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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.

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.

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....