. Chromosome numbers were determined as 2n = 2x = 10 for populations growing at medium altitudes (600–900 m) and 2n = 4x = 20 for those growing at higher altitudes (1000–1300 m) of arid bioclimates. Intermediate chromosome numbers 2n = 6, 8, 9, 12, 14, 15, 17 and 18 were found in individuals of the studied populations and were probably aneuploid forms. The analysis of the karyotype asymmetry indices showed that the diploid cytotype (2n = 2x = 10) is characterized by ancestral chromosomes that are symmetrical, large and homogeneous, while the tetraploid cytotype (2n = 4x = 20) is more evolved with asymmetric, small and heterogeneous chromosomes. Based on our findings, it can be suggested that environmental factors and geographical location might have an effect on the genetic structure and evolution of P....

Bacteria of the faba bean (Vicia faba L.)/Orobanche spp. root environment were evaluated for their potential use as biocontrol agents for the parasitic weed. Bacteria were isolated mainly from the rhizosphere of faba bean as well as from diseased Orobanche underground structures and an Orobanche-suppressive soil from three districts of northern Tunisia. Out of 351 bacterial isolates, 337 were tested for pathogenicity in an inverted pyramidal-shape screening programme including a Lactuca sativa L. seedlings bioassay, root-chamber and pot experiments. In pre-selection screening on L. sativa seedlings, 37 isolates (11%) showed a strong growth inhibitory effect, of which 70 and 84% also had a significant suppressive activity on the pre-emergence structures of O. foetida and O. crenata, respectively, in root-chamber experiments. Among five bacterial isolates selected for pot trials, strain Bf7-9 of Pseudomonas fluorescens showed high biocontrol activity against both species of Orobanche and positively...

Four phytotoxic bi- and tri-cyclic sesquiterpene lactones, named inuloxins A???D, were isolated together with the known a-costic acid, from the aerial parts of Inula viscosa (family Asteraceae), a widespread Mediterranean plant well known for its content of pharmacologically active metabolites. The structures of inuloxins A???D were established by spectroscopic and chemical methods and determined to be: (4E,7R*,8R*,10S*)-3-oxo-germacra-4,11(13)-dien-8b-12-olide (A), its 11,13-dihydro analogue (B), (5*, 7R*,8R*,10R*)-1,15-methylene-5b-hydroxy-eudesm-1(15),11(13)-dien-8b-12-olide (C), and (7R*,8R*)-1,4-dimethyl-4-hydroxy-secoeudesm-5(10),11(13)-dien-8b-12-olide (D). The S absolute stereochemistry at C-5 of 5-hydroxyhexan-2-yl side chain of inuloxin D was assigned by applying an advanced Mosher???s method. The phytotoxic activity of inuloxins A???D, that of the diazo and monoacetyl derivatives (of inuloxin A and C, respectively), as well as that of a-costic acid was evaluated against two parasitic plant species, i.e. crenate broomrape (Orobanche crenata) and field dodder (Cuscuta campestris). Inuloxins A, C and D were the most active on both parasites and caused up to 100% inhibition of the seed germination. Inuloxin B was less active on Cuscuta and completely inactive against Orobanche. The main metabolite a-costic acid had a suppressive effect on the dodder seed germination but had a stimulating action on the broomrape seed germination. These preliminary results allowed to suppose some structure???activity relationships.

Compounds of natural origin, such as phytotoxins produced by fungi or natural amino acids, could be used in parasitic weed management strategies by interfering with the early growth stages of the parasites. These metabolites could inhibit seed germination or germ tube elongation, so preventing attachment to the host plant, or, conversely, stimulate seed germination in the absence of the host, contributing to a reduction in the parasite seed bank. Some of the fungal metabolites assayed were very active even at very low concentrations, such as some macrocyclic trichothecenes, which at 0.1 µM strongly suppressed the germination of Orobanche ramosa L. seeds. Interesting results were also obtained with some novel toxins, such as phyllostictine A, highly active in reducing germ tube elongation and seed germination both of O. ramosa and of Cuscuta campestris Yuncker. Among the amino acids tested, methionine and arginine were particularly interesting, as they were able to suppress seed germination at concentrations lower than 1 mM. Some of the fungal metabolites tested were also able to stimulate the germination of O. ramosa seeds. The major findings in this research field are described and discussed. Copyright © 2009 Society of Chemical Industry