Abstract
Orobanche foetida Poiret is a holoparasitic plant that lacks chlorophyll and totally depending on its host for its growth. Orobanche foetida parasitizes host plant roots and extract nutrient and water via a haustorium. Although O. foetida distributes in the Mediterranean region as a wild plant parasite, it parasitizes faba bean causing serious damages which may reach 90% yield losses in Tunisia. Analysis of genetic diversity of the parasite is important to better understand its evolution and spread, remained largely unknown. In this work, we present the first study on genetic diversity and population structure using the robust technique Restriction-site-Associated DNA sequencing (RADseq) for Orobanche spp. We collected 244 samples of O. foetida from 18 faba bean fields in the north of Tunisia including 17 populations from the north-west and one population form the north-east. To overcome the difficulty of SNP discovery in O. foetida genome as a non-model and tetraploid plant, we utilized three different informatics pipelines, namely UNEAK, pyRAD and Stacks. This study showed that genetic differentiation occurred in the Tunisian O. foetida emphasizing the isolation by distance effect. However, no strong population clustering was detected in this work basing on the three data sets and clustering methods used. The present study shed the light on the current distribution and the genetic variation situation of the fetid broomrape in Tunisia, highlighting the importance of understanding the evolution of this parasite and its genetic background. This will aid in developing efficient strategies to control this parasite and its expansion in Tunisia and worldwide.
Highlights
Orobanche is the largest genus among the holoparasitic members of Orobanchaceae with about 170 species (Uhlich et al, 1995)
We used two Bayesian clustering programs relying on Markov Chain Monte Carlo algorithms (MCMC) to explore genetic structure in the genetic data; fastSTRUCTURE, a non-spatial method and TESS3 a spatial admixture analysis (Caye et al, 2016)
We used Restriction-site-Associated DNA sequencing (RADseq) technique to investigate the genetic diversity and population structure of the Tunisian O. foetida biotype consisting of 244 samples collected from 18 different fields belonging to the main faba bean crop area in Tunisia
Summary
Orobanche is the largest genus among the holoparasitic members of Orobanchaceae with about 170 species (Uhlich et al, 1995). Orobanche foetida Poiret (common name: fetid broomrape) is one of the most virulent species of Orobanche; it is an obligate holoparasite, devoid of chlorophyll, parasitizing plant roots and totally depending on its host for its growth. It establishes a connection at Genetic Diversity of O. foetida by RADseq host root level via a haustorium to extract nutrient and water. Poiret described the fetid broomrape for the first time in North Africa during his surveys on 1783 (Poiret, 1922) It is a tetraploid plant (2n = 4x = 76) (Román et al, 2003; Schneeweiss et al, 2004) characterized by a red color and a fetid smell. It was generally considered as a wild plant parasite widespread in natural habitats in the western Mediterranean countries; Tunisia, Algeria, Morocco, Spain and Portugal (Pujadas-Salvá et al, 2003)
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